Tailored Solid-Liquid Composite for Enhanced Comfort in Orthotic Insoles
Topic(s) : Industrial applications
Co-authors :
Dayna CRACKNELL (NEW ZEALAND), Maedeh AMIRPOUR (NEW ZEALAND)Abstract :
Foot pain and discomfort often result from an uneven pressure distribution and severe tissue stresses. This can lead to tissue injuries and pressure ulcers, which people with diabetes are particularly vulnerable to. Orthotic insoles help mitigate these issues by providing cushioning to high-stress areas and correcting foot mechanics. Traditional orthotics are designed based on static pressure measurements and patient feedback. This overlooks dynamic foot movements and their temporal pressure distribution.
Recent advancements in 3D printing for orthotic insoles offer economical, efficient production with minimal waste and labour. This study utilises these advancements to design custom insoles optimised for each patient. The proposed composite outlined in this paper is a fluid-impregnated cellular structure. It combines a tailored structural stiffness and graded permeability to provide a responsive functionality that can passively redistribute pressure over the foot's irregular topology, both statically and dynamically, to maximise user comfort. The cellular structure will be regionally tailored throughout the orthotic by varying cell size, wall thickness and the unit cell aspect ratio. These properties can dictate the structural response as they affect the effective stiffness of the structure. Altering the geometry will further tailor the fluid behaviour in terms of its permeability, affecting the resistance to flow and regional energy-absorbing capabilities.
A gradient-based optimisation method determines each insole section's ideal structural and fluid properties for individual patient optimisation. The algorithm adjusts the insole’s material properties in a finite element model of the insole interacting with the foot, which is subject to dynamic loading conditions to simulate the patient's gait. The optimal material properties align with a specific structure’s geometry with a unique wall thickness, cell size and aspect ratio. These parameters are then used to design an optimal insole with a manufacturable geometry. Once the optimal insole is designed, it is printed using a stereolithography 3D printer with a highly elastic resin. The insole is then impregnated with the viscous fluid and sealed.
Solid-liquid composite orthotic insoles have the potential to improve foot comfort and prevent injuries in vulnerable patients. The custom stiffness, dynamic pressure redistribution and impact absorption capabilities are tuned to perform with the wearer as they move.
Recent advancements in 3D printing for orthotic insoles offer economical, efficient production with minimal waste and labour. This study utilises these advancements to design custom insoles optimised for each patient. The proposed composite outlined in this paper is a fluid-impregnated cellular structure. It combines a tailored structural stiffness and graded permeability to provide a responsive functionality that can passively redistribute pressure over the foot's irregular topology, both statically and dynamically, to maximise user comfort. The cellular structure will be regionally tailored throughout the orthotic by varying cell size, wall thickness and the unit cell aspect ratio. These properties can dictate the structural response as they affect the effective stiffness of the structure. Altering the geometry will further tailor the fluid behaviour in terms of its permeability, affecting the resistance to flow and regional energy-absorbing capabilities.
A gradient-based optimisation method determines each insole section's ideal structural and fluid properties for individual patient optimisation. The algorithm adjusts the insole’s material properties in a finite element model of the insole interacting with the foot, which is subject to dynamic loading conditions to simulate the patient's gait. The optimal material properties align with a specific structure’s geometry with a unique wall thickness, cell size and aspect ratio. These parameters are then used to design an optimal insole with a manufacturable geometry. Once the optimal insole is designed, it is printed using a stereolithography 3D printer with a highly elastic resin. The insole is then impregnated with the viscous fluid and sealed.
Solid-liquid composite orthotic insoles have the potential to improve foot comfort and prevent injuries in vulnerable patients. The custom stiffness, dynamic pressure redistribution and impact absorption capabilities are tuned to perform with the wearer as they move.