Skin-inspired highly stretchable and conformable matrix networks for multifunctional sensing.

Mechanosensation electronics (or Electronic skin, e-skin) consists of mechanically flexible and stretchable sensor networks that can detect and quantify various stimuli to mimic the human somatosensory system, with the sensations of touch, heat/cold, and pain in skin through various sensory receptors and neural pathways. Here we present a skin-inspired highly stretchable and conformable matrix network (SCMN) that successfully expands the e-skin sensing functionality including but not limited to temperature, in-plane strain, humidity, light, magnetic field, pressure, and proximity. The actualized specific expandable sensor units integrated on a structured polyimide network, potentially in three-dimensional (3D) integration scheme, can also fulfill simultaneous multi-stimulus sensing and achieve an adjustable sensing range and large-area expandability.

Largely Improved Near-Infrared Silicon-Photosensing by the Piezo-Phototronic Effect.

Although silicon (Si) devices are the backbone of modern (opto-)electronics, infrared Si-photosensing suffers from low-efficiency due to its limitation in light-absorption. Here, we demonstrate a large improvement in the performance, equivalent to a 366-fold enhancement in photoresponsivity, of a Si-based near-infrared (NIR) photodetector (PD) by introducing the piezo-phototronic effect via a deposited CdS layer. By externally applying a -0.

Graphene Oxide/Chitosan Aerogel Microspheres with Honeycomb-Cobweb and Radially Oriented Microchannel Structures for Broad-Spectrum and Rapid Adsorption of Water Contaminants.

Multifunctional graphene oxide (GO)/chitosan (CS) aerogel microspheres (GCAMs) with honeycomb-cobweb and radially oriented microchannel structures are prepared by combining electrospraying with freeze-casting to optimize adsorption performances of heavy metal ions and soluble organic pollutants. The GCAMs exhibit superior adsorption capacities of heavy metal ions of Pb(II), Cu(II), and Cr(VI), cationic dyes of methylene blue (MB) and Rhodamine B, anionic dyes of methyl orange and Eosin Y, and phenol. It takes only 5 min to reach 82 and 89% of equilibrium adsorption capacities for Cr(VI) (292.

Piezo-Phototronic Effect on Selective Electron or Hole Transport through Depletion Region of Vis-NIR Broadband Photodiode.

Silicon underpins nearly all microelectronics today and will continue to do so for some decades to come. However, for silicon photonics, the indirect band gap of silicon and lack of adjustability severely limit its use in applications such as broadband photodiodes. Here, a high-performance p-Si/n-ZnO broadband photodiode working in a wide wavelength range from visible to near-infrared light with high sensitivity, fast response, and good stability is reported.

Simultaneously Enhancing Light Emission and Suppressing Efficiency Droop in GaN Microwire-Based Ultraviolet Light-Emitting Diode by the Piezo-Phototronic Effect.

Achievement of p-n homojuncted GaN enables the birth of III-nitride light emitters. Owing to the wurtzite-structure of GaN, piezoelectric polarization charges present at the interface can effectively control/tune the optoelectric behaviors of local charge-carriers (i.e.

Enhanced Performance of a Self-Powered Organic/Inorganic Photodetector by Pyro-Phototronic and Piezo-Phototronic Effects.

Self-powered photodetectors (PDs) have long been realized by utilizing photovoltaic effect and their performances can be effectively enhanced by introducing the piezo-phototronic effect. Recently, a novel pyro-phototronic effect is invented as an alternative approach for performance enhancement of self-powered PDs. Here, a self-powered organic/inorganic PD is demonstrated and the influences of externally applied strain on the pyro-phototronic and the photovoltaic effects are thoroughly investigated.

Piezophototronic Effect in Single-Atomic-Layer MoS for Strain-Gated Flexible Optoelectronics.

Strain-gated flexible optoelectronics are reported based on monolayer MoS . Utilizing the piezoelectric polarization created at the metal-MoS interface to modulate the separation/transport of photogenerated carriers, the piezophototronic effect is applied to implement atomic-layer-thick phototransistor. Coupling between piezoelectricity and photogenerated carriers may enable the development of novel optoelectronics.

Piezotronic Effect Modulated Heterojunction Electron Gas in AlGaN/AlN/GaN Heterostructure Microwire.

The piezotronic effect is applied to modulate the physical properties of heterojunction electron gas and thus tune the electric transport in AlGaN/AlN/GaN heterostructure microwires. At room temperature, the conductance is increased by 165% under -1.78% compressive strains, and reduced by 48% under 1.

Ultrafast Response p-Si/n-ZnO Heterojunction Ultraviolet Detector Based on Pyro-Phototronic Effect.

A light-self-induced pyro-phototronic effect in wurtzite ZnO nanowires is proposed as an effective approach to achieve ultrafast response ultraviolet sensing in p-Si/n-ZnO heterostructures. The relatively long response/recovery time of zinc-oxide-based ultraviolet sensors in air/vacuum has long been an obstacle to developing such detectors for practical applications. The response/recovery time and photoresponsivity are greatly improved by the pyro-phototronic effect.

Theoretical Study of Triboelectric-Potential Gated/Driven Metal-Oxide-Semiconductor Field-Effect Transistor.

Triboelectric nanogenerator has drawn considerable attentions as a potential candidate for harvesting mechanical energies in our daily life. By utilizing the triboelectric potential generated through the coupling of contact electrification and electrostatic induction, the "tribotronics" has been introduced to tune/control the charge carrier transport behavior of silicon-based metal-oxide-semiconductor field-effect transistor (MOSFET). Here, we perform a theoretical study of the performances of tribotronic MOSFET gated by triboelectric potential in two working modes through finite element analysis.

Progress in Piezo-Phototronic-Effect-Enhanced Light-Emitting Diodes and Pressure Imaging.

Wurtzite materials exhibit both semiconductor and piezoelectric properties under strains due to the non-central symmetric crystal structures. The three-way coupling of semiconductor properties, piezoelectric polarization and optical excitation in ZnO, GaN, CdS and other piezoelectric semiconductors leads to the emerging field of piezo-phototronics. This effect can efficiently manipulate the emission intensity of light-emitting diodes (LEDs) by utilizing the piezo-polarization charges created at the junction upon straining to modulate the energy band diagrams and the optoelectronic processes, such as generation, separation, recombination and/or transport of charge carriers.

Temperature Dependence of the Piezotronic and Piezophototronic Effects in a-axis GaN Nanobelts.

The temperature dependence of the piezotronic and piezophototronic effects in a-axis GaN nanobelts from 77 to 300 K is investigated. The piezotronic effect is enhanced by over 440% under lower temp-eratures. Two independent processes are discovered to form a competing mechanism through the investigation of the temperature dependence of the piezophototronic effect in a-axis GaN nanobelts.

Piezo-Phototronic Enhanced UV Sensing Based on a Nanowire Photodetector Array.

A large array of Schottky UV photodetectors (PDs) based on vertical aligned ZnO nanowires is achieved. By introducing the piezo-phototronic effect, the performance of the PD array is enhanced up to seven times in photoreponsivity, six times in sensitivity, and 2.8 times in detection limit.

Self-Powered Triboelectric Nanosensor for Microfluidics and Cavity-Confined Solution Chemistry.

Micro total analysis system (μTAS) is one of the important tools for modern analytical sciences. In this paper, we not only propose the concept of integrating the self-powered triboelectric microfluidic nanosensor (TMN) with μTAS, but also demonstrate that the developed system can be used as an in situ tool to quantify the flowing liquid for microfluidics and solution chemistry. The TMN automatically generates electric outputs when the fluid passing through it and the outputs are affected by the solution temperature, polarity, ionic concentration, and fluid flow velocity.

A Streaming Potential/Current-Based Microfluidic Direct Current Generator for Self-Powered Nanosystems.

A simple but practical method to convert the hydroenergy of microfluids into continuous electrical output is reported. Based on the principle of streaming potential/current, a microfluidic generator (MFG) is demonstrated using patterned micropillar arrays as a quasi-porous flow channel. The continuous electrical output makes this MFG particularly suitable as a power source in self-powered systems.

Light-induced pyroelectric effect as an effective approach for ultrafast ultraviolet nanosensing.

Zinc oxide is potentially a useful material for ultraviolet detectors; however, a relatively long response time hinders practical implementation. Here by designing and fabricating a self-powered ZnO/perovskite-heterostructured ultraviolet photodetector, the pyroelectric effect, induced in wurtzite ZnO nanowires on ultraviolet illumination, has been utilized as an effective approach for high-performance photon sensing. The response time is improved from 5.

Piezotronic Effect in Strain-Gated Transistor of a-Axis GaN Nanobelt.

Due to the non-centrosymmetric crystal structures, wurtzite family semiconducting materials possess piezoelectric properties and exhibit polarizations along certain directions upon straining. Utilizing strain-induced piezoelectric polarization charges to modulate the energy band structures and thus to tune/control the transport processes of charge carriers is referred to as the piezotronic effect. Distinct from the previous studies of c-axis GaN nanowires, here we systematically study the piezotronic-effect-induced modifications of energy band structures and the corresponding influence on electronic transport properties of a-axis GaN nanobelts.

Single-excitation dual-color coherent lasing by tuning resonance energy transfer processes in porous structured nanowires.

Single-excitation dual-color coherent lasing was achieved in a mixed random system of a binary dye and the suspension of gold-silver porous nanowires with plenty of nanogaps. This greatly enhanced the local electromagnetic field in the visible range and guaranteed a low threshold and high Q factor (>10 000) operator for simultaneous dual-color lasing. By tuning the resonance energy transfer process in the stimulated emission, triple output modes (single chartreuse lasing, chartreuse and red dual-color lasing, and single red coherent lasing) were easily obtained.

Recent Progress in Electronic Skin.

The skin is the largest organ of the human body and can sense pressure, temperature, and other complex environmental stimuli or conditions. The mimicry of human skin's sensory ability via electronics is a topic of innovative research that could find broad applications in robotics, artificial intelligence, and human-machine interfaces, all of which promote the development of electronic skin (e-skin). To imitate tactile sensing via e-skins, flexible and stretchable pressure sensor arrays are constructed based on different transduction mechanisms and structural designs.

Enhancing Light Emission of ZnO-Nanofilm/Si-Micropillar Heterostructure Arrays by Piezo-Phototronic Effect.

n-ZnO nanofilm/p-Si micropillar heterostructure light-emitting diode (LED) arrays for white light emissions are achieved and the light emission intensity of LED array is enhanced by 120% under -0.05% compressive strains. These results indicate a promising approach to fabricate Si-based light-emitting components with high performances enhanced by the piezo-phototronic effect, with potential applications in touchpad technology, personalized signatures, smart skin, and silicon-based photonic integrated circuits.

Dynamic pressure mapping of personalized handwriting by a flexible sensor matrix based on the mechanoluminescence process.

A self-powered pressure-sensor matrix based on ZnS:Mn particles for more-secure signature collection is presented, by recording both handwritten signatures and the pressure applied by the signees. This large-area, flexible sensor matrix can map 2D pressure distributions in situ, either statically or dynamically, and the piezophotonic effect is proposed to initiate the mechanoluminescence process once a dynamic mechanical strain is applied.

Piezo-phototronic UV/visible photosensing with optical-fiber-nanowire hybridized structures.

An optical-fiber-nanowire hybridized UV-visible photodetector (PD) is reported. The PD is designed to allow direct integration in optical communication systems without requiring the use of couplers via fiber-welding technology. The PD works in two modes: axial and off-axial illumination mode.

Piezo-phototronic Boolean logic and computation using photon and strain dual-gated nanowire transistors.

Using polarization charges created at the metal-cadmium sulfide interface under strain to gate/modulate electrical transport and optoelectronic processes of charge carriers, the piezo-phototronic effect is applied to process mechanical and optical stimuli into electronic controlling signals. The cascade nanowire networks are demonstrated for achieving logic gates, binary computations, and gated D latches to store information carried by these stimuli.

Optimizing performance of silicon-based p-n junction photodetectors by the piezo-phototronic effect.

Silicon-based p-n junction photodetectors (PDs) play an essential role in optoelectronic applications for photosensing due to their outstanding compatibility with well-developed integrated circuit technology. The piezo-phototronic effect, a three-way coupling effect among semiconductor properties, piezoelectric polarizations, and photon excitation, has been demonstrated as an effective approach to tune/modulate the generation, separation, and recombination of photogenerated electron-hole pairs during optoelectronic processes in piezoelectric-semiconductor materials. Here, we utilize the strain-induced piezo-polarization charges in a piezoelectric n-ZnO layer to modulate the optoelectronic process initiated in a p-Si layer and thus optimize the performances of p-Si/ZnO NWs hybridized photodetectors for visible sensing via tuning the transport property of charge carriers across the Si/ZnO heterojunction interface.

Electret film-enhanced triboelectric nanogenerator matrix for self-powered instantaneous tactile imaging.

We report the first self-powered electronic skin that consists of light-emitting diode (LED) and triboelectric nanogenerator (TENG) arrays that can be utilized for spatially mapping applied instantaneous-touch events and tracking the movement location of the target object by recording the electroluminescent signals of the LEDs without external power sources. The electret film-based TENG can deliver an open-circuit voltage of about -1070 V, a short-circuit current density of 10 mA/m(2), and a power density of 288 mW/m(2) on an external load of 100 MΩ. The LEDs can be turned on locally when the back surface of the active matrix is touched, and the intensity of the emitted light depends on the magnitude of the applied local pressure on the device.