Diabetic foot ulcer patients are usually unaware of excessive pressure on their feet due to lost pressure sensitivity. Offloading insoles are used to alleviate foot pain. This study investigated the effect of infill pattern and infill density on plantar pressure reduction for 3D-printed insoles while walking. The study involves five infill patterns: grid, honeycomb, triangle, cubic, and gyroid, along with several infill densities ranging from 14% to 20%. The test 3D-printed thermoplastic polyurethane specimens were assessed for mechanical properties to identify suitable infill patterns for creating prototypes of insoles. The results indicated that the honeycomb infill pattern exhibited the highest maximum compression load at 50% compressive strain and has a significant area under the loading-unloading curve, signifying high energy absorption. Conversely, the gyroid infill pattern exhibited the lowest maximum compression load at 50% compressive strain and minimal energy absorption. Both infill patterns with 20% infill density were applied in 3D-printed insoles and tested on the foot plantar pressure of healthy male volunteers during walking. No statistically significant differences in plantar pressure were observed between the two infill patterns compared to walking without insoles. A reduction in plantar pressure at hindfoot was observed when using the insoles, although this change was not statistically significant.

This study examines the impact attenuation performance of airbags of different shapes, thicknesses, and internal pressures to assess their effectiveness in hip protection. Three distinct airbag shapes are examined and analyzed under different thicknesses and pressures, with experimental tests conducted to assess the relationships between thickness, pressure, stiffness, and impact absorption efficiency. The results reveal that increasing the thickness of the airbag significantly reduces the peak impact force, while higher internal pressure increases stiffness but does not always lead to improveδ impact attenuation. Among the three airbag shapes, the torus-shaped airbag demonstrates the lowest peak impact force and the highest impact absorption efficiency. Additionally, airbags maintained at atmospheric pressure (0 psi) exhibit the greatest impact absorption efficiency, followed by those at 3 psi and 6 psi, respectively. Comparing existing studies on traditional hip protectors, the results indicate that airbags provide a superior reduction in impact force. Unlike conventional hip protectors, which primarily rely on direct force absorption, the torus airbag employs an off-loading mechanism to dissipate impact energy, thereby enhancing its protective performance. These findings suggest that airbag-based protective systems could serve as an innovative solution for reducing fall-related injuries.