This work has been submitted to the IEEE for possible publication. Copyright
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# State-of-the-Art in Smart Contact Lenses for Human Machine Interaction

Yuanjie Xia, Mohamed Khamis, F. Anibal Fernandez, Hadi Heidari, Haider Butt,
Zubair Ahmed, Tim Wilkinson, Rami Ghannam This work has been submitted to the
IEEE for possible publication. Copyright may be transferred without notice,
after which this version may no longer be accessible.Y. Xia, H. Heidari and R.
Ghannam are with the School of Engineering, University of Glasgow, UK. e-mail:
<EMAIL_ADDRESS>Ahmed is with the Institute of Inflammation and
Ageing, University of Birmingham, UK. email<EMAIL_ADDRESS>Khamis is
with the School of Computing, University of Glasgow, UK. email:
<EMAIL_ADDRESS>Anibal Fernandez is with the Department of
Engineering, University College London, UK. e-mail<EMAIL_ADDRESS>Wilkinson is with the Department of Engineering, University of Cambridge, UK.
email<EMAIL_ADDRESS>Butt is with the Department of Mechanical
Engineering, Khalifa University, Abu Dhabi, UAE. e-mail:
<EMAIL_ADDRESS>received XXXX; revised XXXX

###### Abstract

Contact lenses have traditionally been used for vision correction
applications. Recent advances in microelectronics and nanofabrication on
flexible substrates have now enabled sensors, circuits and other essential
components to be integrated on a small contact lens platform. This has opened
up the possibility of using contact lenses for a range of human-machine
interaction applications including vision assistance, eye tracking, displays
and health care. In this article, we systematically review the range of smart
contact lens materials, device architectures and components that facilitate
this interaction for different applications. In fact, evidence from our
systematic review demonstrates that these lenses can be used to display
information, detect eye movements, restore vision and detect certain
biomarkers in tear fluid. Consequently, whereas previous state-of the-art
reviews in contact lenses focused exclusively on biosensing, our systematic
review covers a wider range of smart contact lens applications in HMI.
Moreover, we present a new method of classifying the literature on smart
contact lenses according to their six constituent building blocks, which are
the sensing, energy management, driver electronics, communications, substrate
and the I/O interfacing modules. Based on recent developments in each of these
categories, we speculate the challenges and opportunities of smart contact
lenses for human-machine interaction. Moreover, we propose a novel self-
powered smart contact lens concept with integrated energy harvesters, sensors
and communication modules to enable autonomous operation. Our review is
therefore a critical evaluation of current data and is presented with the aim
of guiding researchers to new research directions in smart contact lenses.

###### Index Terms:

Contact Lenses, Human Machine Interaction, Human Computer Interaction,
Wearables.

##  I Introduction

Contact lenses are thin lenses which could be placed directly on the surface
of human eyes. They have historically been used for vision correction and they
were first developed by Adolf Fick in 1887 to correct astigmatism [1]. These
lenses have now undergone a series of innovations and are gaining popularity
due to recent developments in materials engineering and microfabrication.
Currently, these innovative platforms are mainly being considered for a
plethora of medical applications since they are noninvasive [2] and and can be
used to deliver medicines [3]. In comparison to traditional implantable
devices, contact lenses do not require surgery and are capable of monitoring
bio-markers continuously. This is especially true since tear fluid carries
philological bio-markers that can be used to monitor the health of its wearer
[4].

Advancements in smart contact lenses was impeded by the ability to communicate
the ‘sensed’ data wirelessly. In fact, this technological challenge hindered
the development of smart contact lenses during the past two decades. However,
advanced microfabrication technologies enabled miniature electronic components
to be integrated on a contact lens. Contact lenses can now integrate sensors,
driver electronics, energy modules, antennae and I/O terminals on the same
platform. Progress in microelectronics packaging technology as well as
nanofabrication and nanocommunications has therefore resulted in multiple
potential applications for smart contact lenses. For example, in addition to
their use for vision correction, medical staff could potentially monitor
diabetes patients in real-time using these smart contact lenses [5, 6, 7].

In addition to the healthcare field, there are a variety of promising smart
contact lens applications, as shown in fig. 1. According to our
investigations, applications of existing smart contact lens could be divided
into four main categories, which are: (a) eye tracking, (b) healthcare
(medical), (c) displays and (d) vision correction. We will discuss recent
progress in each of these application areas in section VI of our article.
Moreover, we have identified five constituent building blocks of smart contact
lenses, which are the (a) Sensor, (b) Energy, (c) Driver Chip, (d)
Communications, (e) Input/Output (I/O) Interface and (f) Substrate &
Interconnection modules. We chose to discuss recent developments in smart
contact lenses according to these five building blocks. As is shown in fig. 1,
the Energy module is concerned with power harvesting and storage, while the
Driver Chip module provides and regulates this energy, ensuring all electronic
modules operate safely. Furthermore, we included a fifth module called
“Substrate & Interconnection”, which hosts and connects all these electronic
modules together.

First, in section II we demonstrate how our eyes can be used for HMI
applications from a physiological and technical perspective. Next, in section
III of the paper we discuss the State-of-the-Art in review papers on smart
contact lenses. In section IV we describe our methodology in compiling
relevant research articles that match our search criteria. Subsequently, we
discuss and analyse results from our search in section V. Moreover, based on
these recent developments and to ensure that smart contact lenses can be used
for a variety of HMI applications, we propose an autonomously driven concept
contact lens in section VI. Finally, the paper ends with concluding remarks
and a proposed outlook in section VII.

Figure 1: (a) Range of contact lens applications for Human-Machine Interaction
(HMI) that include medical, eye tracking, display and vision assistance. (b)
Constituent building blocks of smart contact lenses, which include the Energy
Management, Communications, Driver Chip, Sensing, I/O Interface and the
Substrate & Interconnection modules.

##  II Using our Eyes for HMI

HMI is concerned with how people and automated systems interact and
communicate with each other. This has long ceased to be confined to just
traditional machines in industry and now also relates to computers, digital
systems or devices for the ’internet of things (IoT) [8]. More and more
devices are connected and automatically carry out tasks in the background.
Operating all of these machines, systems and devices need to be intuitive and
must not place excessive demands on users. Therefore, smooth communication
between people and machines requires user-friendly interfaces. A contact lens
is one of those interfaces that could broaden the potential applications and
facilitate HMI. The purpose of this section is to demonstrate that eye
movements could be used to facilitate HMI.

###  II-A Physiology of the Eye

Before reviewing the range of contact lens technologies that can be used for
HMI, it is important to understand the basic physiology of the eye, how it
moves and what are the muscles responsible for this movement. The eye is a
spherical organ with a mean diameter of around 24 mm. As demonstrated in
figure 2, eye rotation is controlled by six ocular muscles, which are the
superior rectus, inferior rectus, lateral rectus, medial rectus, the superior
oblique and the inferior oblique. The contraction of these six eye muscles
result in eye movements [9]. There are mainly three reasons for eye movements,
which are reducing image motion, positioning the fovea and avoiding double
vision [10, 11]. Moreover, there are six types of basic eye movements, which
include abduction, adduction, supraduction, infraduction, incyclotorsion and
excyclotorsion [12]. In abduction and adduction, the cornea moves away from
and towards the midline, respectively. Similarly, supraduction and
infraduction means that the cornea moves upwards and downwards, respectively.
In addition to the previous four movements, the eye can rotate clockwise or
counterclockwise thanks to the superior oblique and inferior oblique muscles,
respectively. In fact, every complex eye movement is made up of these six
basic eye movements, which could be controlled by humans consciously.

Figure 2: Schematic diagram of the eye, which shows six essential muscles that
are responsible for eye movements (adapted from [13] © 2021, StatPearls
Publishing LLC.)

###  II-B Advantages of Eyes for HMI

HMI applications require an input device, which may involve a touch-screen
device, touch pad or keyboard [14]. However, most of these input devices
require manual manipulation. Moreover, since our eyes are used to collect the
necessary visual information from these machines, we can also use them to
control and interact with these machines for HMI application. Consequently,
hardware and software can be developed to detect eye movements and gestures
such as gaze and blinking to facilitate HMI. In fact, there are a variety of
methods in the literature that can be used for gaze and eye tracking, which
include computer vision [15, 16], magnetic sensing [17] and laser sensing
[18].

Therefore, in comparison to traditional input devices, eye-related gesture
recognition and tracking avoids physical contact and benefits people with
impaired movement. For example, previous studies in the literature confirmed
that eye blinking could be used to facilitate HMI [19, 20]. Here, ‘blinking’
is a semi-automatic reflex function that is controlled by two muscles, which
are the levator palpebrae superioris and the orbicularis oculi [21]. People
sometimes blink consciously as a form of body language or gesture, which is
interpreted as ‘winking’. Therefore, by combining blink detection, gaze
tracking and eye movement, our eyes could be used as an effective and user-
friendly interface for HMI applications.

Figure 3: Timeline of smart contact lens development. (a) Earliest smart
contact lens developed by M. Leonardi et al. in 2003 (adapted from [22]). (b)
Subsequent advancements in the micro-fabrication industry led to the
development of more sophisticated contact lenses 6 years later. For example,
the first contact lens designed for intraocular pressure (IOP) monitoring
(reproduced with permission from [23] © 2008 Acta Ophthalmol). In (c), an
antenna was integrated on a contact lens for energy harvesting. The harvested
power was used to power a single-pixel LED (Reproduced with permission from
[24] © 2010 IEEE). (d) The first contact lens designed for glucose monitoring
(reproduced with permission from [25]. ©2011 IEEE). (e) Google aimed to
commercialize contact lenses for glucose measurement, but the project was
discontinued due to inaccuracies when using tear glucose to predict blood
glucose (reproduced with permission from [26] © 2017 American Chemical
Society). (f) SENSIMED also developed and commercialized contact lenses for
IOP sensing (reproduced with permission from [27] © 2018 BMC Ophthalmology).
(g) The first contact lens artificial iris design, which used liquid crystals
(LCs) for changing the transparency of the contact lens (reproduced with
permission from [6] © 2020 Nature). The next images show most recent smart
contact lens applications for (h) dry eye treatment (reproduced with
permission from [28] © 2019 WILEY-VCH), (i) gaze tracking (reproduced with
permission from [29] © 2020 Nature) and (j) hazard perception (reproduced with
permission from [4] © 2020 Elsevier).

##  III State of the Art

Over the past two decades, major advances in electronics have allowed
researchers to design and integrate miniature electronic systems into contact
lens platforms. Smart contact lenses became an increasingly popular topic in
electronic wearable devices. In previous studies, researchers have proposed
and realized contact lens for health monitoring, gaze tracking and many other
applications. The purpose of this section is to survey the latest review
articles of contact lens technology. Additionally, we will also conclude the
limitations of previous review paper and show how our work could address the
limitations.

Farandos et al. published the first review article on smart contact lenses in
2015 [30]. They confirmed that contact lenses are attractive platforms for
health monitoring applications in comparison to other wearable technologies
due to their ‘minimalistic nature’. Their manuscript started with background
information regarding the physical characteristics of the eye, followed by an
analysis into tear fluid composition. They reviewed the state-of-the-art in
contact lens sensor fabrication, detection techniques as well as the energy
harvesting and readout systems. They also analyzed the market for contact
lenses and FDA regulatory requirements for commercialization of contact lens
sensors. Their manuscript focused on reviewing advances in monitoring
intraocular pressure (IOP) and tear glucose, which were the two main
application areas of smart contact lenses at that time. Their paper mentioned
that commercial contact lens products require sufficient selectivity,
sensitivity, reproducibility and could ensure patient compliance. They also
mentioned that treatment capabilities could be integrated in contact lens
platform. For future development, they highlighted three main challenges with
contact lenses, which were energy harvesting, wireless connectivity and sensor
stability.

Moreover, in 2018 Tseng et al. evaluated different kinds contact lenses for
biosensing applications [31]. Their article focused on reviewing the different
methods for using tear fluid as a detection medium for different diseases such
as cancer, ocular disorders and diabetes. They reviewed previous manuscripts
about tear content, and evaluated both active as well as passive sensors for
tear content sensing. Their review paper predicted that future smart contact
lenses would lead to better personalized medical treatment. Similar to the
review article by Farandos et al., they again highlighted that contact lens
stability and sensor data repeatability is a challenge. Other challenges that
were mentioned were wearer comfort and cost.

In 2020, Kim et al. published another review article on smart contact lenses
for biosensing applications that focus on diseases diagnosis [32]. Their
review analysed both physical and chemical sensors. They also briefly
introduced state-of-the-art in contact lenses for drug delivery, data
transmission and power storage. They mentioned that further research is
necessary to fully appreciate what biomarkers can be detected in tear fluid.
They also indicated that an optimisation of sensor accuracy is necessary,
since this depends on the nature of the disease to be detected and some
diseases require higher sensing accuracy than others. Moreover, they raised
concerns regarding sensor stability and bio-compatibility. However, they
concluded that smart contact lenses could enable noninvasive health monitoring
and diagnosis based on people’s tear fluids, which is likely to be used more
extensively.

Based on the above, state-of-the-art review articles on smart contact lenses
have focused on biosensing applications. In this manuscript, we aim to
systematically review the range of contact lens technologies that facilitate
HMI. These technologies include biosensing and other relevant technologies,
such as liquid crystal displays and augmented reality. In this context, our
work goes beyond existing review articles in this field, since it aims to
showcase how contact lenses have supported HMI and have been used in
applications other than the medical field.

##  IV Methodology

In this section, we define our research methodology in collecting and
synthesizing evidence on smart contact lenses using clearly defined criteria.
Academic journal articles and conference papers were chosen for review,
considering their relatively high impact. Web of Science, which was one of the
largest academic database, was used for identifying the articles using certain
keywords to confine the results. In addition, the keywords that were used to
the searching query are shown in table I. The (AND) Boolean operator was used
to connect these descriptors. All manuscripts that contain the aforementioned
keywords were included in our review.

Similar to the methodology described in [33], we first defined the research
questions and the inclusion criteria of our search. Second, we selected
relevant manuscripts that met these criteria. Third, we analyzed and
interpreted our search results. In this case, we defined the following
research questions (RQ):

  1. 1.

RQ1: What are the different ways in which contact lenses have been used to
facilitate HMI?

  2. 2.

RQ2: What are the device architectures?

  3. 3.

RQ3: Where is the research activity on smart contact lenses mainly located?

  4. 4.

RQ3: What are the challenges and what is the future outlook?

Based on the above questions, the following inclusion criteria (InC) were
defined:

  1. 1.

InC 1: Articles written in English;

  2. 2.

InC 2: Articles matching the definitions and descriptors mentioned in table I.

TABLE I: DESCRIPTORS AND SYNONYMS USED FOR OUR SEARCH. Descriptor |  Definition |  Synonyms
---|---|---
Contact Lens |  Contact lenses are thin lenses placed directly on the surface of the eyes [34] |  Contacts, soft lenses and extended-wear lenses
Smart |  A smart device is able to do many of the things that a computer does [35] |  Autonomous
Electronic |  An electronic device has transistors or silicon chips which control and change the electric current passing through the device [36] |  Electronics
Wireless |  Wireless technology uses radio waves rather than electricity and therefore does not require any wires [37] |  RF powered

Having defined our research questions as well as our inclusion criteria, we
defined our approach in searching for the relevant literature. We used ‘Web of
Science’ portal for our search with the descriptors: smart contact lens,
electronic contact lens, wireless contact lens and sensing contact lens. A
forward and backward search was also performed via ’Google scholar’ to make
sure that all literature has been captured.

##  V Results and Discussion

In this section, we analyze the literature on smart contact lenses for HMI
applications. In total, 83 manuscripts satisfied our search criteria, which
were described in the previous section. The majority of these manuscripts
(approximately 61%) were published during the past 5 years.

Accordingly, we noticed an onset of research interest on smart or electronic
contact lenses from 2008, as shown from figure 4. This is just one year after
the emergence of the first Apple iPhone (2007). It is also just four years
after the beginning of the nanometer sized transistors. The year 2008 also
signifies an important milestone in the transistor industry, since it marks
the emergence of the 45 nm node technology, thus paving the way for advanced
processors such as the atom and the core i7 [38]. Such critical technological
advancements had an important role in the development of electronic components
on contact lens system. We will discuss the range of technologies in each of
these sections. In fact, 50 articles have been published since 2015, which
accounts for 73.5% of all the publications on smart or electronic contact
lenses. We also observe an obvious rise in publications in this field from
2000 to 2020.

Figure 4: Comparison between the publications activity on smart or electronic
contact lenses with CMOS gate width dimensions. A rise in publications
activity started in 2008, which corresponded to the 45 nm gate width.

Based on gathered data, recent developments in smart contact lenses were
categorised according to their six previously mentioned building blocks. About
7.2% of those manuscripts reported developments in more than one building
block and a ”Hybrid” category was introduced, as shown in figure 5.
Furthermore, almost a third (33.7%) of all the literature was devoted to the
“Sensing” category, whereas roughly another third reported developments in the
“Energy” and “Driver Chip” modules (16.9% and 14.4% of manuscripts,
respectively). With the exception of the “Hybrid” papers and the four Review
papers, a fifth of all the literature reported developments in the remaining
four building blocks of smart contact lenses. Latest developments in each of
these categories will be discussed in this section. Moreover, details
regarding the application areas of smart contact lenses will be discussed in
Section VI.

Figure 5: Different components and building blocks of a smart contact lens.
These are the Sensing, I/O Interfacing, Communications, Driver Chip and
Substrate & Interconnecting modules. A hybrid category was introduced to
include smart contact lens developments in more than one building block. Our
search also included four review papers. According to our search, the majority
of the literature has focused on developments in the sensing, energy and
driver chip modules, with fewer publications on the Communications and well as
the I/O Interfacing modules. Figure 6: Essential building blocks of a smart
contact lens. We divided these into the following building blocks: (a)
Sensors: (i) Glucose sensing (reproduced with permission from [39] ©2011
IEEE), (ii) IOP sensing by Leonardi et al. (reproduced with permission from
[23] © 2008 Acta Ophthalmol), (iii) IOP sensing by Chen et al. (adapted from
[40]), (iv) IOP sensing by Zhang et al. (reproduced with permission from [41]
© 2019 Nature) and (v) Eye tracking (reproduced with permission from [29] ©
2020 Nature). Subfigure (b) demonstrates different types of antenna design
including: the loop antennae as demonstrated by (i) Vasquez et al. (reproduced
with permission from [42], (ii) Chiou et al. (reproduced with permission from
[43]; the spiral antenna as demonstrated by (iii) Chen et al. (reproduced with
permission from [44], and (iv) Kim et al. (reproduced with permission from
[45]. Subfigure (c) demonstrates different types of energy modules including:
energy harvesters, as demonstrated by (i) Lingley et al. [46], (ii) Falk et
al. [47] and (iii) Takamatsu et al. [48] © 2019 WILEY-VCH). Moreover, power
storage methods in contact lenses were demonstrated by (iv) Lee et al. [49]
and (v) Parking et al. [50] © 2019 American Association for the Advancement of
Science. Subfigure (d) shows a driver chip design by Jeon et al. [51] © 2019
IEEE. Subfigure (e) demonstrates innovative substrate and interconnection
design for smart contact lenses ([52, 53, 2] © 2018 American Chemical Society,
© 2017 WILEY-VCH, © 2018 American Association for the Advancement of Science).
Subfigure (f) demonstrates input/output terminal block for applications that
include, (i) an artificial iris [6] © 2020 Nature, (ii) dry eye treatment
(reproduced with permission from [28] © 2019 WILEY-VCH), (iii) drug delivery
(adapted from [54]), (iv) presbyopia treatment (adapted from [55])), (v)
safety & security (reproduced with permission from [4] © 2020 Elsevier B.V.),
(vi) display demonstrated by Pandey et al. (reproduced with permission from
[24] © 2020 SPIE (v) display demonstrated by Chen et al. [56] © 2010 IEEE).

###  V-A Sensing

Most contact lenses involve a sensing module, especially since they are widely
regarded as a non-invasive platform that could be used to measure vital human
signs, such as glucose levels and intraocular pressure (IOP). In recent
studies, researchers developed contact lenses for gaze tracking and
electroretinogram (ERG) measurement. Common sensor types and applications are
listed in Table II. In this section, we will discuss latest sensor
developments in contact lens design.

TABLE II: Range of sensor technologies for smart or electronic contact lenses. Sensor Type |  Application |  Reference |  Percentage
---|---|---|---
Capacitance Sensor |  IOP measurement |  [57, 54, 27, 58, 45, 59, 60, 61, 62, 40, 63, 64, 65] |
Resistance sensor |  [66, 41, 22, 23] |  52.9%
Inductor sensor |  [67] |
Electrochemistry sensor |  Glucose measurement |  [68, 1, 69, 51, 70, 71, 5, 39, 25, 72, 2] |  32.3%
Laser sensor |  Eye track |  [73, 18, 29, 17, 74] |  14.7%
Graphene electrode array |  ERG measurement |  [75] |  2.9%

####  V-A1 Glucose Monitoring

Yao et al. demonstrated a wireless health monitoring contact lens for
detecting glucose levels in tear [39]. Their design could work as a
noninvasive and continuous glucose monitor for diabetes, as shown in fig. 6a
i. In fact, their contact lens uses enzyme-based electrochemical glucose
sensors due to its high selectivity and efficiency. With the glucose oxidase
catalysing the reaction between glucose and oxygen in free space to form
hydrogen peroxide and gluconolactone [76]. Subsequently, the hydrogen peroxide
will be detected by electrodes after decomposition.

####  V-A2 IOP Monitoring

In addition to glucose monitoring, researchers have demonstrated contact
lenses that are capable of monitoring IOP directly and continuously. High IOP
could be regarded as a driving element for glaucoma, which is a degenerative
condition of the posterior pole of the eye and can lead to irreversible
blindness. Hence, IOP monitoring contact lenses could prevent the development
and progression of this disease [77]. Therefore, an IOP sensor design was
devised by Leonardi et. al [23]. Their IOP sensor relies on mechanical changes
caused by raised IOP levels, which lead to a variation in capacitance, as
demonstrated in fig. 6a ii.

Furthermore, Zhang et. al designed an IOP sensor based on graphene woven
fabrics [41]. They observed that a variation of IOP causes a change in readout
voltage when the sensor current is constant, which implies a change in sensor
resistance. Their design is demonstrated in fig. 6a iv. However, their contact
lens was characterised for a range of voltages from 0-10 V, with a particular
focus on the linear region between 6-10 V, which may be too high for a
practical wearable application. In addition, they also claim that this sensing
contact lens is low-cost and disposable, which makes it a promising platform
for point-of-care medical treatment.

####  V-A3 Gaze Tracking

Apart from IOP and glucose sensing, researchers have also investigated the
feasibility of developing sensors for gaze tracking. In comparison with the
video-based method, eye tracking smart contact lenses are more convenient for
constrained environments. For example, Massin et al. purposed an eye tracking
contact lens using encapsulated photodetectors [73, 18]. An infra-Red (IR)
source emitter was mounted on an external glasses frame. Photodetectors were
illuminated by the external source and eye movement was detected via a
variation in the amount of light that the photodetectors register. A similar
design was also purposed by Khaldi et al., where an IR emitter was mounted on
a smart contact lens that detected eye movements using an external IR camera
[29], as demonstrated in fig. 6a v.

Moreover, instead of photodetecting sensors, Tanwear et al. used spintronic
sensors to detect eye movement. Their sensor concept was based on the tunnel
magnetoresistance (TMR) effect [17]. Their design integrated magnetic
materials on contact lenses to detect the variation of magnetic field via
spintronic sensors on the glasses frame.

####  V-A4 ERG Monitoring

Finally, Yin et al. demonstrated a soft graphene electrode array that was
fabricated on a contact lens for measuring ERG continuously from cynomolgus
monkeys [75]. Their contact lens could be used in ophthalmic diagnosis to
assess if the retina works properly. The graphene sensor array ensures contact
lens transparency and comfort.

As evidenced from the literature, advances in materials design and fabrication
technology lead to further innovations in sensor technology. When integrated
on a soft contact lens platform, these innovative sensors widen the range of
HMI applications that smart contact lenses can be used in.

###  V-B Energy

The ‘Energy’ module in a smart contact lens includes energy harvesting and
power storage, which are two essential components for an electronic contact
lens to function. To ensure uninterrupted and long term operation, contact
lenses require self-sustainable and autonomous power. It can be realized by
harvesting energy from the external environment. Examples of energy sources
include light, heat, RF waves and motion. Additionally, after the energy being
harvested, a power storage system is required to store them and provide a
stable power input. Thus, the energy module of smart contact lens involves
energy harvester and power storage system.

####  V-B1 Energy Harvesting

There has been mainly three ways to harvest energy to power contact lenses: RF
energy, solar energy and biochemical energy. A comparison between the amount
of energy that can be harvested from these sources for wearable applications
has previously been mentioned in the literature [78], with highest energy
densities being achieved with photovoltaic (PV) cells. According to previous
studies, there are multiple alternative energy source in smart contact lens
design. Moreover, there is interest in using machine learning techniques to
predict the amount of harvestable energy from these sources [79, 80]. Table
III contains publications about different energy sources and the maximum
power. This section involves different kinds of energy sources and storage
methods being applied on contact lenses.

TABLE III: Range of energy harvesting techniques for smart contact lenses. Highest energy densities obtained using solar (photovoltaic) energy Sources |  Maximum Power |  References
---|---|---
RF Energy |  110$\mu W$ |  [81, 24, 82, 70, 60, 59, 83, 84, 85, 86, 68, 87, 71, 88, 50, 89, 51, 90, 91]
Biochemical Energy |  2.4$\mu W/cm^{2}$ |  [47, 92, 5, 93, 90]
Solar Energy |  1.24$mW/cm^{2}$ |  [46, 91, 85]

Harvesting RF energy from an external RF source is not intermittent. Thus, RF
energy is a preferable and reliable energy source for smart contact lens
system, as is demonstrated in fig. 6c iii. For example, a loop antenna was
proposed by Takamatsu et al. to harvest RF energy [48]. Here, a external RF
transmitter was placed at glass frame, which is 5 mm away from the contact
lens, provided 1V DC source with up to 50% efficiency.

Apart from RF power, researchers also investigated the possibility of
integrating solar cells on contact lenses, as is shown in fig. 6c i. For
example, Lingley et al. demonstrated a contact lens with $500\times 500\times
10\mu m^{3}$ single crystal silicon solar cells [46]. The implantable solar
cell had a maximum efficiency of 1.24% for a 725 nm source at 310 mV.
Moreover, using a solar simulator that emulates an AM1.5 light source, the
power density of their solar cell 1.24 $mW/cm^{2}$. Despite this relatively
high energy density for a solar cell, the actual harvestable power is small
(3.1 $/muW$) due to the constrained size of contact lenses.

Harvesting energy from the body’s biochemical energy has also been
demonstrated. For example, Frei et. al demonstrated biochemical energy
harvesting from metabolites in tear fluid, as shown in fig. 6c ii [93]. In
their design, the glucose fuel cell could only generate around 2.4$\mu
W/cm^{2}$ at a cell voltage of 0.56 V. In comparison to RF and solar energy
harvesting, biochemicals in tear fluid yield much lower power densities, as
shown in Table III.

In future, triboelectric transducers can also be considered as a feasible
solution for powering electronic or smart contact lenses. These devices have
not been demonstrated in the literature, but they have been used in
implantable devices. With an implanted triboelectric receiver, an external
acoustic wave could transfer energy remotely [94]. Furthermore, to overcome
many of the drawbacks of each of these energy harvesters, a hybrid energy
harvester can be designed for smart contact lenses [91]. Such a harvester
would be designed to leverage the advantages of each energy harvester. Future
energy harvesting techniques may also include scavenging the eye’s movements
as well as blinking and winking. Here, deformation and vibration of
piezoelectric materials enables kinetic energy from these gestures and
movements to be converted to electrical energy [95].

In comparison to other energy harvesting techniques, RF energy harvesting has
been predominantly investigated in the literature. Although solar cells yield
highest energy densities, RF harvesters are capable of scavenging more energy
on the contact lens platform. Moreover, solar (or light) energy is location
and time dependent, which makes it an intermittent energy source. Therefore,
thanks to the advent of 5G technology and the expected proliferation of
transmitter antennae, RF energy harvesters have been widely considered as a
promising energy harvesting solution in smart contact lens design.

####  V-B2 Power Storage

In the literature, there were two methods for power storage in smart contact
lenses: thin film batteries and supercapacitors.

  1. i

First, there were 2 papers that demonstrated a thin film battery for power
storage on contact lenses. An RF powered (flexible) thin film battery was
developed by Nasreldin et al. [89]. The electrodes of battery were were
consisted of lithium nickel manganese oxide (LNMO) and Lithium Titanate (LTO),
which is ring shaped with an area of 0.75 $cm^{2}$ and thickness of 100$\mu
m$. It had a storage capacity of 32.25$\mu Ah$ at room temperature and can
output 1.2 V to the ASIC.

Lee et al. also designed and fabricated a contact lens with a scalable thin
film battery [49]. Their battery used olivine LiFePO4 thin film cathode and
achieved a storage capacity of 35 $\mu$Wh at 0.49 $cm^{2}$ in wet conditions,
which could power a glucose contact lens for 11.7 hours. Their design is
demostrated in fig. 6c iv.

  2. ii

In addition to thin film batteries, researchers considered using
supercapacitors to store energy [88, 50]. For example, Park et al.
successfully printed a supercapacitor on contact lens, which can be fully
charged to 1.8 V around 240 seconds [50]. The discharge time varied from 110
to 560 seconds and depended on current density. This printed supercapacitor
system commonly works with a stable external RF source, which could stably
operate for over 100 hours. The supercapacitor structure is shown in fig. 6c
v. With rechargeable and solid-state supercapacitors, contact lenses can
operate continuously with unpredictable external power sources such as RF
power. In that case, such supercapacitors can provide the energy that a
contact lens needs for a few minutes.

Nevertheless, supercapacitors have relatively short charging and discharging
times, which means that complimentary energy scavengers - such an RF converter
- are necessary to ensure stable energy supply for the contact lens system. In
comparison to supercapacitors, thin film batteries have higher capacities, but
lower energy densities, which means they occupy a larger space. To overcome
this, a hybrid solution comprising supercapacitors and thin film batteries
could be developed to provide stable power supply and extended battery life.
Future work on energy modules for smart contact lenses should focus on both
energy harvesting and power storage to achieve self-sustainable and autonomous
contact lenses.

###  V-C Driver Chip

The driver chip is an essential part of a smart contact lens, since it is
responsible for effectively managing and regulating received energy, thereby
ensuring all electronic modules operate safely. This module often includes
rectifiers, regulators and converters, which power the system with appropriate
and reliable power signals. Moreover, signals are processed in this module via
oscillators, sensor readout circuitry and logic circuitry. This is often
required for reading data from the sensing module or for sending control
signals to the I/O Interface. According to our review, 14.4% of the
literature’s research articles involved driver chip. In fact, researchers have
mainly focused on designing application-specific integrated circuits (ASICs)
for health monitoring applications, as shown from our results in Table IV. The
table lists five representative publications about ASIC design, which covers
three different applications. Although there are other applications of smart
contact lenses, researchers have not made any fully functional prototypes [6].

TABLE IV: Characteristics of different IC driver chip designs for various applications Diagnostic |  CMOS Process (nm) |  Frequency (MHz) |  Power Consumption |  Chip Area ($mm^{2}$) |  Publication Year |  Reference
---|---|---|---|---|---|---
IOP |  130 |  2500 |  1.4mW |  0.49 |  2010 |  [96]
|  350 |  13.56 |  1.2mW |  2 |  2015 |  [97]
Glucose |  0.13 |  1800 |  3$\mu$W |  0.22 |  2012 |  [70]
|  180 |  433 |  <490nW |  2.25 |  2020 |  [51]
|  65 |  4100 |  0.27nW |  0.15 |  2018 |  [87]
Tear Content |  0.18 |  920 |  110$\mu$W |  1.58 |  2017 |  [63]

The power consumption of smart contact lenses typically varies between 0.27 nW
and 1.4 mW, depending on the function and structure of the controller chip, as
shown in Table IV [96, 70, 97, 63, 51]. This energy consumption is for the
whole system rather than only the driver chip. As is shown in fig. 6d, the
most recent integrated circuit (IC) designed by Jeon et al. demonstrated the
possibility of developing a near zero power consumption driver, which was
based on the load-shift keying (LSK) backscattering method [51]. Consequently,
this is an important step in realising autonomously powered smart contact
lenses with an energy efficient driver chip. Therefore, contact lenses for
glucose sensing and monitoring could be designed with less power consumption.

The operating voltage of smart contact lenses is also a crucial parameter,
since low voltages reduce power consumption and protect the eyes from
potential hazards. For wearable devices, typical input voltages are 3.3 V and
5 V. However, contact lenses should operate at lower input voltage in
comparison to other wearable devices since they come into direct contact with
human eyes, and a minor malfunction like short circuit could cause
irreversible damage. From our review, the operating voltage of contact lenses
ranged from 0.165 V to 2 V. For example, Hayashi et al. successfully designed
a self-powered contact lens for glucose monitor with 0.165 V operating
voltage. Their design also consumed 0.27 nW of power, which is lowest among
all contact lens designs.

It is noteworthy to mention that all these articles have been published after
2010, which means that technological advances have enabled researchers to
design and fabricate smart contact lenses in the lab. This highlights an
emerging prospect of smart contact lens-based products in the future and the
prospect of greater functionality and more powerful interface for HMI.

###  V-D Communications

The communications block in smart contact lenses is concerned with
transmitting and receiving data. For transmitter, after processing the sensor
data with coder and mixer, the output signal will be transmitted by antenna.
Consequently, the majority of developments in the communications module is
concerned with antenna design. The important antenna design parameters for a
contact lens includes return loss, bandwidth, operating frequency, flexibility
and vision obstruction.

Smart contact lenses work as an interface in HMI applications, which requires
data transmission between the contact lens platform and an external processor.
Thus, antennae need to be integrated on the contact lens platform [98]. To
maximize the size of the antenna and prevent vision obstruction, researchers
have often used a ring-type antenna geometry, as shown in figure 6b.

In comparison to other antennae, the loop antenna is easier to fabricate and
avoids vision obstruction, which is why it has been used in many contact lens
designs [99, 82, 62]. For example, Chiou et al. proposed a dual loop antenna
design for both the receiver (Rx) and transmitter (Tx), as demonstrated in
fig.6b ii. The return loss of their design was -21 dB at 925 MHz and their -10
dB bandwidth was 21 MHz [43].

From a practical and health perspective, placing an RF source 10 mm away from
the contact lens seems unrealistic and hazardous, since exposure to
concentrated electromagnetic radiation may cause harm to the eyes. Ting et al.
proposed loop antenna integrated on contact lens and using pig eyes to
simulate practical situation and measured antenna radiation patterns, antenna
gains, and radiation efficiency [100]. Their design can cover the frequency
from 1.54 to 6 GHz for ISM band applications, which is suitable for
application of wireless ocular physiological monitoring.

In comparison with the loop antennae, spiral antennae demonstrate better
performance, since the loop antenna is confined by horizontal polarization.
Spiral antennae are more suitable as transmitter due to circular polarization,
so that devices in various positions can receive the same amplitude of
electric signal. Chen et al. designed an antenna with sixteen spiral windings
connected in series in a loop for near field communication, as is shown in
fig.6b iii, which can transmit data from contact lens to mobile phone [44].
Their design has a distributed multi-layer coil structure, which could
eliminate substrate warpage. Kim et al. designed a spiral antenna with
resonant frequency of 4.1 GHz, which is demonstrated in fig.6b iv.
Communication was achieved by coupling the spiral antenna with an external
antenna. With different glucose concentrations, the reflection value is
different from 3.5 to 4.1 GHz, which could be received and recognized by
external receiver [45].

###  V-E Substrate and Interconnect Technology

Finally, all the aforementioned electronic components need to be fabricated on
a particular substrate and interconnected with wires. Flexible and stretchable
substrates and interconnects are therefore required to ensure user comfort.
Below is a discussion regarding the materials as well as the fabrication
methods and technologies used for both the contact lens substrate and its
interconnects.

####  V-E1 Substrate

Traditionally, contact lenses were fabricated on polymer and silicone hydrogel
based substrate [101]. On the other hand, Park et al. proposed a novel way to
fabricate stretchable contact lenses with a hybrid substrate. A photocurable
optical polymer (SPC-414; EOP= 360 MPa) was photolithographically patterned
with a Cu sacrificial layer, as shown in figure 6e.iii. These reinforced
islands were connected by stretchable and transparent conductors [2].
Moreover, Choi and Park published a concept paper regarding the use of
graphene as an effective substrate material for multi-focal contact lenses
[26]. They mentioned that a graphene-based contact lens could protect eyes
from electromagnetic waves and dehydration. Furthermore, graphene is an
extraordinarily flexibile and transparent material, which are crucial
attributes of future contact lenses.

In comparison with traditional (polymer and silicone hydrogel) contact lens
substrates, future devices need better compatibility with electronic
components and further investigation into encapsulation materials is necessary
to prevent wearer harm from potential electronic hazards.

####  V-E2 Interconnects

Ideally, smart contact lens interconnects need to be highly transparent,
conductive, flexible, stretchable and demonstrate low sheet resistance.

Takamatsu et al. proposed an electrochemically printed circuit on a contact
lens. It was based on the polymerization of 3,4-ethylenedioxythiophene (EDOT)
glue at the interface between the circuit and the hydrogel-based substrate.
Their design enabled soft contact lenses to be fabricated as an interface with
more complex circuits and functionality [48]. Kim et al. proposed 3D printed
interconnects for smart contact lenses. They used Ag/AgNW composite ink with
spray printed method to print the circuit on Polyimide substrate. Their
circuit design had a small sheet resistance variation (0.396
$\Omega\cdot\square^{-1}$ ) when the device was significantly deformed.
Moreover, AgNW printed circuit have relatively high conductivity and
transparency, which has less heat generation and allows better vision. Their
design ensured that deformation would not influence the stability of contact
lens operation [52]. Moreover, Alam et al. reviewed substrate materials in
previous smart contact lenses design and fabrication. They suggested that 3D
printing would widely be used in next generation contact lenses.

###  V-F Input/Output Interface

Smart contact lenses need a mechanism to interface with the outside world. As
input, we previously discussed how sensors collect data from the lens’
surroundings. However, smart contact lenses may need to take action, provide
feedback, or to communicate and display information back to the user.
Therefore, the I/O Interface is responsible for this important functionality
in smart contact lenses for HMI applications.

For example, Quintero et al. proposed a design of an artificial iris with
smart contact lens and liquid crystal material [6] for vision correction, as
demonstrated in fig.6e i. Similar design was also made by Raducanu et al. [7]
and Vanhaverbeke et al. [102]. They manipulate liquid crystal material by
voltage variation. The switching of liquid crystal would cause the
transparency variation of the contact lens, therefore it can avoid patients
with iris diseases exposed to intense light. In addition to artificial iris,
Milton et al. proposed a novel contact lens design for presbyopia treatment
using contact lens and liquid crystal [55], which is shown in fig.6e iv. Their
design used the optic and electric properties of liquid crystals. The focus
length of the contact lens could be controlled by voltage. Their design could
help people with presbyopia could adjust the focus length of the contact lens
based on their requirement.

Apart from vision correction module, there are also medical modules such as
dry eye treatment module and drug delivery module. Kusam et al. designed a dry
eye treatment module on contact lens, where electroosmotic flow was generated
in fluid conduit by charged hydrogel [28]. This design could help the dry eye
disease treatment.

Contact lenses with safety and security module could changes color or
transparency based on external environmental variation, which could be
realized by liquid crystal or electrochromic material. In fig. 6e v, Kim et
al. proposed a alarm system using electrochromic material Prussian blue[4].
This contact lens could turn blue automatically to warn its wearer when it
detects hazards.

There are also some modules for display use. Chen et al. proposed a concept
contact lens using light-emitting diodes to achieve augmented reality, as is
shown in fig. 6e vi. Apart from academic field, a company called Mojo Vision
claims to have developed a smart contact lens with display functionality using
microLEDs [103]. They claim that their contact lens could display the size of
a grain of sand to share critical information.

These modules could directly or indirectly effect on contact lens user, which
is a important role in HMI application. The development of electronic devices
and fabrication technology enhanced interaction between smart contact lens and
user.

###  V-G Hybrids

As previously mentioned, we categorised the literature on smart contact lenses
according to six constituent building blocks. However, some references
targeted more than one building block. We grouped these papers in a new block
called the ”hybrids”.

For example, Song et al. designed a contact lens for both Glaucoma diagnosis
and in situ drug delivery [54]. The contact lens stores drugs using nanopores,
which could sustain the drug for up to 30 days. Therefore, this contact lens
design targets both glucose sensing and drug delivery.

Chiou et al. devised an autonomous contact lens system using RF power [84]. In
their design, a radio-frequency identification (RFID) driver chip was used for
capacitive sensor control and data transmission. The whole system consumed 110
$\mu W$ and was powered by external RF sources. In their design, energy can be
harvested from a 30 dB RF source, which was placed 10 to 40 mm away from their
contact lens [43]. They designed the contact lens in system level, which
involves communication, RFID design, energy harvesting.

Lingley et.al devised a smart contact lens with single pixel LCD. This single
pixel LCD that was automatically driven by an external RF energy source. Their
design focused on both energy harvesting and information display [82].

Kim et al. designed a graphene-based silver nanowire (AgNW) hybrid structured
sensor for glucose monitoring. The sensor used the same electrochemical
principle to transform glucose concentration in tear fluid to electric signal
and transmit to receiver via spiral antenna [45]. Silver nanowires were used
to improve the electrical and mechanical performance without adversely
affecting the sensor’s transparency and stretchability. This design involves
sensing, communication and interconnection.

Raducanu et al. designed an artificial iris system, which can change the
transparency with the variation of light intensity of the environment [7]. It
is a systematic design which involves communication, power module, sensing,
I/O interface and driver electronics.

Furthermore, Quintero et al. devised and fabricated a hydrogel-based smart
contact lens which could communicate and harvest energy from near-field
source. They designed a comperhensive smart contact lens system, including
communication, interconnection, energy harvesting and substrate design.

##  VI Applications

From our review, 58 out of our 83 manuscripts mentioned a specific application
for their contact lens. The remaining 25 manuscripts were therefore discarded
from the discussions below. From those 58 manuscripts, we identified four main
applications areas of existing smart contact lenses, which are (i) medical,
(ii) display, (iii) eye tracking and (iv) vision assistance. Moreover, the
percentage of manuscripts devoted to each application area is demonstrated in
fig.7.

Figure 7: Pie chart for smart contact lens applications. The pie chart above
shows the distribution of the application areas in the reviewed manuscripts.

Accordingly, the medical field accounts almost three quarters of all
publications. Medical applications of smart contact lenses include the
measurement of corneal temperature [104], intraocular pressure (IOP) [105,
106] and glucose levels [69, 107, 108]. Continuously monitoring these health
indicators help improve disease diagnosis and treatment. In addition to these
health indicator measurements, contact lenses have also been used for treating
dry eye disease [109, 28] and for releasing drugs [54].

Since 2016, smart contact lenses have been used in other non-medical
applications. For example, they have been used in applications that include
vision assistance, display and eye tracking. In terms of vision assistance,
smart contact lenses were used for improving people’s vision with ocular
defects, such as iris defects [6] and presbyopia [55]. Instead of static or
traditional methods of vision correction, these smart contact lenses change
their state based on their surrounding environmental conditions. For example,
a smart contact lens alarm was demonstrated by Kim et al [4] as well as an
artificial iris by Quintero et. al [6] and Raducanu et al [7].

In terms of human-machine interaction (HMI), eye tracking using smart contact
lenses has also been demonstrated in the literature [73, 18, 17]. Contact lens
with eye tracking functionality could be used in many scenarios. For instance,
in virtual gaming and online education, where there are projected benefits of
contact lenses for entertainment applications in comparison to wearable
devices that have limitations with accuracy and can be remedied using contact
lenses [18]. Additionally, contact lens with display module are also developed
to facilitate the HMI. These contact lenses could be used to transmit
visualized data, which can be applied in augmented reality applications [56].

Moreover, contact lenses have also been demonstrated for eye tracking
applications. Eye tracking is currently a hot topic that enables a computer to
detect where the eye is looking. However, current methods rely on cameras and
computer vision software as well as signal processing and machine learning
algorithms to determine the eye’s position. However, these conventional
hardware configurations accommodate a limited range of head movement and
suffer from poor precision [110]. In contrast, eye-wear based systems have
improved accuracy, tracking speed, mobility and portability, which are
important attributes for a wearable HMI application.

Furthermore, smart contact lenses were used as near eye display (NED) modules.
For example, liquid crystal materials were used for displaying information, as
demonstrated by the early work of de Smet et al. in [111], as well as their
most recent work in [6]. The versatility of such materials in contact lenses
enabled them to be used for both sensing and display applications [112].
Moreover, the concept of using Light Emitting Diodes (LEDs) in contact lenses
for augmented reality (AR) applications were proposed by [56]. Although an
experimental setup was not shown, simulation results using CODE V software
predicted a high resolution smart contact lens with a wide field of view (FOV)
that can move or rotate freely without the need for eye tracking.

In terms of eye and gaze tracking applications, camera-less tracking using
contact lenses was demonstrated by Massin et al., which was 2.5 times better
than current camera-based eye-trackers [73, 18]. In addition to their improved
accuracy, such camera-less systems are more cost effective for eye and gaze
tracking applications [113].

##  VII Challenges and Future Work

Despite the aforementioned benefits of smart contact lenses for HMI
applications, there are still many looming challenges. For example, the
driving voltages required to power the various electronic modules are still
large ($>1$ V). Therefore, since power consumption is high, such smart
electronic platforms may be unsafe for human use on the eye. However, thanks
to advancements in transistor nanofabrication, which led to a steady reduction
in power supply voltage from 1.2 V in 2003 to 0.5 V in 2018, this driving
voltage is expected to decrease with the advent of the 2 nm node fabrication
process in 2024 [114, 115].

Figure 8: Futuristic concept of a smart, self-powered contact lens with
integrated energy harvesters, antennae, sensors, display module and power
management circuitry. Such a contact lens would be a major breakthrough in
Human-Machine Interaction.

Moreover, since contact lenses are regarded as temporary prostheses,
regulatory approval is essential before they can be used. For example, the
U.S.’s Food and Drug Agency (FDA) oversees the safety, effectiveness and
manufacturing of contact lenses. Such a process has been criticised as
expensive and costly [116], which may hinder the introduction of smart contact
lenses in large scale, especially if examination, trialling and practical
training by an ophthalmologist is necessary.

Numerous studies have also shown that contact lenses may lead to serious
ocular health problems if certain cleaning guidelines are poorly observed
[117, 118]. Nevertheless, despite these challenges, surveys have shown that
contact lens wearers are often more satisfied than regular eye glass wearers
[119]. Moreover, in comparison to regular eye glasses, contact lenses help
widen the wearer’s field of vision as well as reduce spheric and chromatic
aberrations.

Based on these developments, it is clear that the smart contact lens of the
future will be autonomously driven, contain multiple sensors and will enable
data processing and visualisation near the eye, as shown in figure 8.
Moreover, to ensure that such a lens is battery-less, energy will be scavenged
from its surroundings using a variety of sources that could include solar
cells, RF harvesters and thermoelectric generators [91].

##  VIII Conclusions

Contact lenses have evolved from vision correction platforms to advanced tools
for healthcare, entertainment as well as safety and security applications.
This is now possible thanks to advancements in nanofabrication, materials
engineering and microelectronics packaging, where electronic modules can be
seamlessly integrated on flexible substrates. In all these applications, the
contact lens platform plays an essential role in facilitating the interaction
between humans and machines. Therefore, the purpose of this paper was to
review the state-of-the-art in smart contact lens technologies and their use
for Human Machine Interaction. We reviewed 83 articles published during the
past 21 years which met our inclusion criteria on smart contact lenses.
According to our review, the majority of research on smart or electronic
contact lenses was devoted to medical applications, with almost half of all
publications focusing on glucose and IOP monitoring. However, during the past
five years there has been a surge in publications demonstrating the use of
contact lenses for a wider range of applications, which include medical, eye
tracking, vision assistance as well as displays. We discussed the feasibility
of smart contact lenses as a more intelligent and powerful interface in HMI
applications. We also provided an outlook into the future use of smart contact
lenses in other HMI applications. Despite the challenges associated with
driving voltages, as well as contact lens regulatory approvals, we believe
that future trends in Very Large Scale Integration and nanofabrication will
enable these electronic platforms to become a reality.

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|  Yuanjie Xia received his BEng Degree in Electrical and Electronics
Engineering at University of Electronic Science and Technology of China
(UESTC) and University of Glasgow in 2020. He is currently a PhD candidate in
the Microelectronics Laboratory (meLAB) at University of Glasgow and his
research interests are in reconfigurable devices for HMI applications.
---|---
|  Mohamed Khamis is a Lecturer (Assistant Professor) in the School of
Computing Science at the University of Glasgow, where he leads the SIRIUS Lab
into research in Human-Computer Interaction, Human-centered Security and Eye
Tracking. He has 90+ publications and his research received funding from
several bodies including the Engineering & Physical Sciences Research Council,
Facebook Reality Labs, the Royal Society of Edinburgh and the National Cyber
Security Centre.
---|---
Tim Wilkinson is a Professor in Electrical Engineering at the University of
Cambridge. Prof. Wilkinson has had a long term research interest into the
applications of liquid crystal (LC) devices, holograms and related photonic
applications. One breakthrough made recently was in algorithms which lead to
the commercialisation of holographic projectors. Core to his research has been
liquid crystal device fabrication and the search for the optimal materials for
different applications.
---
Haider Butt is an Associate Professor in Mechanical Engineering at Khalifa
University. He was awarded both an M.Phil and a PhD in Electrical Engineering
from the University of Cambridge in 2008 and in 2012. He has published over
100 peer-reviewed articles in prestigious journals including Nature
Communications, Advanced Materials, Biotechnology Advances, Light Science and
Applications, and ACS Nano. He has earned international recognition for his
research and leadership in optical sensors where he has contributions to
nanoscale devices by conceiving novel holographic lithography methods to
produce optical transducers. His most pioneering works include glucose sensing
contact lenses, contact lenses for color blind patients and carbon nanotube
holograms.
---
|  Zubair Ahmed is a Professor in Neuroscience in the Institute of
Inflammation and Ageing at the University of Birmingham. He received his PhD
in 1999 from University College London and held positions at the Institute of
Neurology in London before joining Birmingham in 2002. He held a prestigous
RCUK Academic Fellowship, before being promoted to Lecturer and recently to
Full Professor in Neuroscience. He is currently the Lead for Neuroscience and
Ophthalmology and his research interests include the definition of the
molecular mechanisms underpinning ocular, spinal and brain injuries.
---|---
|  Rami Ghannam (SM’18) is a Senior Lecturer (Associate Professor) in
Electronic Engineering at the University of Glasgow. He received his BEng
degree in Electronic Engineering from King’s College London and was awarded
the Siemens Prize. He subsequently received his DIC and MSc degrees from
Imperial College London, as well as his PhD from the University of Cambridge
in 2007. He held previous industrial positions at Nortel Networks and IBM
Research GmbH. His research interests are in Photonics, Sensors and Wearable
Computing. He is a Senior Member of the IEEE, a Senior Fellow of Glasgow’s
Recognising Excellence in Teaching scheme and serves as Scotland’s Regional
Chair of the IEEE Education Society.
---|---