Amplifying and Leveraging Generated Force Upon Heating and Cooling in SMA Knitted Actuators.

This work reexamines traditional shape memory alloy (SMA) loading paths commonly used in SMA-based actuator applications and presents a novel, superimposed condition in which SMA generates substantial forces upon heating and cooling. This atypical effect, which is investigated with a textile-based actuator, was found to be prominent at the completion of material phase transformation, at which point thermal expansion/contraction became the dominant force-generating mechanism. We demonstrate that amplification of generated forces can be accomplished by varying the applied thermal load, applied structural strain, as well as actuator architecture.

Design and Control of Reduced Power Actuation for Active-Contracting Orthostatic Intolerance Garments.

Active-contracting fabrics are an emerging innovation that could revolutionize aerospace compression garment technology, notably orthostatic intolerance garments (OIG), by contracting on demand. Prior research has found that active-contracting fabrics, specifically weft knit garter fabric architectures constructed with shape memory alloy (SMA) filaments, can apply 2-54 mmHg on the body (single-layer construction) or 4-104 mmHg (double layer construction), depending on body radius. Prior garment prototyping and performance validation efforts have been conducted with commercially available Flexinol® wire with an actuation finish temperature of 90°C, a temperature that is not appropriate proximal to the human body.

Dynamic Countermeasure Fabrics for Post-Spaceflight Orthostatic Intolerance.

Aerospace orthostatic intolerance garments (OIG) have historically been pneumatic (e.g., NASA's antigravity suit), an approach that inhibits mobility and requires connection to an air supply.

EXPERIMENTAL INVESTIGATION OF THE MECHANISMS AND PERFORMANCE OF ACTIVE AUXETIC AND SHEARING TEXTILES.

Anisotropic textiles are commonly used in wearable applications to achieve varied bi-axial stress-strain behavior around the body. Auxetic textiles, specifically those that exhibit a negative Poisson's ratio (v), likewise exhibit intriguing behavior such as volume increase in response to impact or variable air permeability. Active textiles are traditional textile structures that integrate smart materials, such as shape memory alloys, shape memory polymers, or carbon nanotubes, to enable spatial actuation behavior, such as contraction for on-body compression or corrugation for haptic feedback.

Functionally Graded Knitted Actuators with NiTi-Based Shape Memory Alloys for Topographically Self-Fitting Wearables.

Advances in actuating fabrics can enable a paradigm shift in the field of smart wearables by dynamically fitting themselves to the unique topography of the human body. Applications including soft wearable robotics, continuous health monitoring, and body-mounted haptic feedback systems are dependent upon simultaneous body proximity and garment stiffness for functionality. Passive fabrics and fitting mechanisms are unable to conform around surface concavities and require either high elasticity or a multiplicity of closure devices to achieve garment fit.

ACTIVE-CONTRACTING VARIABLE-STIFFNESS FABRICS FOR SELF-FITTING WEARABLES.

Self-fitting is the ability of a wearable, garment or body-mounted object to recover the exact shape and size of the human body. Self-fitting is highly desirable for wearable applications, ranging from medical and recreational health monitoring to wearable robotics and haptic feedback, because it enables complex devices to achieve accurate body proximity, which is often required for functionality. While garments designed with compliant fabrics can easily accomplish accurate fit for a range of body shapes and sizes, integrated actuators and sensors require fabric stiffness to prevent drift and deflection from the body surface.

Exploiting Textile Mechanical Anisotropy for Fabric-Based Pneumatic Actuators.

Knit, woven, and nonwoven fabrics offer a diverse range of stretch and strain limiting mechanical properties that can be leveraged to produce tailored, whole-body deformation mechanics of soft robotic systems. This work presents new insights and methods for combining heterogeneous fabric material layers to create soft fabric-based actuators. This work demonstrates that a range of multi-degree-of-freedom motions can be generated by varying fabrics and their layered arrangements when a thin airtight bladder is inserted between them and inflated.

Assisting hand function after spinal cord injury with a fabric-based soft robotic glove.

Background: Spinal cord injury is a devastating condition that can dramatically impact hand motor function. Passive and active assistive devices are becoming more commonly used to enhance lost hand strength and dexterity. Soft robotics is an emerging discipline that combines the classical principles of robotics with soft materials and could provide a new class of active assistive devices.