Leader: Luigi Bruno (UNICAL); Other collaborator(s):
This task will cover the design, development and validation of innovative materials and actuators systems for exoskeletons and prosthetics with a particular focus on nanostructured composite materials and Carbon fiber-based Twisted and Coiled Artificial Muscles (TCAMs). After mechanical and functional characterization studies, which will define a selection framework to identify the proper material(s), structural components, artificial muscles, and actuators systems will be applied to support motor rehabilitation.
Brief description of the activities and of the intermediate results:
During the reference period (November 2023-March 2024), the drafting of the review article on actuators used in upper limb wearable robotics was completed. The article was subsequently submitted and is currently undergoing review. Analysis of the upper limb's condition identified Twisted and Coiled Artificial Muscles (TCAMs) as potential candidates for innovative rehabilitation systems. Consequently, an experimental setup was designed for the production, heat treatment, and characterization of these artificial muscles. Additionally, preliminary tests were conducted to assess the performance of TCAMs in terms of force and displacement capabilities. The results demonstrated how this actuation technology could be utilized for low-load joint manipulation, such as wrist and phalanges movement. Furthermore, the thermo-mechanical behavior of TCAMs was analytically simulated, considering the actuator's geometry akin to a spring and utilizing the second theorem of Castigliano (CST). The analytical model was then implemented in Matlab. The numerical results will be compared in a subsequent phase with experimental data to establish the accuracy of the model employed. TCAMs were employed in the development of a first prototype of an active fixation mechanism for wearable exoskeletons. The system consists of a series of pulleys that accommodate the actuator's contraction and thus ensure the anchoring point's grip.
Main policy, industrial and scientific implications:
The research has several significant policy, industry, and practice implications:
Overall, the research has the potential to drive innovation in both the healthcare and robotics industries, improve rehabilitation practices, and influence policy decisions related to the integration of advanced actuation technologies into medical devices and rehabilitation equipment.
Please see the next reporting period.
An experimental setup was created for the on-site production and characterization of artificial muscles. Consequently, an experimental campaign was initiated to extrapolate the performance of the TCAMs. The tests involved single-ply artificial muscles, made from nylon 6,6 precursor filaments with an external silver layer to allow electrothermal actuation. Specifically, to understand their thermo-electro-mechanical behavior, experimental investigations were carried out by varying some fundamental production parameters, such as rotation speed, applied load, and power supply current. The results were presented in the "Biomechanics 1" session of the 53rd AIAS conference held in Naples on September 4th-7th 2024. Further experimental investigations are currently underway to complete the previously initiated campaign and verify the integrability of the TCAMs in a physical prototype of a wearable exoskeleton.
The results obtained from the experimental campaign conducted during the previous trimester enabled the initiation of a new study aimed at implementing novel actuation technology within a custom-designed exoskeletal gripping device. This device is fabricated using 3D printing techniques and incorporates silicone components to enhance ergonomic performance during use, as well as TCAMs to enable actuation. In parallel with the experimentation on the exoskeletal gripping prototype, efforts are underway to develop a thermo-electro-mechanical model capable of reproducing and predicting the behaviour of TCAMs when actuated by electrical stimulation. Specifically, the model consists of two fundamental components: an electro-thermal component designed to determine the temperature increase induced in the muscles by an electrical input and a thermo-mechanical component aimed at converting the temperature increase into the resulting axial displacement. The analytical model is entirely based on purely physical, macro-, and micromechanical considerations, thereby avoiding any reliance on empirical assumptions. The results provided by the analytical model were directly compared with experimental findings, demonstrating a high degree of accuracy. This has facilitated the drafting of a scientific article focusing on the experimental trials conducted with TCAMs and their analytical modelling.
Scientific publications
Dissemination Events