3D Printed, Customizable, and Multifunctional Smart Electronic Eyeglasses for Wearable Healthcare Systems and Human-Machine Interfaces.

Personal accessories such as glasses and watches that we usually carry in our daily life can yield useful information from the human body, yet most of them are limited to exercise-related parameters or simple heart rates. Since these restricted characteristics might arise from interfaces between the body and items as one of the main reasons, an interface design considering such a factor can provide us with biologically meaningful data. Here, we describe three-dimensional-printed, personalized, multifunctional electronic eyeglasses (E-glasses), not only to monitor various biological phenomena but also to propose a strategy to coordinate the recorded data for active commands and game operations for human-machine interaction (HMI) applications. Soft, highly conductive composite electrodes embedded in the E-glasses enable us to achieve reliable, continuous recordings of physiological activities. UV-responsive, color-tunable lenses using an electrochromic ionic gel offer the functionality of both eyeglass and sunglass modes, and accelerometers provide the capability of tracking precise human postures and behaviors. Detailed studies of electrophysiological signals including electroencephalogram and electrooculogram demonstrate the feasibility of smart electronic glasses for practical use as a platform for future HMI systems.

Non-volatile, phase-transition smart gels visually indicating in situ thermal status for sensing applications.

Non-volatile smart gel platforms that change optical properties according to temperature are successfully prepared based on a random copolymer, poly(styrene-ran-benzyl methacrylate-ran-methyl methacrylate) [(P(S-r-BzMA-r-MMA)]. The P(S-r-BzMA-r-MMA) copolymers are judiciously designed to serve as both polymer hosts for a gel, and thermoresponsive materials. In contrast to typical lower critical solution temperature (LCST) or upper critical solution temperature (UCST) systems including sol-gel (or gel-sol) transition, the thermoresponsive gels consisting of the P(S-r-BzMA-r-MMA) and ionic liquids (ILs) maintain an elastic gel-state due to their network structure irrespective of phase transitions. We investigate the effects of the copolymer composition and copolymer/IL ratio on the gel properties. Temperature dependent self-assembly of the gel is revealed using small-angle X-ray scattering (SAXS). Thermal response of the gel is examined optically and dynamically. Moreover, we propose a simple method to additionally control the response temperature and the mechanical robustness of the gels by incorporating additional salts. Lastly, we successfully demonstrate practical feasibility of the thermoresponsive gels in high-temperature safety indicators and temperature range indicators, in which the gels visually display in situ thermal status by a change in optical transmittance.

Voltage-Tunable Multicolor, Sub-1.5 V, Flexible Electrochromic Devices Based on Ion Gels.

Voltage-tunable multicolor electrochromic devices (ECDs) are fabricated based on flexible ion gels consisting of copolymers and ionic liquids as an electrolyte layer. Dimethyl ferrocene (dmFc) is incorporated into the gel, which serves as an anodic species. In this study, two electrochromic (EC) materials, monoheptyl viologen (MHV+) and diheptyl viologen (DHV2+), are employed and show significantly different EC behavior despite the similar chemical structure. Both MHV+- and DHV2+-containing ECDs are slightly yellowish in the bleached state, whereas the colored states are magenta and blue, respectively. All devices have good coloration efficiency of 87.5 cm2/C (magenta) and 91.3 cm2/C (blue). In addition, the required power of ∼248 µW/cm2 (magenta) and ∼72 µW/cm2 (blue) to maintain the colored state put the ion gel-based ECDs in a class of ultralow power consumption displays. On the basis of the distinct difference in the coloration voltage range between MHV+ and DHV2+, and the rubbery character of the gel, flexible ECDs showing multiple colors are demonstrated. These results imply that voltage-tunable multicolor ECDs based on the gel are attractive to functional electrochemical displays.