Session: Research Posters

Paper Number: 111622

111622 - Water Vapor Based Artificial Muscles 

McKibben air muscles are actuators similar to human muscles in contraction and compliance. They consist of an air-inflatable bladder within a flexible cylindrical braided mesh. When the bladder is inflated, it causes the braided mesh to expand radially while contracting axially in length. While this air muscle can be used in numerous robotic applications, it requires a noisy compressor, a bulky compressed air tank, and interconnecting hoses with actuated valves. The additional weight of an air tank and a compressor also limit potential applications, such as in space applications where a weight limit is imposed.

The objective of this project is to develop a novel artificial muscle design with a water vapor based boiling driving mechanism instead of compressed air. A test fixture is developed for this work and validated using an air actuated muscle where 20% contraction is desired at 4 kg applied load. The muscle used for validation includes a standard braided hose, connected to two hooks at its ends. A deflated ball is included within the braided hose but not attached to the hooks. As 10 psi of compressed air is applied to the ball, the ball is observed to inflate and expand the mesh radially. The muscle lifts the weight the desired contraction with ease. The test fixture validation is a necessary step for use in the novel artificial muscle development. Pictures of this fixture and the air actuated muscle will be presented.

Following the successful validation of the test fixture, a pouch is used instead of the inflatable ball in the artificial muscle. Since the intent is to boil water in the pouch, silicone material is chosen due to its resilience to high temperatures inside the pouch while insulating the braided mesh from the high temperatures. The pouch is completely filled with water but approximately 50% of the water volume is squeezed out, leaving the water-filled pouch deflated. A 10mm x 10mm resistive heater is inserted into the pouch. One side of the heater has electric insulation for the electric wires and cannot be used for heat transfer. A 0.4 mm thick copper sheet with high temperature conductive microporous coating is soldered to the other side of the heater. This coating is highly wetting and can safely dissipate over 200 Watts per square centimeter without reaching the critical heat flux, with water as the working fluid. When power is applied to the heater, boiling occurs rapidly at the copper high temperature conductive microporous coating. The volume expansion due to phase change inflates the silicone pouch. The inflated pouch expands the diameter of the braided hose, and the muscle is observed to achieve 17% contraction while lifting the desired 4 kg while the subcooled water temperature is 80°C.

Using boiling heat transfer with microporous coating to actuate McKibben muscles is a novel concept. The muscle only uses electric power instead of compressed air. It is silent and does not require an air compressor or a compressed air tank. The frequency to lift and lower the weight is currently 90 seconds.  Future plans include additional development of a degassing system, so the water is free from condensable gases. This would improve the response frequency and the percent contraction of the phase-change artificial muscle.

Presenting Author: Dani Fadda The University of Texas at Dallas

Presenting Author Biography: Dr. Dani Fadda is a mechanical engineering Professor of Practice at the University of Texas at Dallas. His background includes two decades of professional engineering practice in the energy industry where he published numerous papers and developed patented products for chemical, petrochemical, and nuclear applications. He enjoys teaching in-person and online classes and is the recipient of prestigious teaching awards. Dr. Fadda is a registered Professional Engineer in the state of Texas and an ASME fellow.

Authors:

Tan Hoang The University of Texas at Dallas
Hootan Rahimi The University of Texas at Dallas
Juan Godinez The University of Texas at Dallas
Yonas Tadesse The University of Texas at Dallas
Seung M. You The University of Texas at Dallas
Dani Fadda The University of Texas at Dallas