A versatile artificial skin platform for sweat sensor development.

Research targeting the development of on-body sensors has been significantly growing in recent years - an example is on-skin sweat sensing. However, the wide inter and intra person variability of skin characteristics make in vivo testing of these sensors and included materials such as skin adhesives difficult, which hampers especially the initial development phase of such wearables. Besides the development of wearable sweat sensors, companies developing deodorants, cosmetics, medical adhesives and wearable textiles now need to perform expensive human subjects testing with little control over the exact sweat mechanisms. Hence, there is a need for a realistic, adaptable and stable test platform, or artificial skin. We present a versatile artificial skin platform that faithfully recapitulates skin topography, active sweat pores, skin wetting behaviour and sweat rate, and that can be tuned to mimic the specifications of the targeted body location and sweating characteristics. The developed artificial skin is capable of generating sweat rates as low as 0.1 nL min-1 pore-1 and as high as 100 nL min-1 pore-1, spanning the whole range of physiological sweat rates. Specifically, the platform can be used for the development of sweat sensors for sedentary persons whose sweat rates are commonly lower than currently delivered by any other artificial skin platform.

Microelectrode Arrays for Simultaneous Electrophysiology and Advanced Optical Microscopy.

Advanced optical imaging techniques address important biological questions in neuroscience, where structures such as synapses are below the resolution limit of a conventional microscope. At the same time, microelectrode arrays (MEAs) are indispensable in understanding the language of neurons. Here, the authors show transparent MEAs capable of recording action potentials from neurons and compatible with advanced microscopy. The electrodes are made of the conducting polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) and are patterned by optical lithography, ensuring scalable fabrication with good control over device parameters. A thickness of 380 nm ensures low enough impedance and >75% transparency throughout the visible part of the spectrum making them suitable for artefact-free recording in the presence of laser illumination. Using primary neuronal cells, the arrays record single units from multiple nearby sources with a signal-to-noise ratio of 7.7 (17.7 dB). Additionally, it is possible to perform calcium (Ca2+) imaging, a measure of neuronal activity, using the novel transparent electrodes. Different biomarkers are imaged through the electrodes using conventional and super-resolution microscopy (SRM), showing no qualitative differences compared to glass substrates. These transparent MEAs pave the way for harnessing the synergy between the superior temporal resolution of electrophysiology and the selectivity and high spatial resolution of optical imaging.