Research Projects

Rationale of the research: Non-healing plantar ulcers in leprosy patients cause significant disability, and they require proper wound care and appropriate control measures to heal. To rehabilitate or treat plantar ulcers, footwear with a proper cushioning effect is emphasized to prevent excessive pressure buildup during gait. In India, all leprosy patients use the MCR insole to reduce the plantar pressure. However, MCR's energy absorption characteristics (cushioning effect), abrasive resistance, elastic recoil, and tackiness properties tend to degrade quickly. The gas-filled polymeric and memory foams also show heat retention, sagging issues, and bottoming-out effects that alter foot pressure distribution over time. Auxetic cellular structures have a negative Poisson's ratio, indicating a potential candidate for energy absorption. The auxetic structures fabricated using elastic-plastic material behavior result in permanent deformation. Further, the three-dimensional auxetic structure shows failure at the interconnected nodes under impact, compared to 2D structures. Hence, there is a need to transform the 2D auxetic cellular geometry into a suitable configuration to promote the development of auxetic insole to reduce the plantar pressure for the leprosy patients. Thus, developing auxetic structures with the right choice of material will actively seek out feasible applications under dynamic conditions with better energy absorption and recoverability. Scientific objectives: This research aims to design and develop an auxetic insole prototype for footwear to protect the plantar tissue by mitigating the ground force. The footwear with the appropriate insoles will efficiently reduce plantar pressure and prevent the recurrence of foot ulcers. Design, analysis, and testing of the prototype: The auxetic footwear insole is designed by sweeping the 2D double U-arrowhead auxetic geometry along the required foot profile. Numerical analysis (FEA) will be carried out to optimize the double-arrowhead auxetic cellular geometry based on deformation pattern and energy absorption capability. The 3D foot model will be constructed using the CBCT scan data of the leprosy patient's foot. FEA of a coupled foot and footwear model with an optimized auxetic insole will be performed to analyze the plantar pressure on the foot under static and dynamic gait conditions. The customized auxetic insole prototype will be fabricated using an SLA printer. The auxetic insole structure will be tested based on compression and shear mode under static and dynamic conditions and with reference to Indian footwear standards. The printed auxetic insole will be bonded to the conventional or existing outsole using a flexible polymer adhesive similar to the existing footwear fabrication process. Clinical trials will be carried out at TLMH (The Leprosy Mission Hospital) to prove the effectiveness of the proposed auxetic insole on leprosy patients. The clinical evaluation for leprosy patients with foot ulcers will be carried out for different age groups, body mass index, and walking speeds. The in-shoe pressure sensor device will be fabricated using PZT sensors to analyze the effect of the insole and compare it with barefoot data obtained using Podiascan. Significance: The proposed auxetic insole prototype will reduce plantar pressure by distributing and absorbing the ground force through the deformation of auxetic cell walls. Due to its symmetric configuration, the swept 2D auxetic structure will experience layer-wise deformation that reduces the peak force, shifts the force-time duration pattern during the gait cycle, and protects the plantar from excessive pressure buildup to avoid the recurrence of ulcers. This work will significantly benefit the leprosy patients during treatment and rehabilitation.