Miniature Stretchable Pump

L‘Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Soft robots have a distinct advantage over rigid robots: they can adapt to complex environments, handle fragile objects, and interact safely with humans. Made from silicone, rubber, or other stretchable polymers, they are ideal for use in rehabilitation exoskeletons and robotic clothing. Soft bio-inspired robots could one day be deployed to explore remote or dangerous environments.

The stretchable pump, made with silver electrodes, bent to a small radius of curvature. (© Vito Cacucciolo/2019 EPFL)

Most soft robots are actuated by rigid, noisy pumps that push fluids into the machines’ moving parts. Because they are connected to these bulky pumps by tubes, these robots have limited autonomy and are cumbersome to wear.

Researchers have developed an entirely soft pump using flexible electrodes. Weighing one gram, the pump is completely silent and consumes very little power that is provided by a 2 × 2-cm circuit that includes a rechargeable battery. To actuate larger robots, several pumps can be connected together.

The stretchable pump embedded in a textile glove for on-body thermal regulation. The closed-loop fluidic circuit consists of the pump and a serpentine flexible tube sewn into the textile glove (the “cold” side) and of a serpentine flexible tube bonded to a flexible heater (the “hot” side). The wearer can easily flex the wrist while the pump is operating. (© Vito Cacucciolo/2019 EPFL)

The pump could eliminate tethers for soft robots. It also could be used to circulate liquids in thin, flexible tubes embedded in smart clothing, leading to garments that can actively cool or heat different regions of the body.

The soft and stretchable pump is based on the physical mechanism used to circulate the cooling liquid in systems like supercomputers. The pump has a tube-shaped channel measuring 1 mm in diameter; rows of electrodes are printed in the channel. The pump is filled with a dielectric liquid. When a voltage is applied, electrons jump from the electrodes to the liquid, giving some of the molecules an electrical charge. These molecules are subsequently attracted to other electrodes, pulling along the rest of the fluid through the tube with them. Flow can be increased by adjusting the electric field.

The researchers successfully implanted the pump in a type of robotic finger widely used in soft robotics labs.

Watch a demo on Tech Briefs TV here. For more information, contact Vito Cacucciolo at This email address is being protected from spambots. You need JavaScript enabled to view it.; +41 21 695 41 06.