Shape memory alloy knitted fabrics: Functional fabrics that work

The recent rise of soft robotics, soft computing, and portable devises has highlighted the potential of functional fabrics. Functional fabrics are a novel approach to create pliable, lightweight structures with intrinsic active functionalities, enhancing diverse engineering applications by providing actuation, sensing, energy harvesting, and communication. The added functionality of such fabrics is accomplished by integrating active fibers into designed textile geometries. Active fibers can be created from various material systems including shape memory alloys (SMA), shape memory polymers (SMP), electro-active polymers (EAP), and carbon-nanotubes (CNT). Shape memory alloy knitted actuators, one type of functional fabric actuator, use shape memory alloy wire as an active fiber within a knitted textile. Utilizing the hierarchical nature of knitted architectures for tailored designs through changes in the knit grid, knit pattern, and the knitted loop itself, a variety of actuation deformations can be achieved. SMA knitted actuators can provide extension, contraction, scrolling, corrugation, and twisting upon thermal actuation. SMA knitted functional fabrics excel at traditional actuation performance metrics such as actuation displacements, actuation forces, and performed mechanical work, while achieving complex, customizable three-dimensional deformations. These multifunctional characteristics within a fabric architecture renders the potential for applications in many fields, including medical devices, rehabilitation, aerospace, and defense.