Nano Therapeutics to Nanobots ~ Nanotechnology is creating new opportunities for fighting disease (w/video)



Nanotechnology is creating new opportunities for fighting disease – from delivering drugs in smart packaging to nanobots powered by the world’s tiniest engines.

Chemotherapy benefits a great many patients but the side effects can be brutal.


When a patient is injected with an anti-cancer drug, the idea is that the molecules will seek out and destroy rogue tumour cells. However, relatively large amounts need to be administered to reach the target in high enough concentrations to be effective. As a result of this high drug concentration, healthy cells may be killed as well as cancer cells, leaving many patients weak, nauseated and vulnerable to infection.

One way that researchers are attempting to improve the safety and efficacy of drugs is to use a relatively new area of research known as nanothrapeutics to target drug delivery just to the cells that need it.

Professor Sir Mark Welland is Head of the Electrical Engineering Division at Cambridge. In recent years, his research has focused on nanotherapeutics, working in collaboration with clinicians and industry to develop better, safer drugs. He and his colleagues don’t design new drugs; instead, they design and build smart packaging for existing drugs.


Nanotherapeutics come in many different configurations, but the easiest way to think about them is as small, benign particles filled with a drug. They can be injected in the same way as a normal drug, and are carried through the bloodstream to the target organ, tissue or cell. 
At this point, a change in the local environment, such as pH, or the use of light or ultrasound, causes the nanoparticles to release their cargo.

Nano-sized tools are increasingly being looked at for diagnosis, drug delivery and therapy. “There are a huge number of possibilities right now, and probably more to come, which is why there’s been so much interest,” says Welland. Using clever chemistry and engineering at the nanoscale, drugs can be ‘taught’ to behave like a Trojan horse, or to hold their fire until just the right moment, or to recognise the target they’re looking for.

“We always try to use techniques that can be scaled up – we avoid using expensive chemistries or expensive equipment, and we’ve been reasonably successful in that,” he adds. “By keeping costs down and using scalable techniques, we’ve got a far better chance of making a successful treatment for patients.”


In 2014, he and collaborators demonstrated that gold nanoparticles could be used to ‘smuggle’ chemotherapy drugs into cancer cells in glioblastoma multiforme, the most common and aggressive type of brain cancer in adults, which is notoriously difficult to treat. The team engineered nanostructures containing gold and cisplatin, a conventional chemotherapy drug. A coating on the particles made them attracted to tumour cells from glioblastoma patients, so that the nanostructures bound and were absorbed into the cancer cells.

Once inside, these nanostructures were exposed to radiotherapy. This caused the gold to release electrons that damaged the cancer cell’s DNA and its overall structure, enhancing the impact of the chemotherapy drug. The process was so effective that 20 days later, the cell culture showed no evidence of any revival, suggesting that the tumour cells had been destroyed.

While the technique is still several years away from use in humans, tests have begun in mice. Welland’s group is working with MedImmune, the biologics R&D arm of pharmaceutical company AstraZeneca, to study the stability of drugs and to design ways to deliver them more effectively using nanotechnology.

“One of the great advantages of working with MedImmune is they understand precisely what the requirements are for a drug to be approved. We would shut down lines of research where we thought it was never going to get to the point of approval by the regulators,” says Welland. “It’s important to be pragmatic about it so that only the approaches with the best chance of working in patients are taken forward.”

The researchers are also targeting diseases like tuberculosis (TB). With funding from the Rosetrees Trust, Welland and postdoctoral researcher Dr Íris da luz Batalha are working with Professor Andres Floto in the Department of Medicine to improve the efficacy of TB drugs.

Their solution has been to design and develop nontoxic, biodegradable polymers that can be ‘fused’ with TB drug molecules. As polymer molecules have a long, chain-like shape, drugs can be attached along the length of the polymer backbone, meaning that very large amounts of the drug can be loaded onto each polymer molecule. The polymers are stable in the bloodstream and release the drugs they carry when they reach the target cell. Inside the cell, the pH drops, which causes the polymer to release the drug.

In fact, the polymers worked so well for TB drugs that another of Welland’s postdoctoral researchers, Dr Myriam Ouberaï, has formed a start-up company, Spirea, which is raising funding to develop the polymers for use with oncology drugs. Ouberaï is hoping to establish a collaboration with a pharma company in the next two years.

“Designing these particles, loading them with drugs and making them clever so that they release their cargo in a controlled and precise way: it’s quite a technical challenge,” adds Welland. “The main reason I’m interested in the challenge is I want to see something working in the clinic – I want to see something working in patients.”

Could nanotechnology move beyond therapeutics to a time when nanomachines keep us healthy by patrolling, monitoring and repairing the body?


Nanomachines have long been a dream of scientists and public alike. But working out how to make them move has meant they’ve remained in the realm of science fiction.

But last year, Professor Jeremy Baumberg and colleagues in Cambridge and the University of Bath developed the world’s tiniest engine – just a few billionths of a metre in size. It’s biocompatible, cost-effective to manufacture, fast to respond and energy efficient.

The forces exerted by these ‘ANTs’ (for ‘actuating nano-transducers’) are nearly a hundred times larger than those for any known device, motor or muscle. To make them, tiny charged particles of gold, bound together with a temperature-responsive polymer gel, are heated with a laser. As the polymer coatings expel water from the gel and collapse, a large amount of elastic energy is stored in a fraction of a second. On cooling, the particles spring apart and release energy.

The researchers hope to use this ability of ANTs to produce very large forces relative to their weight to develop three-dimensional machines that swim, have pumps that take on fluid to sense the environment and are small enough to move around our bloodstream.

Working with Cambridge Enterprise, the University’s commercialisation arm, the team in Cambridge’s Nanophotonics Centre hopes to commercialise the technology for microfluidics bio-applications. The work is funded by the Engineering and Physical Sciences Research Council and the European Research Council.

“There’s a revolution happening in personalised healthcare, and for that we need sensors not just on the outside but on the inside,” explains Baumberg, who leads an interdisciplinary Strategic Research Network and Doctoral Training Centre focused on nanoscience and nanotechnology.

“Nanoscience is driving this. We are now building technology that allows us to even imagine these futures.”

Source: By Sarah Collins, University of Cambridge

NREL: Comparing Costs of Automotive Lithium-Ion Batteries – Know the Context


For Those of You Who Missed this Post – Here is the Re-Post

Great Things from Small Things .. Nanotechnology Innovation


Reported measures of automotive battery costs and prices vary widely.
This is in part because the technology is relatively new and the shape, size, chemistry, and packaging differ between vehicles.

Also, the context for the reported values is often not clearly stated, inviting comparison of inequivalent values from multiple sources.

For example, cells are often combined into packs for specific vehicles at significant added cost, so it is not appropriate to compare a cell cost with a pack cost, even if they are both expressed in the same units ($/kWh).


NREL recently developed a fact sheet that demonstrates the importance of understanding the full context of various cost and price metrics of lithium-ion (Li-ion) battery cell and cell packs.

The fact sheet provides metrics for light-duty vehicle cell and cell pack market price, modeled price, modeled cost, and lab achieved costs.

The data comes from market reports, CEMAC cost models…

View original post 469 more words

NREL: Comparing Costs of Automotive Lithium-Ion Batteries – Know the Context



Reported measures of automotive battery costs and prices vary widely. 
This is in part because the technology is relatively new and the shape, size, chemistry, and packaging differ between vehicles. 

Also, the context for the reported values is often not clearly stated, inviting comparison of inequivalent values from multiple sources. 

For example, cells are often combined into packs for specific vehicles at significant added cost, so it is not appropriate to compare a cell cost with a pack cost, even if they are both expressed in the same units ($/kWh).


NREL recently developed a fact sheet that demonstrates the importance of understanding the full context of various cost and price metrics of lithium-ion (Li-ion) battery cell and cell packs. 

The fact sheet provides metrics for light-duty vehicle cell and cell pack market price, modeled price, modeled cost, and lab achieved costs. 

The data comes from market reports, CEMAC cost models, and the Vehicle Technologies Office (VTO) of the U.S. Department of Energy. At first glance, the metrics (in the figure below) can appear to contradict each other, as VTO Lab Achieved Costs are significantly lower than the others. 

However, the differences can be reconciled by investigating the metrics themselves, specifically by distinguishing between cost and price and the underlying assumptions, such as technology maturity.


Cost versus Price:
Comparing the 2015 modeled price to observed market prices suggests that market factors—not manufacturing cost considerations—currently influence pricing decisions. 

This is further substantiated by comparing both the CEMAC and Bloomberg New Energy Finance (BNEF) cost modeling results to observed prices, which suggests that manufacturers have sold at or even below their costs of production in recent years. (For more on modeled cost versus price, see our earlier blog posts on this topic).

A chart displays market and modeled prices and costs for Lithium Ion batteries in 2014 and 2015. 

The market prices are as follows. BNEF: for 2014, $615 for pack, $367 for cell; for 2015 $399 for pack, $234 for cell. Total Battery Consulting: for 2014, $538 for pack, $316 for cell; for 2015, $477 for pack, $282 for cell. Roland Berger: for 2015, $220 for cell. 

The modeled prices are as follows. CEMAC: for 2015, $570 for pack, $342 for cell. 

The modeled costs are as follows. CEMAC: for 2015, $495 for pack, $297 for cell. BNEF: for 2015, $492 for pack, $276 for cell. The VTO lab achieved costs are as follows. VTO pack + cell costs: for 2014, $289; for 2015 $268.


Technology Maturity: The CEMAC and BNEF cost modeling results in the chart above benchmark the 2015 cost of light-duty, plug-in hybrid electric vehicle cells and packs that were produced using commercially available technology. 

The VTO modeled costs, by contrast, are meant to estimate the projected commercial-scale production cost of technologies that are currently in research and development.

A graph demonstrating that VTO’s lab achieved costs lead modeled manufacturing costs by about 4 years.


Comparing VTO cost targets to the 2015 CEMAC modeled cost of commercially available technology ($495/kWh) shows that the CEMAC modeled costs align with the VTO cost targets from 4 years earlier. 

A 3-to-5-year lag is representative of the time required to move near-commercial VTO portfolio technologies, which have been proven at the lab or pilot scale, into large-scale commercial production.

The examples above demonstrate the importance of understanding the full context of various cost and price metrics that are reported in technical papers, market research reports, and the general media—especially with respect to relatively immature technologies and markets where a standard paradigm has yet to develop. 

Without this context, it is not possible to reasonably compare or analyze cost and price values from multiple sources.

Download the Full Fact Sheet from NREL

Large Emissions from the Electric Car (EV) Battery Makers – Tesla an ‘Eco-Villain’?


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Electric power: When batteries are eco-villains in the production, according to a new report. Photo: Tomas Oneborg / SvD / TT

Huge hopes tied to electric cars as the solution to automotive climate problem. But the electric car batteries are eco-villains in the production. Several tons of carbon dioxide has been placed, even before the batteries leave the factory.

IVL Swedish Environmental Research Institute was commissioned by the Swedish Transport Administration and the Swedish Energy Agency investigated lithium-ion batteries climate impact from a life cycle perspective. There are batteries designed for electric vehicles included in the study. The two authors Lisbeth Dahllöf and Mia Romare has done a meta-study that is reviewed and compiled existing studies.

The report shows that the battery manufacturing leads to high emissions. For every kilowatt hour of storage capacity in the battery generated emissions of 150 to 200 kilos of carbon dioxide already in the factory. The researchers did not study individual bilmärkens batteries, how these produced or the electricity mix they use. But if we understand the great importance of play battery take an example: Two common electric cars on the market, the Nissan Leaf and the Tesla Model S, the batteries about 30 kWh and 100 kWh.

Even when buying the car emissions have already occurred, corresponding to approximately 5.3 tons and 17.5 tons, the batteries of these sizes. The numbers can be difficult to relate to. As a comparison, a trip for one person round trip from Stockholm to New York by air causes the release of more than 600 kilograms of carbon dioxide, according to the UN organization ICAO calculation.

Another conclusion of the study is that about half the emissions arising from the production of raw materials and half the production of the battery factory. The mining accounts for only a small proportion of between 10-20 percent.

Read more: “The potential electric car the main advantage”

The calculation is based on the assumption that the electricity mix used in the battery factory consists of more than half of the fossil fuels. In Sweden, the power production is mainly of fossil-nuclear and hydropower why lower emissions had been achieved.

The study also concluded that emissions grow almost linearly with the size of the battery, even if it is pinched by the data in that field. It means that a battery of the Tesla-size contributes more than three times as much emissions as the Nissan Leaf size. It is a result that surprised Mia Romare.

– It should have been less linear as the electronics used is not increased to the same extent. But the battery cells are so sensitive as production looks today, she says.

– One conclusion is that you should not run around with unnecessarily large batteries, says Mia Romare

The authors emphasize that a large part of the study has been about finding out what data is available and find out what quality they are. They have in many cases been forced to conclude that it is difficult to compare existing studies together.

 

We’ve been frustrated, but it is also part of the result, says Lisbeth Dahllöf.

His colleague, Mats-Ola Larsson at IVL has made a calculation of how long you have to drive a petrol or diesel before it has released as much carbon dioxide as battery manufacturing has caused. The result was 2.7 years for a battery of the same size as the Nissan Leaf and 8.2 years for a battery of the Tesla-size, based on a series of assumptions (see box below).

– It’s great that companies and authorities for ambitious environmental policies and buying into climate-friendly cars. But these results show that one should consider not to choose an electric car with a bigger battery than necessary, he says, noting that politicians should also take this on in the design of instruments.

An obvious part to look at the life cycle analysis is recycling. The authors note that the characteristics of the batteries is the lack of the same, since there is no financial incentive to send batteries for recycling, as well as the volumes are still small.

Cobalt, nickel and copper are recovered but not the energy required to manufacture electrodes, says Mia Romare and points out that the point of recycling the resource rather than the reduction of carbon emissions.

Peter Kasche the report originator Energy Agency emphasizes the close of the linear relationship between the battery size and emissions is important.

– Somehow you really get to see so as to optimize the batteries. One should not run around with a lot of kilowatt hours unnecessarily. In some cases, a plug-in hybrid to be the optimum, in other cases a clean vehicle battery.

So counted IVL

Mats-Ola Larsson has made a number of assumptions in the calculation of emissions from a battery of the Nissan Leaf size and a battery of Tesla’s size takes 2.7 and 8.2 years to “run together into” a normal petrol or diesel:

The average emissions of new Swedish cars in 2016 were 126 grams of carbon dioxide per kilometer. The value has been adjusted to 130 because some of the cars that are classified as electric vehicles are plug-in hybrids, which sometimes runs on fossil fuels.

While adoption of petrol and diesel have 18 percent renewable fuels, which affect emissions.

Average Mileage per year is 1224 mil under Traffic Analysis.

NREL: Semiconducting Single-Walled Carbon Nanotubes in Solar Energy Harvesting


National Renewable Energy Laboratory, Golden, Colorado 

Semiconducting single-walled carbon nanotubes (s-SWCNTs) represent a tunable model one-dimensional system with exceptional optical and electronic properties. 

High-throughput separation and purification strategies have enabled the integration of s-SWCNTs into a number of optoelectronic applications, including photovoltaics (PVs). In this Perspective, we discuss the fundamental underpinnings of two model PV interfaces involving s-SWCNTs. 

We first discuss s-SWCNT–fullerene heterojunctions where exciton dissociation at the donor–acceptor interface drives solar energy conversion. Next, we discuss charge extraction at the interface between s-SWCNTs and a photoexcited perovskite active layer. 

In each case, the use of highly enriched semiconducting SWCNT samples enables fundamental insights into the thermodynamic and kinetic mechanisms that drive the efficient conversion of solar photons into long-lived separated charges. 

These model systems help to establish design rules for next-generation PV devices containing well-defined organic semiconductor layers and help to frame a number of important outstanding questions that can guide future studies.

New chemical method could revolutionize Graphene: U of Illinois – Chicago




“The distinction of our chemistry will enable integration of graphene with almost anything, while retaining its properties.”

University of Illinois at Chicago scientists have discovered a new chemical method that enables graphene to be incorporated into a wide range of applications while maintaining its ultra-fast electronics.

 

Graphene, a lightweight, thin, flexible material, can be used to enhance the strength and speed of computer display screens, electric/photonics circuits, solar cells and various medical, chemical and industrial processes, among other things. It is comprised of a single layer of carbon atoms bonded together in a repeating pattern of hexagons.

 

Isolated for the first time 15 years ago by a physics professor at the University of Manchester in England, it is so thin that it is considered two-dimensional and thought to be the strongest material on the planet.

 

Vikas Berry, associate professor and department head of chemical engineering, and colleagues used a chemical process to attach nanomaterials on graphene without changing the properties and the arrangement of the carbon atoms in graphene. 





By doing so, the UIC scientists retained graphene’s electron-mobility, which is essential in high-speed electronics.

 

The addition of the plasmonic silver nanoparticles to graphene also increased the material’s ability to boost the efficiency of graphene-based solar cells by 11 fold, Berry said.

Instead of adding molecules to the individual carbon atoms of graphene, Berry’s new method adds metal atoms, such as chromium or molybdenum, to the six atoms of a benzoid ring. 

Unlike carbon-centered bonds, this bond is delocalized, which keeps the carbon atoms’ arrangement undistorted and planar, so that the graphene retains its unique properties of electrical conduction.

 

The new chemical method of annexing nanomaterials on graphene will revolutionize graphene technology by expanding the scope of its applications, Berry said.

 

“It’s been a challenge to interface graphene with other nano-systems because graphene lacks an anchoring chemistry,” he said. “And if graphene’s chemistry is changed to add anchors, it loses its superior properties. 

The distinction of our chemistry will enable integration of graphene with almost anything, while retaining its properties.

 We envision that our work will motivate a worldwide move towards ‘ring-centered’ chemistries to interface graphene with other systems.”

 

Source and top image: University of Illinois at Chicago

Electric Bike News. Tesla Brings New Technology to E-Bike Batteries with the 21700 Cell: Video


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Tesla is revolutionizing batteries for electric bicycles and it has to do with the recent changes at the leading battery cell makers BMZ, Panasonic, Sony, Samsung and LG. Together these five make out some 80% of the world production of battery cells.

These five cell makers used to supply huge numbers of cylindrical shaped cells to the IT industry until the industry changed completely from using cylindrical shaped cells to flat shaped batteries which are now used in laptops, tablets and smartphones. Tesla placing huge orders for cylindrical shaped cells pushed battery cell makers to new highs.

Europe’s largest battery maker BMZ boss introduced the 21700 cell that will revolutionize electric bicycles. In particular as the 21700 cell not only offers a much prolonged lifetime but also batteries with a much bigger capacity for more power and pedal-supported mileage.

The extraordinary features that the 21700 battery cell brings to e-bikes will be the new standard in e-bike batteries. And that this new standard will already be available in 2018.

Instead of the current 18650 (18mm diameter and 65mm high) cell size the 21700 cell is 21mm diameter and 70mm high. The bigger size is bringing a bigger output; up to 4.8Ah. With that capacity the battery lifetime is extended from the current some 500 charging cycles up to 1,500 to 2,000 cycles.

BMZ, together with another global battery player, managed to develop batteries that offer a much longer lifespan thanks to the fact that the new batteries create less heat and has up to 60% more capacity.

Solar paint offers endless energy from water vapor: Breakthrough by RMIT Researchers


Credit: CC0 Public Domain


Researchers have developed a solar paint that can absorb water vapour and split it to generate hydrogen – the cleanest source of energy.

The paint contains a newly developed compound that acts like silica gel, which is used in sachets to absorb moisture and keep food, medicines and electronics fresh and dry.

But unlike silica gel, the new material, synthetic molybdenum-sulphide, also acts as a semi-conductor and catalyses the splitting of water atoms into hydrogen and oxygen.

Lead researcher Dr Torben Daeneke, from RMIT University in Melbourne, Australia, said: “We found that mixing the compound with titanium oxide particles leads to a sunlight-absorbing paint that produces hydrogen fuel from solar energy and moist air.

“Titanium oxide is the white pigment that is already commonly used in wall paint, meaning that the simple addition of the new material can convert a brick wall into energy harvesting and fuel production real estate.

“Our new development has a big range of advantages,” he said. “There’s no need for clean or filtered water to feed the system. Any place that has water vapour in the air, even remote areas far from water, can produce fuel.”

 

His colleague, Distinguished Professor Kourosh Kalantar-zadeh, said hydrogen was the cleanest source of energy and could be used in fuel cells as well as conventional combustion engines as an alternative to fossil fuels.

“This system can also be used in very dry but hot climates near oceans. The sea water is evaporated by the hot sunlight and the vapour can then be absorbed to produce fuel.

“This is an extraordinary concept – making fuel from the sun and water vapour in the air.”

 

More information: Torben Daeneke et al, Surface Water Dependent Properties of Sulfur-Rich Molybdenum Sulfides: 
Electrolyteless Gas Phase Water Splitting, ACS Nano (2017). DOI: 10.1021/acsnano.7b01632
Provided by: RMIT University

Rice U: New Lithium metal battery prototype boasts 3X the capacity of current lithium-ions ~ Dendrite Problem Solved?


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Could a new material involving a carbon nanotube and graphene hybrid put an end to the dendrite problem in lithium batteries? (Credit: Tour Group/Rice University)

The high energy capacity of lithium-ion batteries has led to them powering everything from tiny mobile devices to huge trucks. But current lithium-ion battery technology is nearing its limits and the search is on for a better lithium battery. But one thing stands in the way: dendrites. If a new technology by Rice University scientists lives up to its potential, it could solve this problem and enable lithium-metal batteries that can hold three times the energy of lithium-ion ones.

Dendrites are microscopic lithium fibers that form on the anodes during the charging process, spreading like a rash till they reach the other electrode and causing the battery to short circuit. As companies such as Samsung know only too well, this can cause the battery to catch fire or even explode.

“Lithium-ion batteries have changed the world, no doubt,” says chemist Dr. James Tour, who led the study. “But they’re about as good as they’re going to get. Your cellphone’s battery won’t last any longer until new technology comes along.”

Rice logo_rice3So until scientists can figure out a way to solve the problem of dendrites, we’ll have to put our hopes for a higher capacity, faster-charging battery that can quell range anxiety on hold. This explains why there’s been no shortage of attempts to solve this problem, from using Kevlar to slow down dendrite growth to creating a new electrolyte that could lead to the development of an anode-free cell. So how does this new technology from Rice University compare?

For a start, it’s able to stop dendrite growth in its tracks. Key to it is a unique anode made from a material that was first created at the university five years ago. By using a covalent bond structure, it combines a two-dimensional graphene sheet and carbon nanotubes to form a seamless three-dimensional structure. As Tour explained back when the material was first unveiled:

“By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it’s all one seamless material.”

Close-up of the lithium metal coating the graphene-nanotube anode (Credit: Tour Group/Rice University)

 

Envisioned for use in energy storage and electronics applications such as supercapacitors, it wasn’t until 2014, when co-lead author Abdul-Rahman Raji was experimenting with lithium metal and the graphene-nanotube hybrid, that the researchers discovered its potential as a dendrite inhibitor.

“I reasoned that lithium metal must have plated on the electrode while analyzing results of experiments carried out to store lithium ions in the anode material combined with a lithium cobalt oxide cathode in a full cell,” says Raji. “We were excited because the voltage profile of the full cell was very flat. At that moment, we knew we had found something special.”

Closer analysis revealed no dendrites had grown when the lithium metal was deposited into a standalone hybrid anode – but would it work in a proper battery?

To test the anode, the researchers built full battery prototypes with sulfur-based cathodes that retained 80 percent capacity after more than 500 charge-discharge cycles (i.e. the rough equivalent of what a cellphone goes through in a two-year period). No signs of dendrites were observed on the anodes.

How it works

The low density and high surface area of the nanotube forest allow the lithium metal to coat the carbon hybrid material evenly when the battery is charged. And since there is plenty of space for the particles to slip in and out during the charge and discharge cycle, they end up being evenly distributed and this stops the growth of dendrites altogether.

According to the study, the anode material is capable of a lithium storage capacity of 3,351 milliamp hours per gram, which is close to pure lithium’s theoretical maximum of 3,860 milliamp hours per gram, and 10 times that of lithium-ion batteries. And since the nanotube carpet has a low density, this means it’s able to coat all the way down to substrate and maximize use of the available volume.

“Many people doing battery research only make the anode, because to do the whole package is much harder,” says Tour. “We had to develop a commensurate cathode technology based upon sulfur to accommodate these ultrahigh-capacity lithium anodes in first-generation systems. We’re producing these full batteries, cathode plus anode, on a pilot scale, and they’re being tested.”

The study was published in ACS Nano.

Source: Rice University

 

Quantum Dot Transistor Simulates Synaptic Responses and Functions of Neurons


 

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This research demonstrates a nanoscaled memdevice able to act as an electronic analogue of tipping buckets that allows reducing the dimensionality and complexity of a sensing problem by transforming it into a counting problem. The device offers a well adjustable, tunable, and reliable periodic reset that is controlled by the amounts of transferred quantum dot charges per gate voltage sweep. When subjected to periodic voltage sweeps, the quantum dot (bucket) may require up to several sweeps before a rapid full discharge occurs thus displaying period doubling, period tripling, and so on between self-governing reset operations. (© ACS)

A transistor that simulates some of the functions of neurons has been invented based on experiments and models developed by researchers at the Federal University of São Carlos (UFSCar) in São Paulo State, Brazil, Würzburg University in Germany, and the University of South Carolina in the United States.The device, which has micrometric as well as nanometric parts, can see light, count, and store information in its own structure, dispensing with the need for a complementary memory unit.It is described in an article in the journal Nano Letters (“Nanoscale tipping bucket effect in a quantum dot transistor-based counter”

“In this article, we show that transistors based on quantum dots can perform complex operations directly in memory. This can lead to the development of new kinds of device and computer circuit in which memory units are combined with logical processing units, economizing space, time, and power consumption,” said Victor Lopez Richard, a professor in UFSCar’s Physics Department and one of the coordinators of the study.
The transistor was produced by a technique called epitaxial growth, which consists of coating a crystal substrate with thin film. On this microscopic substrate, nanoscopic droplets of indium arsenide act as quantum dots, confining electrons in quantized states. Memory functionality is derived from the dynamics of electrical charging and discharging of the quantum dots, creating current patterns with periodicities that are modulated by the voltage applied to the transistor’s gates or the light absorbed by the quantum dots.
“The key feature of our device is its intrinsic memory stored as an electric charge inside the quantum dots,” Richard said. “The challenge is to control the dynamics of these charges so that the transistor can manifest different states. Its functionality consists of the ability to count, memorize, and perform the simple arithmetic operations normally done by calculators, but using incomparably less space, time, and power.”
According to Richard, the transistor is not likely to be used in quantum computing because this requires other quantum effects. However, it could lead to the development of a platform for use in equipment such as counters or calculators, with memory intrinsically linked to the transistor itself and all functions available in the same system at the nanometric scale, with no need for a separate space for storage.
“Moreover, you could say the transistor can see light because quantum dots are sensitive to photons,” Richard said, “and just like electric voltage, the dynamics of the charging and discharging of quantum dots can be controlled via the absorption of photons, simulating synaptic responses and some functions of neurons.”
Further research will be necessary before the transistor can be used as a technological resource. For now, it works only at extremely low temperatures – approximately 4 Kelvin, the temperature of liquid helium.
“Our goal is to make it functional at higher temperatures and even at room temperature. To do that, we’ll have to find a way to separate the electronic spaces of the system sufficiently to prevent them from being affected by temperature. We need more refined control of synthesis and material growth techniques in order to fine-tune the charging and discharging channels. And the states stored in the quantum dots have to be quantized,” Richard said.
Source: Fundação de Amparo à Pesquisa do Estado de São Paulo

Read more: Quantum dot transistor simulates functions of neurons

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