Mechanical Behaviour of Silicone Membranes Saturated with Short Strand, Loose Polyester Fibres for Prosthetic and Rehabilitative Surrogate Skin Applications.

Richard Arm,Tilak Dias,Arash Shahidi

doi:10.3390/ma12223647

Abstract

Silicone-based elastomers saturated with embedded, short-strand fibres are used for their ability to mimic the aesthetic qualities of skin in clinical and theatrical maxillofacial appliance design. Well-known to prostheses fabricators and technicians, the mechanical impact of fibre addition on elastomeric behaviour endures as tacit, embodied knowledge of the craft, almost unknown in the literature. To examine mechanical changes caused by fibre addition, 100 modified polydimethylsiloxane (PDMS) elastomeric compounds containing incremental amounts of loose polyester fibres were prepared and examined in a variety of mechanical tests. It was found that elasticity and strain percentage at breaking point was reduced by increasing fibre content, but Young’s modulus and ultimate tensile strength (UTS) increased. As fibre content was increased, strain hardening was seen at low strain rates, but exaggerated plastic deformation at high strain rates. PDMS hardness increased by 5 degrees of hardness (Shore-00 scale) for every additional percentage of fibres added and a strong positive linear coefficient (0.993 and 0.995) was identified to reach the hardness values given in the literature for living human skin. The apparent reorienting of loose fibres in the PDMS interrupts and absorbs stress during the loading process similar to the organic response to soft tissue loading, except in extension.

Highlights

Elastomers saturated with embedded, loose, short-strand fibres are known in clinical anaplastology and theatrical prosthesis appliance design for their ability to mimic the aesthetic qualities of skin
Our study investigates the mechanical behaviour of fibre filled poly-di-methyl-siloxane elastomeric gel (PDMS) viscoelastic gel membranes, which identify with a variety of standard, repeatable mechanical tests that explore the relationship between synthetic (PDMS composites) and biological fibrous membranes
Throughout this study, we referred to PlatSil® Gel 10 and additional components constituting a compound PDMS elastomer as ‘PDMS A-10’

Summary

Introduction

Elastomers saturated with embedded, loose, short-strand fibres (flock) are known in clinical anaplastology and theatrical prosthesis appliance design for their ability to mimic the aesthetic qualities of skin. Fibres such as polyester, rayon or polyamide are produced in various lengths and colours and blended with a translucent liquid, poly-di-methyl-siloxane elastomeric gel (PDMS) to reflect the translucency, intrinsic pigmentation and texture of the living equivalent. The aesthetic value of short-strand fibre flock saturation in PDMS elastomeric gels was noted by Materials 2019, 12, 3647; doi:10.3390/ma12223647 www.mdpi.com/journal/materials. Debreceni [3] and Montgomery [4], but they focused on aesthetic aspects and frequency of use in maxillofacial and theatrical prosthesis fabrication, lacking data on the behavioural implications or explicit, repeatable production methodology. Medical grade, flexible composites (ethylene-propylene-diene-monomer) used in the manufacture of medical devices such as vascular stents, heart valves cardiac assistive devices, surgical grafts and sutures draw their biomechanical design inspiration from the arrangement and function of natural fibres such collagen and elastin, that are found in their organic counterparts [5,6]

Methods

Results

Discussion

Conclusion