Eleksen is one of the first companies that entered the Wearable Electronic market with a commercial product. This product is a textile based sensor called ElekTex.
ElekTex is a highly versatile and innovative technology that provides the basis for a soft, flexible, and lightweight interface between users and electronic devices. This unique fabric structure can accurately sense location on three axes – X, Y and to a certain degree Z – within a material that is less than 1mm thick. Therefore ElekTex not only senses where it is being touched (the X and Y axes), but also how hard it is pressed, the Z axis.
The ability to sense the applied pressure is major advantages ElekTex has over technologies, such as plastic touchpads.
The working principle of ElekTex:
ElekTex is essentially a laminate of textiles comprising two conductive outer layers separated by a partially conductive central layer. The outer layers each have two conductive-fabric electrode strips arranged so that the upper conductive layer has tracks which make contact across its opposing top and bottom edges and the lower conductive layer has conductive tracks up its left and right sides.
The partially conductive central layer provides the magic which makes ElekTex work. Its role is to act as an insulator in the resting state which, when touched, allows electrical current to flow between the top and bottom layer. Pressure applied to the ElekTex fabric causes two effects.
First, the conducting fibres in the central layer are locally compressed allowing contact between neighbouring conducting fibres to form a conductive channel through the central layer. Second, the applied pressure brings the two outer layers into contact with the conductive channel running through the central layer allowing a local circuit to be established between the upper and lower layers.
X, Y sensing:
The conductive outer layers are constructed using moderately resistive components so that when a voltage is applied across the sheet, via the electrodes, there is a distinct voltage drop across the conductive sheet. When the voltage is measured at points across the lower sheet, it acts like the track of a potentiometer allowing the x-position to be calculated from the voltage which can be measured, when the sensor is pressed, via the top sheet. The y-position is made by applying a voltage to the top sheet and measuring on the lower sheet.
These measurements can be made up to 1000 times a second providing, in effect, continuous X,Y positional data.
Z-axis pressure sensing:
When pressure is applied to an ElekTex sensor, for example when it is touched, a conductive channel is formed. If the pressure is light the conductive fibres in the central layer will only just make sufficient contact to open up a continuous channel and the resistance of the channel will be high. Conversely, when a high force is applied to an ElekTex sensor many more of the conductive fibres in the central layer will be brought into close proximity and thus the resistance in the channel will be relatively low. The variable resistance in the channel is, therefore, dependant on the pressure applied. To determine the Z axis force the electronic controller supplies a current to the upper and lower conductive layers which in the resting state presents an open circuit and no current flows between the outer layers. When the sensor is touched and the pressure increases, a conductive channel of decreasing resistance forms the circuit whereupon the resulting current flow is high and related to the pressure applied.
Although the ElekTex sensor technology is great for detecting the position on a given area, it’s not the most efficient technology to be used as keypad.
That ElekTex can be (miss) used as keypad can be seen in the many products in the market but again, this sensor has a much higher potential as just mimicking a 5 or 6 button keypad.