What’s just a bit thicker than a human hair and has ten times the capability of a human muscle? Polymer-coated carbon nanotube yarn. Researchers at the University of Texas at Dallas created this yarn using carbon nanotubes coated with a polymer and coiled with a diameter of about 140 microns.
Passing a voltage through the fiber causes the muscle yarn to expand or contract. Previous similar fibers have to do both actions. That is, they expand and then contract in a bipolar movement. The polymer coating allows for unipolar fibers, critical to using the fibers as artificial muscles.
Continue reading “Nanotube Yarn Makes Strong Bionic Muscles”
We’ve said it before, but we cast a wary eye at any superlative claims that come our way. “World’s fastest” or “world’s first” claims always seem to be quickly debunked, but when the claim of “World’s Smallest Benchy” is backed up by a tugboat that two dozen E. coli would have a hard time finding space on, we’re pretty comfortable with it.
Of course the diminutive benchmark was not printed just for the sake of it, but rather as part of a demonstration of what’s possible with “microswimmers”, synthetic particles which are designed to move about freely in microscopic regimes. As described in a paper by [Rachel P. Doherty] et al from the Soft Matter Physics lab at Leiden University, microswimmers with sizes on the order of 10 to 20 μm can be constructed repeatably, and can include a small area of platinum catalyst. The catalyst is the engine of the microswimmer; hydrogen peroxide in the environment decomposes on the catalyst surface and provides a propulsive force.
Artificial microswimmers have been around for a while, but most are made with chemical or evaporative methods which result in simple shapes like rods and spheres. The current work describes much more complex shapes — the Benchy was a bit of a flex, since the more useful microswimmers were simple helices, which essentially screw themselves into the surrounding fluid. The printing method was based on two-photon polymerization (2PP), a non-linear optical process that polymerizes a resin when two photons are simultaneously absorbed.
The idea that a powered machine so small could be designed and manufactured is pretty cool. We’d love to see how control mechanisms could be added to the prints — microfluidics, perhaps?
In a report published by Science Advances, a research team from the United States and Korea revealed a strain-sensitive, stretchable, and autonomous self-healing semiconductor film. In other words, they’ve created an electronic skin that’s capable of self-regulation. Time to cue the ending track from Ex Machina? Not quite.
Apart from the inevitable long timeline it will take to see the material in production, there are still challenges to improve sensing for active semiconductors. The methods used by the team – notably using a dynamically cross-linked blend of polymer semiconductor and self-healing elastomer – have created a film with a gauge factor of 5.75×10^5 at full strain. At room temperature, even with fracture strains, the material demonstrated self healing.
The technique mimics the self healing properties of human skin, accelerating the development of biomedical devices and soft robots. While active-matrix transistor array-based sensors can provide signals that reduce crosstalk between individual pixels in electronic skin, embedding these rigid sensors and transistors into stretchable systems causes mechanical mismatch between rigid and soft components. A strain-sensing transistor simplifies the process of fabrication, while also improving mechanical conformability and the lifetime of the electronic skin.
The synthetic skin was also shown to operate within a medically safe voltage and to be waterproof, which will prevent malfunctions when placed in contact with ionic human sweat.
[Thanks Qes for the tip!]
Researchers may have created the smallest-ever radio-frequency antennas, a development that should be of interest to any nanotechnology enthusiasts. A group of scientists from Korea published a paper in ACS Nano that details the fabrication of a two-dimensional radio-frequency antenna for wearable applications. Most antennas made from metallic materials like aluminum, cooper, or steel which are too thick to use for nanotechnology applications, even in the wearables space. The newly created antenna instead uses metallic niobium diselenide (NbSe2) to create a monopole patch RF antenna. Even with its sub-micrometer thickness (less than 1/100 the width of a strand of human hair), it functions effectively.
The metallic niobium atoms are sandwiched between two layers of selenium atoms to create the incredibly thin 2D composition. This was accomplished by spray-coating layers of the NbSe2 nanosheets onto a plastic substrate. A 10 mm x 10 mm patch of the material was able to perform with a 70.6% radiation efficiency, propagating RF signals in all directions. Changing the length of the antenna allowed its frequency to be tuned from 2.01-2.80 GHz, which includes the range required for Bluetooth and WiFi connectivity.
Within the ever-shrinking realm of sensors for wearable technologies, there is sure to be a place for tiny antennas as well.
[Thanks Qes for the tip!]
In a recent article in Nature, you can find the details of a RISC-V CPU built using carbon nanotubes. Of course, Nature is a pricey proposition, but you can probably find the paper by its DOI number if you bother to look for it. The researchers point out that silicon transistors are rapidly reaching a point of diminishing returns. However, Carbon Nanotube Field Effect Transistors (CNFETs) overcome many of these disadvantages.
The disadvantage is that the fabrication of CNFETs has been somewhat elusive. The tubes tend to clump and yields are low. The paper describes a method that allowed the fabrication of a CPU with over 14,000 transistors. A wafer gets nanotubes grown all over it and then some of them are removed. In addition, some design rules mitigate other problems.
In particular, a small percentage of the CNFETs will become metallic and have little to no bandgap. However, the DREAM design rules can increase the tolerance of the design to metallic CNFETs with no process changes.
Before you get too excited, limitations in channel length and contact size keep the processor running at a blazing 10 kHz. To paraphrase Weird Al, your operating system boots in a day and a half. The density isn’t great either since working around stray and metallic CNFETs means each transistor has multiple nanotubes in use.
On the other hand, it works. New technology doesn’t always match old technology at first, but you have to crawl before you walk, and walk before you run.
We imagine you won’t be able to buy this for $8 any time soon even if you wanted to. At 10 kHz, it probably isn’t going to make much of a desktop PC anyway.
The more things change, the more things stay the same. Early electronic devices used a spark gap. These have been almost completely replaced with tubes and then semiconductor devices such as transistors. However, transistors will soon reach a theoretical limit on how small they can be which is causing researchers to find the next thing. If the Royal Melbourne Institute of Technology has its way, we’ll go back to something that has more in common with a spark gap than a conventional transistor. You can find the source paper on the Nano Papers website although the text is behind a paywall.
The transistor uses metal, but instead of a semiconductor channel — which is packed with atoms that cause collisions as electrons flow through the channel — the new device uses an air gap. You might well think that if fewer atoms in the channel are better, why not use a vacuum?
Continue reading “New Transistor Uses Metal And Air Instead Of Semiconductors”
Ever hear of a piezo-optomechanical circuit? We hadn’t either. Let’s break it down. Piezo implies some transducer that converts motion to and from energy. Opto implies light. Mechanical implies…well, mechanics. The device, from National Institute of Standards and Technology (NIST), converts signals among optical, acoustic and radio waves. They claim a system based on this design could move and store information in future computers.
At the heart of this circuit is an optomechanical cavity, in the form of a suspended nanoscale beam. Within the beam are a series of holes that act as mirrors for very specific photons. The photons bounce back and forth thousands of times before escaping the cavity. Simultaneously, the nanoscale beam confines phonons, that is, mechanical vibrations. The photons and phonons exchange energy. Vibrations of the beam influence the buildup of photons and the photons influence the mechanical vibrations. The strength of this mutual interaction, or coupling, is one of the largest reported for an optomechanical system.
In addition to the cavities, the device includes acoustic waveguides. By channeling phonons into the optomechanical device, the device can manipulate the motion of the nanoscale beam directly and, thus, change the properties of the light trapped in the device. An “interdigitated transducer” (IDT), which is a type of piezoelectric transducer like the ones used in surface wave devices, allows linking radio frequency electromagnetic waves, light, and acoustic waves.
The work appeared in Nature Photonics and was also the subject of a presentation at the March 2016 meeting of the American Physical Society. We’ve covered piezo transducers before, and while we’ve seen some unusual uses, we’ve never covered anything this exotic.