Posts Tagged ‘micromachines’
Microbots Spin Molecules to Swim Through Blood Vessels and Make Repairs
The motors turn on, as it were, when one side of a Janus microsphere grows a suite of molecules on one side. Eventually, the lopsided sphere creates an osmotic gradient. As fluid flows toward the area with fewer particles, the whole sphere moves.
Janus microspheres have two distinct hemispheres made of different substances. In this case, one half is gold and the other is silicon dioxide. Researchers led by Ayusman Sen at Penn State attached a molecule called a Grubbs catalyst, which induces polymerization, to the silica side. Then they added a monomer, which the catalyst strings into long chains. The monomer strings gather on the SiO2 side, which that sends the whole sphere moving the opposite direction.
To prove it can deliver substances, the scientists filled a gel substance with the monomer, which was slowly leached out. The micromotors moved toward the gel stream, like a single-celled organism following a trail of nutrient breadcrumbs.
This could be a handy, electricity-free way to send tiny devices into the bloodstream to do various tasks. The microspider motors could drive nanorobots that destroy tumor cells, or they could target drugs to specific organs more quickly, for instance.
The research is reported in the journal Angewandte Chemie.
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New Fuel-Free System Moves Objects By Dissolving Them At One End and Rebuilding Them At The Other
The method requires an electrical current to work, so it’s not completely energy-free, but it could be an effective way to propel nanoscale materials inside nano- or micro-devices. It could even lead to disappearing magical motors that vanish once their task is complete.
The process is based on bipolar electrochemistry, according to researchers in France. In an electric field, one end of a metallic object grows while the other end dissolves. This self-regeneration essentially allows an object to move at the excruciatingly slow speeds of 100 micrometers per second.
It’s difficult to make nanoscale chemical reactions that are powerful enough to move something in a specific direction. Scientists are studying several possibilities, including “fuel molecules” that decompose to move an object forward. Bipolar electrochemistry is a new method that could be simpler and easier to control. It involves exposing a metal material to an electrical field so that it has a positive charge at one end and a negative charge at the other. According to CNRS, the French National Center for Scientific Research, this enables chemical reactions to occur on both ends of an object — one end is oxidized and dissolves, and deposited at the other end. A paper describing the method appears in the Journal of the American Chemical Society.
The main advantage is that it requires no conventional fuel, but researchers say its adaptability is an added bonus. You could control an object’s speed by varying the energy potential between the electrodes, and you could even make micromotors that push objects in a predetermined direction and then vanish.
The approach could provide propulsion for nanodevices used in medicine and other applications, according to CNRS.
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Micro-Supercapacitors Could Boost Lifetime of Portable Devices
The new micro-supercapacitors have at least double the energy storage density of the best supercapacitors
Batteries can store electrical energy in chemical reactants and typically have higher energy storage densities than supercapacitors. But supercapacitors simply store energy as electrical charge and can endure a charge-discharge cycle millions of times, compared to just several thousand cycles for batteries.
"We have known for some time that supercapacitors are faster and longer-lasting alternatives to conventional batteries, so we decided to see if it would be possible to incorporate them into microelectronic devices and if there would be any advantage to doing so," said Yury Gogotsi, a materials engineer at Drexel University in Philadelphia.
Gogotsi worked with John Chmiola, a chemist at the Lawrence Berkeley National Laboratory. They etched electrodes made of monolithic carbon film into a conducting substrate of titanium carbide, and created micro-supercapacitors with an energy storage density at least twice as much as existing supercapacitors.
That suggests micro-supercapacitors can more efficiently store energy within ever-smaller physical spaces. By directly integrating the supercapacitors with the devices they power, researchers can boost the density of microelectronic devices and allow for more functionality, less complexity and enhanced redundancy.
The almost infinite cycle life of micro-supercapacitors would make them ideal for capturing and storing energy from renewable resources, and for on-chip operations to make electronic devices longer lasting, according to Chmiola.
More short-term applications would likely combine micro-supercapacitors with micro-batteries for the most possible energy storage. But the researchers eventually hope to boost super-capacitor storage to levels closer to batteries, and hold onto the supercapacitor edge regarding charge-discharge cycles. The looks bright indeed -- and we can think of a which could use more juice while doing recon.
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