Wearable electrocutaneous feedback system: A smart device to compensate for sensation loss
Start date: 10 April 2012
Electrocutaneous stimulation can be used to give feedback for sensory loss based on the data received from external sensors. A device is presented that uses the input from force sensors integrated into a shoe insole to detect the force applied and uses smart algorithms to classify the collected data and react to the environmental changes. The device is designed to help people with sensation loss to compensate for their disability by redirecting the sensation from the affected areas on the feet to sensing skin, e.g. in the upper limb. If electrical stimulation is used as a way of giving feedback, the device has to be flexible so that the wearer’s requirements can be addressed in terms of the range of comfortable stimulation and sensor drifts or faults. The device presented in this paper has three main units. The first unit is called Sensor Unit which consists of piezo-resistive force sensors that can detect force which is applied to the sensors. The second unit is a Pulse Creation Unit which is a microcontroller that creates a pulse with a fixed frequency and amplitude. The Pulse Creation Unit uses the input of the sensor unit to modulate the pulse-width of the pulse. The third unit is the Electrical Stimulation Unit that consists of the transformers and electrodes that are attached to the skin. The microcontroller offers smart approach to the device operation. The sensor unit has to be calibrated so that the maximum force input can be stored and compared to the maximum electrical stimulation. The value is obtained automatically. The algorithm also detects sensor drift and sensors faults and triggers the required actions. The Electrical Stimulation Unit needs to be calibrated too. The calibration routine defines a comfortable range of stimulation for each pair of electrodes and matches the values to the sensor values. The device has the potential to be applied for many other medical conditions where people have irreparable damage to their sensory pathways.