Wearable sensors measure pressure on the foot
A new type of textile sensor can be used to determine the pressure on the bottom of the foot with 3D measurements. An electronic measurement stocking monitors the pressure on the feet and warns the wearer of uncomfortable or dangerous pressure points. This is particularly interesting for diabetics who are often less sensitive to pain, which increases the risk that wounds or sores will form.
Fraunhofer IIS, in conjunction with the Fraunhofer Institute for Silicate Research ISC and the Center for Telematics at the University of Würzburg, have developed special diagnostic electronics inside an ASIC that work together wit 40 soft pressure sensors to measure the amount and distribution of pressure on the sole, heel, instep and ankle. The signals generated by the sensors are then converted into a 3D analysis.
The sensors, which are woven into the stocking material, are made from a soft and highly-malleable silicon elastomer film that is easily integrated into the textile. The film is coated on both sides with highly-flexible electrodes. If deformation of the film occurs through pressure or stretching, this simultaneously leads to less thickness and a larger surface area. The pressure increases the electrical capacity, an effect that can be measured. If the patient stands in one place for a longer period of time for instance, this increases the pressure. The sensor recognizes the change and sends a measurement signal over an electrical path to a set of electronics that consist of an ASIC chip, a controller and a wireless interface. The wireless diagnostic electronics can be used to display the measurements on a smartphone or tablet so that diabetes patients know when they should alter the position of or pressure on the foot. This innovative sensor stocking offers utility in a wide range of applications. Apart from the long-term monitoring of diabetes patients, it's suitable for the field of orthopedics, such as analyzing gait and posture, as well as for sports and fitness applications. Joggers can wear the stocking to monitor their running style and foot position for instance.
At the embedded world trade fair being held in Nürnberg from February 23 to February 25, researchers will be demonstrating how these integrated sensors react to human contact and how the measurement values are read out.