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A theoretical model is proposed to investigate the mechanism of shape formation in polydimethylsiloxane (PDMS) assisted thermal reflow. The thermal curing of PDMS is characterized by a dual-Arrhenius equation and its effect on the reflow process is discussed. It shows that due to the thermal curing of PDMS, the dynamic wetting and interface evolution are constrained successively. This is quite different from the traditional thermal reflow, and will result in unique flow performance, which will facilitate the abilities of the base constraint and shape retaining for the thermal reflow process. These advantages are critical to obtain well-defined microstructures in a simple and controllable way. Theoretical simulations of shape formation are in good agreement with the experimental results. These results provide a comprehensive understanding on PDMS assisted thermal reflow and offer a theoretical guideline for a facile yet versatile fabrication method for high quality microstructures.

Microlens arrays with diverse morphologies are difficult to be formed in one thermal reflow process for they require different process conditions. Here, we present a stable and universal method to overcome this challenge with PDMS (polydimethylsiloxane) assisted thermal reflow. By this method, different microlenses with spherical, aspheric and tilted asymmetric morphology can be obtained under the same experimental conditions. All the microlens arrays show good shape and the roughness is about 1nm. It demonstrates a facile and cost-effective method for fabrication of versatile microlens arrays with controllable morphologies in a universal process.

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