In the UIST2022 demo session, we presented two types of knitted resistive force sensors for both pressure and strain sensing. They can be manufactured ready-made on a two-bed weft knitting machine, without requiring further post-processing steps. Due to their softness, elasticity, and breathability our sensors provide an appealing haptic experience. They were presented as standalone demonstrators, accompanied by exemplary applications to provide insights into their haptic qualities and sensing capabilities.
Common FSRs are multi-material elements, usually printed on plastic substrates. The piezo-resistive material is sandwiched between two conductive traces, that are in loose contact at rest. When under stress, the materials’ surfaces are tightly compressed, which increases the contact area and consequently reduces the electrical resistance. We translated this concept to a single knit fabric. We used common polyamide (PA) yarn to provide the surrounding knit structure for embedding the sensor which also acts as insulator between the traces.
We exhibited a set of diferent functional prototypes showing many variations of knitted sensors. We showed stretch sensing capabilities of resistive tubular felds, as well as the pressure sensing performance of our spacer knits. We demonstrated an application of the stretch sensor, in which the user can close blinds by pulling on the fabric, emulating the movement of closing curtains. We also showed a use-case of a textile pressure sensor being used as a button to control functions of a digital UI, like scrolling. This application showed how knitted sensors can be used to embed digital functions into furniture. Attendees were encouraged to experience the demonstrators firsthand and get a sense of both the haptic qualities and sensing performance.