Schematic diagram of a tunable liquid lens operated by electromagnetic actuation. According to Faraday’s law of electromagnetic induction, when electric current flows in an electric coil, a magnetic field is generated in its surroundings. The magnetic field is used to actuate or pull a ring-shaped neodymium magnet placed on the top of an elastic polydimethylsiloxane (PDMS) membrane in the liquid lens, resulting that the liquid inside an actuation chamber flows into the lens chamber through open walls. It brings the change of the surface profile and focal length of the liquid lens.