Category Archives: electronics

Swallow your technology and wear it inside (wearable tech: 2 of 3)

While there are a number of wearable and fashionable pieces of technology that monitor heart rate and breathing, they are all worn on the outside of your body. Researchers are working on an alternative that can be swallowed and will monitor vital signs from within the gastrointestinal tract. I believe this is a prototype of the device,

This ingestible electronic device invented at MIT can measure heart rate and respiratory rate from inside the gastrointestinal tract. Courtesy: MIT

This ingestible electronic device invented at MIT can measure heart rate and respiratory rate from inside the gastrointestinal tract. Image: Albert Swiston/MIT Lincoln Laboratory Courtesy: MIT

From a Nov. 18, 2015 news item on,

This type of sensor could make it easier to assess trauma patients, monitor soldiers in battle, perform long-term evaluation of patients with chronic illnesses, or improve training for professional and amateur athletes, the researchers say.

The new sensor calculates heart and breathing rates from the distinctive sound waves produced by the beating of the heart and the inhalation and exhalation of the lungs.

“Through characterization of the acoustic wave, recorded from different parts of the GI tract, we found that we could measure both heart rate and respiratory rate with good accuracy,” says Giovanni Traverso, a research affiliate at MIT’s Koch Institute for Integrative Cancer Research, a gastroenterologist at Massachusetts General Hospital, and one of the lead authors of a paper describing the device in the Nov. 18 issue of the journal PLOS One.

A Nov. 18, 2015 Massachusetts Institute of Technology (MIT) news release by Anne Trafton, which originated the news item, further explains the research,

Doctors currently measure vital signs such as heart and respiratory rate using techniques including electrocardiograms (ECG) and pulse oximetry, which require contact with the patient’s skin. These vital signs can also be measured with wearable monitors, but those are often uncomfortable to wear.

Inspired by existing ingestible devices that can measure body temperature, and others that take internal digestive-tract images, the researchers set out to design a sensor that would measure heart and respiratory rate, as well as temperature, from inside the digestive tract.

The simplest way to achieve this, they decided, would be to listen to the body using a small microphone. Listening to the sounds of the chest is one of the oldest medical diagnostic techniques, practiced by Hippocrates in ancient Greece. Since the 1800s, doctors have used stethoscopes to listen to these sounds.

The researchers essentially created “an extremely tiny stethoscope that you can swallow,” Swiston says. “Using the same sensor, we can collect both your heart sounds and your lung sounds. That’s one of the advantages of our approach — we can use one sensor to get two pieces of information.”

To translate these acoustic data into heart and breathing rates, the researchers had to devise signal processing systems that distinguish the sounds produced by the heart and lungs from each other, as well as from background noise produced by the digestive tract and other parts of the body.

The entire sensor is about the size of a multivitamin pill and consists of a tiny microphone packaged in a silicone capsule, along with electronics that process the sound and wirelessly send radio signals to an external receiver, with a range of about 3 meters.

In tests along the GI tract of pigs, the researchers found that the device could accurately pick up heart rate and respiratory rate, even when conditions such as the amount of food being digested were varied.

“The authors introduce some interesting and radically different approaches to wearable physiological status monitors, in which the devices are not worn on the skin or on clothing, but instead reside, in a transient fashion, inside the gastrointestinal tract. The resulting capabilities provide a powerful complement to those found in wearable technologies as traditionally conceived,” says John Rogers, a professor of materials science and engineering at the University of Illinois who was not part of the research team.

Better diagnosis

The researchers expect that the device would remain in the digestive tract for only a day or two, so for longer-term monitoring, patients would swallow new capsules as needed.

For the military, this kind of ingestible device could be useful for monitoring soldiers for fatigue, dehydration, tachycardia, or shock, the researchers say. When combined with a temperature sensor, it could also detect hypothermia, hyperthermia, or fever from infections.

In the future, the researchers plan to design sensors that could diagnose heart conditions such as abnormal heart rhythms (arrhythmias), or breathing problems including emphysema or asthma. Currently doctors require patients to wear a harness (Holter) monitor for up to a week to detect such problems, but these often fail to produce a diagnosis because patients are uncomfortable wearing them 24 hours a day.

“If you could ingest a device that would listen for those pathological sounds, rather than wearing an electrical monitor, that would improve patient compliance,” Swiston says.

The researchers also hope to create sensors that would not only diagnose a problem but also deliver a drug to treat it.

“We hope that one day we’re able to detect certain molecules or a pathogen and then deliver an antibiotic, for example,” Traverso says. “This development provides the foundation for that kind of system down the line.”

MIT has provided a video with two of the researchers describing their work and and plans for its future development,

Here’s a link to and a citation for the paper,

Physiologic Status Monitoring via the Gastrointestinal Tract by G. Traverso, G. Ciccarelli, S. Schwartz, T. Hughes, T. Boettcher, R. Barman, R. Langer, & A. Swiston. PLOS DOI: 10.1371/journal.pone.0141666 Published: November 18, 2015

This paper is open access.

Note added Nov. 25, 2015 at 1625 hours PDT: US National Public Radio (NPR) has a story on this research. You can find Nov. 23, 2015 podcast (about six minutes) and a series of textual excerpts featuring Albert Swiston, biomaterials scientist at MIT, and Stephen Shankland, senior writer for CNET covering digital technology, from the podcast here.

Shape memory in a supercapacitor fibre for ‘smart’ textiles (wearable tech: 1 of 3)

Wearable technology seems to be quite trendy for a grouping not usually seen: consumers, fashion designers, medical personnel, manufacturers, and scientists.

The first in this informal series concerns a fibre with memory shape. From a Nov. 19, 2015 news item on Nanowerk (Note: A link has been removed),

Wearing your mobile phone display on your jacket sleeve or an EKG probe in your sports kit are not off in some distant imagined future. Wearable “electronic textiles” are on the way. In the journal Angewandte Chemie (“A Shape-Memory Supercapacitor Fiber”), Chinese researchers have now introduced a new type of fiber-shaped supercapacitor for energy-storage textiles. Thanks to their shape memory, these textiles could potentially adapt to different body types: shapes formed by stretching and bending remain “frozen”, but can be returned to their original form or reshaped as desired.

A Nov. 19, 2015 Wiley Publishers press release, which originated the news item, provides context and detail about the work,

Any electronic components designed to be integrated into textiles must be stretchable and bendable. This is also true of the supercapacitors that are frequently used for data preservation in static storage systems (SRAM). SRAM is a type of storage that holds a small amount of data that is rapidly retrievable. It is often used for caches in processors or local storage on chips in devices whose data must be stored for long periods without a constant power supply. Some time ago, a team headed by Huisheng Peng at Fudan University developed stretchable, pliable fiber-shaped supercapacitors for integration into electronic textiles. Peng and his co-workers have now made further progress: supercapacitor fibers with shape memory.

Any electronic components designed to be integrated into textiles must be stretchable and bendable. This is also true of the supercapacitors that are frequently used for data preservation in static storage systems (SRAM). SRAM is a type of storage that holds a small amount of data that is rapidly retrievable. It is often used for caches in processors or local storage on chips in devices whose data must be stored for long periods without a constant power supply.
Some time ago, a team headed by Huisheng Peng at Fudan University developed stretchable, pliable fiber-shaped supercapacitors for integration into electronic textiles. Peng and his co-workers have now made further progress: supercapacitor fibers with shape memory.

The fibers are made using a core of polyurethane fiber with shape memory. This fiber is wrapped with a thin layer of parallel carbon nanotubes like a sheet of paper. This is followed by a coating of electrolyte gel, a second sheet of carbon nanotubes, and a final layer of electrolyte gel. The two layers of carbon nanotubes act as electrodes for the supercapacitor. Above a certain temperature, the fibers produced in this process can be bent as desired and stretched to twice their original length. The new shape can be “frozen” by cooling. Reheating allows the fibers to return to their original shape and size, after which they can be reshaped again. The electrochemical performance is fully maintained through all shape changes.

Weaving the fibers into tissues results in “smart” textiles that could be tailored to fit the bodies of different people. This could be used to make precisely fitted but reusable electronic monitoring systems for patients in hospitals, for example. The perfect fit should render them both more comfortable and more reliable.

Here’s a link to and a citation for the paper,

A Shape-Memory Supercapacitor Fiber by Jue Deng, Ye Zhang, Yang Zhao, Peining Chen, Dr. Xunliang Cheng, & Prof. Dr. Huisheng Peng. Angewandte Chemie International Edition  DOI: 10.1002/anie.201508293  First published: 3 November 2015

This paper is behind a paywall.

The sound of moving data

In fact, scientists from the University of Sheffield (UK) and the University of Leeds (UK) have found a way to move data easily and quickly by using sound waves. From a Nov. 3, 2015 news item on ScienceDaily,

Nothing is more frustrating that watching that circle spinning in the centre of your screen, while you wait for your computer to load a programme or access the data you need. Now a team from the Universities of Sheffield and Leeds may have found the answer to faster computing: sound.

The research — published in Applied Physics Letters — has shown that certain types of sound waves can move data quickly, using minimal power.

A Nov. 3, 2015 University of Sheffield news release on EurekAlert, which originated the news item, explains some of the issues with data and memory before briefly describing how sound waves could provide a solution,

The world’s 2.7 zettabytes (2.7 followed by 21 zeros) of data are mostly held on hard disk drives: magnetic disks that work like miniaturised record players, with the data read by sensors that scan over the disk’s surface as it spins. But because this involves moving parts, there are limits on how fast it can operate.

For computers to run faster, we need to create “solid-state” drives that eliminate the need for moving parts – essentially making the data move, not the device on which it’s stored. Flash-based solid-state disk drives have achieved this, and store information electrically rather than magnetically. However, while they operate much faster than normal hard disks, they last much less time before becoming unreliable, are much more expensive and still run much slower than other parts of a modern computer – limiting total speed.

Creating a magnetic solid-state drive could overcome all of these problems. One solution being developed is ‘racetrack memory’, which uses tiny magnetic wires, each one hundreds of times thinner than a human hair, down which magnetic “bits” of data run like racing cars around a track. Existing research into racetrack memory has focused on using magnetic fields or electric currents to move the data bits down the wires. However, both these options create heat and reduce power efficiency, which will limit battery life, increase energy bills and CO2 emissions.

Dr Tom Hayward from the University of Sheffield and Professor John Cunningham from the University of Leeds have together come up with a completely new solution: passing sound waves across the surface on which the wires are fixed. They also found that the direction of data flow depends on the pitch of the sound generated – in effect they “sang” to the data to move it.

The sound used is in the form of surface acoustic waves – the same as the most destructive wave that can emanate from an earthquake. Although already harnessed for use in electronics and other areas of engineering, this is the first time surface acoustic waves have been applied to a data storage system.

Dr Hayward, from Sheffield’s Faculty of Engineering, said: “The key advantage of surface acoustic waves in this application is their ability to travel up to several centimetres without decaying, which at the nano-scale is a huge distance. Because of this, we think a single sound wave could be used to “sing” to large numbers of nanowires simultaneously, enabling us to move a lot of data using very little power. We’re now aiming to create prototype devices in which this concept can be fully tested.”

Here’s a link to and a citation for the paper,

A sound idea: Manipulating domain walls in magnetic nanowires using surface acoustic waves by J. Dean, M. T. Bryan, J. D. Cooper, A. Virbule, J. E. Cunningham, and T. J. Hayward. Appl. Phys. Lett. 107, 142405 (2015);

This is an open access paper.

Dexter Johnson in a Nov. 5, 2015 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) provides a few additional details about the work such as a brief mention of IBM’s work developing racetrack memory, also known as, a non-volatile memory device.

A nanoscale bacteria power grid

It’s not often you see the word ‘spectacular’ when reading a science news item but it can be found in an Oct. 21, 2015 news item on ScienceDaily,

Electrical energy from the socket — this convenient type of power supply is apparently used by some microorganisms. Cells can meet their energy needs in the form of electricity through nano-wire connections. Researchers from the Max Planck Institute for Marine Microbiology in Bremen have discovered these possibly smallest power grids in the world when examining cell aggregates of methane degrading microorganisms. They consist of two completely different cell types, which can only jointly degrade methane. Scientists have discovered wire-like connections between the cells, which are relevant in energy exchanges.

It was a spectacular [emphasis mine] scientific finding when researchers discovered electrical wiring between microorganisms using iron as energy source in 2010. Immediately the question came up if electric power exchange is common in other microbially mediated reactions. One of the processes in question was the anaerobic oxidation of methane (AOM) that is responsible for the degradation of the greenhouse gas methane in the seafloor, and therefore has a great relevance for Earth climate. The microorganisms involved have been described for the first time in 2000 by researchers from Bremen and since then have been extensively studied.

This image accompanies the research,

Caption: Electron micrograph of the nanowires shows connecting archaea and sulphate reducing bacteria. The wires stretch out for several micrometres, longer than a single cell. The white bar represents the length of one micrometre. The arrows indicate the nanowires (A=ANME-Archaeen, H=HotSeep-1 partner bacteria). Credit: MPI f. Biophysical Chemistry

Caption: Electron micrograph of the nanowires shows connecting archaea and sulphate reducing bacteria. The wires stretch out for several micrometres, longer than a single cell. The white bar represents the length of one micrometre. The arrows indicate the nanowires (A=ANME-Archaeen, H=HotSeep-1 partner bacteria).
Credit: MPI f. Biophysical Chemistry

A Oct. 21, 2015 Max Planck press release (also on EurekAlert), which originated the news item, provides more information about methane in the ocean, power wires, and electron transporters,

In the ocean, methane is produced from the decay of dead biomass in subsurface sediments. The methane rises upwards to the seafloor, but before reaching the water column it is degraded by special consortia of archaea and bacteria. The archaea take up methane and oxidise it to carbonate. They pass on energy to their partner bacteria, so that the reaction can proceed. The bacteria respire sulphate instead of oxygen to gain energy (sulphate reducers). This may be an ancient metabolism, already relevant billions of years ago when the Earth’s atmosphere was oxygen-free. Yet today it remains unknown how the anaerobic oxidation of methane works biochemically.

Gunter Wegener, who authors the publication together with PhD student Viola Krukenberg, says: “We focused on thermophilic AOM consortia living at 60 degrees Celsius. For the first time we were able to isolate the partner bacteria to grow them alone. Then we systematically compared the physiology of the isolate with that of the AOM culture. We wanted to know which substances can serve as an energy carrier between the archaea and sulphate reducers.” Most compounds were ruled out quickly. At first, hydrogen was considered as energy source. However, the archaea did not produce sufficient hydrogen to explain the growth of sulphate reducers – hence the researchers had to change their strategy.

Direct power wires and electron transporters

One possible alternative was to look for direct connections channelling electrons between the cells. Using electron microscopy on the thermophilic AOM cultures this idea was confirmed. Dietmar Riedel, head of electron microscopy facilities at the Max Planck Institute in Goettingen says: “It was really challenging to visualize the cable-like structures. We embedded aggregates under high pressure using different embedding media. Ultrathin sections of these aggregates were then examined in near-native state using transmission electron microscopy.”

Viola Krukenberg adds: “We found all genes necessary for biosynthesis of the cellular connections called pili. Only when methane is added as energy source these genes are activated and pili are formed between bacteria and archaea.”

With length of several micrometres the wires can exceed the length of the cells by far, but their diameter is only a few nanometres. These wires provide the contact between the closely spaced cells and explain the spatial structure of the consortium, as was shown by a team of researchers led by Victoria Orphan from Caltech.

“Consortia of archaea and bacteria are abundant in nature. Our next step is to see whether other types also show such nanowire-like connections. It is important to understand how methane-degrading microbial consortia work, as they provide important functions in nature”, explains Antje Boetius, leader of the research group at the Institute in Bremen.

Here’s a link to and a citation for the paper,

Intercellular wiring enables electron transfer between methanotrophic archaea and bacteria by Gunter Wegener, Viola Krukenberg, Dietmar Riedel, Halina E. Tegetmeyer, & Antje Boetius. Nature 526, 587–590 (22 October 2015) doi:10.1038/nature15733 Published online 21 October 2015

This paper is behind a paywall.

A perovskite memristor with three stable resistive states

Thanks to Dexter Johnson’s Oct. 22, 2015 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers]) website, I’ve found information about a second memristor with three terminals, aka, three stable resistive states,  (the first is mentioned in my April 10, 2015 posting). From Dexter’s posting (Note: Links have been removed),

Now researchers at ETH Zurich have designed a memristor device out of perovskite just 5 nanometres thick that has three stable resistive states, which means it can encode data as 0,1 and 2, or a “trit” as opposed to a “bit.”

The research, which was published in the journal ACS Nano, developed model devices that have two competing nonvolatile resistive switching processes. These switching processes can be alternatively triggered by the effective switching voltage and time applied to the device.

“Our component could therefore also be useful for a new type of IT (Information Technology) that is not based on binary logic, but on a logic that provides for information located ‘between’ the 0 and 1,” said Jennifer Rupp, professor in the Department of Materials at ETH Zurich, in a press release. “This has interesting implications for what is referred to as fuzzy logic, which seeks to incorporate a form of uncertainty into the processing of digital information. You could describe it as less rigid computing.”

An Oct. 19, 2015 Swiss National Science Foundation press release provides context for the research,

Two IT giants, Intel and HP, have entered a race to produce a commercial version of memristors, a new electronics component that could one day replace flash memory (DRAM) used in USB memory sticks, SD cards and SSD hard drives. “Basically, memristors require less energy since they work at lower voltages,” explains Jennifer Rupp, professor in the Department of Materials at ETH Zurich and holder of a SNSF professorship grant. “They can be made much smaller than today’s memory modules, and therefore offer much greater density. This means they can store more megabytes of information per square millimetre.” But currently memristors are only at the prototype stage. [emphasis mine]

There is a memristor-based product on the market as I noted in a Sept. 10, 2015 posting, although that may not be the type of memristive device that Rupp seems to be discussing. (Should you have problems accessing the Swiss National Science Foundation press release, you can find a lightly edited version (a brief [two sentences] history of the memristor has been left out) here on Azonano.

Jacopo Prisco wrote for CNN online in a March 2, 2015 article about memristors and Rupp’s work (Note: A link has been removed),

Simply put, the memristor could mean the end of electronics as we know it and the beginning of a new era called “ionics”.

The transistor, developed in 1947, is the main component of computer chips. It functions using a flow of electrons, whereas the memristor couples the electrons with ions, or electrically charged atoms.

In a transistor, once the flow of electrons is interrupted by, say, cutting the power, all information is lost. But a memristor can remember the amount of charge that was flowing through it, and much like a memory stick it will retain the data even when the power is turned off.

This can pave the way for computers that will instantly turn on and off like a light bulb and never lose data: the RAM, or memory, will no longer be erased when the machine is turned off, without the need to save anything to hard drives as with current technology.

Jennifer Rupp is a Professor of electrochemical materials at ETH Zurich, and she’s working with IBM to build a memristor-based machine.

Memristors, she points out, function in a way that is similar to a human brain: “Unlike a transistor, which is based on binary codes, a memristor can have multi-levels. You could have several states, let’s say zero, one half, one quarter, one third, and so on, and that gives us a very powerful new perspective on how our computers may develop in the future,” she told CNN’s Nick Glass.

This is the CNN interview with Rupp,

Prisco also provides an update about HP’s memristor-based product,

After manufacturing the first ever memristor, Hewlett Packard has been working for years on a new type of computer based on the technology. According to plans, it will launch by 2020.

Simply called “The Machine”, it uses “electrons for processing, photons for communication, and ions for storage.”

I first wrote about HP’s The Machine in a June 25, 2014 posting (scroll down about 40% of the way).

There are many academic teams researching memristors including a team at Northwestern University. I highlighted their announcement of a three-terminal version in an April 10, 2015 posting. While Rupp’s team achieved its effect with a perovskite substrate, the Northwestern team used a molybdenum disulfide (MoS2) substrate.

For anyone wanting to read the latest research from ETH, here’s a link to and a citation for the paper,

Uncovering Two Competing Switching Mechanisms for Epitaxial and Ultrathin Strontium Titanate-Based Resistive Switching Bits by Markus Kubicek, Rafael Schmitt, Felix Messerschmitt, and Jennifer L. M. Rupp. ACS Nano, Article ASAP DOI: 10.1021/acsnano.5b02752 Publication Date (Web): October 8, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Finally, should you find the commercialization aspects of the memristor story interesting, there’s a June 6, 2015 posting by Knowm CEO (chief executive officer) Alex Nugent waxes eloquent on HP Labs’ ‘memristor problem’ (Note: A link has been removed),

Today I read something that did not surprise me. HP has said that their memristor technology will be replaced by traditional DRAM memory for use in “The Machine”. This is not surprising for those of us who have been in the field since before HP’s memristor marketing engine first revved up in 2008. While I have to admit the miscommunication between HP’s research and business development departments is starting to get really old, I do understand the problem, or at least part of it.

There are two ways to develop memristors. The first way is to force them to behave as you want them to behave. Most memristors that I have seen do not behave like fast, binary, non-volatile, deterministic switches. This is a problem because this is how HP wants them to behave. Consequently a perception has been created that memristors are for non-volatile fast memory. HP wants a drop-in replacement for standard memory because this is a large and established market. Makes sense of course, but its not the whole story on memristors.

Memristors exhibit a huge range of amazing phenomena. Some are very fast to switch but operate probabilistically. Others can be changed a little bit at a time and are ideal for learning. Still others have capacitance (with memory), or act as batteries. I’ve even seen some devices that can be programmed to be a capacitor or a resistor or a memristor. (Seriously).

Nugent, whether you agree with him or not provides, some fascinating insight. In the excerpt I’ve included here, he seems to provide confirmation that it’s possible to state ‘there are no memristors on the market’ and ‘there are memristors on the market’ because different devices are being called memristors.

US White House’s grand computing challenge could mean a boost for research into artificial intelligence and brains

An Oct. 20, 2015 posting by Lynn Bergeson on Nanotechnology Now announces a US White House challenge incorporating nanotechnology, computing, and brain research (Note: A link has been removed),

On October 20, 2015, the White House announced a grand challenge to develop transformational computing capabilities by combining innovations in multiple scientific disciplines. See The Office of Science and Technology Policy (OSTP) states that, after considering over 100 responses to its June 17, 2015, request for information, it “is excited to announce the following grand challenge that addresses three Administration priorities — the National Nanotechnology Initiative, the National Strategic Computing Initiative (NSCI), and the BRAIN initiative.” The grand challenge is to “[c]reate a new type of computer that can proactively interpret and learn from data, solve unfamiliar problems using what it has learned, and operate with the energy efficiency of the human brain.”

Here’s where the Oct. 20, 2015 posting, which originated the news item, by Lloyd Whitman, Randy Bryant, and Tom Kalil for the US White House blog gets interesting,

 While it continues to be a national priority to advance conventional digital computing—which has been the engine of the information technology revolution—current technology falls far short of the human brain in terms of both the brain’s sensing and problem-solving abilities and its low power consumption. Many experts predict that fundamental physical limitations will prevent transistor technology from ever matching these twin characteristics. We are therefore challenging the nanotechnology and computer science communities to look beyond the decades-old approach to computing based on the Von Neumann architecture as implemented with transistor-based processors, and chart a new path that will continue the rapid pace of innovation beyond the next decade.

There are growing problems facing the Nation that the new computing capabilities envisioned in this challenge might address, from delivering individualized treatments for disease, to allowing advanced robots to work safely alongside people, to proactively identifying and blocking cyber intrusions. To meet this challenge, major breakthroughs are needed not only in the basic devices that store and process information and the amount of energy they require, but in the way a computer analyzes images, sounds, and patterns; interprets and learns from data; and identifies and solves problems. [emphases mine]

Many of these breakthroughs will require new kinds of nanoscale devices and materials integrated into three-dimensional systems and may take a decade or more to achieve. These nanotechnology innovations will have to be developed in close coordination with new computer architectures, and will likely be informed by our growing understanding of the brain—a remarkable, fault-tolerant system that consumes less power than an incandescent light bulb.

Recent progress in developing novel, low-power methods of sensing and computation—including neuromorphic, magneto-electronic, and analog systems—combined with dramatic advances in neuroscience and cognitive sciences, lead us to believe that this ambitious challenge is now within our reach. …

This is the first time I’ve come across anything that publicly links the BRAIN initiative to computing, artificial intelligence, and artificial brains. (For my own sake, I make an arbitrary distinction between algorithms [artificial intelligence] and devices that simulate neural plasticity [artificial brains].)The emphasis in the past has always been on new strategies for dealing with Parkinson’s and other neurological diseases and conditions.

Water evaporation at the nanoscale

An Oct. 16, 2015 news item on ScienceDaily highlights an algorithm designed to simulate water evaporation at the nanoscale,

We are all familiar with boiling a pot of water–flame from a stove heats the base of a metal pot, the metal transfers the heat to the water, and the temperature goes up and up until the water boils. Professor Shalabh Maroo and graduate student Sumith YD are looking closer — much closer. They are looking at heat transfer in water at the nanoscale, where the heat from the pot’s atoms transfers to the atoms that make up water.

An Oct. 16, 2015 Syracuse University news release on EurkeAlert, which originated the news item, provides more insight into what occurs at the nanoscale,

The evaporation of water that occurs when it meets a hot surface is understood in continuum theory and in experimentation. Before now, researchers were unable to study it at nanoscales in molecular simulation. YD and Maroo’s algorithm has made that possible, and their paper, “Surface-Heating Algorithm for Water at Nanoscale,” has garnished notable attention in the Journal of Physical Chemistry Letters.

Within their paper, the pair details their development of a new algorithm that simulates the evaporation of water at the molecular scale that matches theoretical, numerical, and real-world observations. In doing so, the team has provided a molecular dynamics tool that allows for the study of various heat transfer problems at the nanoscale, including understanding and utilizing passive liquid flows.

“By capturing realistic differential thermal gradients in water heated at the surface, our algorithm can be an incredibly valuable tool for studying a range of heating and cooling problems. It’s also simple enough to be easily integrated into various molecular simulation software and user codes,” describes Maroo.

This research is part of Maroo’s CAREER award research, in which he is investigating the fundamental physics associated with nanoscale meniscus evaporation and passive liquid flow to remove large amounts of heat from small surfaces in very short amounts of time. This work aims to provide rapid and efficient cooling of next-generation computer chips and energy conversion devices.

Here’s a link to and a citation for the paper,

Surface-Heating Algorithm for Water at Nanoscale by Sumith YD and Shalabh C. Maroo. J. Phys. Chem. Lett., 2015, 6 (18), pp 3765–3769 DOI: 10.1021/acs.jpclett.5b01627
Publication Date (Web): September 3, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Memristor shakeup

New discoveries suggest that memristors do not function as was previously theorized. (For anyone who wants a memristor description, there’s this Wikipedia entry.) From an Oct. 13, 2015 posting by Alexander Hellemans for the Nanoclast blog (on the IEEE [Institute for Electrical and Electronics Engineers]), Note: Links have been removed,

What’s going to replace flash? The R&D arms of several companies including Hewlett Packard, Intel, and Samsung think the answer might be memristors (also called resistive RAM, ReRAM, or RRAM). These devices have a chance at unseating the non-volatile memory champion because, they use little energy, are very fast, and retain data without requiring power. However, new research indicates that they don’t work in quite the way we thought they do.

The fundamental mechanism at the heart of how a memristor works is something called an “imperfect point contact,” which was predicted in 1971, long before anybody had built working devices. When voltage is applied to a memristor cell, it reduces the resistance across the device. This change in resistance can be read out by applying another, smaller voltage. By inverting the voltage, the resistance of the device is returned to its initial value, that is, the stored information is erased.

Over the last decade researchers have produced two commercially promising types of memristors: electrochemical metallization memory (ECM) cells, and valence change mechanism memory (VCM) cells.

Now international research teams lead by Ilia Valov at the Peter Grünberg Institute in Jülich, Germany, report in Nature Nanotechnology and Advanced Materials that they have identified new processes that erase many of the differences between EMC and VCM cells.

Valov and coworkers in Germany, Japan, Korea, Greece, and the United States started investigating memristors that had a tantalum oxide electrolyte and an active tantalum electrode. “Our studies show that these two types of switching mechanisms in fact can be bridged, and we don’t have a purely oxygen type of switching as was believed, but that also positive [metal] ions, originating from the active electrode, are mobile,” explains Valov.

Here are links to and citations for both papers,

Graphene-Modified Interface Controls Transition from VCM to ECM Switching Modes in Ta/TaOx Based Memristive Devices by Michael Lübben, Panagiotis Karakolis, Vassilios Ioannou-Sougleridis, Pascal Normand, Pangiotis Dimitrakis, & Ilia Valov. Advanced Materials DOI: 10.1002/adma.201502574 First published: 10 September 2015

Nanoscale cation motion in TaOx, HfOx and TiOx memristive systems by Anja Wedig, Michael Luebben, Deok-Yong Cho, Marco Moors, Katharina Skaja, Vikas Rana, Tsuyoshi Hasegawa, Kiran K. Adepalli, Bilge Yildiz, Rainer Waser, & Ilia Valov. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.221 Published online 28 September 2015

Both papers are behind paywalls.

Touchless displays with 2D nanosheets and sweat

Swiping touchscreens with your finger has become a dominant means of accessing information in many applications but there is at least one problem associated with this action. From an Oct. 2, 2015 news item on,

While touchscreens are practical, touchless displays would be even more so. That’s because, despite touchscreens having enabled the smartphone’s advance into our lives and being essential for us to be able to use cash dispensers or ticket machines, they do have certain disadvantages. Touchscreens suffer from mechanical wear over time and are a transmission path for bacteria and viruses. To avoid these problems, scientists at Stuttgart’s Max Planck Institute for Solid State Research and LMU Munich have now developed nanostructures that change their electrical and even their optical properties as soon as a finger comes anywhere near them.

Here’s what a touchless screen looks like when tracking,

Touchless colour change: A nanostructure containing alternating layers of phosphatoantimonate nanosheets and oxide ... [more] © Advanced Materials 2015/MPI for Solid State Research

Touchless colour change: A nanostructure containing alternating layers of phosphatoantimonate nanosheets and oxide … [more]
© Advanced Materials 2015/MPI for Solid State Research

An Oct. 1, 2015 Max Planck Institute press release, which originated the news item, gives technical details,

A touchless display may be able to capitalize on a human trait which is of vital importance, although sometimes unwanted: This is the fact that our body sweats – and is constantly emitting water molecules through tiny pores in the skin. Scientists of the Nanochemistry group led by Bettina Lotsch at the Max Planck Institute for Solid State Research in Stuttgart and the LMU Munich have now been able to visualize the transpiration of a finger with a special moisture sensor which reacts as soon as an object – like an index finger – approaches its surface, without touching it. The increasing humidity is converted into an electrical signal or translated into a colour change, thus enabling it to be measured.

Phosphatoantimonic acid is what enables it to do this. This acid is a crystalline solid at room temperature with a structure made up of antimony, phosphorous, oxygen and hydrogen atoms. “It’s long been known to scientists that this material is able to take up water and swells considerably in the process,” explained Pirmin Ganter, doctoral student at the Max Planck Institute for Solid State Research and the Chemistry Department at LMU Munich. This water uptake also changes the properties of the material. For instance, its electrical conductivity increases as the number of stored water molecules rises. This is what enables it to serve as a measure of ambient moisture.

A sandwich nanomaterial structure exposed to moisture also changes its colour

However, the scientists aren’t so interested in developing a new moisture sensor. What they really want is to use it in touchless displays. “Because these sensors react in a very local manner to any increase in moisture, it is quite conceivable that this sort of material with moisture-dependent properties could also be used for touchless displays and monitors,” said Ganter. Touchless screens of this kind would require nothing more than a finger to get near the display to change their electrical or optical properties – and with them the input signal – at a specific point on the display.

Taking phosphatoantimonate nanosheets as their basis, the Stuttgart scientists then developed a photonic nanostructure which reacts to the moisture by changing colour. “If this was built into a monitor, the users would then receive visible feedback to  their finger motion” explained Katalin Szendrei, also a doctoral student in Bettina Lotsch’s group. To this end, the scientists created a multilayer sandwich material with alternating layers of ultrathin phosphatoantimonate nanosheets and silicon dioxide (SiO2) or titanium dioxide nanoparticles (TiO2). Comprising more than ten layers, the stack ultimately reached a height of little more than one millionth of a metre.

For one thing, the colour of the sandwich material can be set via the thickness of the layers. And for another, the colour of the sandwich changes if the scientists increase the relative humidity in the immediate surroundings of the material, for instance by moving a finger towards the screen. “The reason for this lies in the storage of water molecules between the phosphatoantimonate layers, which makes the layers swell considerably,” explained Katalin Szendrei. “A change in the thickness of the layers in this process is accompanied by a change in the colour of the sensor – produced in a similar way to what gives colour to a butterfly wing or in mother-of-pearl.”

The material reacts to the humidity change within a few milliseconds

This is a property that is fundamentally well known and characteristic of so-called photonic crystals. But scientists had never before observed such a large colour change as they now have in the lab in Stuttgart. “The colour of the nanostructure turns from blue to red when a finger gets near, for example. In this way, the colour can be tuned through the whole of the visible spectrum depending on the amount of water vapour taken up,” stressed Bettina Lotsch.

The scientists’ new approach is not only captivating because of the striking colour change. What’s also important is the fact that the material reacts to the change in humidity within a few milliseconds – literally in the blink of an eye. Previously reported materials normally took several seconds or more to respond. That is much too slow for practical applications. And there’s another thing that other materials couldn’t always do: The sandwich structure consisting of phosphatoantimonate nanosheets and oxide nanoparticles is highly stable from a chemical perspective and responds selectively to water vapour.

A layer protecting against chemical influences has to let moisture through

The scientists can imagine their materials being used in much more than just future generations of smartphones, tablets or notebooks. “Ultimately, we could see touchless displays also being deployed in many places where people currently have to touch monitors to navigate,” said Bettina Lotsch. For instance in cash dispensers or ticket machines, or even at the weighing scales in the supermarket’s vegetable aisle. Displays in public placesthat are used by many different people would have distinct hygiene benefits if they were touchless.

But before we see them being used in such places, the scientists have a few more challenges to overcome. It’s important, for example, that the nanostructures can be produced economically. To minimize wear, the structures still need to be coated with a protective layer if they’re going to be used in anything like a display. And that, again, has to meet not one but two different requirements: It must protect the moisture-sensitive layers against chemical and mechanical influences. And it must, of course, let the moisture pass through. But the Stuttgart scientists have an idea for how to achieve that already. An idea they are currently starting to put into practice with an additional cooperation partner on board.

Dexter Johnson’s Oct. 2, 2015 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) provides some additional context for this research (Note: A link has been removed),

In a world where the “swipe” has become a dominant computer interface method along with moving and clicking the mouse, the question becomes what’s next? For researchers at Stuttgart’s Max Planck Institute for Solid State Research and LMU Munich, Germany, the answer continues to be a swipe, but one in which you don’t actually need to touch the screen with your finger. Researchers call these no-contact computer screens touchless positioning interfaces (TPI).

Here’s a link to and a citation for the paper,

Touchless Optical Finger Motion Tracking Based on 2D Nanosheets with Giant Moisture Responsiveness by Katalin Szendrei, Pirmin Ganter, Olalla Sànchez-Sobrado, Roland Eger, Alexander Kuhn, and Bettina V. Lotsch. Advanced Materials DOI: 10.1002/adma.201503463 Article first published online: 22 SEP 2015

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Smart windows need anti-aging treatments

I’ve long been interested in electrochromic windows and this is the first I’ve heard of a problem with limited lifespans. Here’s more from an Oct. 1, 2015 news item on Nanowerk (Note: A link has been removed),

Electrochromic windows, so-called ‘smart windows’, share a well-known problem with rechargeable batteries – their limited lifespan. Researchers at Uppsala University [Sweden] have now worked out an entirely new way to rejuvenate smart windows which have started to show signs of age. The study, published in Nature Materials (“Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO3 thin films”), may open the way to other areas of application.

An Oct. 1, 2015 Uppsala University press release (also on EurekAlert), which originated the new item, describes previous work on electrochromic windows to provide context for the current research,

The electrochromic smart windows are controlled electrically. This kind of window is the result of research carried out at Uppsala University. Commercial production has recently been started by the company ChromoGenics AB.

The electrochromic smart window is made up of a series of thin layers on top of each other. The most important of these are two layers of tungsten oxide and nickel oxide, both about a third of a micrometer thick. They are separated by an electrolyte layer. The window’s opacity to visible light and solar energy varies when an electrical current flows between the oxide layers.

“The principle is the same as for an electric battery. Here the tungsten-oxide is the cathode and the nickel-oxide the anode. Opacity depends on how much the ‘battery’ is charged,” says Rui-Tao Wen, a doctoral student who carried out the study as part of his thesis.

The lifespan of both electric batteries and electrochromic smart windows is a well-known problem. They need to work after being charged and discharged many times if they are to be really profitable.

In the study, the researchers show that an electrochromic tungsten oxide layer which has been charged and discharged many times and has started to lose its capacity can be restored to its former high capacity. This is achieved by running a weak electric current through it while it is in light mode. This takes about an hour. In this way, the electric charge which has ‘fastened’ in the material is removed and the tungsten oxide layer is like new again.

“This is a new way to rejuvenate smart windows so that they last much longer. And the same principle might perhaps be used for electric batteries,” says Claes-Göran Granqvist, senior professor at the Ångström Laboratory, Uppsala University and one of the authors of the study.

Here’s a link to and a citation for the paper,

Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO3 thin films by Rui-Tao Wen, Claes G. Granqvist, & Gunnar A. Niklasson. Nature Materials 14, 996–1001 (2015) doi:10.1038/nmat4368 Published online 10 August 2015

This paper is behind a paywall.