A Chemical Pump that Generates High‐Pressure Gas by Transmitting Liquid Fuel against Pressure Gradient

Abstract

A pneumatic soft robot can be made autonomous by carrying a liquid chemical fuel. In the existing design, to transmit the fuel, the pressure of the fuel tank must exceed that of the actuator. Consequently, the fuel tank must be sufficiently stiff, which hardens the robot. Herein, inspired by pit membranes in trees, a chemical pump is developed, which is consisting of a nanoporous membrane between the fuel tank and the actuator, and coated with a catalyst on the side of the actuator. The fuel in the fuel tank migrates across the membrane and, on meeting the catalyst, decomposes into a pressurized gas and inflates the actuator. The chemical pump is driven by the free energy of reaction, against the difference in pressure. The pores in the membrane are large enough for the fuel molecules to migrate through, but small enough to block the pressurized gas to tunnel back. In a demonstration, the fuel tank has ambient pressure, and the actuator has a pressure of 350 kPa, comparable to the pressure in a car tire. The chemical pump enables pneumatic robots to be autonomous, powerful, and soft.

Logic-enabled textiles

“…To permit untethered operation of our robot, we employed a portable compressed gas cartridge to power both the controller and the actuators. Our assistive robot is capable of standalone operation provided a source of compressed gas is available; this could in the future be a wearable textile tank that is refilled periodically or an integrated energy-harvesting device that generates pressurized gas onboard ( 26 , 41 – 45 ).…”

Soft Electrohydraulic Bending Actuators for Untethered Underwater Robots

“…However, it requires an external, bulky, and highnoise rigid pump, which puts a limit on its further development. The method of driving the movement of the actuator by generating gas through a chemical reaction [37,38] has the advantages of small size and high integration. However, its shortcomings of slow actuation frequency and low efficiency lead to the slow swimming speed of the underwater robot.…”