Wearable human-machine interfaces, and in particular smart clothing, are drawing attention because of their potential to improve users’ experience and enable the development of the Internet of Things. Stemming from this, research from Kansai University sees scholars looking into smart fabrics for controlling robots.
Piezoelectric ceramics have long been investigated for the development of human-machine interfaces, but the most common materials have the disadvantage of also being pyroelectric – ie they generate electrical charges in response of both strain and heat, making it difficult to ensure that they react to body movement but not to body heat. A promising alternative material is poly-L-lactic acid (PLLA), which is a piezoelectric polymer that is transparent and exhibits no pyroelectricity.
In a recent publication in Ferroelectrics, Yoshiro Tajitsu at Kansai University, Osaka, presented a smart fabric based on PLLA fibres. The fibres were woven together with polyethylene terephthalate (PET) fibres and conductive carbon fibres (which served as electrodes) in different ways: a plane, till and satin weave. Each of the three resulting fabrics was tested tracking the movements of a robotic arm. The fabrics based on the different weavings are sensitive to different types of movement: the plane weave detects the speed at which the arm moves, the till weave tracks the direction of rotation, and the satin weave is sensible to its own expansion and contraction. Thus, by combining the three fabrics it is possible to determine the type and direction of movement.
As a next step, a piece of fabric combining the three different types of weaving was made using a technique traditionally used to fabricate Japanese kimonos. When fitted on a person’s clothes and wirelessly connected to a humanoid robot, the fabric could be used to make the robot replicate the human's movements. Simple movements such as bending of the arm and twisting of the wrist were successfully replicated, even though more complex movements are still out of reach for the current system. “Our future aim is to be able to handle complex movements, which we hope to achieve by increasing the detection accuracy of the smart fabric”, said Tajitsu in the paper. Such advancements will be important for the development of better wearable human-machine interfaces.
This development stems from research conducted in partnership between Kansai University and high-performance fibre manufacturer Tejin. The sensing function incorporates Teijin’s weaving and knitting technologies and allows fabric to be applied to the actuator or sensor to detect complicated, three-dimensional movements.
Back in 2012, Kansai University and Teijin developed a flexible, transparent piezoelectric film by alternately laminating PLLA and optical isomer poly-D-lactic acid (PDLA). This new wearable piezoelectric fabric is the latest application of this technology.
Smart textiles may be popular, but it certainly hasn’t been easy for companies operating in this field to clinch commercial breakthroughs, as WTiN’s Fiona Haran reported from the recent Wearable Technology Show.
That said, Cath Rogan, principal of Smart Garment People, a producer of intelligent clothing solutions, said at the event: “We’re seeing a new focus on old interfaces, for example haptic interfaces,” referring to systems that allow a human to interact with a computer through bodily sensations and movements, exactly like the Kansai University and Teijin development.
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