Functional buckling behavior of silicone rubber shells for biomedical use

Area of Science:

• Biomaterials Engineering
• Mechanical Engineering
• Medical Device Design

Background:

• Soft elastic biomaterials offer design simplification and cost reduction in medical devices compared to traditional hard materials.
• Functional bi-stable buckling, a mechanism enabled by soft materials, has been underexplored in small-scale silicone rubber shells within physiological parameters.
• The study investigates the feasibility and predictability of functional buckling in silicone shells for physiological applications, using an automatic speech valve as a model.

Purpose of the Study:

• To investigate the functional elastic buckling behavior of small-sized silicone rubber shells under physiological pressure conditions.
• To determine if existing theories can accurately predict the buckling and reverse buckling pressures of these shells.
• To explore the influence of geometric configurations, such as hinged and double-hinged boundaries, on buckling characteristics.

Main Methods:

• Fabrication of silicone rubber spherical shells (30mm diameter) with varying hinged boundary conditions.
• Application of controlled air pressure loading to induce buckling and reverse buckling.
• Systematic testing of twelve geometric configurations and comparison of experimental data with theoretical predictions.

Main Results:

• Buckling and reverse buckling pressures demonstrated a linear relationship with shell thickness and height.
• Reverse buckling pressures were consistently lower than normal buckling pressures.
• Secondary hinges were observed to modify buckling pressure ratios and promote symmetrical buckling, with all configurations functioning within physiological pressure ranges.

Conclusions:

• Functional bi-stable buckling is achievable in silicone rubber shells at adjustable properties suitable for the physiological pressure range.
• The study provides predictive relations and equations for the buckling behavior of these shells.
• The findings support the potential application of this buckling mechanism in medical devices, such as automatic speech valves.