Recent Advances in Tactile Sensory Systems: Mechanisms, Fabrication, and Applications.

Flexible electronics is a cutting-edge field that has paved the way for artificial tactile systems that mimic biological functions of sensing mechanical stimuli. These systems have an immense potential to enhance human-machine interactions (HMIs). However, tactile sensing still faces formidable challenges in delivering precise and nuanced feedback, such as achieving a high sensitivity to emulate human touch, coping with environmental variability, and devising algorithms that can effectively interpret tactile data for meaningful interactions in diverse contexts. In this review, we summarize the recent advances of tactile sensory systems, such as piezoresistive, capacitive, piezoelectric, and triboelectric tactile sensors. We also review the state-of-the-art fabrication techniques for artificial tactile sensors. Next, we focus on the potential applications of HMIs, such as intelligent robotics, wearable devices, prosthetics, and medical healthcare. Finally, we conclude with the challenges and future development trends of tactile sensors.

Ultrafast and Low-Power 2D Bi2O2Se Memristors for Neuromorphic Computing Applications.

Memristors that emulate synaptic plasticity are building blocks for opening a new era of energy-efficient neuromorphic computing architecture, which will overcome the limitation of the von Neumann bottleneck. Layered two-dimensional (2D) Bi2O2Se, as an emerging material for next-generation electronics, is of great significance in improving the efficiency and performance of memristive devices. Herein, high-quality Bi2O2Se nanosheets are grown by configuring mica substrates face-down on the Bi2O2Se powder. Then, bipolar Bi2O2Se memristors are fabricated with excellent performance including ultrafast switching speed (<5 ns) and low-power consumption (<3.02 pJ). Moreover, synaptic plasticity, such as long-term potentiation/depression (LTP/LTD), paired-pulse facilitation (PPF), and spike-timing-dependent plasticity (STDP), are demonstrated in the Bi2O2Se memristor. Furthermore, MNIST recognition with simulated artificial neural networks (ANN) based on conductance modification could reach a high accuracy of 91%. Notably, the 2D Bi2O2Se enables the memristor to possess ultrafast and low-power attributes, showing great potential in neuromorphic computing applications.

Crystal-Orientation-Related Dynamic Tuning of the Lasing Spectra of CdS Nanobelts by Piezoelectric Polarization.

Realizing dynamic wavelength tunability could bring about tremendous impacts in laser technology, pressure nanosensing, and lab-on-a-chip devices. Here, we demonstrate an original strategy to operate the lasing mode shift through reversible length changes of a CdS nanobelt, which is determined by the direction of piezoelectric polarization. The relationships between the direction of applied strain, the lasing mode shift, and the tunable effective refractive index are elaborated in detail. The correlation between the piezoelectric polarization-induced lasing mode red shift and the blue shift in the wavelength of the lasing mode output caused by the Poisson effect is discussed in depth, as well. Our study comprehensively considers the influence of both the cavity size variations and refractive index changes on the control of the lasing mode and provides a deeper understanding of the strain-induced lasing mode shift.

Sr2Mn3Sb2O2 type oxyselenides: structures, magnetism, and electronic properties of Sr2AO2M2Se2 (A=Co, Mn; M=Cu, Ag).

Four new oxyselenides with nominal formula Sr(2)AO(2)M(2)Se(2) (A=Co, Mn; M=Cu, Ag) have been synthesized. They all crystallize in an I4/mmm space group and consist of alternating perovskite-like (Sr(2)AO(2))(2+) blocks and antiflourie (M(2)Se(2))(2-) layers, which are relatively rare layered oxyselenides reported so far that are isostructural to Sr(2)Mn(3)Sb(2)O(2). From powder X-ray diffraction data, compounds Sr(2)CoO(2)Cu(2)Se(2) and Sr(2)CoO(2)Ag(2)Se(2) are found near stoichiometric, whereas Sr(2)MnO(2)Cu(2-δ)Se(2) and Sr(2)MnO(2)Ag(2-δ)Se(2) possess substantial copper or silver vacancies (δ≈0.5), consistent with their oxysulfide analogues. X-ray photoelectron spectroscopy measurements indicate the readily oxidization of Mn(2+) ions should be responsible for the occurrence of Cu/Ag vacancies. The rigid (Sr(2)AO(2))(2+) blocks within these compounds constrain the basal lattice parameters in the ab plane and result in largely deformed tetrahedral sites for the large silver ions. Magnetic susceptibility measurements of Sr(2)CoO(2)M(2)Se(2) (M=Cu, Ag) show complex antiferromagnetic transitions, while Sr(2)MnO(2)M(2-δ)Se(2) (M=Cu, Ag) show high-temperature Curie-Weiss behavior, followed by low-temperature antiferromagnetic transitions at 54 K and 67 K, respectively. Except for Sr(2)MnO(2)Ag(2-δ)Se(2), the other three compounds exhibit p-type semiconducting transport properties, with the measured resistivities several orders lower than their oxysulfide analogues. Hall measurement reveals high mobilities of Sr(2)CoO(2)M(2)Se(2) (M=Cu, Ag) compounds at room temperature. The unusually small optical band gaps (~0.07 eV) of Sr(2)CoO(2)Cu(2)Se(2), Sr(2)CoO(2)Ag(2)Se(2), and Sr(2)MnO(2)Cu(2-δ)Se(2) are also reported.