Wearable technology is advancing quickly, and that includes smart textiles. Most of the focus for these kinds of electronics seems to be on giving our clothing new technological capabilities. For instance, you could outfit your workout clothes with sensors that keep track of your heart rate, count your steps, and so on. But there are other uses for smart textiles. An international team of researchers have recently developed Tessutivo, which is interactive fabric that allows for contextual interactions through inductive sensing.
Inductive sensing is a well-known technique for detecting the presence of metallic objects, and even some of their properties. A coil with electricity running through it will naturally generate a magnetic field. Any metallic objects in that field will affect it, and those changes can be detected. To create Tessutivo, the researchers used conductive thread to sew a number of inductive sensing coils onto fabric in a grid. Two layers of fabric contain the coils, and those are sandwiched between a pair of insulating fabric layers. The team has experimented with a range of different conductive thread types, as well as different kinds of fabric “substrates,” in order to find the optimal combination.
The research team also developed a custom sensing board to monitor the coils. It’s based on an Arm Cortex-M4 that is running Teensy 3.2 firmware. It has four 4:1 multiplexer chips, a Texas Instruments LDC1614 inductive sensing chip, a power management circuit for a LiPo battery, and a Microchip RN42 Bluetooth module. With this hardware Tessutivo is able to sense any metallic objects that are placed on it, and even identify them by the unique way they affect the magnetic fields created by the coils. Non-metallic objects can be “tagged” with simple copper foil to make them identifiable, as well. Tessutivo can, for example, detect your water bottle and remind you to take a drink every so often in order to maintain your hydration. By laying Tessutivo fabric over a desk, users can convert the entire surface into an interactive interface.