Fuel Powered Artificial Muscles

Introduction

We experimentally demonstrate artificial muscles that convert the energy of a high-energy-density fuel to mechanical energy. These muscles are fuel cells that in some versions store electrical charge and use changes in stored charge for mechanical actuation.

diagram

(A) Illustration of a cantilever-based nanotube fuel cell muscle. (B) Illustration of a one compartment cell mounted in a dynamic mechanical analyzer (DMA) for tensile measurements. (C) Potential and actuator strain versus time for a tensile nanotube actuator that is alternately exposed to pure O2 (red) or a mixture of 5 volume percent H2 in inert gas (blue). (D) Measured tensile actuator strain versus potential and injected charge for an electrically powered nanotube actuator.

The highest demonstrated actuator generated strains and mechanical output power densities for fuel cell muscles are comparable to natural skeletal muscle, and the actuator generated stresses are over a hundred times higher than for natural skeletal muscle. Important possible applications of this research are artificial arms and legs, which have the ability to move and manipulate objects-both for amputees and robots.

diagram

Fig. 2. Continuously shorted fuel cell muscle based on a NiTi shape-memory alloy. (A) Schematic illustration, with cut-away to reveal details, of the fuel-powered artificial muscle mounted in the dynamic mechanical analyzer used for measurements. (B) Actuator strain versus time during exposure of the chemically powered actuator to a mixture of N2, 2.5% by volume hydrogen and 50 % oxygen (red curves) and during exposure to pure oxygen (blue curves). (C) Actuator strain versus time for different volume percents of hydrogen for the experiment in B. The insert shows the dependence of actuator strain on the H2 volume % in the fuel.