As miniaturization progresses, microrobots and nanomachines have moved beyond the realm of pure speculation. This technology requires tiny components that can respond to stimulation by undergoing controlled movements.
Piezoelectric crystals are known to make a bending motion when subjected to an electric field, however the cables required are a barrier to microscale applications or those in liquids. In the journal Angewandte Chemie, a research team led by Masahiro Irie at Rikkyo University (Tokyo, Japan) has now introduced a cable-free microrobotic arm that can be triggered to bend and stretch by light.
The tiny robotic arms are made of crystals shaped like micro- or millimeter-sized flat rods. When they are irradiated with UV light (365 nm), the rods bend toward the light source; when irradiated with visible light (>500 nm) they stretch back into their original straight shape.
What causes the bending motion? The molecules in the crystals are an organic ring system containing five rings. The central structural unit is a diarylethene group. UV light induces rearrangement of the chemical bonds (isomerization) and causes a ring closure within the molecule.
This results in the shape change of each molecule, which leads to a geometry change of the crystal. The crystal contracts, but only where it was exposed to the UV light, that is, on the outer layer of the irradiated side of the rod. This causes bending similar to that of a bimetallic strip. Visible light triggers the reverse reaction, the newly formed sixth ring opens, the original crystal structure is restored, and the crystal straightens out.
The trick lies in the mixture of two slightly different diarylethene derivatives that are present in just the right ratio. In this type of mixed crystal, the interactions between the individual molecules are weaker than those in a homogeneous crystal. The crystals can withstand over 1000 bending cycles without evidence of fatigue. Depending on the irradiation, it is possible to induce extreme bending—to the point of a hairpin shape.
In contrast to previous concepts for “molecular muscles”, this new approach offers the unique possibility of translating the motion of individual molecules to the macroscopic level. Also, unlike synthetic micromuscles based on polymers, this new microrobotic arm is wireless and responds very fast—even at low temperatures and in water.
If one end of the crystal rod is anchored, alternating irradiation with UV and visible light can be used to induce the loose end to cause a small gear to turn. It can also work as a freight elevator: If attached to a ledge, the rod can lift a weight that is over 900 times as heavy as the crystal itself. This makes it stronger than polymer muscles and equivalent to piezoelectric crystals.Author: Masahiro Irie, Rikkyo University, Tokyo (Japan), http://www.rikkyo.ne.jp/web/iriem/irielab/
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201105585
Further reports about: > Angewandte Chemie > Light-triggered microscale robotic arm > Nanomachines > Piezoelectric crystals > UV light > bimetallic strip > chemical bond > individual molecules > isomerization > microrobots > miniaturization progresses > molecular muscles > robotic arm > visible light
Scientists unlock ability to generate new sensory hair cells
22.02.2017 | Brigham and Women's Hospital
New insights into the information processing of motor neurons
22.02.2017 | Max Planck Florida Institute for Neuroscience
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
22.02.2017 | Power and Electrical Engineering
22.02.2017 | Life Sciences
22.02.2017 | Physics and Astronomy