Abstract

A comprehensive background is herein presented for lumbar skin strain and its effect on skin adhered wearable (SAW) products. A background of the development of computational models of the interaction of skin and novel SAWs being researched is also presented. These include products involving the use of high deflection strain gauges to measure skin strain during functional movements (FMs) as a method to address the complicated phenotyping of the etiological causes of low back pain (LBP). The background concludes with the mathematical calculation of the principal skin strain magnitudes and orientations using retroreflective marker coordinate data in a motion capture lab setting and the potential role of principal skin strain on the post-operative management of wounds to accelerate healing and minimize infection and scarring. The mechanics response of lumbar skin among 30 participants was measured during various FMs, for which high strain movements (Flexion, Flexion right/left, Sit To Stand) exhibited principal strain magnitudes repeatedly above 50% while others (Rotation right/left, Lateral Bending right/left, Extension, and Extension right/left) exhibited magnitudes repeatedly below 50%. Principal strain orientation was presented in easily visualizable mappings that demonstrated minimal variability both within and between participants for a given FM. Principal strain rates were measured, ranging between 25% and 151% per second among movements. The mechanics response of lumbar skin was again measured for a single participant, albeit this time between bare skin and skin with a SAW; which in this example was kinesiology tape with a high deflection nanocomposite strain gauge. Results indicated very significant skin restriction during Flexion, for which a macroscopic skin strain of 65% was reduced to 22% because of the KT tape and additionally down to 13% because of the addition of the sensor (on top of the KT tape). A FEM was created based off this scenario, for which it was shown that the mechanical properties of skin in vitro are insufficient in representing the mechanical response of skin due to its stiffness. This was hypothesized to be due to the increased hydration (lower stiffness) of in vivo skin, for which high deformation stiffness in the literature is not available. The thesis is concluded with future research directions that would benefit the design of SAWs where high deformation is considered. Future research directions are also discussed regarding post-operative wound healing and the potential role of repeated skin strains, such as concerning scarring and infection.

Degree

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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