Dynamic Mechanical Materials for Orthotic and Prosthetic Applications

Case Western Reserve University, Cleveland OH

Investigators

Abstract

PI: Weder, Christoph and Rowan, Stuart Proposal Number: 0828155 Polymeric materials are used in many orthotic and prosthetic devices - examples range from ankle-foot orthoses to prosthetic limbs to neural electrodes. Significant activities are focused on the development of new medical devices which are referred to as 'active', 'smart', or 'intelligent', for example knee-ankle-foot orthoses that rely on elastic actuators to enhance knee extension, adjustable and expandable prostheses that permit expansion for growing children, and active brace systems for the treatment of scoliosis. Rather interestingly, the polymers employed in these new devices merely serve a passive role. Adaptive polymers with electrically switchable mechanical properties would have a tremendous impact on the development of orthotic and prosthetic devices, allowing for simpler and more compact design and enhanced functionality. Proposed is an interdisciplinary research program focused on the design, fabrication, investi-gation and application of a novel family of synthetic polymer nanocomposites with electrically controllable mechanical properties. The targeted materials mimic the architecture and switching mechanism found in the deep dermis of sea cucumbers and build on the team's recent success in the development of chemo-responsive, dynamic mechanical materials. The proposed nano-composites will be comprised of a low-modulus matrix polymer and rigid nanofibers, which are decorated with electroactive molecules. The electrically-controlled switching state of these molecules governs fiber-fiber and fiber-matrix interactions and thereby the overall mechanical properties of the material. Uniting researchers with expertise in supramolecular chemistry, polymer science and engineering, and orthopaedics and rehabilitation, the proposed research will embrace (i) the design, synthesis and investigation of novel adaptive nanocomposites, (ii) the combination of rheological studies and theoretical models to develop a predictive understanding for the structure-property relationship of these adaptive materials, (iii) the fabrication and testing of electromechanical elements based on the new polymers, and (iv) the use of the latter in 'smart' brace systems for dynamic trunk control. The research is complemented with educational elements that amalgamate research and education and provide stimulating experiences at both the undergraduate and graduate levels. The interdisciplinary nature and the integrative research approach will provide students with an unusually broad education. The main approach to integrated research and education are Project Research Teams, which include minority high school students, undergraduate and graduate students, and faculty. Minority high school students will be integrated through interactions with a suburban school district. Other elements include a pioneering outreach activity in collaboration with the Cleveland+ Biomimicry Design Collaborative, a program of the Northeast Ohio Entrepreneurs for Sustainability (E4S) initiative. Intellectual merit: On account of its exemplary and fundamental character the proposed interdisciplinary research program will provide a broad intellectual basis for the future design, synthesis and manufacturing of advanced functional materials based on active nanostructures. The development of polymer materials with electrically switchable mechanical properties is a breakthrough achievement and the targeted materials and devices will enable a range of technologically relevant applications. The initially targeted applications are orthotic devices with controllable characteristics, but the novel materials also enable many other important applications, for example adaptive protective clothing, and active vibration dampening systems. Broader impact: The proposed research will yield blueprints for advanced polymers with a substantial application potential. The integrated research approach will provide students with broad educational experiences. The high-school and undergraduate research and outreach activities are designed to increase the fraction of underrepresented minorities in engineering, to integrate research and education, to provide an exciting learning environment, and to create teaching opportunities for graduate researchers. The partnership with E4S will enhance the scientific and technological education of local entrepreneurs that are interested in building the social and knowledge infrastructure for Biomimicry in the region.