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Electrohydrodynamic-jet (E-jet) printing is an on-demand additive manufacturing method that allows various functional materials to be directly deposited on the target substrate. Many theoretical and experimental results indicate that E-jet has scale effect, and reducing the inner diameter of the nozzle can effectively improve printing resolution. Herein, a method for fabricating SU-8 polymer micro/nanoscale nozzle by oxygen plasma assisted room temperature bonding was proposed. It can prevent channel deformation and blockage caused by excessive bonding temperature. The surface modification parameters of silicon nano-mold were optimized, the influence of hot embossing parameters on the replication precision of nano patterns was investigated, the effect of UV lithography parameters on the micro and nanochannel was analyzed, the relationship between the oxygen plasma treatment parameters on the contact angle of SU-8 was revealed, the influence of bonding pressure on the morphology of the nanochannel was discussed, and the bonding principle at room temperature was deeply analyzed. This method can fabricate SU-8 polymer micro/nanoscale nozzle with low cost and high precision, and provide a new idea for the realization of room temperature bonding to manufacture SU-8 polymer nozzle.

Electrohydrodynamic-jet printing (E-jet printing) is a direct-writing technology for manufacturing micro-nano devices. To further reduce the inner diameter of the nozzle to improve the printing resolution, a large-scale manufacturing method of SU-8 polymer micro/nanoscale nozzle by means of a process combining UV exposure and hot embossing was proposed. To improve the adhesive strength between the UV mask and SU-8, the influence of the oxygen plasma treatment parameters on the water contact angles of the UV mask was analyzed. The effect of hot embossing time and temperature on the replication precision was studied. The influence of UV exposure parameters and thermal bonding parameters on the micro and nanochannel pattern was investigated. The SU-8 polymer nozzles with 188 ± 3 nm wide and 104 ± 2 nm deep nanochannels were successfully fabricated, and the replication precision can reach to 98.5%. The proposed manufacturing method of SU-8 polymer nozzles in this study will significantly advance the research on the transport properties of nanoscale channels in E-jet nozzles and facilitate further advancements in E-jet based applications. [ABSTRACT FROM AUTHOR]

Ultrahigh molecular weight polyethylene (UHMWPE) fiber orthogonally laid laminate is widely used in ballistic protection due to its excellent properties. Research on its response under bullet impact is meaningful for understanding the antiballistic mechanism and designing personal protection. In this article, three‐dimensional digital image correlation measurement and analysis method is applied to study the response of UHMWPE orthogonally laid laminates under the impact of pistol bullets. A corresponding smoothed particle hydrodynamics (SPH)–finite element method coupled numerical model is established to study the impact phenomenon. The bullet model is developed using the SPH method. The laminate is developed with multiple equivalent sublaminate finite element models. The experimental results show the damage mode and back‐face features of the laminate. First, the damage mode has two stages: the first stage includes a small number of layers that are penetrated on the impact surface and the second stage includes the expansion of the back‐face deformation. Second, the average maximum bulge height in three repeated experiments is 14.59 mm. Third, the average maximum velocity of the bulge apex position in experiments on the z‐axis is 92.32 m/s. Fourth, the maximum and minimum back‐face in‐plane shear values are 0.0893 and −0.0928, respectively. Finally, the numerical results have good agreement with the experimental results and show that the compression waves mainly propagate along the x and y directions. The experimental results can provide quantifiable features for studying the impact responses of UHMWPE laminates. The numerical model could be applied to study features that cannot be measured by experiments. [ABSTRACT FROM AUTHOR]