Electrohydrodynamically printed microlens arrays with controllable curvature based on surface functionalization

Precisely controlling the optical characteristics of the microlens array (MLA) is a key issue for the MLA's fabrication and its applications. A cost-effective method for fabricating MLA with different curvatures and diameters by surface functionalization and electrohydrodynamic inkjet (E-jet) printing is proposed. The surface with self-assembled monolayers has low surface energy, which greatly improves the contact angle of the microlens. The UV-ozone treatment and neutral density filters with different optical densities are used to control the wettability of the substrates. Based on this method, the curvatures of the microlens can be controlled easily and the numerical aperture (NA) of the microlens can be adjusted from 0.18 to 0.49. Compared with traditional fabrication techniques, the method we demonstrated is flexible, low-cost, rapid, and capable of fabricating MLA with large area, high packing density, desirable NA, and diameters.