Programmable Second Skin For Re-Educating Injured Nervous Systems

Abstract:

The purpose of this grant was to develop clothing-like material with embedded sensors and synthetic muscles. When eventually worn by brain-injured individuals over one or more limbs, this clothing may be used to restore their capability for independent mobility. The material, called a "second skin", is a cyberphysical system designed as a soft robot that cooperates with the biological muscles of the body. Because the second skin will have to learn to cooperate with the body on which it is worn, the work during this grant period also includes a study that measures how infants learn to kick. Like infants, the second skin must learn how to use the muscles in order to gain control of body motion for particular tasks. Although we study infants in this grant, the same second skin technology may apply to many mobility-impaired populations, including children and adults with brain injury, the ageing population, and individuals injured during military combat. In order to build the device, we followed the same principles to build sensors and synthetic muscles that nature has used to design and build biological muscles. For example, nature uses the same mechanism for controlling how skeletal muscles contract, regardless of their location. Muscles around the joints are used in different combinations in order to perform particular kinds of motion. We similarly fabricated material consisting of groups of synthetic muscles and sensors around the knee and ankle joints, and developed biologically-inspired programming techniques for controlling these groups of synthetic muscles. A second step in building the device was to use data from typically developing infants to discover how we might best use the second skin to assist infant kicking. We used a multi-camera motion capture system to measure infant kicking over multiple visits to our laboratory, when the infants were 3, 4.5, and 6 months old. We then used actual body measurements from these infants to build a physical model of an infant leg. Finally, we placed the second skin device over the model leg in order to conduct tests of the way that the synthetic muscles worked together to flex and extend the leg at the knee joint, and at the ankle joint. The synthetic muscles work by means of compressed air. Our tests of the muscles worn on the model leg indicated that a group of multiple muscles around the knee could flex and extend the knee in much the same way as biological muscles do. Similarly, our tests of second skin muscles worn at the ankle indicated that synthetic muscles may be used to perform the more complex motions that move the foot. A next step in this research will be to determine how to control the timing of the synthetic muscles at the ankle and knee joints, respectively, as the model leg performs more complex motions. Other challenges ahead include tests of muscles used at the hip joint, control of muscles at hip, knee, and ankle joints worn on two model legs as they kick together, and developing a way to control synthetic muscles so that they cooperate with biological muscles when the device is worn on both legs by infants during kicking, crawling, and walking.