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This paper presents the simulated performance assessment of an artificial iris embedded on a scleral contact lens using real data from an aniridia patient. The artificial iris is based on guest–host liquid crystal cells (GH-LCD) in order to actively modify the transmittance of the lens and effective pupil size. Experimental validation of the GH-LCD spectrum and iris contrast (determined to be 1:2.1) enabled the development of optical models that include the effect of a small pupil on image quality and visual quality on an optical system with aniridia characteristics. Visual simulations at different light conditions (high/low photopic and mesopic) demonstrated the theoretical capacity of the customized artificial iris smart contact lens to expand the depth-of-focus and decrease the optical aberrations (in particular, the spherical aberration). The visual modelling suggests a maximum depth-of-focus value for a 2-mm pupil diameter for both eyes as follows: 3D (1,000 cd/m2), 2D (10 cd/m2) and 0.75D (1 cd/m2). This work demonstrates the beneficial optical effects of an active artificial iris, based on visual simulations in response to different light levels, and enables further experimental investigation on patients to validate the dynamic light attenuation and visual performance of smart contact lenses with GH-LCD.

In a normally functioning eye, the iris controls the pupil diameter to regulate the amount of light reaching the retina. Various iris deficiencies exist, manifesting as defects in the iris or an absence of one which result in too much light reaching the retina. Some iris deficiencies, such as aniridia or leiomyoma, can be mitigated with fixed or adaptive artificial irises. As an alternative, adaptive transparency glasses may also alleviate this situation, however, both solutions do not mimic the other normal functionality of the natural iris: adaptive aperture. To address this, we developed a fully encapsulated, self-contained artificial iris embedded in a smart contact lens. The control ASIC of the contact lens is developed in 0.18- $\mu \text{m}$ 16-V BCD TSMC and has a typical power consumption of 1.9 $\mu \text{W}$ from a 3-V supply voltage at office light condition.

Many of today’s stretchable interconnection technologies make extensive use of meandered interconnections, these provide 2-D in-plane springs capable of extending and compressing as the need arises. While a significant quantity of research work exists on these interconnects, few generic methodologies exist to design circuits in a consistent manner. This shortfall leads to questionable design practices, which can negatively affect reliability and performance. Presented within this paper is a method to quickly determine which meander fits within a given area based on common geometric boundary conditions.

In a functional eye, the iris controls the pupil diameter to regulate the exposure of the retina. While iris deficiencies such as aniridia or leiomyoma can be mitigated with fixed or adaptive artificial irises [1] and adaptive transparency glasses exist to alleviate this situation, they do not mimic the normal functionality of the natural iris. To address this, a fully encapsulated, self-contained artificial iris embedded in a smart contact lens is proposed. A control ASIC is developed in 0.18 μm 16 V BCD TSMC with typ. 1.9 μw current consumption from 3 V supply voltage at office light condition.

An electrochemical smart contact lens (ESCL) capable of real-speed spatiotemporal electrochemical sensing across the surface of the eye is demonstrated. Four microelectrode arrays, each comprising 33 gold microdiscs of 30 μm diameter, and a distributed common gold counter electrode, are integrated into a soft smart contact lens platform based on polyimide and thermoplastic polyurethane. Using a novel fast-switching chronoamperometric method, an electrochemical ‘video’ of concentration variation in a model eye under flow conditions is produced, in which the introduction, progress, mixing and drainage of fluid of varying concentration can be observed. The device builds on previous work towards a platform suitable for clinical use and has proven to be robust under expected use conditions, with sensing performance remaining unchanged after thermoforming and repeated mechanical deformation. This work represents a significant step forward in ESCL design, and constitutes significant progress towards a technology with real clinical utility.

We demonstrate a real-speed spatiotemporal electrochemical map showing both time- and position-varying concentration of an analyte in contact with a flexible microelectrode array. A polymer-based device of 11 μm in thickness comprising patterned gold metallisation on a polyimide substrate was fabricated, with eight individually addressable working electrodes (diameter 30 μm) and an integrated counter electrode. We performed a repeated sequence of high-speed chronoamperometric measurements at each electrode and processed the data to generate a spatiotemporal concentration map, in which a number of fluid effects, including bulk flow, diffusive mixing and homogenisation of two miscible fluids of different concentration were observed. This device was fabricated using processes compatible with an existing smart contact lens platform, with a view to develop integrated sensors in future work. We believe this technique has significant potential in the field of electrochemical smart contact lenses, both in introducing new functionality and in improving our ability to draw accurate and clinically-relevant conclusions from measurements made in the tear film.

This paper presents an automated test bench, based on a rigorous measurement procedure, used to fully characterize vibration energy harvesters including determination of the resonance frequency, impedance, optimal load, and output power as a function of both frequency and acceleration. The potential of this method and the performance of the automated test bench allows systematic data acquisition which is essential for a good comparison of all harvesters. A dedicated automation circuit was designed and fabricated. It uses stepper motors to mechanically control trimmers to vary the resistive load and reed relays to switch between the measurement sequences. With this, the setup is able to determine the optimal load of the device-under-test at its resonant frequency for a given acceleration. The test bench was used to fully characterize several types of vibration harvesters fabricated on both silicon and polymeric substrates. A comparison of the characterized devices is discussed using a figure of merit proposed here. A survey and compilation of current practices used to benchmark vibration harvesters is also reported.

A stretchable platform with spherical-shaped electronics based on thermo- plastic polyurethane (TPU) is introduced for soft smart contact lenses. The low glass transition temperature of TPU, its relatively low hardness, and its proven biocompatibility (i.e., protection of exterior body wounds) fulfill the essential requirements for eye wearable devices. These requirements include optical transparency, conformal fitting, and flexibility comparable with soft contact lenses (e.g., hydrogel-based). Moreover, the viscoelastic nature of TPU allows planar structures to be thermoformed into spherical caps with a well-defined curvature (i.e., eye’s curvature at the cornea: 9 mm). Numerical modeling and experimental validation enable fine-tuning of the thermo - forming parameters and the optimization of strain-release patterns. Such tight control is proven necessary to achieve oxygen permeable, thin, nonde- velopable, and wrinkle-free contact lenses with integrated electronics (silicon die, radio-frequency antenna, and stretchable thin-film interconnections). This work paves the way toward fully autonomous smart contact lenses potentially for vision correction or sensing applications, among others.

We show an active artificial iris based on solely thin-film components, wherein several LCD elements are controlled a metal-oxide TFT and by powered by thin-film photovoltaics (TFPV). Key aspects for the driver are size and low power consumption. We demonstrate power consumption down to 25μW for the full iris.

The emergence of the fields of wearable devices, e-textiles and smart packaging brings new requirements on electronics and sensing systems. One or a combination of the following properties can be desired for their proper operation and to meet the functionalities required by the application in order to improve market penetration. Very low-cost, thin, large area, lightweight, flexibility, conformability, transparency, stretchability are some of the characteristics that can be offered by making sensors on polymeric foil. We propose printing processes for the fabrication of these devices to mainly reduce their production cost and to improve the environmental friendliness of their manufacturing. In this communication, we discuss the benefits, drawbacks, potential, and challenges of printing sensors on plastic substrates illustrated with some examples of technical developments performed in our laboratory. We present environmental sensors fabricated on plastic foil and the associated flexible encapsulation method at the foil level. Integration of printed sensing devices on smart RFID tags is also discussed. By using thin polymeric substrates, very small bending radius of curvature can be achieved. Besides the challenges linked to the large area printing of the sensing devices on flexible foil and the reliability of these devices under mechanical cycling, new developments are required on the interconnectivity of these devices with other electronics components to achieve efficient system integration. (C) 2011 Published by Elsevier Ltd.

This paper reports a study on the dynamics of foil-based functional component self-alignment onto patterned test substrates and its demonstration when integrating a flexible sensor onto a printed circuitry. We investigate the dependence of alignment time and final precision of stacking of mm- and cm-sized foil dies on a number of system parameters, such as amount of assembly medium dispensed on target positions, size and weight of assembling dies and their initial misalignment. Using water as a medium for direct self-alignment, mm- and cm-sized square-shaped pre-marked foil dies were aligned with accuracy down to 30 μm and smaller, which reflects a high precision relatively to their lateral dimensions on patterned marked carriers. High-speed camera stage and image recognition tools were used for analyzing rapid capillary-driven self-alignment processes of marked foil dies. It is shown that there is a definite range of initial misalignment values allowing dies to align with high accuracy and yield within the same time window, whereas both under smaller and larger initial offsets, i.e. with dies correspondingly too close or too far from their target positions, yield and alignment precision is significantly lower. The high-alignment accuracy of mm- to cm-sized functional foils was demonstrated by means of the integration of an interdigitated electrodes (IDE) capacitive sensor to a flexible polymeric substrate. Additionally, high-yield electrical interconnection was performed using anisotropic conductive adhesives (ACA). The latter opens the perspective of efficiently assembling interesting new systems such as separately manufactured sensors, paper batteries and RFIDs components through the direct capillary-driven self-alignment approach and ACA electrical interconnection.

This work presents an approach for increasing operational bandwidth of a vibration energy harvester in low-frequency environments by effectively exploiting contact-based frequency up-conversion. It was implemented by a couple of low-frequency resonators with appropriately spaced natural frequencies impacting high-frequency piezoelectric generators when the device is harmonically excited in 10-40 Hz range. A proof of concept was designed, modeled, fabricated and characterized, demonstrating improved power and bandwidth performance (up to 37 μW and 9 Hz at 1g) with respect to traditional single-resonator designs. © 2014 The Authors. Published by Elsevier Ltd.

International audience; Conducting polyaniline-based chemiresistors on printed polymeric micro-hotplates were developed, showing sensitive and selective detection of ammonia vapor in air. The devices consist of a fully inkjet-printed silver heater and interdigitated electrodes on a polyethylene naphthalate substrate, separated by a thin dielectric film. The integrated heater allowed operation at elevated temperatures, enhancing the ammonia sensing performance. The printed sensor designs were optimized over two different generations, to improve the thermal performance through careful design of the shape and dimension of the heater element. A vapor-phase deposition polymerization technique was adapted to produce polyaniline sensing layers doped with poly(4-styrenesulfonic acid). The resulting sensor had better thermal stability and sensing performance when compared with conventional polyaniline-based sensors, and this was attributed to the polymeric dopant used in this study. Improved long-term stability of the sensors was achieved by electrodeposition of gold on the silver electrodes. Response to sub-parts-per-million concentrations of ammonia even under humid conditions was observed.