Design of Semirigid Wearable Devices Based on Skin Strain Analysis

Abstract

Nowadays, both usability and comfort play a key role in the development of medical and wearable products. When designing any device that is in contact with the human body, the mechanical behaviour of the embraced soft tissue must be known. The unavoidable displacement of the soft tissue during motion may lead to discomfort adn, thus, the withdrawal of the wearable product. This work presents a new methodology to design and test a wearable device based on the measurement of the dynamic skin strain field. Furthermore, from this field, the anatomical lines with minimum strain (Lines of non extension, LoNEs) are calculated to design the structural parts of the wearable device. Whith this new criteria, the resulting product is not only optimized to reduce the friction in skin-device interface, but fully personalized to the patient's morphology and motion. The methodology is applied to the design of an ankle-foot wearable orthosis for subjects with ankle dorsiflexors muscles weakness due to nervous system disorders. The results confirm that the use of LoNEs may benefit the design of products with a high interaction with the skin.

Advances in Orthotic and Prosthetic Manufacturing: A Technology Review

“…A sensor measures the distance to the surface, typically a charge-coupled device or a position sensitive device. For static objects, data is collected in relation to an internal coordinate system and, for dynamic conditions, the position of the scanner must be determined to correctly define the point cloud [47]. Structured light methods use a projector-camera system with pre-defined light patterns projected on the moving object.…”

Design, Control, and Assessment of a Synergy-Based Exosuit for Patients with Gait-Associated Pathologies

“…In this preliminary version, customized thigh pads and ankle braces were used to place the anchor points at different positions to test different configurations. In the future, it will be necessary to replace these elements with usercentered design garments, using concepts such as lines of nonextension (LoNEs) [30,31], to improve comfort. Regarding the overall working principle, as soon as the exosuit is switched on, the wearer is made to stand still, while a few samples are taken from the IMUs to establish a baseline reading to characterize the particular user's stance and also to account for any variances in IMU position relative to the leg, etc., in order to minimize its effect on the control algorithm.…”

Integration of capillaric strain sensors toward recognition of human movements

“…Obropta et al used 3D DIC for detecting lines of no extension on the skin surface of a large upper body area during arm movements [44]. Barrios-Muriel et al has used SSF to design wearables with better comfort [45]. Chen et al employed mirror-assisted multi-view DIC to measure strain maps on human skin and deformation [46].…”

“…44 Barrios-Muriel et al have used the SSF to design wearables with better comfort. 45 Chen et al employed mirror-assisted multi-view DIC to measure strain maps on the human skin and deformation. 46 Alternatively, 2D DIC is preferred for the analysis of planar samples due to its simplicity.…”