Artificial iris performance for smart contact lens vision correction applications.

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.

Development of a new generation of ammonia sensors on printed polymeric hotplates.

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.