Facile fabrication of flexible concave microlens arrays with a well-controlled curvature

We report the facile fabrication of flexible concave microlens arrays (MLAs) with a well-controlled curvature using a leaky dielectric (LD) via the electrowetting-on-dielectrics (EWOD) phenomenon. MLAs with a larger curvature (up to 0.46 μm-1) are fabricated using the LD compared with the perfect dielectric (PD) (∼0.40 μm-1). The improved curvature is attributed to the better electrowettability (i.e., the smaller contact angle) of the LD on the inner-wall of the microhole arrays of the Si-template. Moreover, the curvature of the MLAs can be well controlled by the applied external voltage or the spin rate. Finally, the as-fabricated MLAs show a favorable reflective focusing performance, refractive imaging performance and scattering performance for potential applications in miniaturized and high-performance flexible optical micro-devices.