The Advanced Prosthetic Hand Project Jessica Reddy, IMSURE Fellow Mentor: Dr. William C. Tang

Jessica’s Journey… Hurdles: 1.Bio-major’ness I know how a muscle works, but an artificial muscle? 2.Purchasing FEMLAB 3. Where do I begin? Solutions: 1.Read, read, and read. 2.Solved. 3.Grad Student! (Shawn)

Current Artificial Limb Technology Myoelectric Prostheses –Electrode in prosthesis socket detects EMG signals from residual muscle remnant –Prosthetic Hook Thumb-index finger pinch Sgt. Joseph Bozik Walter Reed Medical Center

Proposed Advancements Implantation of Neural Prosthetic into: –Brachial Plexus nerve (short term goal) –Cortical brain area (long term goal) Multiple sites Develop a prosthetic hand with multiple degrees of freedom –Use skeletal model of human hand for frame –Tactile sensing –Low weight, low energy consumption

Pneumatic Artificial Muscle Contractile and linear motion engine operated by gas pressure Flexible closed membrane attached at both ends to fittings Mechanical power is transferred to a load

Course of action: As contraction, volume to max  force to 0 & contraction max Pneumatic Artificial Muscle

Characterization of the Optimal Artificial Muscle Generated force depends on… Type of membrane –Geometry –The way it inflates Length Gauge pressure

Braided Muscles Gas-tight elastic tube surrounded by a braided shell Braid fibers run helically about the muscle’s longitudinal axis at an angle When pressurized the tube presses laterally against the shell

Mckibben Artificial Muscle Muscle contracts axially – (With lateral expansion) Causes pulling force on its load

Drawbacks: 1.Friction between braid and tube Hysteresis 2.Requires complex control algorithm 3.Deformation of rubber tube 4.Pressure Threshold 5.Flaws in membrane material 6.Maximum displacement is limited % contraction 7.Low force output 650 N (rest); 300 N (15% contraction); 0 N (30% contraction) –Applied pressure: 300 kPa, length=15 cm; rest diameter=1.4cm Mckibben Artificial Muscle

1.Avoid friction: use a single layer actuator 2.Therefore, simplifying the control 3.Avoid deformation: use membrane material with high tensile stiffness 4.No pressure threshold: use elastic membrane material Building a more suitable design…

Want little stress in lateral direction to minimize elastic deformation (strain) How to achieve lateral expansion with a high tensile stiffness material? Rotationally repeated pattern  Pleats

Pleated Pneumatic Artificial Muscle Pack membrane into many folds along axis of muscle Maximum displacement: 40-50% Force output: – 3,300 N at 5% contraction; 1,300 N at 20% contraction; 0 N at 43% contraction  Applied pressure: 300 kPa, length=10 cm, diameter=2.5 cm

With these considerations in mind, let’s build a model!

Kevlar 49: High tensile strength High elastic modulus Low density

Y-Displacement Throughout Cross section

X-Displacement Throughout Cross section

Upcoming endeavors… Introduce pleats Represent other layers of muscle –Polyproylene lining Extend model to 3D –Include End Fittings Miniaturization of the Artificial Muscle

UCI Subsystem Development Team Members Artificial Muscle William C. Tang (Team Lead), Professor, Biomedical Engineering Department, Electrical Engineering & Computer Science Department –Ryan Langan, UROP SURP Fellowship Neural Interface William E. Bunney, Distinguished Professor & Co-Chair, Department of Psychiatry & Human Behavior James H. Fallon, Professor, Department of Anatomy and Neurobiology Communications Payam Heydari, Assistant Professor, Department of Electrical Engineering & Computer Science Tactile Sensor Abraham P. Lee, Professor, Biomedical Engineering Department, Mechanical & Aerospace Engineering Department Interface and Algorithm Zoran Nenadić, Assistant Professor, Biomedical Engineering Department Pending DARPA Award.

Please visit our website: Webmaster: Ryan LanganDr. William C. Tang