Spectrally–selective monitoring of ultraviolet radiations (UVR) is of paramount importance across diverse fields, including effective monitoring of excessive solar exposure. Current UV sensors cannot differentiate between UVA, B, and C, each of which has a remarkably different impact on human health. Here we show spectrally selective colorimetric monitoring of UVR by developing a photoelectrochromic ink that consists of a multi-redox polyoxometalate and an e− donor. We combine this ink with simple components such as filter paper and transparency sheets to fabricate low-cost sensors that provide naked-eye monitoring of UVR, even at low doses typically encountered during solar exposure. Importantly, the diverse UV tolerance of different skin colors demands personalized sensors. In this spirit, we demonstrate the customized design of robust real-time solar UV dosimeters to meet the specific need of different skin phototypes. These spectrally–selective UV sensors offer remarkable potential in managing the impact of UVR in our day-to-day life.

Vanadium has 11 oxide phases, with the binary VO2 presenting stimuli-dependent phase transitions that manifest as switchable electronic and optical features. An elevated temperature induces an insulator–to–metal transition (IMT) as the crystal reorients from a monoclinic state (insulator) to a tetragonal arrangement (metallic). This transition is accompanied by a simultaneous change in optical properties making VO2 a versatile optoelectronic material. However, its deployment in scalable devices suffers because of the requirement of specialised substrates to retain the functionality of the material. Sensitivity to oxygen concentration and larger-scale VO2 synthesis have also been standing issues in VO2 fabrication. Here, we address these major challenges in harnessing the functionality in VO2 by demonstrating an approach that enables crystalline, switchable VO2 on any substrate. Glass, silicon, and quartz are used as model platforms to show the effectiveness of the process. Temperature-dependent electrical and optical characterisation is used demonstrating three to four orders of magnitude in resistive switching, >60% chromic discrimination at infrared wavelengths, and terahertz property extraction. This capability will significantly broaden the horizon of applications that have been envisioned but remained unrealised due to the lack of ability to realise VO2 on any substrate, thereby exploiting its untapped potential.

The human skin is the largest sensory organ, made up of complex sensors that detect noxious stimuli to rapidly send warning signals to the central nervous system to initiate a motor response. It is complex to mimic key skin features using existing tactile sensors, and there exists no somatosensor that responds to real stimuli of pressure, temperature, and touch. Herein, three critical skin receptors created by realizing integrated electronic systems that mimic the feedback response of somatosensors are experimentally demonstrated. Fully functional Pacinian corpuscles, thermoreceptors, and nociceptors are realized using a combination of stretchable pressure sensors, phase‐change oxide thin films, and threshold‐based resistive switching (memristor) memory elements. The ability to detect and respond to pressure, temperature, and pain stimuli above a threshold with real‐life performance characteristics is demonstrated with explanation of underlying mechanisms. The ability to design and realize artificial skin receptors enables replacement of affected human skin regions, augment skin sensitivity for agile applications in defense and sports, and drive advancements in intelligent robotics.

A photonic switch is an integral part of optical telecommunication systems. A plasmonic bandpass filter integrated with materials exhibiting phase transition can be used as a thermally reconfigurable optical switch. This paper presents the design and demonstration of a broadband photonic switch based on an aluminium nanohole array on quartz utilising the semiconductor-to-metal phase transition of vanadium dioxide. The fabricated switch shows an operating range over 650 nm around the optical communication C, L, and U band with maximum 20%, 23% and 26% transmission difference in switching in the C band, L band, and U band, respectively. The extinction ratio is around 5 dB in the entire operation range. This architecture is a precursor for developing micron-size photonic switches and ultra-compact modulators for thin film photonics.

structure due to its ability to be designed in high capacity 3D crossbar arrays. [1] The major disadvantage of 3D crossbars currently is the high-leakage or sneak-path current. [2] Complex class of vanadium oxide spans a broad range of 20 phases. [3] Depending on the stoichiometry, crystal structure, and device structure it has demonstrated bipolar resistive switching (BRS) [4][5][6][7][8][9][10] as well as apolar threshold switching (TS). [11][12][13] Apolar TS property in the above papers is desirable as a selector element in crossbar arrays to reduce the sneak-path current (which disrupts stored data). Crystalline VO 2 (c-VO 2 ) as TS element shows significant OFF-current, [12,13] which defeats its primary purpose as a selector. For this reason, a few recent studies [10,[14][15][16] demonstrated TS based on amorphous vanadium oxide (a-VO x ). However, due to the amorphous nature of the film, devices based on same stoichiometry of vanadium oxide show multifunctional memory behavior, [17] which is not desirable for the practical application. This variability highlights that nanostructural investigations are needed to understand the origins of different memory behaviors, in particular the reasons for observing volatile and apolar TS in a-VO x films for its practical utilization as a selector element. Further, in-depth electrical characterization is required to ascertain the electrical conditions for the occurrence of volatile or non-volatile switching in the single device.Here, we present asymmetric cross-point device (Pt/Ti/a-VO x /Pt) with ≈100 nm a-VO x film as a functional switching layer which shows multifunctional behavior in a single device. We further introduce a fabrication procedure (Section S1, Supporting Information) to incorporate a-VO x in crossbar architecture, which has been found to dissolve in water. We choose amorphous films because crystalline films are porous due to grain boundaries and pin-holes, [11] which is unsuitable for stacked architectures. Through X-ray photoelectron spectroscopy (XPS) we analyze the stoichiometry of as-deposited film which revealed the mixed-phased oxidation, including V 3+ , V 4+ , and V 5+ (corresponding to V 2 O 3 , VO 2 , and V 2 O 5 , respectively).