Abstract:
The evaluation of collagen architecture of the dermis in response to mechanical stimulation is important as it
affects the macroscopic mechanical properties of the dermis. A detailed understanding of the processes involved
in the alteration of the collagen structure is required to correlate the mechanical stimulation with tissue
remodeling. This study investigated the effect of cyclic frequencies i.e. low (0.1 Hz), medium (2.0 Hz), and high
(5.0 Hz) (physiological range) in the alteration of pig dermis collagen structure and its correlation with the
macroscopic mechanical response of the dermis. The assessment of the collagen structure of virgin and mechanical
tested specimens at tropocollagen, collagen fibril, and fiber level was performed using Fourier-transform
infrared-attenuated total reflection (FTIR-ATR), atomic force microscopy (AFM), and scanning electron microscopy
(SEM) respectively. After 103 cycles, a significantly higher alteration in collagen structure with discrete
plastic-type damage was found for low frequency. This frequency dependent alteration of the collagen structure
was found in correlation with the dermis macroscopic response. The value of inelastic strain, stress softening,
damage parameter (reduction in elastic modulus), and reduction in energy dissipation were observed significantly
large for slow frequency. A power-law based empirical relations, as a function of frequency and number of
cycles, were proposed to predict the value of inelastic strain and damage parameter. This study also suggests that
hierarchical structural response against the mechanical stimulation is time-dependent rather than cycledependent,
may affect the tissue remodeling.
