Artificial muscles based on coiled UHMWPE fibers with shape memory effect

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) fibers drawn at drawing ratio of 6 (pre-deformation strain 500%) demonstrating the obtained one-way shape memory effect. Artificial muscles have been manufactured in the form of coiled UHMWPE fibers. Isometric recovery stress and recovery strain of the fibers were measured during heating by using a dynamic mechanical analyzer (DMA). As a result, the fibers were capable to demonstrate large contraction of 78% (recovery strain of 93%) due to the entropic elasticity. The recovery stresses of the fibers reach up to 27 MPa. The work of stroke cycle for coiled artificial muscles with a constant stress of 1 MPa was recorded. Artificial muscles based on coiled UHMWPE fibers have a large stroke of 64 %. The structural mechanisms of muscle-like behavior were discussed.

Facile design of heat-triggered shape memory ethylene-acrylic acid copolymer/chloroprene rubber thermoplastic vulcanizates

“…In the recent decades, SMPs have gained much attention and technological interest in the academia and industry because of their superior and desirable qualities, such as low density, potentially recyclable at relatively low cost, high recoverable strain within a wide range of stimuli, transparence and easier processing [1]. As a result of their easy tailoring and programming, SMPs have been extensively applied in drug releasing systems, self-healing materials, smart fabrics, intelligent packaging, biomedical devices, sensors, and actuators [2][3][4][5][6][7], etc. SMPs are also a kind of stimuli-responsive materials, which can recover to their permanent shape from large deformations by exposure to various external stimuli such as temperature, light, pH, moisture, electric and magnetic field [2,[8][9][10][11][12][13], etc.…”

A Single Polymer Artificial Muscle Having Dual‐Mode Contractibility, Temperature Sensibility, and Trainability through Enthalpy Change

“…Polymeric materials are cheap, light weight, easy to control, and suitable for soft robots thus such artificial muscles due to their positive or negative thermal expansion become increasingly favored . However, up to now, these polymeric materials are either in the form of electroactive polymer composites or with special structures typically twisted coils . This is because, using thermal expansion or entropy change for simple materials like nylon fiber, only 4% reversible contraction can be produced .…”

“…This is because, using thermal expansion or entropy change for simple materials like nylon fiber, only 4% reversible contraction can be produced . Many thermosensitive polymer artificial muscles also require higher response temperatures, such as polyethylene fiber to be heated to 130 °C to shrink 16%, and ultra‐high molecular weight polyethylene (UHMWPE) to be heated above 150 °C to get better contraction . All these have hindered the application in areas where mild conditions apply.…”

Non-Conventional Deformations: Materials and Actuation

“…This makes these materials extremely useful where high deformations are needed (e.g., biomedicine), unlike SMAs, which have approximately 8% maximum strain [50]. The shape memory effect can also be exploited to produce artificial muscles with coiled geometries [51]. Despite the outstanding recoverable strain capacity, the applicability of SMPs is limited due to their low strength and recovery stress.…”