Tactile Evaluation
The sense of touch is the most powerful and least understood of the human senses. The way a product feels creates strong impressions about its quality, desirability and value, yet the underlying features that make one product feel better than another can be elusive.
Until now, designers have had to rely on expensive expert consultants to provide subjective and often inconsistent opinions about haptics. Conventional testing equipment can produce quantifiable measurements, but they don’t correlate with human perception. We combine humanlike perception with the precision of a machine.
Inspired By Biology
The SynTouch Standard is a proprietary multidimensional space that quantifies how objects feel to human fingertips. The breakthrough technology is SynTouch’s BioTac sensor, a patented design that mimics both the mechanical properties and sensory capabilities of the human fingertip. It senses what your fingertips can sense, only much more precisely. The SynTouch Standard Instrument is programmed to make exploratory movements similar to humans, only much more precisely. The 15 dimensions of the SynTouch Standard were derived from language used by human subjects and are computed according to the neurophysiology of tactile perception. These biomimetic features are combined to extract human-like percepts.
The SynTouch Standard
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Sensory Capabilities
A complete set of tactile dimensions that correlate with human perception of texture, friction, compliance, thermal and adhesive properties. SynTouch’s pioneering biologically-inspired research continues to advance these capabilities as we progress towards capturing all aspects of human touch with performance and repeatability exceeding human capabilities.
We offer the tactile equivalent of the Pantone® Color Matching System, pioneered by Lawrence Herbert in the 1960s. Creating a similar standard for touch requires the same two capabilities that enabled the Pantone color system: sensors that measure the same attributes that humans perceive and a systematic way to describe all humanly appreciable combinations of those attributes.
SynTouch now offers a biomimetic tactile sensor (BioTac) that replicates the mechanical properties and sensory modalities of the human fingertip plus an informatic representation of human tactile perception. Together, they enable Machine Touch.
The SynTouch Standard Dimensions
There are currently 15 standard, trademarked dimensions; Each dimension is presented below with its formal abbreviation.
Macrotexture
- mTX: Macrotexture (Smooth-Textured) reflects the intensity of low-frequency tactile vibrations arising from large-scale features (greater than 1 mm spatial wavelength) when sliding. A lower value indicates no detectable macrotexture features (e.g silk) and a higher value indicates more noticeable macrotexture features (e.g. burlap).
- mCO: Macrotexture Coarseness (Fine-Coarse) reflects the spacing of macrotexture features derived from the frequency of the above-described macrotexture vibrations when sliding. A lower value indicates a fine macrotexture just above the cutoff spatial frequency of 1 mm (e.g window screen mesh) and a higher value indicates a coarse macrotexture (e.g. tile mosaic). In the event of a surface with no macrotexture (mTX is low, or smooth) this measurement tends to be very low and meaningless.
- mRG: Macrotexture Regularity (Random-Regular) reflects the degree to which macrotexture features repeat periodically (as opposed to randomly) as derived from the frequency of the above-described macrotexture vibrations when sliding. A lower value indicates macrotexture features that are randomly spaced (e.g. sponge) while a higher value indicates macrotexture features that are regularly spaced (e.g. window screen mesh). In the event of a surface with no macrotexture (mTX is low, or smooth) this measurement tends to be very low and meaningless.
Microtexture
- μRO: Microtexture Roughness (Smooth-Rough) reflects the intensity of high-frequency tactile vibrations arising from small-scale features (less than 1 mm spatial wavelength) when sliding. The filters used in this frequency band have been designed to reflect the sensory capabilities of the Pacinian corpuscles in the human skin, which are also sensitive to features of this size. A lower value indicates a smoother surface (e.g. glass) while a higher value indicates a rougher surface (e.g. denim). This is different from traditional measurements of surface roughness (e.g. Ra values) and is more reflective of the mechanisms of human roughness perception.
- μCO: Microtexture Coarseness (Fine-Coarse) reflects the spacing of microtexture features derived from the frequency of the above-described microtexture vibrations when sliding. A lower value indicates a fine surface (e.g. bedsheet) and a higher value indicates a coarse surface (e.g. denim). In the event of a surface with no microtexture roughness ( μRO is low: smooth) this measurement tends to be meaningless.
Friction
- fST: Tactile Stiction (Weak-Gripped) reflects the level of effort required to initiate sliding derived from the force required to start motion over the surface. A low value indicates a surface that weakly resists initial sliding movement (e.g. Teflon) and a higher value indicates a surface that has more grip and requires more effort to begin sliding (e.g. rubber).
- fRS: Sliding Resistance (Slippery-Resistive) reflects the level of effort required to continue sliding after it has been initiated, derived from the force required to maintain velocity. A low value indicates a slippery surface (e.g. Teflon) and a higher value indicates a surface more resistive to continued sliding (e.g. sandpaper). This is conceptually similar to dynamic friction.
Compliance
- cCM: Tactile Compliance (Rigid-Compliant) reflects the deformation observed for the BioTac and surface under load. A lower value indicates a stiffer surface (e.g. rigid glass) while a higher value indicates a more compliant surface (e.g. foam rubber). Due to the compliance of the BioTac sensor, this property is not identical to the Elastic modulus but similar in concept.
- cDF: Local Deformation (None-Deformable) reflects the way a surface deforms or wraps around the BioTac when pushing into a surface. A low value is nondeformable; a high value deforms and wraps around the BioTac. A surface that can be depressed but does not wrap (e.g. metal compression spring) would have a low value cDF while a surface that can be depressed and wraps around the BioTac (e.g. foam rubber) would have a high value. This property is not identical to hardness but similar in concept.
- cDP: Damping (Springy-Damped) reflects the hysteresis between loading and unloading. A low value indicates that a surface quickly rebounds to its original shape and is more spring-like (e.g. silicone elastomer); a high value indicates that the surface rebounds slowly to its original shape (e.g. memory foam).
- cRX: Relaxation (Resilient-Relaxed) reflects the decay of force while pressing and holding for a period of time. A low value indicates that the surface maintains resistance force while deformed (e.g. silicone elastomer); a high values indicates that the surface relaxes into deformed shape and does not continue to provide resisting force (e.g. memory foam).
- cYD: Yielding (None-Yielding) reflects the degree to which a surface stays deformed after released. A low value indicates that the surface returns to its original shape completely (e.g. rubber) while a high value indicates that the surface tends not return to the original shape completely (e.g. clay)
Thermal
- tCO: Thermal Cooling (Warm-Cool) reflects the degree of heat transfer from the heated BioTac into a surface when making initial contact. A low value indicates a surface that feels warmer and does not draw as much heat (e.g. foam) while a high value indicates a surface that feels cooler and draws a lot of heat from the sensor (e.g. copper). Note that for the lowest values of tCO (<10), the material is actually acting like a thermal insulator that is less conductive than ambient air, so the BioTac is actually warming rather than cooling.
- tPR: Thermal Persistence (Transient-Persistent) reflects the sustained duration for which thermal cooling continues. A low value indicates that these effects only exist for a short duration (e.g. a thin veneer of highly conductive material on a thermal insulator) while a larger value indicates that this cooling persists (e.g. block of copper). For objects that do not have very much thermal cooling or are actually insulative (low tCO) this value tends to be meaningless.
Adhesive
- aTK: Adhesive Tack (None-Adhesive) reflects the adhesive forces a surface exhibits on the sensor when breaking contact (i.e. negative contact force). A low value indicates that the surface does not have adhesive tack and the sensor is easy to lift off the surface while a larger value indicates that the surface has more adhesive tack and pulls downward on the BioTac while it is lifted to break contact (e.g. adhesive tape). This property tends to be unstable as contaminants build up on adhesive surfaces.
