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Design of the touch stimulator

A project log for TouchYou: a wearable touch sensor and stimulator

TouchYou, is a pair of wearable interfaces that enables affective touch interactions with people at long distance.

leonardo-gomesLeonardo Gomes 08/27/2018 at 04:070 Comments

The touch stimulation interface was designed for providing the feeling of being touched remotely. This interface is wearable and its output, or stimulation response, depends on the touch detected by the sensitive interface. The design of the touch stimulation interface considered meeting the requirement that it should create a sensation of a moving touch through the skin, not only by mechanical stimulation, but also by other stimuli. Besides the vibrations, the interface is able of stimulating thermally and electrically the skin and muscles.

For covering a relatively large surface of the skin while the interface was being worn, we decided to place the electrodes in a matrix pattern, where each element of the matrix is a pair of electrodes. We used two types of electrodes: 15 spike dry electrodes  and 9 wet electrodes, combined in a total of 12 pairs. The using of spike dry electrodes was preferable in this design, because those electrodes don’t need the use of conductive gel and have a better performance when in contact with hairy skin, but the total required number wasn’t available at the moment of building the prototype. The electrodes of the lines and columns (3x4) were connected to each other respectively, and a 3D printed cap was fitted over the head of each electrode and wire, keeping the connection safe and fixing the set in the elastic fabric. 

For creating the sensation of a moving touch, we change the pair of conducting electrodes by changing what line and column are active, and the electrical stimulation will occur in the closest pair of electrodes. In addition to the electrical stimulation, we included 6-coin vibration motors, as shown in the figure below, between the electrode pairs. The motors were used for creating an additional sensation of touch, for example simulating the moment that the finger touches the skin or when the finger slides from one point to another. 

The third touch stimulation method is by thermally stimulating, simulating the temperature of the human body. For creating this effect, we used 3 flexible heaters, or polyamide heating film plate. Each heater had 30x40 mm dimension, could be supplied with 5 V and provide 1 W of power, which was enough for keeping their temperature at about 37°C. The heaters were glued to a smaller elastic fabric (A) and then, fixed over the initial set of electrodes and motors by using velcro (B). We also installed temperature sensors for each heater, so we could control the temperature for no overheating the system and the skin in contact with the interface. 

The touch stimulation interface can be worn in any part of the body, and in the figure below we show the interface being worn in the arm.


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