Tunable binary Fresnel lens based on stretchable PDMS/CNT composite

This paper presents a tunable micro Fresnel lens made by a polydimethylsiloxane/carbon nanotubes (PDMS/CNTs) configuration that can change its focal length by simply stretching the substrate. We believe this is the first time that this configuration has been realized and demonstrated. The Fresnel lens is formed by embedding vertically aligned CNTs bundles in a 2mm thick PDMS layer. It utilizes the transparency and flexibility of the PDMS and the excellent optical absorption properties of CNTs. The lens is fabricated using a straightforward process, which requires only one lithography step. Preliminary results show that this Fresnel lens has good optical properties, and focal length change can be realized by simply stretching the polymer substrate.