Modern optical components and devices are usually precisely machined and highly optimized in their performance for robust and durable operation. Nevertheless, it usually comes at expense of their ability to tune and adapt that would be very beneficial for various applications.  Examples of such application areas include dynamic imaging, scanning, optical communication, sensing, and high power beam delivery. The main objective of this project is to develop adaptive optical components and devices based on microscopic flows of liquids and on soft materials. The adaptation is achieved either by alternating injection of liquids with different optical properties (e. g., indices of refraction or excitability) into microchannels, or by deforming thin flexible membranes using pneumatically generated tensile forces. The devices are made with the technique of soft lithography: a master mold (fabricated with contact UV-lithography) is used to cast a transparent silicon elastomer, PDMS. We have recently demonstrated a 2×2 microfluidic optical switch, based on alternating injection of water and an index-matching salt solution into a flat-parallel microchannel. Two incident laser beams are introduced from opposite sides of the channel at high angles (≥75º), so that conditions of total internal reflection are created on the boundaries of the PDMS channel, if filled with water (n = 1.41 vs. n = 1.33 for PDMS and water, respectively). The same channel becomes a transparent optical window, when the water is replaced by a salt solution, which is index-matching with PDMS. A microphotograph of the device is shown in Fig. 1.

Fig. 1: A microphotograph of the switch device. Purple – mirror channel. Orange – rounded flow channels for valve sealing. Grin – valve control layer. Control layer inlets are labeled by numbers of the membrane valves they actuate.

Publication:

K. Campbell, A. Groisman, U. Levy, L. Pang, S. Mookherjea, D. Psaltis and Y. Fainman, “A microfluidic 2´2 optical switch,” Applied physics letters, 85, 6119 (2004)


Research Group