Computationally controlled commercial knitting machines were used to create knitted objects that are actuated by tendons. New software makes it possible for the objects to emerge from the knitting machines in their desired shapes and with tendons already embedded. They can then be stuffed and the tendons attached to motors as necessary.
Using this approach, a garment could be part of a personal information system — a sweater, for example, could tap its wearer on the shoulder. The fabric of a chair might serve as a haptic interface, and backpacks might open themselves.
Commercial knitting machines are well developed and widely used but generally require painstaking programming for each garment. This new work automates the process, making it easier to use these mass-production machines to produce customized and one-off designs.
Embedding tendons in the materials as they are created saves time and effort and adds precision to the actuation. The researchers developed methods for embedding tendon paths horizontally, vertically, and diagonally in fabric sheets and tubes. The shape of the fabric, combined with the orientation of the tendon path, can produce a variety of motion effects including asymmetric bends, S-shaped bends, and twists. Stiffness of the objects can be adjusted by stuffing them with various materials such as those available to hobbyists. A number of tendon materials can be used including polyester-wrapped quilting thread, pure silk yarn, and nylon monofilament.
In addition to actuating the objects, these techniques also can add sensing capabilities to objects. By attaching sensors to each tendon, for instance, it's possible to sense the direction in which the object is being bent or twisted. By knitting with conductive yarn, researchers showed they could create both contact pads for capacitive touch sensing and strain sensors to detect if a swatch is stretched.