The fabrication of microlens array in PMMA material with the assistant of nickel pillars by LIGA technology and thermal reflow method

Through the combination of the LIGA technology and the thermal reflow method, the contact angles of the microlens array increase a lot with the assistance of the nickel pillars. The nickel pillar with rough surface is inserted in the middle of the polymethyl methacrylate (PMMA) pillar by the LIGA technology, which increases the contact area between PMMA fluid and solid, and it is beneficial to increase the contact angles of the microlens array. From the experimental results, the contact angles of the microlens array obtained by melting the sample with nickel pillars achieve 115°, while the contact angles of the microlens array obtained by melting the sample without nickel pillars are only 66°. Simulating the thermal reflow process of the PMMA pillar with and without the nickel pillar by Ansys fluent, the results suggest that the nickel pillar can indeed improve the contact angle of the microlens, which is consistent with the experimental results. In the research about the impact of thermal reflow temperature and the thermal reflow time on the samples with nickel pillars, most microlens arrays have angles over 90°, and the largest angle of the microlens arrays is 132°. What is more, most microlens arrays possess spherical profiles and the uniformity of the microlens array is good.