Every 30 seconds, a diabetic patient in the world is forced to have his or her leg amputated due to the disease. These patients often suffer from neuropathy and loss of sensation in the lower extremities, and therefore are unable to detect damage caused by ill-fitting prostheses, leading to amputation. Canadian scientists recently demonstrated in the American Physical Society journal Biomicrofluidics their development of a new prosthesis using microfluidic-supported flexible robotic technology that promises to greatly reduce skin ulcers and pain in patients with ankle and knee amputations.
Prostheses typically used after amputation in diabetic patients include fabric and silicone pads that can be added or removed to improve fit. Amputees need to replace the pads manually, but neuropathy can cause poor sensation, making this difficult and potentially causing more damage to the remaining limb.
Rather than creating a new type of prosthetic socket, the typical silicon/fabric limb liner was replaced by a single-layer liner that integrates soft fluid actuators as an interface layer, the University of Waterloo researchers said. These actuators are designed to inflate the residual limb to different pressures based on its anatomy to reduce pain and prevent pressure sores.
The research team developed a method to miniaturize the actuators. They designed a microfluidic chip with 10 integrated pneumatic valves to control each actuator. The entire system is controlled by a miniature air pump and two solenoid valves that supply air to the microfluidic chip. The control box is small and light enough to be worn as part of a prosthesis.
The research team, which included medical personnel with extensive experience in prosthetic devices, provided detailed data on the pressure required in the prosthetic socket. The team took extensive measurements of the contact pressures provided by each actuator and compared these with the required pressures for the working prosthesis.
The results found that all 10 actuators produced pressures within the required range, suggesting that the new device will work well in practical application scenarios. The research team plans to conduct further studies to integrate the pressure sensors directly into the prosthetic liner, possibly also using the newly introduced knitted soft fabric containing the pressure sensing material.
