Microscope objective made by “water”
People usually can see a droplet on lotus leaf which is beautifully wrought and keeps its spherical shape, as shown in Fig. 1 (a). Through the droplet, people can see the magnified microscopic structure. In fact, it is a natural lens. Based on this phenomenon, scientists proposed a tunable lens using liquid, called liquid lens, as shown in Fig. 1(b). The liquid lens can not only be used for imaging but also zooming the focal length due to the tunable feature of water. In other words, one liquid lens is equal to many solid lenses, which helps to realize compact structure. And, this kind of lens has been used in microscope, as shown in Fig. 1(c).
Fig. 1 Liquid lens. (a) Natural liquid lens; (b) Electrowetting liquid lens; (c) Liquid for microscope
Prof. Li from Sichuan University and Prof. Qiong-Hua Wang from Beihang University work on liquid lens for 10 years. They have developed electrowetting liquid lens and zoom microscope based on liquid lens, as shown in Fig. 2.
Fig. 2 Zoom microscope
Recently, Profs. Li and Wang proposed a movable electrowetting optofluidic lens, as shown in Fig. 3. Compared with the conventional tunable lens, the proposed optofluidic lens has two liquid-liquid (L-L) interfaces, which can move in the cell by an external voltage. The object distance and image distance are adjusted by shifting the L-L interface position. It can be used to realize optical axial scanning without moving part, which eliminates the oscillation caused by mechanically moving objectives. The lens is low-cost and has the potential to be commercialized.
Fig. 3 Imaging experiment using the movable electrowetting optofluidic lens. (a) Experiment setup. (b) Specimen A. (c) Specimen B. (d) Specimen A and B stacked together. (e) Focusing on specimen A. (f) Focusing on specimen B
Prof. Qiong-Hua Wang founded the Institute of Information Display in Sichuan University in 2006, she is the director, and Prof. Li is the deputy director. Prof. Wang was a Changjiang Scholar and the winner of the National Outstanding Youth Fund Project. Her team engages in the research of 3D displays and optical fluidic devices. Her team published approximately 200 SCI papers, authored 2 books, and holds 5 U. S. patents and 100 Chinese patents. Prof. Wang is a Fellow of the Society for Information Display and an associate editor of Optics Express.
Li L, Xiao L, Wang J H, Wang Q H. Movable electrowetting optofluidic lens for optical axial scanning in microscopy. Opto-Electron Adv 2, 180025 (2019).