BACKGROUND

Several groups have begun conducting research on the production of soft flexible touch sensors. Recently, Google's Project Jaquard developed a method of using industry standard jacquard machinery to produce textiles with integrated sensors for use in bespoke smart garments. Georgia Tech's Healthcare Robotics Lab developed silicone sensors with “taxels”—tactile pixels—used to characterize force applied to a robotic arm. Other methods have also been investigated such as use of conductive rubber, layering of piezo-resistive and conductive textiles, combinations of conductive knit or woven textiles and threads, screen printing, splicing of optical sensors into individual fibers and knitting of structures containing silver coated nylon, stainless steel, and carbon or polymeric conductive yarns. Sensors knit with carbon fiber filament show may improve the sensitivity of wearable devices. The knitting process helps with consistency of the design, while the carbon fiber has been shown to function well in a wider range of conditions.

While progress has been made, many of these solutions still face a number of challenges with respect to manufacturability and robustness. Hard and fragile embedded electronic components and the need for bundles of wire leads often diminish the feasibility of some solutions. Human factors can change the efficacy of these devices, for instance, the need to recalibrate antenna components that can function at different frequencies on the human body than in free space. Particularly in the case of sewn sensors, the production process is lengthy, complex, and cannot easily conform to exact measurements. Additionally, the need to wash and clean these garments or medical devices with sensors will arise, adding complexity to the design and production.

Previous fabric-based touch sensing has required a large number of sensing electrodes (wires) to form a discrete sensing mesh or has used a dense weaving of conductive yarn in an XY grid pattern to sense human touch using self-capacitance or mutual capacitance. Covering a surface with discrete electrodes is impractical for scalability of the sensor as it increases the number of required connections to a sensing integrated circuit.

SUMMARY OF THE EMBODIMENTS

A planar (two-dimensional, XY location) touch sensor may include a knitted structure and supplementary method of sensing detects human touch on a fabric surface. This sensor may be fully knitted and detect the continuous planar location and contact force of human touch along the surface of the structure. The fabric may conform to any arbitrary surface and may be a rectangle for touch pad applications. This sensor may be used for applications that include robotics and human-machine interaction, smart garments and wearables, as well as medical textiles and flexible embedded sensors. This touch sensor may require as few as only two electrode connections from the fabric to sense both planar touch and pressure, which allows it to work in areas with limited space that allow for limited complexity for wiring.

