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Memristors are regarded as one of the key devices to break through the traditional Von Neumann computer architecture due to their capability of simulating the function of neural synapses. Among various memristive materials, two-dimensional (2D) materials are promising candidates to build advanced memristors with extremely high integration density and low power consumption. However, memristors based on 2D materials usually suffer from poor endurance and retention due to their vulnerability to material degradation during the formation/fusing processes of conductive filament channels within the switching media of 2D materials. Here, a new memristor architecture based on a WS2/MoS2 2D semiconducting heterojunction (metal/heterojunction/metal, MHM) is proposed, which is completely different from the conventional metal/insulator/metal (MIM) sandwich structure. Through the introduction of a type-II 2D heterojunction, a resistance switching mechanism based on band modulation rather than the conductive filaments can be realized to eliminate the material degradation during the set/reset processes. A prototype MHM memristor based on the WS2/MoS2 heterojunction is successfully developed with a large switching on/off ratio up to 104 and a clearly extended endurance over 120 switching cycles, showing the advantage of the 2D WS2/MoS2 heterojunction over the individual MoS2 or WS2 layers in memristive performance. The proposed method for the MHM-type 2D memristor has the potential to achieve a large-scale integrated memristor matrix with low power consumption and high integration density, which is promising for future artificial intelligence and brain-like computing systems.

Plasma expansion is anisotropic, which necessitates new plasma expansion kinetic models to precisely describe the evolution of the processes. The physical properties of the plasma during isothermal expansion during the nanosecond laser ablation of a bronze-bonded diamond grinding wheel were demonstrated in this work. Based on the regularities of the physical distribution, three-dimensional plasma equations were established, and the equations were applied to a numerical analysis of the ablation processes. Measurements using a grating spectrometer were carried out to detect the emission spectrum of the nanosecond laser ablation of a bronze-bonded diamond grinding wheel. The splash phenomena in the laser ablation process were observed with a high-speed camera. The expansion pressure of the plasma involved was low. According to the Boltzmann plot method and the Stark broadening method, the electron temperature was calculated to be 7206 K, and the electron density ranged from 5 × 1015 to 8 × 1015 cm−3. The experimental results and numerical simulation were consistent. The distribution of the plasma expansion processes presented in this work can contribute to the investigation of plasma characteristics in future research.

Electrically conductive polymers have emerged as functional materials for future electronics due to their high electrical conductivity, real-time responsiveness, easy film-formation ability and desirable stretchability. However, the previously developed conductive polymer electronics are still limited to macroscopic hydrogels or films without complicated designs of fine features. Herein, a carbon nanotube-doped hydrophilic photoresist was ultrafast laser processed as an absorbent 3D scaffold to fabricate nanostructured electrically conductive hydrogels (NECHs) for the first time. Taking advantage of the intermolecular forces, we in situ interpenetrated π-conjugated poly(3,4-ethylenedioxythiophene) into NECHs by self-assembly to combine fine features (resolution down to 500 nm, at least two-order accuracy improvement than that in the case of standard 3D-printed electronics) and achieve a high electrical conductivity (0.1-42.5 S m-1), device-level mechanical properties and desirable tolerance to humid/acid environments. Consequently, several reliable, nanostructured, metal-free electrical circuits, alcohol micro-sensors, interdigital capacitors, and loop inductors have been experimentally identified and characterized. The NECHs successfully break current limitations by making better use of the two photon hydrogelation and highly conductive polymer. Optical clarity, conductivity, and extensibility of the NECHs promise their applications in micro energy storage devices, epidermal electronics, nanorobotics and electrical circuit boards for challenging conditions.

We analysed the plasma expansion characteristics during a laser ablation process and derived dynamics equations to describe the plasma expansion. The equations include the plasma concentration spatial distribution equation, plasma expansion pressure equation and plasma dynamics equation for both the isothermal expansion stage and adiabatic expansion stage. The equations are reasonable, and the required parameters are related only to the laser parameters and materials properties, imparting the model with high versatility and practicability. The models were applied to a numerical simulation of plasma expansion characteristics in the laser ablation of a bronze-bonded diamond grinding wheel. The dimension of plasma isothermal expansion and plasma adiabatic expansion, the expansion velocity of the isothermal plasma, and the contour evolution of plasma expansion were determined. Experiments were then conducted with a high-speed camera to observe the same plasma expansion process for ablating the grinding wheel. A grating spectrometer was used to measure the emission spectrum during the laser ablation process, and the electron temperature and electron density were characterized. The results of the experiments and numerical simulation were found to be essentially consistent, verifying the accuracy and feasibility of the as-developed plasma dynamics equations, with positive implications for optimizing the laser ablation process.

A carrier separating method associated with noise-elimination had been introduced into a sinusoidal phase-shifting self-mixing interferometer. The conventional sinusoidal phase shifting self-mixing interferometry was developed into a more competitive instrument with high computing efficiency and nanometer accuracy of λ / 100 in dynamical vibration measurement. The high slew rate electro-optic modulator induced a sinusoidal phase carrier with ultralow insertion loss in this paper. In order to extract phase-shift quickly and precisely, this paper employed the carrier-separating to directly generate quadrature signals without complicated frequency domain transforms. Moreover, most noises were evaluated and suppressed by a noise-elimination technology synthesizing empirical mode decomposition with wavelet transform. The overall laser system was described and inherent advantages such as high computational efficiency and decreased nonlinear errors of the established system were demonstrated. The experiment implemented on a high precision PZT (positioning accuracy was better than 1 nm) and compared with laser Doppler velocity meter. The good agreement of two instruments shown that the short-term resolution had improved from 10 nm to 1.5 nm in dynamic vibration measurement with reduced time expense. This was useful in precision measurement to improve the SMI with same sampling rate. The proposed signal processing was performed in pure time-domain requiring no preprocessing electronic circuits.

Pure high frequency periodic triangle phase shift is introduced into optical interference, calculates nine data points in each period and obtains discrete phase values. This paper proposes a novel phase demodulation technology analyzing phase information with a symmetric linear method for depressing sampling error. Traditional low finesse Fabry–Perot interferometer produces typical cosine interference signal, performance of which is greatly improved by proposed technology. In experimental configuration we situate an electro-optics crystal to induce phase shift. The variation of Fabry-Perot cavity length is measured with a resolution much higher than the fringe counting or frequency modulation techniques. Simulation and experimentation both demonstrate feasibility and robustness of proposed algorithm. Reconstructed deviation and noise sources are discussed in detail. Various vibration formats are measured as deeper verification.

A signal-processing synthesizing Wavelet transform and Hilbert transform is employed to measurement of uniform or non-uniform vibrations in self-mixing interferometer on semiconductor laser diode with quantum well. Background noise and fringe inclination are solved by decomposing effect, fringe counting is adopted to automatic determine decomposing level, a couple of exact quadrature signals are produced by Hilbert transform to extract vibration. The tempting potential of real-time measuring micro vibration with high accuracy and wide dynamic response bandwidth using proposed method is proven by both simulation and experiment. Advantages and error sources are presented as well. Main features of proposed semiconductor laser self-mixing interferometer are constant current supply, high resolution, simplest optical path and much higher tolerance to feedback level than existing self-mixing interferometers, which is competitive for non-contact vibration measurement.

Phthalate diesters are a group of plasticizers extensively used in the manufacturing and processing of plastics. Phthalate monoesters are the primary degradation products of the diesters. Accumulation of endocrine disruptive diesters and monoesters in soil is of great concern because of the extensive use of plastic mulching and misdisposal of plastics. Accurate determination of their levels in soil is critical to assess the occurrence, exposure, and risks of phthalate diesters and monoesters. In this study, we aimed to develop a robust and environmentally friendly method for the simultaneous determination of phthalate diesters and monoesters in soil. Ultra-performance liquid chromatography coupled with electrospray tandem mass spectrometry was used for quantification, combined with accelerated solvent extraction and in-line cleanup for sample preparation. The method detection limits for the 14 diesters and 11 monoesters were in the range of 0.59 to 10.08 ng g-1 d.w. Acceptable recoveries (69%–131%) for these analytes were obtained when four deuterated analogs were used for internal calibration, and intra- and inter-day variations were less than 15%. This method was later successfully applied to five soil samples, and 8 diesters and 7 monoesters were detected with the maximum concentration up to 1142.2 ng g-1 d.w. The method developed in this study can be used for screening and accurate quantification of phthalate diesters and monoesters in soil and possibly in other environmental matrices.

Integration of phase manipulation and polarization multiplexing was introduced to self-mixing interferometry (SMI) for high-sensitive measurement. Light polarizations were used to increase measuring path number and predict manifold merits for potential applications. Laser source was studied as a microwave-photonic resonator optically-injected by double reflected lights on a two-feedback-factor analytical model. Independent external paths exploited magnesium-oxide doped lithium niobate crystals at perpendicular polarizations to transfer interferometric phases into amplitudes of harmonics. Theoretical resolutions reached angstrom level. By integrating two techniques, this SMI outperformed the conventional single-path SMIs by simultaneous dual-targets measurement on single laser tube with high sensitivity and low speckle noise. In experimental demonstration, by nonlinear filtering method, a custom-made phase-resolved algorithm real-time figured out instantaneous two-dimensional displacements with nanometer resolution. Experimental comparisons to lock-in technique and a commercial Ploytec-5000 laser Doppler velocity meter validated this two-path SMI in micron range without optical cross-talk. Moreover, accuracy subjected to slewing rates of crystals could be flexibly adjusted.

Two-photon polymerization (TPP) based on laser direct writing is currently one of the most prevailing 3D micro/nano fabrication techniques. Nanomaterials can be doped in resins and assembled by TPP for developing advanced 3D functional devices. However, there lacks an effective visualization tool to determine the distribution and orientation of the nanomaterials as-doped in the composite resins. Herein, we present a nondestructive, in situ, and rapid characterization method to determine the orientation and distribution of the nanomaterials within cured resins using polarized second-harmonic generation (p-SHG). The directional assembly of the ZnO nanowires within micro/nanostructures fabricated by TPP is, for the first time to the best of our knowledge, characterized by p-SHG optical microscopy with a fast imaging speed by two orders of magnitude higher than that of the Raman mapping technique. Our method opens a window for nondestructive, rapid, in situ, and polarization-resolved characterization of functional devices made by TPP micro/nanofabrication.

Signals of a self-mixing interferometer established on a semiconductor laser diode are analyzed. Phase is extracted out for decoding measurement which contained in self-mixing fringes. The semiconductor laser diode works as light source and receiver without modulation. By combining Hilbert transform with phase condition of self-mixing interference, micron- displacement is reconstructed by phase information at week or even moderate feedback level. Theoretical analysis and simulation results are presented before verification of experimental measurement. Practical feedback level is estimated by a data fitting technique with a programmable high-resolution PZT. Consistence of the results promises that direct phase extraction on self-mixing interferometer is available for micron-displacement measurement with a nanometer accuracy.