Category Archives: nanotechnology

Second order memristor

I think this is my first encounter with a second-order memristor. An August 28, 2019 news item on Nanowerk announces the research (Note: A link has been removed),

Researchers from the Moscow Institute of Physics and Technology [MIPT} have created a device that acts like a synapse in the living brain, storing information and gradually forgetting it when not accessed for a long time. Known as a second-order memristor, the new device is based on hafnium oxide and offers prospects for designing analog neurocomputers imitating the way a biological brain learns.

An August 28, 2019 MIPT press release (also on EurekAlert), which originated the news item, provides an explanation for neuromorphic computing (analog neurocomputers; brainlike computing), the difference between a first-order and second-order memristor, and an in depth view of the research,

Neurocomputers, which enable artificial intelligence, emulate the way the brain works. It stores data in the form of synapses, a network of connections between the nerve cells, or neurons. Most neurocomputers have a conventional digital architecture and use mathematical models to invoke virtual neurons and synapses.

Alternatively, an actual on-chip electronic component could stand for each neuron and synapse in the network. This so-called analog approach has the potential to drastically speed up computations and reduce energy costs.

The core component of a hypothetical analog neurocomputer is the memristor. The word is a portmanteau of “memory” and “resistor,” which pretty much sums up what it is: a memory cell acting as a resistor. Loosely speaking, a high resistance encodes a zero, and a low resistance encodes a one. This is analogous to how a synapse conducts a signal between two neurons (one), while the absence of a synapse results in no signal, a zero.

But there is a catch: In an actual brain, the active synapses tend to strengthen over time, while the opposite is true for inactive ones. This phenomenon known as synaptic plasticity is one of the foundations of natural learning and memory. It explains the biology of cramming for an exam and why our seldom accessed memories fade.

Proposed in 2015, the second-order memristor is an attempt to reproduce natural memory, complete with synaptic plasticity. The first mechanism for implementing this involves forming nanosized conductive bridges across the memristor. While initially decreasing resistance, they naturally decay with time, emulating forgetfulness.

“The problem with this solution is that the device tends to change its behavior over time and breaks down after prolonged operation,” said the study’s lead author Anastasia Chouprik from MIPT’s Neurocomputing Systems Lab. “The mechanism we used to implement synaptic plasticity is more robust. In fact, after switching the state of the system 100 billion times, it was still operating normally, so my colleagues stopped the endurance test.”

Instead of nanobridges, the MIPT team relied on hafnium oxide to imitate natural memory. This material is ferroelectric: Its internal bound charge distribution — electric polarization — changes in response to an external electric field. If the field is then removed, the material retains its acquired polarization, the way a ferromagnet remains magnetized.

The physicists implemented their second-order memristor as a ferroelectric tunnel junction — two electrodes interlaid with a thin hafnium oxide film (fig. 1, right). The device can be switched between its low and high resistance states by means of electric pulses, which change the ferroelectric film’s polarization and thus its resistance.

“The main challenge that we faced was figuring out the right ferroelectric layer thickness,” Chouprik added. “Four nanometers proved to be ideal. Make it just one nanometer thinner, and the ferroelectric properties are gone, while a thicker film is too wide a barrier for the electrons to tunnel through. And it is only the tunneling current that we can modulate by switching polarization.”

What gives hafnium oxide an edge over other ferroelectric materials, such as barium titanate, is that it is already used by current silicon technology. For example, Intel has been manufacturing microchips based on a hafnium compound since 2007. This makes introducing hafnium-based devices like the memristor reported in this story far easier and cheaper than those using a brand-new material.

In a feat of ingenuity, the researchers implemented “forgetfulness” by leveraging the defects at the interface between silicon and hafnium oxide. Those very imperfections used to be seen as a detriment to hafnium-based microprocessors, and engineers had to find a way around them by incorporating other elements into the compound. Instead, the MIPT team exploited the defects, which make memristor conductivity die down with time, just like natural memories.

Vitalii Mikheev, the first author of the paper, shared the team’s future plans: “We are going to look into the interplay between the various mechanisms switching the resistance in our memristor. It turns out that the ferroelectric effect may not be the only one involved. To further improve the devices, we will need to distinguish between the mechanisms and learn to combine them.”

According to the physicists, they will move on with the fundamental research on the properties of hafnium oxide to make the nonvolatile random access memory cells more reliable. The team is also investigating the possibility of transferring their devices onto a flexible substrate, for use in flexible electronics.

Last year, the researchers offered a detailed description of how applying an electric field to hafnium oxide films affects their polarization. It is this very process that enables reducing ferroelectric memristor resistance, which emulates synapse strengthening in a biological brain. The team also works on neuromorphic computing systems with a digital architecture.

MIPT has provided this image illustrating the research,

Caption: The left image shows a synapse from a biological brain, the inspiration behind its artificial analogue (right). The latter is a memristor device implemented as a ferroelectric tunnel junction — that is, a thin hafnium oxide film (pink) interlaid between a titanium nitride electrode (blue cable) and a silicon substrate (marine blue), which doubles up as the second electrode. Electric pulses switch the memristor between its high and low resistance states by changing hafnium oxide polarization, and therefore its conductivity. Credit: Elena Khavina/MIPT Press Office

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

Ferroelectric Second-Order Memristor by Vitalii Mikheev, Anastasia Chouprik, Yury Lebedinskii, Sergei Zarubin, Yury Matveyev, Ekaterina Kondratyuk, Maxim G. Kozodaev, Andrey M. Markeev, Andrei Zenkevich, Dmitrii Negrov. ACS Appl. Mater. Interfaces 2019113532108-32114 DOI: https://doi.org/10.1021/acsami.9b08189 Publication Date:August 12, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Control your electronics devices with your clothing while protecting yourself from bacteria

Purdue University researchers have developed a new fabric innovation that allows the wearer to control electronic devices through the clothing. Courtesy: Purdue University

I like the image but do they really want someone pressing a cufflink? Anyway, being able to turn on your house lights and music system with your clothing would certainly be convenient. From an August 8, 2019 Purdue University (Indiana, US) news release (also on EurekAlert) by Chris Adam,

A new addition to your wardrobe may soon help you turn on the lights and music – while also keeping you fresh, dry, fashionable, clean and safe from the latest virus that’s going around.

Purdue University researchers have developed a new fabric innovation that allows wearers to control electronic devices through clothing.

“It is the first time there is a technique capable to transform any existing cloth item or textile into a self-powered e-textile containing sensors, music players or simple illumination displays using simple embroidery without the need for expensive fabrication processes requiring complex steps or expensive equipment,” said Ramses Martinez, an assistant professor in the School of Industrial Engineering and in the Weldon School of Biomedical Engineering in Purdue’s College of Engineering.

The technology is featured in the July 25 [2019] edition of Advanced Functional Materials.

“For the first time, it is possible to fabricate textiles that can protect you from rain, stains, and bacteria while they harvest the energy of the user to power textile-based electronics,” Martinez said. “These self-powered e-textiles also constitute an important advancement in the development of wearable machine-human interfaces, which now can be washed many times in a conventional washing machine without apparent degradation.

Martinez said the Purdue waterproof, breathable and antibacterial self-powered clothing is based on omniphobic triboelectric nanogeneragtors (RF-TENGs) – which use simple embroidery and fluorinated molecules to embed small electronic components and turn a piece of clothing into a mechanism for powering devices. The Purdue team says the RF-TENG technology is like having a wearable remote control that also keeps odors, rain, stains and bacteria away from the user.

“While fashion has evolved significantly during the last centuries and has easily adopted recently developed high-performance materials, there are very few examples of clothes on the market that interact with the user,” Martinez said. “Having an interface with a machine that we are constantly wearing sounds like the most convenient approach for a seamless communication with machines and the Internet of Things.”

The technology is being patented through the Purdue Research Foundation Office of Technology Commercialization. The researchers are looking for partners to test and commercialize their technology.

Their work aligns with Purdue’s Giant Leaps celebration of the university’s global advancements in artificial intelligence and health as part of Purdue’s 150th anniversary. It is one of the four themes of the yearlong celebration’s Ideas Festival, designed to showcase Purdue as an intellectual center solving real-world issues.

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

Waterproof, Breathable, and Antibacterial Self‐Powered e‐Textiles Based on Omniphobic Triboelectric Nanogenerators by Marina Sala de Medeiros, Daniela Chanci, Carolina Moreno, Debkalpa Goswami, Ramses V. Martinez. Advanced Functional Materials DOI: https://doi.org/10.1002/adfm.201904350 First published online: 25 July 2019

This paper is behind a paywall.

Space debris, water, and DIY biology, science events in Canada (Jan. 22 – 23, 2020)

There is a lot happening in the next day or two. I have two Vancouver (Canada) science events and an online event, which can be attended from anywhere.

Space debris on January 23, 2020 in Vancouver

I was surprised to learn about space debris (it was described as a floating junkyard in space) in 1992. It seems things have not gotten better. Here’s more from the Cosmic Nights: Space Debris event page on the H.R. MacMillan Space Centre website,

Cosmic Nights: Space Debris

….

There are tens of thousands of pieces of man-made debris, or “space junk,” orbiting the Earth that threaten satellites and other spacecraft. With the increase of space exploration and no debris removal processes in place that number is sure to increase.

Learn more about the impact space debris will have on current and future missions, space law, and the impact human activity, both scientific, and commercial are having on space as we discuss what it will take to make space exploration more sustainable. Physics professors Dr. Aaron Rosengren, and Dr. Aaron Boley will be joining us to share their expertise on the subject.

Tickets available for 7:30pm or 9:00pm planetarium star theatre shows.
________________

7:30 ticket holder schedule:
6:30 – check-in
7:00 – “Pooping in Space” (GroundStation Canada Theatre)
7:30 – 8:30 “Go Boldly and Sustainably” show (Planetarium Star Theatre)
9:00 – 9:30 “Space Debris” lecture

9:00 ticket holder schedule:
6:30 – check-in
7:00 – 9:00 (runs every 30 mins) “Pooping in Space” show (GroundStation Canada Theatre)
8:00 – 8:30 “Space Debris” lecture
9:00 – 10:00 “Go Boldly and Sustainably” show (Planetarium Star Theatre)
The bar will be open from 6:30 – 10:00pm in the Cosmic Courtyard.

Only planetarium shows are ticketed, all other activities are optional.

7:00pm, 7:30pm, 8:00pm, 8:30pm – “Pooping in Space” – GroundStation Canada Theatre
The ultimate waste! What happens when you have to “GO” in space? In this live show you’ll see how astronauts handle this on the ISS, look at some new innovations space suit design for future missions, and we’ll have some fun astronaut trivia.

7:30pm and 9:00pm – “Go Boldly and Sustainably” – Planetarium Star Theatre
As humans venture into a solar system, where no one can own anything, it is becoming increasingly important to create policies to control for waste and promote sustainability. But who will enact these policies? Will it be our governments or private companies? Our astronomer Rachel Wang, and special guest Dr. Aaron Boley will explore these concepts under the dome in the Planetarium Star Theatre. For the 7:30 show SFU’s Paul Meyer will be making an appearance to talk about the key aspects of space security diplomacy and how it relates to the space debris challenge.

Dr. Aaron Boley is an Assistant Professor in the Physics and Astronomy department at UBC whose research program uses theory and observations to explore a wide range of processes in the formation of planets, from the birth of planet-forming discs to the long-term evolution of planetary systems.

Paul Meyer is Fellow in International Security and Adjunct Professor of International Studies at Simon Fraser University and a founding member of the Outer Space Institute. Prior to his assuming his current positions in 2011, Mr. Meyer had a 35-year career with the Canadian Foreign Service, including serving as Canada’s Ambassador to the United Nations and to the Conference on Disarmament in Geneva (2003-2007). He teaches a course on diplomacy at SFU’s School for International Studies and writes on issues of nuclear non-proliferation and disarmament, outer space security and international cyber security.

8:00pm and 9:00pm – “Space Junk: Our Quest to Conquer the Space Environment Problem” lecture by Dr. Aaron Rosengren

At the end of 2019, after nearly two decades, the U.S. government issued updated orbital debris mitigation guidelines, but the revision fell short of the sweeping changes many in the space debris research community expected. The updated guidelines sets new quantitative limits on events that can create debris and updates the classes of orbits to be used for the retirement of satellites, even allowing for the new exotic idea of passive disposal through gravitational resonances (similar phenomena have left their mark on the asteroid belt between Mars and Jupiter). The revised guidelines, however, do not make major changes, and leave intact the 25-year time frame for end-of-life disposal of low-Earth orbit satellites, a period many now believe to be far too long with the ever increasing orbital traffic in near-Earth space. In this talk, I will discuss various approaches to cleaning up or containing space junk, such as a recent exciting activity in Australia to use laser photo pressure to nudge inactive debris to safe orbits.

Dr. Aaron J. Rosengren is an Assistant Professor in the College of Engineering at the University of Arizona and Member of the Interdisciplinary Graduate Program in Applied Mathematics. Prior to joining UA in 2017, he spent one year at the Aristotle University of Thessaloniki in Greece working in the Department of Physics, as part of the European Union H2020 Project ReDSHIFT. He has also served as a member of the EU Asteroid and Space Debris Network, Stardust, working for two years at the Institute of Applied Physics Nello Carrara of the Italian National Research Council. His research interests include space situational awareness, orbital debris, celestial mechanics, and planetary science. Aaron is currently part of the Space Situational Awareness (SSA)-Arizona initiative at the University of Arizona, a member of the Outer Space Institute (OSI) for the sustainable development of Space at the University of British Columbia, and a research affiliate of the Center for Orbital Debris Education and Research (CODER) at the University of Maryland.

*Choose between either the 7:30pm or 9:00pm planetarium show when purchasing your ticket.*

This is a 19+ event. All attendees will be required to provide photo ID upon entry.

Date and Time

Thu, 23 January 2020
6:30 PM – 10:00 PM PST

Location

H.R. MacMillan Space Centre
1100 Chestnut Street
Vancouver, BC V6J 3J9

Cosmic Nights is the name for a series of talks about space and astronomy and an opportunity to socialize with your choice of beer or wine for purchase.

Canada-wide 2nd Canadian DIY Biology Summit (live audio and webcast)

This is a January 22, 2020 event accessible Canada-wide. For anyone on Pacific Time, it does mean being ready to check-in at 5 am. The first DIY Biology (‘do-it-yourself’ biology) Summit was held in 2016.

Here’s more about the event from its Open Science Network events page on Meetup,

Organizers of Community Biolabs across Canada are converging on Ottawa this Wednesday for the second Canadian DIY Biology Summit organized by the Public Health Agency of Canada (PHAC). OSN [Open Science Network] President & Co-Founder, Scott Pownall, has been invited to talk about the Future of DIY/Community Biology in Canada.

The agenda was just released. Times are East Standard Time.
https://www.opensciencenet.org/wp-content/uploads/2020/01/2020-2nd-Canadian-DYI-Biology-Summit-Agenda.pdf

You can join in remotely via WebEx or audio conferencing.

WebEx Link: https://gts-ee.webex.com/webappng/sites/gts-ee/meeting/info/1144bc57660846349f15cf6e80a6a35f

A few points of clarification: DIYbio YVR has been renamed Open Science Network on Meetup and, should you wish to attend the summit virtually, there is information about passwords and codes on the agenda, which presumably will help you to get access.

Nerd Nite v. 49: Waterslides, Oil Tankers, and Predator-Prey Relationships on January 22, 2020 in Vancouver

Here’s more about Nerd Nite Vancouver v.49 from its event posting,

When you were young, did you spend your summers zooming down waterslides? We remember days where our calves ached from climbing stairs, and sore bums from well… you know. And, if you were like us, you also stared at those slides and thought “How are these things made? And, is it going to disassemble while I’m on it?”. Today, we spend more of our summer days staring out at the oil tankers lining the shore, or watching seagulls dive down to retrieve waste left behind by tourists on Granville Island, but we maintain that curiousity about the things around us! So, splash into a New Year with us to learn about all three: waterslides, oil tankers, and predator-prey relationships.

Hosted by: Kaylee Byers and Michael Unger

Where: The Fox Cabaret

When: Wednesday January 22nd; Doors @ 7, show starts @ 7:30

Tickets: Eventbrite

Poster by: Armin Mortazavi

Music by: DJ Burger

1. Ecology

Zachary Sherker 

Zachary is completing an MSc at UBC investigating freshwater and estuarine predation on juvenile salmon during their out-migration from natal rivers and works as a part-time contract biologist in the lower mainland. Prior to coming out west, Zach completed an interdisciplinary BSc in Aquatic Resources and Biology at St. F.X. University in Antigonish, N.S. During his undergraduate degree, Zach ran field and lab experiments to explore predator-induced phenotypic plasticity in intertidal blue mussels exposed to the waterborne cues of a drilling predator snail. He also conducted biological surveys on lobster fishing boats and worked as a fisheries observer for the offshore commercial snow crab fleet.

2. Waterslides

Shane Jensen

Shane is a professional mechanical engineer whose career transitioned from submarine designer to waterslide tester. He is currently a product manager for waterslides at WhiteWater West.

3. Oil Tankers 101

Kayla Glynn 

Kayla is an ocean enthusiast. She earned her Masters in Marine Management at Dalhousie University, studying compensation for environmental damage caused by ship-source oil spills. Passionate about sharing her knowledge of the ocean with others, Kayla’s shifted her focus to the realm of science communication to help more people foster a deeper relationship with science and the ocean. Kayla now works as a producer at The Story Collider, a non-profit dedicated to sharing true, personal stories about science, where she hosts live storytelling events and leads workshops on behalf of the organization. Follow her at @kaylamayglynn and catch her live on the Story Collider stage on February 11th, 2020!

There you have it.

Gold glue?

If you’re hoping for gold flecks in your glue, this is not going to satisfy you, given that it’s all at the nanoscale. An August 7, 2019 news item on Nanowerk briefly describes this gold glue (Note: A link has been removed),

It has long been known that gold can be used to do things that philosophers have never even dreamed of. The Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow has confirmed the existence of ‘gold glue’: bonds involving gold atoms, capable of permanently bonding protein rings. Skilfully used by an international team of scientists, the bonds have made it possible to construct molecular nanocages with a structure so far unparalleled in nature or even in mathematics (Nature, “An ultra-stable gold-coordinated protein cage displaying reversible assembly”).

Caption: The ‘impossible’ sphere, i.e. a molecular nanocage of 24 protein rings, each of which has an 11-sided structure. The rings are connected by bonds with the participation of gold atoms, here marked in yellow. Depending on their position in the structure, not all gold atoms have to be used to attach adjacent proteins (an unused gold atom is marked in red). Credit: Source: UJ, IFJ PAN

An August 6, 2019 Polish Academy of Sciences press release (also on EurekAlert but published August 7, 2019), which originated the news item, expands on the theme,

The world of science has been interested in molecular cages for years. Not without reason. Chemical molecules, including those that would under normal conditions enter into chemical reactions, can be enclosed within their empty interiors. The particles of the enclosed compound, separated by the walls of the cage from the environment, have nothing to bond with. These cages can be therefore be used, for example, to transport drugs safely into a cancer cell, only releasing the drug when they are inside it.

Molecular cages are polyhedra made up of smaller ‘bricks’, usually protein molecules. The bricks can’t be of any shape. For example, if we wanted to build a molecular polyhedron using only objects with the outline of an equilateral triangle, geometry would limit us to only three solid figures: a tetrahedron, an octahedron or an icosahedron. So far, there have been no other structural possibilities.

“Fortunately, Platonic idealism is not a dogma of the physical world. If you accept certain inaccuracies in the solid figure being constructed, you can create structures with shapes that are not found in nature, what’s more, with very interesting properties,” says Dr. Tomasz Wrobel from the Cracow Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN).

Dr. Wrobel is one of the members of an international team of researchers who have recently carried out the ‘impossible’: they built a cage similar in shape to a sphere out of eleven-walled proteins. The main authors of this spectacular success are scientists from the group of Prof. Jonathan Heddle from the Malopolska Biotechnology Centre of the Jagiellonian University in Cracow and the Japanese RIKEN Institute in Wako. The work described in Nature magazine took place with the participation of researchers from universities in Osaka and Tsukuba (Japan), Durham (Great Britain), Waterloo (Canada) and other research centres.

Each of the walls of the new nanocages was formed by a protein ring from which eleven cysteine molecules stuck out at regular intervals. It was to the sulphur atom found in each cysteine molecule that the ‘glue’, i.e. the gold atom, was planned to be attached. In the appropriate conditions, it could bind with one more sulphur atom, in the cysteine of a next ring. In this way a permanent chemical bond would be formed between the two rings. But would the gold atom under these conditions really be able to form a bond between the rings?

“In the Spectroscopic Imaging Laboratory of IFJ PAS we used Raman spectroscopy and X-ray photoelectron spectroscopy to show that in the samples provided to us with the test nanocages, the gold really did form bonds with sulphur atoms in cysteines. In other words, in a difficult, direct measurement, we proved that gold ‘glue’ for bonding protein rings in cages really does exist,” explains Dr. Wrobel.

Each gold atom can be treated as a stand-alone clip that makes it possible to attach another ring. The road to the ‘impossible’ begins when we realize that we don’t always have to use all of the clips! So, although all the rings of the new nanocages are physically the same, depending on their place in the structure they connect with their neighbours with a different number of gold atoms, and thus function as polygons with different numbers of vertices. 24 nanocage walls presented by the researchers were held together by 120 gold atoms. The outer diameter of the cages was 22 nanometres and the inner diameter was 16 nm.

Using gold atoms as a binder for nanocages is also important due to its possible applications. In earlier molecular structures, proteins were glued together using many weak chemical bonds. The complexity of the bonds and their similarity to the bonds responsible for the existence of the protein rings themselves did not allow for precise control over the decomposition of the cages. This is not the case in the new structures. On the one hand, gold-bonded nanocages are chemically and thermally stable (for example, they withstand hours of boiling in water). On the other hand, however, gold bonds are sensitive to an increase in acidity. By its increase, the nanocage can be decomposed in a controlled way and the contents can be released into the environment. Since the acidity within cells is greater than outside them, gold-bonded nanocages are ideal for biomedical applications.

The ‘impossible’ nanocage is the presentation of a qualitatively new approach to the construction of molecular cages, with gold atoms in the role of loose clips. The demonstrated flexibility of the gold bonds will make it possible in the future to create nanocages with sizes and features precisely tailored to specific needs.

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

An ultra-stable gold-coordinated protein cage displaying reversible assembly by Ali D. Malay, Naoyuki Miyazaki, Artur Biela, Soumyananda Chakraborti, Karolina Majsterkiewicz, Izabela Stupka, Craig S. Kaplan, Agnieszka Kowalczyk, Bernard M. A. G. Piette, Georg K. A. Hochberg, Di Wu, Tomasz P. Wrobel, Adam Fineberg, Manish S. Kushwah, Mitja Kelemen, Primož Vavpetič, Primož Pelicon, Philipp Kukura, Justin L. P. Benesch, Kenji Iwasaki & Jonathan G. Heddle Nature volume 569, pages438–442 (2019) Issue Date: 16 May 2019 DOI: https://doi.org/10.1038/s41586-019-1185-4 Published online: 08 May 2019

This paper is behind a paywall.

Finding killer bacteria with quantum dots and a smartphone

An August 5, 2019 news item on Nanowerk announces a new technology for detecting killer bacteria (Note: A link has been removed),

A combination of off-the-shelf quantum dots and a smartphone camera soon could allow doctors to identify antibiotic-resistant bacteria in just 40 minutes, potentially saving patient lives.

Staphylococcus aureus (golden staph), is a common form of bacterium that causes serious and sometimes fatal conditions such as pneumonia and heart valve infections. Of particular concern is a strain that does not respond to methicillin, the antibiotic of first resort, and is known as methicillin-resistant S. aureus, or MRSA.

Recent reports estimate that 700 000 deaths globally could be attributed to antimicrobial resistance, such as methicillin-resistance. Rapid identification of MRSA is essential for effective treatment, but current methods make it a challenging process, even within well-equipped hospitals.

Soon, however, that may change, using nothing except existing technology.

Researchers from Macquarie University and the University of New South Wales, both in Australia, have demonstrated a proof-of-concept device that uses bacterial DNA to identify the presence of Staphylococcus aureus positively in a patient sample – and to determine if it will respond to frontline antibiotics.

An August 12,2019 Macquarie University press release (also on EurekAlert but published August 4, 2019), which originated the news item, delves into the work,

In a paper published in the international peer-reviewed journal Sensors and Actuators B: Chemical the Macquarie University team of Dr Vinoth Kumar Rajendran, Professor Peter Bergquist and Associate Professor Anwar Sunna with Dr Padmavathy Bakthavathsalam (UNSW) reveal a new way to confirm the presence of the bacterium, using a mobile phone and some ultra-tiny semiconductor particles known as quantum dots.

“Our team is using Synthetic Biology and NanoBiotechnology to address biomedical challenges. Rapid and simple ways of identifying the cause of infections and starting appropriate treatments are critical for treating patients effectively,” says Associate Professor Anwar Sunna, head of the Sunna Lab at Macquarie University.

“This is true in routine clinical situations, but also in the emerging field of personalised medicine.”

The researchers’ approach identifies the specific strain of golden staph by using a method called convective polymerase chain reaction (or cPCR). This is a derivative of a widely -employed technique in which a small segment of DNA is copied thousands of times, creating multiple samples suitable for testing.

Vinoth Kumar and colleagues then subject the DNA copies to a process known as lateral flow immunoassay – a paper-based diagnostic tool used to confirm the presence or absence of a target biomarker. The researchers use probes fitted with quantum dots to detect two unique genes, that confirms the presence of methicillin resistance in golden staph

A chemical added at the PCR stage to the DNA tested makes the sample fluoresce when the genes are detected by the quantum dots – a reaction that can be captured easily using the camera on a mobile phone.

The result is a simple and rapid method of detecting the presence of the bacterium, while simultaneously ruling first-line treatment in or out.

Although currently at proof-of-concept stage, the researchers say their system which is powered by a simple battery is suitable for rapid detection in different settings.

“We can see this being used easily not only in hospitals, but also in GP clinics and at patient bedsides,” says lead author, Macquarie’s Vinoth Kumar Rajendran.

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

Smartphone detection of antibiotic resistance using convective PCR and a lateral flow assay by Vinoth Kumar Rajendran, Padmavathy Bakthavathsalam, Peter L.Bergquist, Anwar Sunna. Sensors and Actuators B: Chemical Volume 298, 1 November 2019,126849 DOI: https://doi.org/10.1016/j.snb.2019.126849 Available online 23 July 2019

This paper is behind a paywall.

Neuronal regenerative-interfaces made of cross-linked carbon nanotube films

If I understand this research rightly, they are creating a film made of carbon nanotubes that can stimulate the growth of nerve cells (neurons) thus creating a ‘living/nonliving’ hybrid or as they call it in the press release a ‘biosynthetic hybrid’.

An August 2, 2019 news item on Nanowerk introduces the research (Note 1: There seem to be some translation issues; Note 2: Links have been removed),

Carbon nanotubes able to take on the desired shapes thanks to a special chemical treatment, called crosslinking and, at the same time, able to function as substrata for the growth of nerve cells, finely tuning their growth and activity.

The research published in ACS Nano (“Chemically Cross-Linked Carbon Nanotube Films Engineered to Control Neuronal Signaling”), is a new and important step towards the construction of neuronal regenerative-interfaces to repair spinal injuries.

The study is the new achievement of a long-term and, in terms of results, successful collaboration between the scientists Laura Ballerini of SISSA (Scuola Internazionale Superiore di Studi Avanzati), Trieste, and Maurizio Prato of the University of Trieste. The work team has also been assisted by CIC biomaGUNE of San Sebastián, Spain.

Caption: Carbon nanotubes able to take on the desired shapes thanks to a special chemical treatment, called crosslinking and, at the same time, able to function as substrata for the growth of nerve cells, finely tuning their growth and activity. Credit: Rossana Rauti

An August 2, 2019 SISSA press release (also on EurekAlert), which originated the news item, adds detail,

The carbon nanotubes used in the research have been modified by appropriate chemical treatments: “For many years, in our laboratories we have been working on the chemical reactivity of carbon nanotubes, a fascinating but very difficult material to work. Thanks to our experience, we have crosslinked them or, to say it more clearly, we have treated the nanotubes so they could link themselves to one another thanks to specific chemical reactions. We have discovered that this procedure gives the material very interesting characteristics. For example, the material organises itself in a stable manner according to a precise shape, we choose: a tissue where nerve cells need to be planted, for example. Or around some electrodes” explains Professor Prato. “We know from previous research that nerve cells grow well on carbon nanotubes so they could be used as a surface to build hybrid devices to regenerate nerve tissues. It was necessary to ensure that this chemical modification did not compromise this process and study whether the interaction with neurons was altered”.

Towards biosynthetic hybrids

Professor Ballerini continues: “We have discovered that the chemical process has important effects because through this treatment we can modulate the activity of neurons, in terms of growth, adhesion and survival. These materials can also regulate the communication between neurons. We can say that the carpet of crosslinked carbon nanotubes interacts intensely and constructively with the nerve cells”. This interaction depends on how much the different carbon nanotubes are linked to each other, or rather crosslinked. The lower the link number among the nanotubes the higher the activity of neurons that grow on their surface. Through the chemical control of their properties, and of the links between them, it is possible to regulate the response of the neurons. Ballerini and Prato explain: “This is an intriguing result that emerges from the important and fruitful collaboration between our research groups involving advanced research in chemistry, nanoscience and neurobiology . This study provides a further step in the design of future biosynthetic hybrids to recover injured nerve tissues functions”.

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

Chemically Cross-Linked Carbon Nanotube Films Engineered to Control Neuronal Signaling by Myriam Barrejón, Rossana Rauti, Laura Ballerini, Maurizio Prato. ACS Nano2019 XXXXXXXXXX-XXX Publication Date:July 22, 2019 DOI: https://doi.org/10.1021/acsnano.9b02429 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

So thin and soft you don’t notice it: new wearable tech

An August 2, 2019 news item on ScienceDaily features some new work on wearable technology that was a bit of a surprise to me,

Wearable human-machine interfaces — devices that can collect and store important health information about the wearer, among other uses — have benefited from advances in electronics, materials and mechanical designs. But current models still can be bulky and uncomfortable, and they can’t always handle multiple functions at one time.

Researchers reported Friday, Aug. 2 [2019], the discovery of a multifunctional ultra-thin wearable electronic device that is imperceptible to the wearer.

I expected this wearable technology to be a piece of clothing that somehow captured health data but it’s not,

While a health care application is mentioned early in the August 2, 2019 University of Houston news release (also on EurekAlert) by Jeannie Kever the primary interest seems to be robots and robotic skin (Note: This news release originated the news item on ScienceDaily),

The device allows the wearer to move naturally and is less noticeable than wearing a Band-Aid, said Cunjiang Yu, Bill D. Cook Associate Professor of Mechanical Engineering at the University of Houston and lead author for the paper, published as the cover story in Science Advances.

“Everything is very thin, just a few microns thick,” said Yu, who also is a principal investigator at the Texas Center for Superconductivity at UH. “You will not be able to feel it.”
It has the potential to work as a prosthetic skin for a robotic hand or other robotic devices, with a robust human-machine interface that allows it to automatically collect information and relay it back to the wearer.

That has applications for health care – “What if when you shook hands with a robotic hand, it was able to instantly deduce physical condition?” Yu asked – as well as for situations such as chemical spills, which are risky for humans but require human decision-making based on physical inspection.

While current devices are gaining in popularity, the researchers said they can be bulky to wear, offer slow response times and suffer a drop in performance over time. More flexible versions are unable to provide multiple functions at once – sensing, switching, stimulation and data storage, for example – and are generally expensive and complicated to manufacture.

The device described in the paper, a metal oxide semiconductor on a polymer base, offers manufacturing advantages and can be processed at temperatures lower than 300 C.

“We report an ultrathin, mechanically imperceptible, and stretchable (human-machine interface) HMI device, which is worn on human skin to capture multiple physical data and also on a robot to offer intelligent feedback, forming a closed-loop HMI,” the researchers wrote. “The multifunctional soft stretchy HMI device is based on a one-step formed, sol-gel-on-polymer-processed indium zinc oxide semiconductor nanomembrane electronics.”

In addition to Yu, the paper’s co-authors include first author Kyoseung Sim, Zhoulyu Rao, Faheem Ershad, Jianming Lei, Anish Thukral and Jie Chen, all of UH; Zhanan Zou and Jianliang Xiao, both of the University of Colorado; and Qing-An Huang of Southeast University in Nanjing, China.

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

Metal oxide semiconductor nanomembrane–based soft unnoticeable multifunctional electronics for wearable human-machine interfaces by Kyoseung Sim, Zhoulyu Rao, Zhanan Zou, Faheem Ershad, Jianming Lei, Anish Thukral, Jie Chen, Qing-An Huang, Jianliang Xiao and Cunjiang Yu. Science Advances 02 Aug 2019: Vol. 5, no. 8, eaav9653 DOI: 10.1126/sciadv.aav9653

This paper appears to be open access.

Desalination with nanowood

A new treatment for wood could make renewable salt-separating membranes. Courtesy: University of Maryland

An August 6, 2019 article by Adele Peters for Fast Company describes a ‘wooden’approach to water desalinization (also known as desalination),

“We are trying to develop a new type of membrane material that is nature-based,” says Z. Jason Ren, an engineering professor at Princeton University and one of the coauthors of a new paper in Science Advances about that material, which is made from wood. It’s designed for use in a process called membrane distillation, which heats up saltwater and uses pressure to force the water vapor through a membrane, leaving the salt behind and creating pure water. The membranes are usually made from a type of plastic. Using “nanowood” membranes instead can both improve the energy efficiency of the process and avoid the environmental problems of plastic.

An August 2, 2019 University of Maryland (UMD) news release provides more detail about the research,

A membrane made of a sliver of wood could be the answer to renewably sourced water cleaning. Most membranes that are currently used to distill fresh water from salty are made of polymers based on fossil fuels.

Inspired by the intricate system of water circulating in a tree, a research team from the University of Maryland, Princeton University, and the University of Colorado Boulder have figured out how to use a thin slice of wood as a membrane through which water vapor can evaporate, leaving behind salt or other contaminants.

“This work demonstrates another exciting energy/water application of nanostructured wood, as a high-performance membrane material,” said Liangbing Hu, a professor of materials science and engineering at UMD’s A. James Clark School of Engineering, who co-led the study.

The team chemically treated the wood to become hydrophobic, so that it more efficiently allows water vapor through, driven by a heat source like solar energy.

“This study discovered a new way of using wood materials’ unique properties as both an excellent insulator and water vapor transporter,” said Z. Jason Ren, a professor in environmental engineering who recently moved from CU Boulder to Princeton, and the other co-leader of the team that performed the study.

The researchers treat the wood so that it loses its lignin, the part of the wood that makes it brown and rigid, and its hemicellulose, which weaves in and out between cellulose to hold it in place. The resulting “nanowood” is treated with silane, a compound used to make silicon for computer chips. The semiconducting nature of the compound maintains the wood’s natural nanostructures of cellulose, and clings less to water vapor molecules as they pass through. Silane is also used in solar cell manufacturing.

The membrane looks like a thin piece of wood, seemingly bleached white, that is suspended above a source of water vapor. As the water heats and passes into the gas phase, the molecules are small enough to fit through the tiny channels lining the walls of the leftover cell structure. Water collected on the other side is now free of large contaminants like salt.
To test it, the researchers distilled water through it and found that it performed 1.2 times better than a conventional membrane.

“The wood membrane has very high porosity, which promotes water vapor transport and prevents heat loss,” said first author Dianxun Hou, who was a student at CU Boulder.
Inventwood, a UMD spinoff company of Hu’s research group, is working on commercializing wood based nanotechnologies.

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

Hydrophobic nanostructured wood membrane for thermally efficient distillation by Dianxun Hou, Tian Li, Xi Chen, Shuaiming He, Jiaqi Dai, Sohrab A. Mofid, Deyin Hou, Arpita Iddya, David Jassby, Ronggui Yang, Liangbing Hu, and Zhiyong Jason Ren. Science Advances 02 Aug 2019: Vol. 5, no. 8, eaaw3203 DOI: 10.1126/sciadv.aaw3203

This paper appears to be open access.

In my brief survey of the paper, I noticed that the researchers were working with cellulose nanofibrils (CNF), a term which should be familiar for anyone following the nanocellulose story, such as it.

Gold sheets that are two atoms thick

The gold sheets in question are effectively 2D. I’m surprised they haven’t named them ‘goldene’ as everything else that’s 2D seems to have an ‘ene’ suffix (e.g. graphene, germanene, tellurene).

Of course, these gold sheets are not composed of single atoms but of two according to an August 6, 2019 news item on Nanowerk,

Scientists at the University of Leeds [UK] have created a new form of gold which is just two atoms thick – the thinnest unsupported gold ever created.

The researchers measured the thickness of the gold to be 0.47 nanometres – that is one million times thinner than a human finger nail. The material is regarded as 2D because it comprises just two layers of atoms sitting on top of one another. All atoms are surface atoms – there are no ‘bulk’ atoms hidden beneath the surface.

Caption: Image shows gold nanosheets that are just two atoms thick Credit: University of Leeds

I’m pretty sure they’ve added colour to those images and not just in the background; they’ve likely added a gold colour to the gold.

An August 6, 2019 University of Leeds press release (also on EurekAlert), which originated the news item, gives some insight into the scientists’ ambitions and some technical details about the work,

The material could have wide-scale applications in the medical device and electronics industries – and also as a catalyst to speed up chemical reactions in a range of industrial processes.

Laboratory tests show that the ultra-thin gold is 10 times more efficient as a catalytic substrate than the currently used gold nanoparticles, which are 3D materials with the majority of atoms residing in the bulk rather than at the surface.

Scientists believe the new material could also form the basis of artificial enzymes that could be applied in rapid, point-of-care medical diagnostic tests and in water purification systems.

The announcement that the ultra-thin metal had been successfully synthesised was made in the journal Advanced Science.

The lead author of the paper, Dr Sunjie Ye, from Leeds’ Molecular and Nanoscale Physics Group and the Leeds Institute of Medical Research, said: “This work amounts to a landmark achievement.

“Not only does it open up the possibility that gold can be used more efficiently in existing technologies, it is providing a route which would allow material scientists to develop other 2D metals.

“This method could innovate nanomaterial manufacturing.”

The research team are looking to work with industry on ways of scaling-up the process.

Synthesising the gold nanosheet takes place in an aqueous solution and starts with chloroauric acid, an inorganic substance that contains gold. It is reduced to its metallic form in the presence of a ‘confinement agent’ – a chemical that encourages the gold to form as a sheet, just two atoms thick.

Because of the gold’s nanoscale dimensions, it appears green in water – and given its shape, the researchers describe it as gold nanoseaweed.

Images taken from an electron microscope reveal the way the gold atoms have formed into a highly organised lattice. Other images show gold nanoseaweed that has been artificially coloured. The images are available for download: https://drive.google.com/drive/folders/
1-jxr7KW_RW4vF4-zReh9rnfOQMesb6MI?usp=sharing

Professor Stephen Evans, head of the Leeds’ Molecular and Nanoscale Research Group who supervised the research, said the considerable gains that could be achieved from using these ultra-thin gold sheets are down to their high surface-area to volume ratio.

He said: “Gold is a highly effective catalyst. Because the nanosheets are so thin, just about every gold atom plays a part in the catalysis. It means the process is highly efficient.”

Standard benchmark tests revealed that gold nanoscale sheets were ten times more efficient than the gold nanoparticles conventionally used in industry.

Professor Evans said: “Our data suggests that industry could get the same effect from using a smaller amount of gold, and this has economic advantages when you are talking about a precious metal.”

Similar benchmark tests revealed that the gold sheets could act as highly effective artificial enzymes.

The flakes are also flexible, meaning they could form the basis of electronic components for bendable screens, electronic inks and transparent conducting displays.

Professor Evans thinks there will inevitably be comparisons made between the 2D gold and the very first 2D material ever created – graphene, which was fabricated at the University of Manchester in 2004.

He said: “The translation of any new material into working products can take a long time and you can’t force it to do everything you might like to. With graphene, people have thought that it could be good for electronics or for transparent coatings – or as carbon nanotubes that could make an elevator to take us into space because of its super strength.

“I think with 2D gold we have got some very definite ideas about where it could be used, particularly in catalytic reactions and enzymatic reactions. We know it will be more effective than existing technologies – so we have something that we believe people will be interested in developing with us.”

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

Sub‐Nanometer Thick Gold Nanosheets as Highly Efficient Catalysts by Sunjie Ye, Andy P. Brown, Ashley C. Stammers, Neil H. Thomson, Jin Wen, Lucien Roach, Richard J. Bushby, Patricia Louise Coletta, Kevin Critchley, Simon D. Connell, Alexander F. Markham, Rik Brydson, Stephen D. Evans. Advnaced Science https://doi.org/10.1002/advs.201900911 First published: 06 August 2019

This paper is open access.