A small plastic strip can do “weight training” to effortlessly lifts many times its own weight, driven by cyclic changes in the humidity of the surrounding air.
Polymer materials that perform work in response to a chemical or physical stimulus are often called “artificial muscles”.
These are very interesting for a number of applications, including controlling the movements of “gentler” robots. All components of such robots need to be soft and flexible so that they don’t damage delicate objects and can move in tight spaces.
The arm developed by researchers working with Michael J. Serpe at the University of Alberta is constructed in the following way: A strip of a plastic film is coated with chromium and gold, followed by a microgel monolayer.
Microgels are cross-linked polymers that swell up with a solvent such as water to form gel particles with diameters of up to a few micrometers. The Canadian researchers used negatively charged microgels made from poly(N-isopropylacrylamide) and acrylic acid. A solution containing polycations is deposited onto the gel. These act as positive counterions.
When this system dries out, the hydrophobic interactions between the hydrocarbon regions of the polymer cations increase considerably, which causes the layer containing the polymer cations to shrink. Because the electrostatic attraction between the polycations and the microgel is very strong and the microgel layer is very firmly attached to the coated sheet of plastic, the ends of the strip bend upwards and the system curls up. When the air humidity is increased, it stretches back out.
The researchers hung one of their strips up in a chamber with controlled humidity conditions. By changing the humidity, they were able to make their artificial arm “grip” the handle of a small package and to “hold on” as it rose up. In another experiment, they hung a chain of paperclips to the end of one extended mini-arm. Cyclic changes in the humidity caused the arm to raise and lower this weight, which was 14 times as heavy as the arm itself, like a miniature weight-lifting exercise.
“Given that a human arm is approximately 6.5 % of the total mass of the human body, this is equivalent to a 75 kg human with a single arm that is capable of lifting 68.3 kg,” Serpe says to illustrate the strength of his miniature arm. Even hanging 52.2 g of weight from a curled-up arm was not enough to stretch it out. If a 75 kg human wanted to achieve a similar feat, he would have to keep his arm bent even with 1280 kg pulling on it.About the Author
Author: Michael J. Serpe, University of Alberta, Edmonton (Canada), http://www.chemistry.ualberta.ca/FacultyandStaff/Faculty/MichaelSerpe.aspxTitle: Polymer-Based Muscle Expansion and Contraction
The original article is available from our online pressroom at http://pressroom.angewandte.org.
Michael J. Serpe | Angewandte Chemie
Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard
New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences