中文摘要：

提出了基于硅模具的热辅助超声波压印成形方法,用于高效率、高精度地复制热塑性聚合物微结构。该方法利用作用于聚合物基片与模具间的超声波振动,快速升高界面温度,以达到聚合物的成形温度。为了降低破坏模具的风险,将模具预热到低于玻璃点转化温度（Tg）以下35℃至50℃之后再施加超声波进行成形。最后,通过正交实验研究了超声振幅、超声波压力、超声波时间、热辅助温度以及聚合物基片厚度对压印结果的影响,揭示了超声波压印工艺的成形机理。实验结果表明,热辅助温度对压印影响最大,其次为超声波振幅,而超声波压力是影响复制均匀性的最重要的参数；薄的聚合物基片在同样的超声波参数和模具结构下更容易成形。通过优化参数,对聚甲基丙烯酸甲酯（PMMA）基片的深度复制精度达到了99%,复制周期小于50s。研究表明,热辅助超声波压印成形效率高,是一种具有批量制造潜力的聚合物微结构成形方法。

英文摘要：

A thermal-assisted ultrasonic embossing method was proposed based on silicon molds to replicate thermoplastic substrates in a low cost and high efficiency.The ultrasonic vibration was applied to the mold-polymer interface to heat the polymer rapidly to the embossing temperature.To reduce the risk of damaging the mold,the die was preheated to a temperature which is 35-50℃ below the glass transition temperature（Tg）of the polymer.Then,the influences of the ultrasonic amplitude, ultrasonic force,ultrasonic time,and the thermal-assisted temperature were studied by orthogonal array experiments to reveal the mechanism of ultrasonic embossing.The influence of the substrate thickness was also investigated.The experimental results show that the most important parameter for replication is the thermal-assisted temperature,follows by the ultrasonic amplitude.Moreover,the ultrasonic force is the most important parameter for replication uniformity,while the thinner polymersheets are more conducive to be replicated under the same circumstances.With the optimized parameters,the replication accuracy has reached 99%on a Polymethyl Methacrylate（PMMA）substrate,and the cycle time is less than 50s.All theses studied show that thermal assisted ultrasonic embossing has high replication efficiency and is a potential way to mass formation of polymer microstructures.