Session: SYMP 4-4: Human Integrated Smart Systems

Paper Number: 141345

141345 - Electropneumatic Sleeve for Rapid and Precise Electrical Muscle Stimulation 

Spinal cord injury often leads to the loss of upper-limb motor control required to perform activities of daily living. Functional electrical stimulation (FES) represents a promising intervention to restore motor control because it directly activates the paralyzed muscles to assist in daily tasks. However, FES is mostly constrained to laboratories and clinical settings because it suffers from issues related to the accurate and reproducible placement of electrodes. Extensive training is required to place the electrodes due to the specificity needed to generate complex movements. Finding the proper placement to stimulate the corresponding muscles is a time-consuming process that must be redone each session due to the nonlinear response in muscular actuation. Additionally, repeated stimulation from finding the ideal electrode placement to generate desired trajectories causes muscle fatigue.

To address the aforementioned limitations, we designed a sleeve that eliminates the burden imposed by careful electrode placement and improves the specificity of electrodes when using functional electrical stimulation to restore limb function in people with tetraplegia. The FES sleeve consists of a high-density electrode array fabricated from patterned electrically conductive textiles, capable of delivering biphasic stimulation to the user. The array consists of twenty conductive textile electrodes integrated directly into a base layer of nylon taffeta fabric using a scalable thermal laminate manufacturing process. A parallel heat-sealable textile layer is used to ensure proper contact between the electrodes and the skin via pneumatic pressurization. This fluidic platform inflates while the sleeve is in use, holding the electrodes against the surface of the skin upon their actuation.

The framework of this conductive textile electrode matrix enables the use of a demultiplexer through which stimulation can be applied over sixteen different electrode pair combinations using only four electrical inputs; this system could be expanded to any N² grid of electrodes in future designs using the same demultiplexed approach for a significant reduction in required tethering infrastructure. In addition to reducing the number of control lines required to address each electrode combination, an algorithm rasters through all the electrode pairs to identify the pair that produces the most muscle contraction based on local torque maxima. Ongoing work is targeting identification of a multiple pairs of electrodes that are activated through different phases of joint movement to track the muscle point for optimal actuation. This smart and compliant system reduces the time and effort required to don electrodes compared to the traditional methodology of electrode placement, which often takes tens of minutes even by a skilled practitioner, while generating comparable torque outputs. This electropneumatic sleeve will help translate FES from clinical settings into at-home rehabilitation.

Presenting Author: Sofia Urbina Rice University

Presenting Author Biography: Sofia Urbina is a Ph.D. student at Rice University in the Department of Mechanical Engineering working in the Preston Innovation (PI) Lab advised by Dr. Daniel Preston. She graduated from Louisiana Tech University with a B.S. in Biomedical Engineering. At the PI Lab, Sofia’s research focuses on integrating electrically conductive and fluidic systems in soft and wearable rehabilitative devices.

Authors:

Sofia Urbina
Erin Mahan
Shane King
Barclay Jumet
Marquise Bell
Marcia O'malley
Daniel Preston