查看更多>>摘要：Contactless acoustic manipulation of micro/nanoscale particles has attracted considerable attention owing to its near independence of the physical and chemical properties of the targets, making it universally applicable to almost all biological systems. Thin-film bulk acoustic wave (BAW) resonators operating at gigahertz (GHz) frequencies have been demonstrated to generate localized high-speed microvortices through acoustic streaming effects. Benefitting from the strong drag forces of the high-speed vortices, BAW-enabled GHz acoustic streaming tweezers (AST) have been applied to the trapping and enrichment of particles ranging in size from micrometers to less than 100 nm. However, the behavior of particles in such 3D microvortex systems is still largely unknown. In this work, the particle behavior (trapping, enrichment, and separation) in GHz AST is studied by theoretical analyses, 3D simulations, and microparticle tracking experiments. It is found that the particle motion in the vortices is determined mainly by the balance between the acoustic streaming drag force and the acoustic radiation force. This work can provide basic design principles for AST-based lab-on-a-chip systems for a variety of applications.
查看更多>>摘要：The capability to sense complex pressure variations comprehensively is vital for wearable electronics and flexible human–machine interfaces. In this paper, inspired by button switches, a duplex tactile sensor based on the combination of triboelectric and piezoresistive effects is designed and fabricated. Because of its excellent mechanical strength and electrical stability, a double-networked ionic hydrogel is used as both the conductive electrode and elastic current regulator. In addition, micro-pyramidal patterned polydimethylsiloxane (PDMS) acts as both the friction layer and the encapsulation elastomer, thereby boosting the triboelectric output performance significantly. The duplex hydrogel sensor demonstrates comprehensive sensing ability in detecting the whole stimulation process including the dynamic and static pressures. The dynamic stress intensity (10–300 Pa), the action time, and the static variations (increase and decrease) of the pressure can be identified precisely from the dual-channel signals. Combined with a signal processing module, an intelligent visible door lamp is achieved for monitoring the entire"contact–hold–release–separation"state of the external stimulation, which shows great application potential for future smart robot e-skin and flexible electronics.
查看更多>>摘要：It is possible to achieve selective electrochemical etching between different materials, such as p-and n-type silicon. However, achieving selec-tive electrochemical etching on two different regions of the same p-type silicon material is a problem that has rarely been considered. Herein, a novel selective electrochemical etching technique for cantilever-type silicon-on-insulator (SOI) wafer-based microswitches is proposed. In this study, a p-type handle layer was selectively etched, and a p-type device layer was passivated. This was achieved using a circuit with two voltage sources:voltages of−1.2 and 0 V were applied to the handle and device layers, respectively. It was found that the proposed etching process can effectively prevent the in-use sticking of a cantilever-type switch. This is accomplished by increasing the gap between the device layer and its underlying handle layer and increasing the roughness of these layers. The technique is applicable to the fabrication of various cantilever-type SOI microelectromechanical systems, irrespective of the resistivity of the SOI wafer.
查看更多>>摘要：The atomic force microscope (AFM) can measure nanoscale morphology and mechanical properties and has a wide range of applications. The traditional method for measuring the mechanical properties of a sample does so for the longitudinal and transverse properties separately, ignoring the coupling between them. In this paper, a data processing and multidimensional mechanical information extraction algorithm for the composite mode of peak force tapping and torsional resonance is proposed. On the basis of a tip–sample interaction model for the AFM, longitudinal peak force data are used to decouple amplitude and phase data of transverse torsional resonance, accurately identify the tip–sample longitudinal contact force in each peak force cycle, and synchronously obtain the corresponding characteristic images of the transverse amplitude and phase. Experimental results show that the measured longitudinal mechanical characteristics are consistent with the transverse amplitude and phase characteristics, which verifies the effectiveness of the method. Thus, a new method is provided for the measurement of multidimensional mechanical characteristics using the AFM.
查看更多>>摘要：A fast tool servo (FTS) system can be used to efficiently manufacture optical freeform surfaces. This paper investigates the dynamic perfor-mance of an FTS system driven by a voice coil motor and guided by air bearings. A simulation model and testing platform are developed to evaluate the load capacity and stiffness of the air bearings. The mechanical dynamic performance of the designed FTS, including modal and harmonic analyses, is assessed using finite element analysis. A nonlinear relation between air-bearing stiffness and mechanical bandwidth is obtained. The working dynamic performance is tested through system runout, tracking performance, and closed-loop tests. Quantitative relations between air-bearing stiffness and the mechanical and working bandwidths are established and analyzed. Machining experiments verify the feasibility of the FTS system with 31.05 N/μm stiffness air-bearings.
查看更多>>摘要：Abnormal refraction and reflection refers to the phenomenon in which light does not follow its traditional laws of propagation and instead is subject to refraction and reflection at abnormal angles that satisfy a generalization of Snell's law. Metasurfaces can realize this phenomenon through appropriate selection of materials and structural design, and they have a wide range of potential applications in the military, com-munications, scientific, and biomedical fields. This paper summarizes the current state of research on abnormal refractive and reflective metasurfaces and their application scenarios. It discusses types of abnormal refractive and reflective metasurfaces based on their tuning modes (active and passive), their applications in different wavelength bands, and their future development. The technical obstacles that arise with existing metasurface technology are summarized, and prospects for future development and applications of abnormal refractive and reflective metasurfaces are discussed.
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