Microscopic magnetic mimic of bacterial motor

Basics of Bacterial motion (The trivial):

One of the most fascinating areas of research is biomimetics, where researchers attempt to replicate nature's creative accomplishments in the lab. For pure inspiration, look no further than to bacteria. Bacteria seem to go everywhere and do pretty much everything. The natural tendency of those of us with a inclination towards geekiness is to think of micro-robots. There are a number of natural roles that micro-robots could play, such as cleaning plaques from artery walls or defouling pipelines.

One of the problems with micro-robots has been making them small enough. One millimeter might seem small to us, but not to a bacteria. One of the primary constraints on shrinking these devices is the method of locomotion, which, because it requires moving parts, tends to be on the bulky side. This is about to change as some recent results published in Applied Physics Letters show researchers building their very own artificial bacterial flagella. In the publication, controlled motion and the simple task of separating cell-sized polystyrene beads were both demonstrated.

The bacteria flagellum is an interesting little piece of nature. Apart from providing endless amusement and artificial controversy, they also self-assemble—put the right proteins and some fuel in a test tube of water and the result is a bunch of little flagella propelling themselves about at random. Physicists are interested in them for two reasons: they are one of the few mechanisms for transporting micro-robots that might be replicable using inorganic materials, and, given the size of the micro-robot and the viscosity of relevant mediums (close to water in the human body), flagella are very close to an optimal propulsion system.

Research **

Researchers from ETH Zurich have recently published the results from their successful attempts to replicate flagella at the same size scale as natural flagella. To make a flagellum, they deposited layers of aluminium gallium arsenide, indium gallium arsenide, gallium arsenide, and chromium on top of a gallium arsenide crystal. They then use an ion beam to mill away most of the layers, leaving a long, thin rectangle of material.

At one end of this, they deposited a small square of chromium-nickel-gold to provide a magnetic head. The rectangle of material is separated from the gallium arsenide substrate by dissolving the aluminium gallium arsenide. The remaining strip of material is stressed because of the layering, so it curls up into a helix. This process is so well-controlled that the researchers can choose any helix they desire simply by changing the materials and thickness of the different layers.

This tiny scroll was then dropped into a swimming pool sitting under a microscope, where the researchers could observe and control it. The magnetic head of the scroll responds to any magnetic field—changing the field causes the orientation of the scroll to change and induces swimming motions. As a result, the flagella swims in controlled curves, allowing researchers to direct it to any location with any orientation. This was demonstrated by swimming the flagella to a polystyrene sphere, after which they were directed to rotate and push the sphere. The researchers also showed that two spheres could be separated by drilling a flagella between them. Videos of the swimmers in action can be found here.

This is, of course, a very cool piece of research, but it probably won't be used for any sort of remote activity. Although external fields are used to power and direct the swimmer, we still require sensors to see where it is. This probably eliminates any chance of putting these deep inside the human body to scrape plaque from artery walls or doing the equivalent inside mechanical systems. So there is certainly more research required in that direction. On the other hand, the rotary motion can certainly be used as a power source for micro-robots, and that doesn't require being able to sense where the micro-robot is.

Introduction:

A number of robotic swimming methods have been proposed at relatively small scales. Because many of these methods rely on reciprocating motions, they do not scale downwards. Yet over three billion years ago bacteria evolved a swimming strategy at micrometer dimensions that nature has had difficulty improving upon. Just over thirty-five years ago their swimming technique using rotating flagella was first described by H.C. Berg and R.A. Anderson (Nature vol. 245, pp. 380-382, 1973). Inspired by the flagellar motion of bacteria such as Escherichia Coli (see video 4), we have recently developed artificial bacterial flagella (ABF). Our ABF represent the first demonstration of wireless swimming microrobots similar in size and geometry to natural bacterial flagella, and are many orders of magnitude smaller than existing artificial helical swimmers.

Manufacturing:

Helical swimming robot consists of two parts: a helical tail and a soft-magnetic metal head. The tails are 27 to 42 nm thick, less than 2um wide, and coil into diameters smaller than three microns. The fabrication of ABF is based on a self-scrolling technique. The helical tail is patterned in 2D as an InGaAs/GaAs bilayer nanoribbon or an InGaAs/GaAs/Cr trilayer nanoribbon. The metal head is fabricated from a Cr/Ni/Au thin film using a lift-off process. The 2D films detach from the GaAs wafer and self-organize to form tethered helical robots. To untether the helical swimming microrobots from the substrate, micromanipulation is performed to cut, pick, and release them in water. After that, the helical swimming microrobots are propelled and steered precisely in water by a low-strength (1-2 mT), rotating magnetic field. Details of the experimental process can be found in (APL, 94, 064107, 2009).

By adjusting the rotating speed and direction of the magnetic field, the velocity and direction of motion of the helical swimmer can be tuned in a controlled fashion. The figure below shows an example where a 74µm long helical swimmer is driven to reach a target. The average velocity is approximately 5µm/s at 470 rpm. By inverting the rotating magnetic field, the swimmer turns in the opposite direction, and the linear motion is reversed.

Ref : here.

-------------

** Please visit here for more information and videos and pictures.

http://www.iris.ethz.ch/msrl/research/micro/helical_swimmers/

http://www.rowland.harvard.edu/labs/bacteria/projects_filament.html

The PZ10 processor

Researchers from IBM and Georgia Institute of Technology designed and built a computer processor that broke the world speed record reaching an astonishing 500GHz speed, more than one hundred times faster than the fastest commonly available computer chip.

Most processors are made from silicon, but
in recent years several discoveries were made that revealed that there are other materials better suited for high processing speeds than silicon. There are a number of time critical systems, like collision-warning systems, where the silicon based processor is already being replaced by CPUs made from a layer of gallium arsenide, even if the materials needed are expensive and more difficult to produce. Because an extensive transition to another base material would be very costly and would take huge amount of time to complete, the computer hardware industry is searching for ways to improve existing silicon based CPUs. Such a way is to add small amount of germanium inside the silicon-based chips that are designed for mobile phones in order to make them more efficient.

Germanium allows chips to reach higher clock speeds and use less power and such processors can be fabricated using the existing production lines. Even so, reaching the 500GHz frequency was no easy feat, as the IBM researchers super cooled the processor prototype to -268.5 degrees Celsius, using liquid helium. The extremely low temperature, just above the minimum theoretical possible one known as "absolute zero", enabled the processor perform half a trillion calculations every second, which translates into a speed of 500GHz. "A decade ago we couldn't even envisage being able to run at these speeds," said Professor David Ahlgren of IBM.

The extreme speed of the prototype processor was greater than the conventional design even at room temperature where it reached 350 billion calculations per second and there are hopes that the mark can be pushed further. "We observe effects in these devices at cryogenic temperatures which potentially make them faster than simple theory would suggest," said Professor John Cressler of the Georgia Institute of Technology, who was cited by the news site related to BBC.

__________________

Original article can be found here.

Light powered Motor

Research team at Tokyo institute of technology has developed a motor which entirely runes on light, rather than photovoltaic cells which convert light to electricity this motor has special elastomer whose molecular structure expands or contracts when when light falls on it, this is how this motor can convert light energy directly into the mechanical energy.

Team was working on this project since 2003 when they found that plastic compound containing azobenze can expand in ultraviolet light and regain its original shape in normal visible light since then they had improved very much. They performed the test by rotating a pair of wheels measuring 3 millimeters and 10 millimeters in diameter looped with shape shifting plastic coated 0.08 millimeter belt, when ultraviolet light was shine on small wheels and visible light on small wheel they starts rotating with a top speed of 1 rpm.

The coated film measured 4 times elastic than human muscle, this thing is not very efficient but it can be improved to convert light energy into mechanical energy.

Brief History of Light Emitting Diode (LED)

LED lamp History

The phenomenon of solid state junctions producing light was discovered in the crystal detector era. In the 1960s commercial red LED’s became available, and by the 1970s these were in widespread use as indicators in a very wide range of equipment. These early LED’s had much too small an output to be useful as lighting. They replaced the previously widely used indicator types of filament lamps and neon. Compared to neon, indicator LED’s have longer lifetimes and run on lower voltage; compared to miniature filament lamps, indicator LED’s have much longer lifetimes, such that they do not require replacement, and consume less power. The lack of need for replacement also eliminates the need for bulb sockets and a user access port.

Commercial amber (yellow) and orange LED’s followed, and were used where differentiation of multiple LEDs was required. For many years LED’s came in infra-red, red, orange, yellow, and green. Blue, cyan, and violet LEDs finally appeared in the 1990s.

To produce a white SSL device, a blue LED was needed. In 1993, Shuji Nakamura of Nichia Corporation came up with a blue LED using gallium nitride (GaN). With this invention, it was now possible to create white light by combining the light of separate LED’s (red, green, and blue), or by placing a blue LED in a package with an internal light converting phosphor. With the phosphor type, some of the blue output becomes either yellow or red and green with the result that the LED light emission appears white to the human eye.

In 2008, SSL technology advanced to the point that Sentry Equipment Corporation in Oconomowoc, Wis. was able to light its new factory almost entirely with LEDs, both interior and exterior. Although the initial cost was three times more than a traditional mixture of incandescent and fluorescent bulbs, the extra cost will be repaid within two years from electricity savings, and the bulbs should not need replacement for 20 years.