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.

Atomically thin materials face an ongoing challenge of scalability, hampering practical deployment despite their fascinating properties. Tin monosulfide (SnS), a low‐cost, naturally abundant layered material with a tunable bandgap, displays properties of superior carrier mobility and large absorption coefficient at atomic thicknesses, making it attractive for electronics and optoelectronics. However, the lack of successful synthesis techniques to prepare large‐area and stoichiometric atomically thin SnS layers (mainly due to the strong interlayer interactions) has prevented exploration of these properties for versatile applications. Here, SnS layers are printed with thicknesses varying from a single unit cell (0.8 nm) to multiple stacked unit cells (≈1.8 nm) synthesized from metallic liquid tin, with lateral dimensions on the millimeter scale. It is reveal that these large‐area SnS layers exhibit a broadband spectral response ranging from deep‐ultraviolet (UV) to near‐infrared (NIR) wavelengths (i.e., 280–850 nm) with fast photodetection capabilities. For single‐unit‐cell‐thick layered SnS, the photodetectors show upto three orders of magnitude higher responsivity (927 A W−1) than commercial photodetectors at a room‐temperature operating wavelength of 660 nm. This study opens a new pathway to synthesize reproduceable nanosheets of large lateral sizes for broadband, high‐performance photodetectors. It also provides important technological implications for scalable applications in integrated optoelectronic circuits, sensing, and biomedical imaging.

that offers novel electrical, electronic, and optical properties that are distinct from their bulk counterparts along with mechanical flexibility and high compatibility with state-of-the-art silicon-based platform. [2][3][4] Among prominently studied materials in the last few decades is zinc oxide (ZnO), a highly versatile tunable material. [5] The optoelectronic properties of ZnO in various morphologies have been investigated widely. [6] Due to its strong absorption in the UV region, ZnO is an attractive candidate for visible-blind photodetectors. [7] With a wide bandgap of 3.39 eV, exciton binding energy as large as 60 meV at room temperature, and the ability to undergo a strong quantum confinement effect, atomically thin ZnO promises an excellent platform for optoelectronic applications. [8] Most importantly, oxygen adsorbed onto the surface of ZnO provides low electron densities that can enable low dark current which is ideal for low energy applications. [9] Though thin nanosheets (<20 nm) ZnO has been used as an active layer for various applications, the lack of a reliable and controllable synthesis technique to obtain large area few atoms thin ZnO has prevented the miniaturization of ZnO based optoelectronic devices slowly making the material less competitive compared to other emerging systems relying on atomically thin functional layers. [10][11][12] Also, ZnO and other planar metal-semiconductormetal (MSM) based UV photodetectors developed to date have Atomically thin 2D materials are highly sought for high-performance electronic and optoelectronic devices. Despite being a widely recognized functional material for a plethora of applications, ultra-thin nanosheets of zinc oxide (ZnO) at a millimeter-scale for developing high-performance electronic/optoelectronic devices have not been reported. This has prevented the exploration of electronic and optical properties of ZnO when it is only a few atoms thick. Here, a liquid metal exfoliation technique is used that takes advantage of the van der Waals forces between the interfacial oxide and the chosen substrate to obtain ZnO nanosheets with lateral dimensions in the millimeter scale and thickness down to 5 nm. Their suitability for applications is shown by demonstrating a visible-blind photodetector with high figures of merit as compared to other ZnO morphologies. At extremely low operating bias of 50 mV and low optical intensity of 0.5 mW cm −2 , the ZnO photodetector demonstrates an external quantum efficiency (EQE), responsivity (R), and detectivity (D*) of 4.3 × 10 3 %, 12.64 A W −1 , and 5.81 × 10 15 Jones at a wavelength of 365 nm. The trap-mediated photoresponse in the ZnO nanosheets is further utilized to demonstrate optoelectronic synapses. Versatile synaptic functions of the nervous systems are optically emulated with the ultra-thin ZnO nanosheets.

Chalcohalide semiconductors are an emergent class of materials for optoelectronics. Here, the first work on BiSI chalcohalide thin film photodetectors (PDs) is presented. An entirely new method for the fabrication of bismuth chalcohalide thin films (BiOI and BiSI) is developed. This method circumvents the use of any ligands or counter ions during fabrication and provides highly pure thin films free of carbon residues and other contaminants. When integrated into lithographically patterned lateral PDs these BiSI thin films show outstanding performances and high stability. The direct ≈1.55 eV bandgap of BiSI perfectly accommodates optical sensing over the full visible spectrum. The responsivity (R) of the BiSI PDs reaches 62.1 A W−1, which is the best value reported to date across chalcohalide materials of any type. The BiSI PDs display remarkable sensitivity to low light levels, supporting a broad operational detectivity ≈1012 Jones over four decades in light intensity, with a peak specific detectivity (D*) of 2.01 × 1013 Jones. The dynamics of photocurrent generation are demonstrated to be dominated by photoconductive gain. These results cement BiSI as an exciting candidate for high performance photodetector applications and encourage ongoing work in BiSX (X = Cl, Br, I) materials for optoelectronics.

Thin film transistors (TFTs) are key components for the fabrication of electronic and optoelectronic devices, resulting in a push for the wider exploration of semiconducting materials and cost‐effective synthesis processes. In this report, a simple approach is proposed to achieve 2‐nm‐thick indium oxide nanosheets from liquid metal surfaces by employing a squeeze printing technique and thermal annealing at 250 °C in air. The resulting materials exhibit a high degree of transparency (>99 %) and an excellent electron mobility of ≈96 cm2 V−1 s−1, surpassing that of pristine printed 2D In2O3 and many other reported 2D semiconductors. UV‐detectors based on annealed 2D In2O3 also benefit from this process step, with the photoresponsivity reaching 5.2 × 104 and 9.4 × 103 A W−1 at the wavelengths of 285 and 365 nm, respectively. These values are an order of magnitude higher than for as‐synthesized 2D In2O3. Utilizing transmission electron microscopy with in situ annealing, it is demonstrated that the improvement in device performances is due to nanostructural changes within the oxide layers during annealing process. This work highlights a facile and ambient air compatible method for fabricating high‐quality semiconducting oxides, which will find application in emerging transparent electronics and optoelectronics.