Molecular Machines...

The use of pulses of chemical fuel to directionally transport components and substrates via an energy ratchet mechanism is operationally simple, effective, generates relatively innocuous waste products, and can function in a range of rotary and linear molecular motor and pump designs. Such a universally applicable chemically-fuelled molecular motor-mechanism has the potential to find broad application in molecular nanotechnology. Courtesy: D Leigh

Topics: Brownian Motion, Chemistry, Nanotechnology, NEMS

Chemists at the University of Manchester in the UK say they have succeeded in developing a new and simple technique for powering both linear and rotary molecular motors made from catenanes. These are mechanically interlocked rings of DNA that could be used to make devices that can be switched between different states using external triggers like changes in pH. The breakthrough method – until now it was only possible to power either rotary or linear motors – might be used to power future molecular machines.

“In the molecular machines we are familiar with in the ‘big world’, the parts, such as cogs, flywheels and pistons, do not move unless a force is applied to them,” explains team leader David Leigh. “At the molecular scale, however, molecules and their parts are constantly moving through Brownian motion and we need to find ways to control the direction of this motion if we are to develop fully-functioning nanomachines.”

Last year, Leigh’s team made the first autonomous chemically-fuelled molecular motor that runs as long as a chemical fuel is present. This rotary motor relies on information transfer between the machine components: a blocking group adds as soon as the ring has moved past a certain point in a given direction and that group also prevents the ring moving backwards through Brownian motion.

The researchers use trichloroacetic acid (Cl₃CCOOH) as the fuel in their motor. Cl₃CCOOH undergoes base-catalysed decarboxylation, and by adding an excess of this acid to a solution containing the molecular motor and another chemical (triethylamine, or Et3N), they were first able to make the medium acidic and then, as the Cl₃CCOOH decomposes, basic.

Chemical fuel pulses power rotary and linear nanomotors, Belle Dumé, Nanotechweb.org

Micro-Gami...

Image Source: Origami Resource Center

Topics: Graphene, Nanotechnology, NEMS, Robotics

Thirty years ago, a professor in Japan folded an origami crane smaller than a pinhead. Peering through a microscope, he used a sewing needle to carefully crimp the paper.

Now researchers at Cornell University in Ithaca, New York, have gone one step further, creating origami about the size of a red blood cell. Too small for human hands, their origami folds itself. This new take on an old tradition is made not from paper, but from sheets of glass and carbon only a few atoms thick.

“It’s the world’s thinnest origami … comparable in size to a biological microorganism,” said Marc Miskin, a postdoctoral associate in the laboratory of applied physicist Itai Cohen at Cornell. He described the new research in a March 14 talk at an American Physical Society meeting in New Orleans.

The simple shapes formed by the micro-gami, such as cubes and pyramids, lack the grace and sophistication of a bird. But they could be a step toward miniature machines that fold themselves up into packages small enough to be injected into the body.

Inside Science: World's Thinnest Origami Could Build Microscopic Machines
Devin Powell

Subatomic Motion Detector...

Images Sources: See link below

Topics: Atomic Force Microscopy, Nanotechnology, NEMS, NIST, Thin Films

Scientists at the National Institute of Standards and Technology (NIST) have developed a new device that measures the motion of super-tiny particles traversing distances almost unimaginably small—shorter than the diameter of a hydrogen atom, or less than one-millionth the width of a human hair. Not only can the handheld device sense the atomic-scale motion of its tiny parts with unprecedented precision, but the researchers have devised a method to mass produce the highly sensitive measuring tool.

It’s relatively easy to measure small movements of large objects but much more difficult when the moving parts are on the scale of nanometers, or billionths of a meter. The ability to accurately measure tiny displacements of microscopic bodies has applications in sensing trace amounts of hazardous biological or chemical agents, perfecting the movement of miniature robots, accurately deploying airbags and detecting extremely weak sound waves traveling through thin films.

NIST physicists Brian Roxworthy and Vladimir Aksyuk describe their work (link is external) in the Dec. 6, 2016, Nature Communications.

The researchers measured subatomic-scale motion in a gold nanoparticle. They did this by engineering a small air gap, about 15 nanometers in width, between the gold nanoparticle and a gold sheet. This gap is so small that laser light cannot penetrate it.

However, the light energized surface plasmons—the collective, wave-like motion of groups of electrons confined to travel along the boundary between the gold surface and the air.

The researchers exploited the light’s wavelength, the distance between successive peaks of the light wave. With the right choice of wavelength, or equivalently, its frequency, the laser light causes plasmons of a particular frequency to oscillate back and forth, or resonate, along the gap, like the reverberations of a plucked guitar string. Meanwhile, as the nanoparticle moves, it changes the width of the gap and, like tuning a guitar string, changes the frequency at which the plasmons resonate.

NIST Device for Detecting Subatomic-Scale Motion Has Potential Robotics, Homeland Security Applications
Ben Stein

Squitches...

The metal–molecule–metal switching gap lowers the surface adhesion forces and allows nanoscale force control through compression of the molecular layer, while enabling formation of a few nanometer-thick gaps for sub-1 V operation. Courtesy of ACS Nano

Topics: Electrical Engineering, Nanotechnology, NEMS, Quantum Mechanics, Semiconductor Technology

The transistor – a switching element that defined technological progress through the 20th century – may be reaching its limits as demands for smaller devices continue. One alternative is the nanoelectromechanical (NEM) switch, but so far these have fallen short of the performance criteria required. Now an improved NEM switch based on tunnelling has demonstrated how these switches may yet be a viable contender to succeed the conventional transistor in low-power devices.

“To be competitive, the NEM switch operation must be made more energy efficient and reliable,” says Farnaz Niroui, a researcher at the Organic and Nanostructured Electronics Laboratory at the Massachusetts Institute of Technology in the US. “Our proposed tunnelling switching mechanism based on molecular thin films enables us to achieve drastic miniaturization of the devices to lower the operating voltages and provide nanoscale force control for more repeatable and reliable performance.”

Traditional electromechanical switches complete a circuit when the two electrodes are in contact, and break it – ‘turn off’ – when they are not. Scaling these elements down to the nanoscale offers a switching mechanism that may outperform conventional transistors in terms of the on/off ratio and low leakage current that can be achieved. However, operating reliably at low voltages requires control over the nanoscale distance between the electrodes that is tricky in itself, and further complicated by adhesive ‘stiction’ forces that cause the device to fail.

Here, the tunnelling approach appears to provide the answer for Niroui and her team at MIT led by Vladimir Bulović, Jeffrey Lang and Timothy Swager. They sandwich a self-assembled organic molecular film – poly(ethylene glycol)-dithiol (PEG-dithiol) – between the electrodes and modulate the tunnelling current through the film as it compresses and recovers.

Nanotechweb.org:
Low-voltage electromechanical 'squitches' make their debut, Anna Demming

NEMS Transistor...

An Oscillating Graphene Drum. Source: Link below

Researchers at Columbia University in the US have built the smallest frequency-modulated (FM) radio transmitter ever. Based on a graphene nanomechanical system (NEMS), the device oscillates at a frequency of 100 MHz. It could find use in a variety of applications, including sensing tiny masses and on-chip signal processing. It also represents an important first step towards the development of advanced wireless technology and the design of ultrathin mobile phones, says team co-leader James Hone.

"Our device is much smaller than any other radio-signal source ever made and, importantly, can be put on the same chip that is used for data processing," he explains.

Graphene is a sheet of carbon atoms arranged in a honeycomb-like lattice that is just one atom thick. Since its discovery in 2004, this "wonder material" has continued to amaze scientists with its growing list of unique electronic and mechanical properties, which include high electrical conductivity and exceptional strength. Indeed, some researchers believe that graphene might even replace silicon as the electronic industry's material of choice in the future.

Physics World: Nanomechanical FM transistor is smallest yet