Battery-free, wireless microfluidic/electronic system for multiparameter sweat analysis.

Recently developed classes of ultrasmall, fully implantable devices for optogenetic neuromodulation eliminate physical tethers associated with conventional setups and avoid bulky head-stages and batteries in alternative wireless technologies. The resulting systems enable completely untethered, battery-free operation for high fidelity behavioral studies that eliminate motion constraints and enable experiments in a range of environments and contexts (e.g. social interactions) that would be otherwise difficult or impossible to explore. These devices are, however, purely passive in their electronics design, thereby precluding any form of active control or programmability; independent operation of multiple devices or of multiple active components in a single device is impossible. This paper introduces a series of important concepts in integrated circuit and antenna design which, taken together, enable low power operation, energy efficient and position and angle independent wireless power harvesting with full user-programmability over individual devices or collections of them, in integrated platforms that have sizes and weights not significantly larger than those of previous, passive systems. The results qualitatively expand options in output stabilization, intensity control and multimodal operation, with broad potential applications in neuroscience research, with specific advances in precise dissection of neural circuit function during unconstrained behavioral studies.

The predicted strong piezoelectricity for monolayers of group IV monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators. Within this group, SnS is a potential choice for such nanogenerators due to its favourable semiconducting properties. To date, access to large-area and highly crystalline monolayer SnS has been challenging due to the presence of strong inter-layer interactions by the lone-pair electrons of S. Here we report single crystal across-the-plane and large-area monolayer SnS synthesis using a liquid metal-based technique. The characterisations confirm the formation of atomically thin SnS with a remarkable carrier mobility of~35 cm 2 V −1 s −1 and piezoelectric coefficient of~26 pm V −1. Piezoelectric nanogenerators fabricated using the SnS monolayers demonstrate a peak output voltage of~150 mV at 0.7% strain. The stable and flexible monolayer SnS can be implemented into a variety of systems for efficient energy harvesting.

To harvest the unique properties offered by 2D HSs, creation of well-defined heterointerfaces on a large scale is a prerequisite, where the chemistry and nature of heterointerfaces define the targeted applications.