What is Tactile Sensing Technology?

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Defining Tactile

Tactile sensing relates to mapping contact pressures across a surface, often across complex surfaces like the hand, head, and other human body parts. The more often-used terms "pressure" and "force" are related to "tactile," but both cannot capture the full complexity of contact mechanics. "Pressure" is a scalar value capturing solely magnitude and "force" is a vector expressing magnitude and direction. Tactile measurement goes beyond by portraying the magnitude and distribution of contact pressures between two objects over an area as a matrix.


 
Red Dot

Pressure

Omnidirectional Scalar

Red dot + directional right upward arrow

Force

One Direction Vector

Tactile graph

Tactile

Multi-DOF Surface

 
 
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How It Works

Tactile sensing is the technology of mapping and measuring the contact mechanics between two objects. Tactile sensing is closely related to pressure and force. If you are searching for pressure measurement and mapping solutions, the two main types of sensors of interest are either capacitance-based or resistance-based. Whereas resistive sensors work by measuring changes in the resistance of a semi-conductive materials, capacitive sensors work by measuring changes in the gap distance between two electrodes. To function, the semi-conductive inks on a resistive sensor must go from a non-contacting state to a contacting state so the sensor performance is poor at low pressures.  As the electrodes contact and rub against one another, the surface properties change on a microscopic level, which also changes the sensor behavior and thus requires frequent re-calibration or software compensation.

Hand sensor graphic
 
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The Benefits

The benefits of capacitive technology are that the two electrodes never touch and operate in an elastic region, so the sensor is more sensitive and stable.  Another key benefit is that electrodes can be formed from any conductive material (conductive cloth, FPCB, metal fixtures) giving our sensors a wide range of design flexibility. Capacitive sensing has emerged as the preferred method for capturing contact-based pressure changes due to sensitivity, repeatability, stability and design flexibility.

A Comparison

Capacitive Tactile Sensors Resistive Tactile Sensors
Construction Conductive material separated by
compressible dielectric
Resistive ink printed on membrane
Sensitivity Excellent Fair
Repeatability Excellent Poor
Number of Elements Good Excellent
Design Flexibility Excellent Fair
Speed Fair Excellent
Temperature Stability Excellent Fair
 

Capacitance

Capacitance is a measure of an object’s ability to store electrical charge and has been demonstrated countless times through the classic physics class example of two electrodes with area A separated by an air gap D as shown. As the air gap decreases, the capacitance C increases. (Diagram already created on old site)

We use this property to build sensor pads and arrays by separating the electrodes using a proprietary compressible dielectric matrix, which acts as a spring. Precision manufacturing techniques allow excellent repeatability and sensitivity, while advanced conductive materials allow for conformable, stretchable, industrial, and other hybrid sensor designs. The simplicity of the capacitive sensor design gives us a large degree of flexibility when creating custom sensor solutions.

Our Array Sensors

To build our Tactile Array Sensors, we arrange electrodes as orthogonal, overlapping strips separated by a proprietary compressible dielectric matrix, which acts as a spring. A distinct capacitor is formed at each point where the electrode strips overlap. Precision manufacturing techniques allow excellent repeatability and sensitivity, while advanced conductive materials allow for conformable, stretchable, industrial, and other hybrid sensor designs. By selectively scanning a single row and column, the capacitance, or local pressure, at that location is measured. Our proprietary drive and conditioning electronics can scan through an array at high speed while optimizing settings to achieve the maximum sensor response from each sensing element.


 
capacitance equation
how tactile sensors work
array sensors explained - array sensor layout
 

Conformable

Wrap, mold, or fold this sensor around complex surfaces

Industrial

Made for extreme temperatures, and extreme pressures

Hybrid

Ultra-thin and capable of flat-mounting and mild curvature

Stretchable

Can be flexed and deformed while still maintaining data accuracy