A Sacrificial Route for Soft Porous Polymers Synthesized via Frontal Photo-Polymerization.

Within the very large range of porous polymers and a related immense scope of applications, we investigate here a specific route to design soft porous polymers with controlled porosity: we use aqueous-based formulations of oligomers with mineral particles which are solidified into a hydrogel upon photo-polymerization; the embedded particles are then chemically etched and the hydrogel is dried to end up with a soft porous polymeric scaffold with micron-scale porosity. Morphological and physical features of the porous polymers are measured and we demonstrate that the porosity of the final material is primarily determined by the amount of initially dispersed sacrificial particles. In addition, the liquid formulations we use to start with are convenient for a variety of material forming techniques such as microfluidics, embossing, etc., which lead to many different morphologies (monoliths, spherical particles, patterned substrates) based on the same initial material.

Patterning Highly Conducting Conjugated Polymer Electrodes for Soft and Flexible Microelectrochemical Devices.

There is a need for soft actuators in various biomedical applications to manipulate delicate objects such as cells and tissues. Soft actuators are able to adapt to any shape and limit the stress applied to delicate objects. Conjugated polymer (CP) actuators, especially in the so-called trilayer configuration, are interesting candidates for driving such micromanipulators. However, challenges involved in patterning the electrodes in a trilayer with individual contact have prevented further development of soft micromanipulators based on CP actuators. To allow such patterning, two printing-based patterning techniques have been developed. First, an oxidant layer is printed using either syringe-based printing or microcontact printing, followed by vapor-phase polymerization of the CP. Submillimeter patterns with electronic conductivities of 800 S·cm-1 are obtained. Next, laser ablation is used to cleanly cut the final device structures including the printed patterns, resulting in fingers with individually controllable digits and miniaturized hands. The methods presented in this paper will enable integration of patterned electrically active CP layers in many types of complex three-dimensional structures.

Knitting and weaving artificial muscles.

A need exists for artificial muscles that are silent, soft, and compliant, with performance characteristics similar to those of skeletal muscle, enabling natural interaction of assistive devices with humans. By combining one of humankind's oldest technologies, textile processing, with electroactive polymers, we demonstrate here the feasibility of wearable, soft artificial muscles made by weaving and knitting, with tunable force and strain. These textile actuators were produced from cellulose yarns assembled into fabrics and coated with conducting polymers using a metal-free deposition. To increase the output force, we assembled yarns in parallel by weaving. The force scaled linearly with the number of yarns in the woven fabric. To amplify the strain, we knitted a stretchable fabric, exhibiting a 53-fold increase in strain. In addition, the textile construction added mechanical stability to the actuators. Textile processing permits scalable and rational production of wearable artificial muscles, and enables novel ways to design assistive devices.

Smarter Actuator Design with Complementary and Synergetic Functions.

A general synthetic strategy for multifunctional actuators is presented, by confining desired functions in separate domains of interpenetrating polymer network materials. Specifically, complementary ionic actuator and shape-memory functions are demonstrated by simultaneous, orthogonal reaction pathways. Synergistic effects also allow dynamic programming and two-way linear shape-memory actuation.