Kansai University and Teijin Ltd developed a “piezoelectric fabric” that can be used for wearable sensors and actuators.
At a press conference that they had Jan 8, 2015, they demonstrated the fabric by using a robot, 3D model, etc. The piezoelectric fabric is a fabric consisting of various fibers including PLLA (poly-L-lactic acid) and carbon fibers. PLLA features piezoelectricity; therefore, when it is bent or stretched, it generates an alternating electric potential.
When PLLA is used for a fabric, it is possible to realize a piezoelectric fabric that can detect various movements such as bend and twist. When an alternating electric potential is applied to PLLA, it can also be used as an actuator. The carbon fibers function as electrodes.
A shirt made of the “piezoelectric fabric.” It has a structure in which the PLLA fiber is sandwiched by a pair of carbon fibers.
[Click to enlarge image]
The PLLA fiber can detect only bending (stretching) movements. However, if a fabric is made of it, the fabric can detect other movements such as twisting movements. Depending on the kind of fabric (weaving technique), the “constraint condition” at the point where warp and weft threads cross each other changes, thus, changing detectable movements. Therefore, it is possible to realize a wearable sensor that can detect various movements by combining different kinds of fabrics.
For example, “plain weave,” in which warp and weft threads cross each other by alternately going over one thread, then under the next and so on, has many “crossing points” and a stable structure. So, it is suited for detecting simple bending movements.
On the other hand, “satin weave,” in which warp and weft threads cross each other for every five threads, has a loose structure. And crossing points are arranged in two directions that are perpendicular to each other (diagonal to the fiber). Therefore, it is suited for detecting twisting movements.
Human movements being copied by a robot wearing the fabric