Skin Stretch Strain

Tests with a benchtop skin stretch apparatus are being conducted to characterize skin stretch as a tactile display method suitable for wireless applications such as wearable medical or activity monitors. Tests to date indicate that skin stretch may be less sensitive to “masking” effects from rapid human motion (e.g. when walking or jogging on a treadmill) than vibrations, which are commonly used for portable devices. Understanding how skin stretch can be applied and what the best method of stretch application is important to designing an intuitive and compact skin stretch haptic interface.

One important aspect of skin stretch is understanding how the skin can be stretched, and how different methods of applying stretch differ from each other, both in terms of mechanics as well as perception.

A simple experiment was completed to measure how skin moves with different types of skin stretch applied. The first is linear skin stretch, where one contact point is moved along a single axis. The second is rotational skin stretch. In this case, rotational stretch is applied by rotating a contact point with a center of rotation located approximately 0.5 inches from the center of the contact point.

Because a portable haptic device would inevitably need to be strapped to some portion of the body, the effect of adding constraints to limit the area of skin stretch was also observed.

Linear Skin Stretch, unconstrained-------------------------------Linear Skin Stretch, constrained

Rotational Skin Stretch, unconstrained-------------------------Rotational Skin Stretch, constrained

Perception

References

• Agache1980.pdf: - torque (single point twists) applied to skin on subjects of varying ages, forearm

• DynamicFinlay_1970.pdf: -torsional skin stretch (single point twist), discusses how using tape effects measurements

• ManschottBrakke_Measurement1988.pdf: - uniaxial stretch on calf

• ManschottBrakke_Model_1988.pdf: - same as above- presents models using data from above paper

• Mechanical_Behavior_Henriks_2005_thesis.pdf: - thesis on mechanical properties of skin using suction/ultrasound/advanced imaging techniques. Provides good background on skin properties and previous work

• TissueMechanics1975.pdf: - discusses basic properties of tissues and behaviors.

• TorsionalElasticity_Sanders1973.pdf: - torsional skin stretch, various ages