State-of-the-Art in Smart Contact Lenses for Human Machine Interaction

TL;DR

A systematic review of the range of smart contact lenses materials, device architectures, and components that facilitate this interaction for different applications and develops guidelines for the future design of a self-powered smart contact lens concept with integrated energy harvesters, sensors, and communications modules.

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 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.

Figures (8)

• 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.
• Figure 2: Schematic diagram of the eye, which shows six essential muscles that are responsible for eye movements (adapted from eyemodel © 2021, StatPearls Publishing LLC.)
• Figure 3: Timeline of smart contact lens development. (a) Earliest smart contact lens developed by M. Leonardi et al. in 2003 (adapted from leonardi2003soft). (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 leonardi2009wireless © 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 pandey2010fully © 2010 IEEE). (d) The first contact lens designed for glucose monitoring (reproduced with permission from yao2011dual. ©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 choi2017smart © 2017 American Chemical Society). (f) SENSIMED also developed and commercialized contact lenses for IOP sensing (reproduced with permission from rabensteiner2018influence © 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 quintero2020artificial © 2020 Nature). The next images show most recent smart contact lens applications for (h) dry eye treatment (reproduced with permission from kusama2020self © 2019 WILEY-VCH), (i) gaze tracking (reproduced with permission from khaldi2020laser © 2020 Nature) and (j) hazard perception (reproduced with permission from kim2020electrochromic © 2020 Elsevier).
• 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.
• 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.