#pdms

Chip-free wireless sensors could reduce environmental impact of electronic tags

A more sustainable new form of electronic tag could help reduce the vast environmental impact caused by single-use RFID technologies, researchers say. Engineers from the University of Glasgow have developed the new wireless tag system, which can identify objects and measure temperature without the use of microchips. Instead, the tags use inexpensive coils and a sensing material made from a form of silicon rubber called PDMS and carbon fibers. The coils, smaller than the ones found in credit cards, absorb electromagnetic signals from a hand-held reader using electromagnetic waves. The researchers say their new, less wasteful tags could help reduce the retail sector's reliance on RFID chips, which uses more than 10 billion tags each year. Most tags are used just once, and end up in a landfill without appropriate recycling of the electronics.

Strong carbon fiber artificial muscles can lift 12,600 times their own weight

The pull-up, an exercise dreaded by most, answers a basic question: are your muscles strong enough to lift your own body weight?

Some Illinois researchers working on artificial muscles are seeing results even the fittest individuals would envy, designing muscles capable of lifting up to 12,600 times their own weight.

Assistant professor of mechanical science and engineering Sameh Tawfick, Beckman postdoctoral fellow Caterina Lamuta, and Simon Messelot recently published a study on how to design super strong artificial muscles in the journal Smart Materials and Structures. The new muscles are made from carbon fiber-reinforced siloxane rubber and have a coiled geometry.

These muscles are capable of not only lifting up to 12,600 times their own weight, but also supporting up to 60 MPa of mechanical stress, providing tensile strokes higher than 25% and specific work of up to 758 J/kg. This amount is 18 times more than the specific work natural muscles are capable of producing. When electrically actuated, the carbon fiber-based artificial muscles show excellent performance without requiring a high input voltage: the authors showed how a 0.4 mm diameter muscle bundle is able to lift half a gallon of water by 1.4 inches with only 0.172 V/cm applied voltage.

Combining experts and automation in 3D printing

Researchers in Carnegie Mellon University's College of Engineering have developed a novel approach to optimizing soft material 3-D printing. The researchers' Expert-Guided Optimization (EGO) method combines expert judgment with an optimization algorithm that efficiently searches combinations of parameters relevant for 3-D printing, enabling high-fidelity soft material products to be printed.

The researchers -- which include lead author Sara Abdollahi, a Ph.D. student in biomedical engineering; Adam Feinberg, associate professor of biomedical engineering and materials science and engineering; Alex Davis, assistant professor of engineering and public policy; and Dietrich College of Humanities and Social Sciences Professor John Miller -- designed the EGO method to optimize high quality 3-D prints of soft materials.

In their paper, "Expert-guided optimization for 3D printing of soft and liquid materials," which was recently published in PLOS One, the researchers demonstrate the EGO method using liquid polydimethylsiloxane (PDMS) elastomer resin, a material often used in wearable sensors and medical devices. The researchers used a printing method called freeform reversible embedding (FRE), in which soft materials are deposited within a gel support bath.

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Nature-inspired material uses liquid reinforcement

Nanoengineers create liquid-solid composites using clues from nature

Materials scientists at Rice University are looking to nature -- at the discs in human spines and the skin in ocean-diving fish, for example -- for clues about designing materials with seemingly contradictory properties -- flexibility and stiffness.

In research appearing online in the journal Advanced Materials Interfaces, graduate student Peter Owuor, research scientist Chandra Sekhar Tiwary and colleagues from the laboratories of Rice Professor Pulickel Ajayan and Jun Lou found they could increase the stiffness, or "elastic modulus," of a soft silicon-based polymer by infusing it with tiny pockets of liquid gallium.

Such composites could find use in high-energy absorption materials and shock absorbers and in biomimetic structures like artificial intervertebral discs, they said.

Owuor said conventional wisdom in composite design for the past 60 years has been that adding a harder substance increases modulus and adding a softer one decreases modulus. In most instances, that's correct.