0 Replies Latest reply on Feb 19, 2019 8:42 AM by PaAr_3783191

    [How to] 5 Electrode Materials for Capacitive Touch Sensors

    PaAr_3783191

      Electrode behavior heavily depends on the material they are made off.

      In order to know if emerging materials can potentially be used as electrodes in touch sensors, we must first describe the properties we would want such a material to have.

       

      Desired properties differ depending on one’s point of view. Engineers tend to focus more on physical properties and performance, while managers focus more on the cost-effectiveness of the proposed material.

       

      How to choose the ideal electrode material for your touch sensor?

       

      Engineers are mostly concerned about three main performance categories:
      electrical, optical and mechanical.

       

      a. Electrical properties
      Electrical performance boils down to the resistivity and capacitance of the electrodes. The capacitance is affected, among other parameters, by the shape and size of the electrodes.

      To compare resistivities, the industry uses the term sheet resistance. Sheet resistance needs to be as low as possible. This allows for faster response times, and use in large screens.

       

      b. Optical properties
      Optical performance is crucial when a screen is housed underneath the touch sensor. Great optical performance is crucial as it allows the user to have an unobstructed
      view of the screen. Focus lies on two properties here, transmittance and haze.

       

      c. Mechanical properties
      The device’s design dictates the mechanical properties the electrodes should have. For example, if a device is bent or flexible, then electrodes should also be able to bend or flex. The main property engineers take into account when it comes to mechanical properties is that of brittleness. Brittleness expresses how much energy can a material absorb prior to fracture. Common measures of brittleness include the strain-stress graph and the material’s bending radius.

       

      The materials we examine:

       

      ITO

      Maturity: Very high
      Sheet resistance: Moderate
      Flexibility: Very limited
      Optical performance: Very high
      Applications: Most of flat touch sensors under 22”

       

      Metal Mesh

      Maturity: Medium
      Sheet resistance: Low
      Flexibility: Moderate
      Optical performance: Moderate-High
      Applications: Large flat (up to 65”),curved, bent touch sensors

       

      Silver Nanowires (AgNW)

      Maturity: High
      Sheet resistance: Low
      Flexibility: High
      Optical performance: High
      Applications: Flat (up to 15”), bend, flexible touch sensors

       

      Carbon Nanotubes (CNT)
      Maturity: High
      Sheet resistance: Moderate
      Flexibility: High
      Optical performance: Moderate
      Applications: Wearables, flexible, stretchable touch sensors

       

      PEDOT:PSS
      Maturity: High
      Sheet resistance: Moderate
      Flexibility: High
      Optical performance: Moderate
      Applications: Flexible, stretchable touch sensor

       

      You can learn more about the processing, the cost along with technical details such as the sheet resistance and the transmittance of each material in our electrode materials guide.

       

      You can get more details and learn more here.