Christopher Suprock, founder of product-design firm Suprock Technologies, made the demonstration pump using flexible membranes and a ferrofluid, or magnetic liquid. Suprock injected the ferrofluid between two 0.005-inch-thick elastic membranes and placed an electromagnet less than an inch away. When the electromagnet is turned on, it attracts the ferrofluid, stretching the membrane toward the magnet. When the electromagnet is off, the membrane springs back to its original position. Suprock says his next step is to team up with a medical-device maker, refine the design, and test it in a living animal.