Tunable liquid lens for three-photon excitation microscopy
Samuel Gilinsky, Diane N. Jung, Gregory L. Futia, M. Zohrabi, T. Welton, Omkar D. Supekar, Emily A. Gibson, Diego Restrepo, Victor M. Bright, Juliet T. Gopinath
Abstract
We demonstrate a novel electrowetting liquid combination using a room temperature ionic liquid (RTIL) and a nonpolar liquid, 1-phenyl-1-cyclohexene (PCH) suitable for focus-tunable 3-photon microscopy. We show that both liquids have over 90% transmission at 1300 nm over a 1.1 mm pathlength and an index of refraction contrast of 0.123. A lens using these liquids can be tuned from a contact angle of 133 to 48° with applied voltages of 0 and 60 V, respectively. Finally, a three-photon imaging system including an RTIL electrowetting lens was used to image a mouse brain slice. Axial scans taken with an electrowetting lens show excellent agreement with images acquired using a mechanically scanned objective.