In this paper, we synergistically combine electrohydrodynamic (EHD) printing and replica molding for the fabrication of microlenses. Glycerol solution microdroplets was sprayed onto the ITO glass to form liquid mold by an EHD printing process. The liquid mold is used as a master to fabricate a polydimethylsiloxane (PDMS) mold. Finally, the desired micro-optical device can be fabricated on any substrate using a PDMS soft lithography mold. We demonstrate our strategy by generating microlenses of photocurable polymers and by characterizing their optical properties. It is a new method to rapidly and cost-effectively fabricate molds with small diameters by exploiting the advantages of EHD printing, while maintaining the parallel nature of soft-lithography.

Precision glass molding is a revolutionary technology for achieving high precision and efficient manufacturing of glass aspheric lenses. The material properties of glass, including elastic modulus and viscosity, are highly dependent on temperature fluctuations. This paper aims to investigate the effect of elastic modulus on the high-temperature viscoelasticity of glass and the accuracy of the finite element simulation of the molding process for glass aspheric lenses. The high-temperature elastic modulus of D-ZK3L glass is experimentally measured and combined with the glass cylinder compression creep curve to calculate the high temperature viscoelasticity of D-ZK3L. Three groups of viscoelastic parameters are obtained. Based on this, the molding process of the molded aspheric lens is simulated by the nonlinear finite element method (FEM). The surface curves of lenses obtained by simulation and theoretical analyses are consistent. The simulation results obtained at different initial elastic modulus values indicate that the elastic modulus has a great influence on the precision of the FEM-based molding process of glass aspheric lenses.

Near-field electrospinning direct writing of array-nozzle is an efficient method for preparing large-area aligned fibers. However, electric field between the array-nozzle interferes with the stability and uniformity of near-field electrospinning, and little research has been done in this field. To clarify the electric field interference generated by array-nozzle, the experimental results compared with the simulation are discussed. In this work, electric field interference between the five-nozzle linear arrangement near-field electrospinning process was demonstrated by the initial ejection behavior, the electric field distribution of near-field electrospinning environment and the deposition spacing of fibers. In addition, we developed a simple and flexible method serving as a quantitative evaluation index for evaluating the degree of electric field interference. Then, the mapping effects of electric field interference of nozzle structure on the surface morphology and uniformity of aligned fibers were studied, including the number of nozzle, nozzle spacing and nozzle length with linear and toothed arrangement. According to the result of experiment and characterization, suitable arrayed nozzle parameters for stably direct-write aligned array pattern with near-field electrospinning were available, whose geometric parameters are linear two-nozzle with a nozzle spacing of 2 mm and a nozzle length of 6.35 mm. Finally, on the basis of our previous research, a microfluidic channel was successfully prepared on polydimethylsiloxane by two-nozzle cooperation, which verified the rationality of the geometry.

For small aspherical molds, it is difficult for the existing polishing method to take into account the correction of the surface error and the control of the uniformity of the surface roughness (SR) distribution, because the polishing tool is always larger than the small mold. Therefore, we used viscoelastic polyester fiber cloth to wrap the small steel ball as a polishing tool to adapt to the surface shape change of the aspherical mold, and designed a semi-flexible small polishing disc tool with microstructure, which can better adapt to the curvature change of aspherical surface and obtain better SR Ra. At the same time, a combined polishing method of constant speed and variable speed for screw feed was proposed to improve the uniformity of SR distribution in the paper. Then, a series of theoretical analysis and experimental verification were carried out in this paper to predict the tool influence function (TIF) of the two polishing tools and the effectiveness of the combined polishing method. In the experiment, a TIF bandwidth of about 0.46 mm was obtained with a small spherical polishing tool, which favors the surface shape correction of the small aspherical mold. The experiment of uniform removal with a small polishing disc tool was carried out to quickly reduce the Ra. Finally, the surface quality of the aspherical mold was effectively improved, combined with the constant speed and variable speed polishing modes of screw feed of the small spherical polishing tool and the smoothing effect of the small polishing disc tool. The peak valley (PV) of two small aspherical molds with an optical effective diameter less than 13 mm converged from 0.3572 μm and 0.2075 μm to 0.1282 μm and 0.071 μm, respectively. At the same time, the SR dispersion coefficient was reduced from 27.9% and 41.6% to 14.2% and 12.7%, respectively. The study provides a good solution for the surface quality control of small aspherical molds.

Channel variations caused by motility would introduce inter-carrier interference (ICI), which degrades channel estimation and data detection in underwater orthogonal frequency division multiplexing (OFDM) systems. To deal with this problem, a joint time-varying channel estimation and inter-carrier interference mitigation method is proposed in this paper, where time domain channel estimation and interference auto-cancellation are merged into an iterative scheme. Meanwhile, linear approximation is used to track the time-varying channel while interference auto-cancellation is achieved via pre-coding to reduce the sensibility of OFDM systems to frequency shifts. Unlike frequently-used opposite or conjugate mapping, which leads to an inevitable decrease in frequency utility ratio, differential coding is introduced for pre-coding without adding redundancy. Simulations show that the proposed algorithm can accurately estimate channel state information (CSI), and robustly mitigate ICI over time-varying underwater acoustic channels (UWAC).