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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.

The widespread use of stimuli-responsive hydrogels is closely related to their synthesis efficiency. However, the widely used thermal-responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogels usually require a time-consuming synthesis process to produce (more than 12 h) and exhibit a relatively slow response speed in the field of cryo-polymerization. In this study, a sequence of thawing polymerization after freezing polymerization by a two-step method of free radical polymerization for the efficient synthesis of PNIPAM hydrogels (merely 2 h) with an excellent comprehensive performance is demonstrated. Results show that the overall performance of the as-synthesized PNIPAM hydrogels is at the top level among reported works despite the significantly reduced preparation time. Moreover, after incorporating multi-walled carbon nanotubes (MWNTs), the PNIPAM hydrogels exhibit a rapid near-infrared (NIR) light-response and programmable shape-morphing capability. It is believed that such a viable and time-saving synthetic method for producing PNIPAM hydrogels of high performance will lay a solid foundation for drug delivery and smart actuators.

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.

We unexpectedly found a femtosecond laser deposition (fs-LD) technique for single-step fabricating Tin-oxide gas sensors coupling with peripheral interdigitated electrodes. Photons hit the precursor for an ultrafast nucleation and crystal growth at a nanometric voxel to grow non-directional SnO2 nanocrystal. We utilized the tunable laser exposure dose for morphological control, and the SnO2 nanospheres were optically assembled into micro-structured bridges interconnecting metal electrodes. Au-based interdigital electrodes (thickness

Due to the ecosystem and public health concerns, contaminants must be removed from the water, and water purification methods aim to find superior materials with superior chemistry and unique structures. We developed a new 3D flower-like double-oxide hydrotalcite composite as an extraction phase for the enrichment of quinolone antibiotics (QAs). In this work, NiAl double-oxide composite microspheres (Al2O3-C@NiAl-LDO) with 3D flower-like structure were prepared by calcining pollen to prepare Al2O3-C carbon templates and homogeneously coating LDO nanosheets on Al2O3-C microspheres. Compared with the pristine NiAl-LDH (82.70 m2/g), the Al2O3-C@NiAl-LDO microspheres exhibited a higher specific surface area (139.70 m2/g), making them rich in active adsorption sites. In addition, a large number of anions that can be exchanged between the layers can effectively enhance adsorption capacity through multiple interactions. The adsorption performance of Al2O3-C@NiAl-LDO microspheres on QAs was investigated in detail. The prepared composites proved to be suitable for the adsorption of QAs in complex samples with a maximum adsorption capacity of 64.08 mg g−1. The developed method was successfully applied to the analysis of QAs in real samples with a satisfactory recovery.

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.

This paper, originally published on 17 May 2019, was withdrawn on 24 July 2019 at the request of the authors.

An effective characterization tool is highly desired to investigate mechanism and properties in femtosecond laser directing for 3D nanomaterial assembly. Here we demonstrate real-time and noninvasive visualization of laser-directed processing using multimodal nonlinear spectroscopic imaging.

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.

Fiber-pigtailed self-mixing sensor employs waveguide modulator in polarization maintaining fiber to introduce phase carrier. Quadrature phases are extracted from amplitudes of harmonics to recur displacement. High sensitivity is experimentally verified by comparison to laser LDV.