ABSTRACT
Loss of an upper limb exerts a negative influence on an individual's ability to perform their activities of daily living (ADLs), reducing quality of life and self-esteem. A prosthesis capable of performing basic ADLs functions has the capability of restoring independence and autonomy to amputees. However, current technologies present in robotic prostheses are based on rigid actuators with several drawbacks, such as high weight and low compliance. Recent advances in robotics have allowed for the development of flexible actuators and artificial muscles to overcome the limitations of rigid actuators. Dielectric elastomer actuators (DEAs) consist of a thin elastomer membrane arranged between two compliant electrodes capable of changing dimensions when stimulated with an electrical potential difference. In this work, we present the design and testing of a finger prosthesis driven by two DEAs arranged as agonist-antagonist pairs as artificial muscles. The soft actuators are designed as fiber-constrained dielectric elastomers (FCDE), enabling displacement in just one direction as natural muscles. The finger prosthesis was designed and modeled to show bend movement using just one pair of DEAs and was made of PLA in an FDM 3D printer to be lightweight. The experimental results show great agreement with the proposed model and indicate that the proposed finger prosthesis is promising in overcoming the limitations of the current rigid based actuators.
ABSTRACT
Soft pneumatic artificial muscles are a well actuation scheme in soft robotics due to its key features for robotic machines being safe, lightweight, and conformable. In this work, we present a versatile vacuum-powered artificial muscle (VPAM) with manually tunable output motion. We developed an artificial muscle that consists of a stack of air chambers that can use replaceable external reinforcements. Different modes of operation are achieved by assembling different reinforcements that constrain the output motion of the actuator during actuation. We designed replaceable external reinforcements to produce single motions such as twisting, bending, shearing and rotary. We then conducted a deformation and lifting force characterization for these motions. We demonstrated sophisticated motions and reusability of the artificial muscle in two soft machines with different modes of locomotion. Our results show that our VPAM is reusable and versatile producing a variety and sophisticated output motions if needed. This key feature specially benefits unpredicted workspaces that require a soft actuator that can be adjusted for other tasks. Our scheme has the potential to offer new strategies for locomotion in machines for underwater or terrestrial operation, and wearable devices with different modes of operation.
ABSTRACT
In this work, the influence of carbon nanotubes (CNTs) content on the mechanical and electrical properties of four series of polymeric matrix were made and their cytotoxicity on cells was evaluated to consider their use as a possible artificial muscle. For that, polymer composite yarns were electrospun using polymeric solutions at 10 wt.%. of poly(styrene-co-acrylonitrile) P(S:AN) and P(S:AN-acrylic acid) P(S:AN-AA) at several monomeric concentrations, namely 0:100, 20:80, 40:60, 50:50 (wt.%:wt.%), and 1 wt.% of AA. Carbon nanotubes (CNTs) were added to the polymeric solutions at two concentrations, 0.5 and 1.0 wt.%. PMCs yarns were collected using a blade collector. Mechanical and electrical properties of polymeric yarns indicated a dependence of CNTs content into yarns. Three areas could be found in fibers: CNTs bundles zones, distributed and aligned CNTs zones, and polymer-only zones. PMCs yarns with 0.5 wt.% CNTs concentration were found with a homogenous nanotube dispersion and axial alignment in polymeric yarn, ensuring load transfer on the polymeric matrix to CNTs, increasing the elastic modulus up to 27 MPa, and a maximum electrical current of 1.8 mA due to a good polymer-nanotube interaction.
ABSTRACT
The flexibility in polymer properties has allowed the development of a broad range of materials with electroactivity, such as intrinsically conductive conjugated polymers, percolated conductive composites, and ionic conductive hydrogels. These smart electroactive polymers can be designed to respond rationally under an electric stimulus, triggering outstanding properties suitable for biomedical applications. This review presents a general overview of the potential applications of these electroactive smart polymers in the field of tissue engineering and biomaterials. In particular, details about the ability of these electroactive polymers to: (1) stimulate cells in the context of tissue engineering by providing electrical current; (2) mimic muscles by converting electric energy into mechanical energy through an electromechanical response; (3) deliver drugs by changing their internal configuration under an electrical stimulus; and (4) have antimicrobial behavior due to the conduction of electricity, are discussed.