Page 502 – Physics World

Home » Page 502

Cinzia Casiraghi: celebrating the contributions of female scientists to 2D materials

Female scientists make some amazing contributions to advanced materials, with almost a third of all researchers on the European Union’s €1bn Graphene Flagship project, for example, being women. But when it comes to, say, positions of leadership or invitations to speak at conferences, we’re far from reaching gender equality.

That’s one reason why JPhys Materials, which is published by IOP Publishing, the publishers of Physics World, decided to bring out a focus issue dedicated to female contributions to 2D materials. Guest edited by Cinzia Casiraghi from the University of Manchester, UK, Annick Loiseau from CNRS-ONERA, University Paris Saclay, France, and Cecilia Mattevi from Imperial College London, UK, it’s now been a year since the first papers in the issue appeared.

I caught up recently with Casiraghi to find out more about the issue and how it’s gone.

What was your motivation for the focus issue?

We wanted to celebrate the work of women investigators at different stages of their careers – not only to recognize their excellent science, but also to show the next generation of women scientists that there are lots of female role models out there. We wanted to fix the “leaky pipeline” by helping and supporting the progression of other women scientists. Long term, we are also planning a series of focus issues in all areas of advanced materials, which would provide a list of top women researchers who could be used for subject reviews, invited talks and so on.

What’s been your impression of the overall quality of the papers published so far?

The issue currently has 13 research papers, one review article and one perspective, with a further three papers under peer-review. The quality has been very good, as shown by the incredible number of downloads – on average 850 each – in the first five months. The work on “Spectroscopic properties of few-layer tin chalcogenides”, led by Zeila Zanolli from the Catalan Institute of Nanoscience and Nanotechnology in Barcelona, has already been cited five times. Indeed, no matter what the gender of the author, quality has been always the number one criterion for whether a paper gets accepted in JPhys Materials.

By publishing this focus issue, did you come across talented women scientists whose work you personally hadn’t been aware of before?

Yes, and, unfortunately, I am sure there are many other talented women I am also not aware of. I have been very impressed by the collaborative and supportive network that this special issue has initiated. Women are often accused of not being able to build networks, but for this issue, that has certainly not been true.

What’s been the reaction from the authors and the wider community to this focus issue – did they find it a worthwhile exercise?

In general, both female and male scientists have enthusiastically supported this focus issue, often saying how very much needed it was. Remarkably, it wasn’t just the women we’d invited to write for the issue who suggested other female contributors; we also received names from male colleagues, showing they’re also sensitive to the subject too. Only in a very few cases were our invitations turned down because of the gender angle to this project. This feedback was very useful as it gave rise to interesting discussions with the scientists around gender issues and how to improve female representation in science.

Why carbon is an amazing material – part one

Have any of the women who contributed papers found it has helped their research careers, raised their profiles, or led to new opportunities?

I hope so. Zeila Zanolli, for example, became an associate professor after publishing her work, while Lucia Gemma Delogu from the University of Padua, Italy, on the back of her JPhys Materials paper, used this opportunity to write a review article on the results obtained from the two European projects she has co-ordinated, by providing visibility to her role in the projects.

Did you learn any lessons yourself from the focus issue?

Yes, several. First, although I have been involved in 2D materials ever since the discovery of graphene, it’s remarkable how fast the field’s been growing, and, as consequence, how many people, especially emerging scientists, are struggling to get visibility. Second, it has been interesting to see how female scientists from different geographical areas or at different stages of their careers reacted in different ways to the special issue. There are lots of data we could extract from this exercise that could be used to improve gender equality in this field.

You’ve published 15 papers so far – are there any more in the pipeline?

We expect a total of 16 papers.

What progress has been made on plans for further JPhys Materials focus issues covering the work women scientists in other areas of advanced materials?

The next focus issue – on “materials for energy” – is already open for submissions. But as it’s on a different topic, I personally am not involved in it, although I am delighted that JPhys Materials is following up on our exercise. It’s being guest-edited by Giulia Grancini (University of Pavia, Italy), Serena Corr (University of Sheffield, UK), Deli Wang (Huazhong University, China), Claudia Schnohr (University of Leipzig, Germany) and Mari-Ann Einarsrud (Norwegian University of Science and Technology). More than 40 confirmed submissions have already been received, which is amazing. I am looking forward to that focus issue being published and comparing the reactions between the two communities.

Metallic nanoribbons fill missing link for all-carbon devices

Pushing the limits of silicon electronics to make smaller, faster and more efficient devices is getting harder. One possible way forward is to take advantage of the many phenomenal properties of nanocarbon structures that have been discovered over the past 40 years. However, amongst this suite of carbon nanomaterials there has been a conspicuous lack of wire-like materials with metallic properties that can be reliably customized and produced. This poses a challenge because connecting nanocarbon semiconductor components with the same old copper or silver wires can take the shine off their appeal.

While carbon nanotubes with metallic properties can be made with relative ease, the snag is that a heap of nanotubes with semiconducting properties are inevitably produced at the same time. Unfortunately, separating metallic nanotubes from semiconductor nanotubes en masse remains something of a dark art. Another option is graphene; with the unprecedented mobility of its π-electrons, doping can push graphene’s conductivity well above copper. But if graphene is cut into strips called graphene nanoribbons (GNRs) to make wires for interconnects, the material’s delocalized electrons become confined by the width of the nanoribbon. This opens a bandgap that makes the material a semiconductor or even an insulator.

Now, researchers in the US have shown how to produce graphene nanoribbons with robust metallic properties to order, providing the missing link for all-carbon electronic devices. The work was led by Daniel Rizzo, Gregory Veber and Jingwei Jiang, who are researchers in the labs of Michael Crommie, Felix Fischer and Steven Louie at the University of California, Berkeley.

Synthesis of theory and experiment

“The search for metallic GNRs has been a long-standing question in this field,” says experimental physicist Crommie. Not only is demand high for metallic GNRs, but for quite a while now people have known what is needed to make them. Somehow, nanoribbons must be decorated with features that have an electronic state right in the middle of the bandgap – a so-called zero-mode state. Then, it must be ensured these zero-mode states are effectively equidistant from each other so that electrons can hop with equal ease between these states along the length of the nanoribbon.

“That idea is actually a century old,” says theoretical physicist Louie, adding that pioneers right at the beginning of quantum mechanics were contemplating similar ideas. The catch, as Louie points out, is that this is very hard to do in practice. Just getting the zero-mode state at all is far from trivial, not only to design in the first place but then to synthesize. What often happens is that the states end up paired so that electrons can hop about within each pair much more easily than they can hop to the adjacent pair, making the material a semiconductor. Conversely, when the building blocks are made evenly spaced, there is typically no zero mode.

Despite these challenges, the possibility of producing metallic GNRs retains its allure because of the atomically tailored features of GNRs that can be reliably and selectively produced when stitching GNRs together from specific precursor molecules. This is something that is simply not possible for carbon nanotubes. The hunt was on not just for the right precursors but also the reaction conditions to make them assemble into nanoribbons with equidistant zero mode states.

“Cross your fingers”

“You can’t go in there with a pair of tweezers to guide their assembly,” says chemist Fischer. “Once you put the molecular precursors on the surface and provide the energy they need to form a nanoribbon all you can do is cross your fingers and hope that all the planning and design that went into the structure of the precursor pays off and channels the self-assembly to the one desired GNR.”

The whole scenario may sound like a parent hopelessly trying to nudge their wayward offspring back onto the straight and narrow, but in this case the group’s collective expertise in materials physics, precursor design and synthetic chemistry paid off. The researchers used a precursor made of linked strips of aromatic rings, which stitch into the graphene nanoribbon backbone, and a methyl group that adds an extra carbon atom along the edge. They then stitched them together head-to-tail on a gold surface to produce nanoribbons where the extra carbon atom resulted in a tiny promontory alongside a sheltered cove of atoms, thus producing equally spaced zero mode states stemming from alternating sides of the nanoribbon. Sure enough, scanning tunnelling spectroscopy maps of the nanoribbons revealed the much hoped for metallic behaviour due to hopping between the zero mode states.

The inbuilt fix

But that is where the plot thickens. When the researchers further explored the properties of their system with ab initio calculations, they realised the underlying gold surface was inducing doping and surface fields that were actually helping to hold together the extremely narrow bandwidth of metallic behaviour in their GNR. Take the gold surface away and a bandgap would open up again.

To get around this, one must remember that the honeycomb structure of carbon atoms in graphene can also be described by two superposed overlapping triangular lattices. This symmetry affects the electron behaviour because mobility along the metallic zero-mode states is confined to one sublattice as opposed to hopping also between two sublattices. However, hopping along just one sublattice is harder because an electron must hop to its second nearest neighbour, and so has further to go.

The problem was easy to fix in theory, as Louie points out, because it involves breaking the symmetry of the sublattices. Achieving this in practice is quite another matter, but fortunately the researchers were able to exploit the tiny cove structures on the edges. Using further chemical reactions to join the carbons on either side of the mouth of these coves they formed five-membered carbon rings, thus directly connecting two sites from one sublattice (something not allowed in regular graphene). This broke the symmetry, increasing the metallicity by a factor of twenty. “We got lucky with our design,” says Fischer. “The fix was built-in essentially.”

Having demonstrated a procedure for producing graphene nanoribbons with a robust broad metallic mode, Crommie is confident that with “all the tricks of organic chemistry,” the process could be improved to make these materials widely available. Possible next steps include creating electronic devices with the nanoribbons to evaluate their performance directly, and exploring their behaviour on different surfaces and in heterostructures.

The research is described in Science.

Watch a wobbling black-hole shadow, ‘π planet’ has 3.14 day orbit, retracting racist and sexist papers

“The wobbling shadow of the M87* black hole” is a video made by astronomers working on the Event Horizon Telescope (EHT), which in 2019 found the first direct visual evidence of a black hole and its “shadow”. The video above is an animation of three years in the life of the black hole M87* as its shadow wobbles. It shows extremely hot and turbulent gas swirling around the event horizon of the black hole before plunging into the abyss.

The animation is done in the wavelength of radio waves that EHT is sensitive to and towards the end of the video the image is blurred to simulate the limited resolution of the EHT.

Baking a pie

One of the most remarkable things about the plethora of known exoplanets is that many of them orbit extremely close to their stars while travelling at extremely high speeds. K2-315b is no exception, moving at a blistering 81 km/s in a tight orbit around a cool star that is about one fifth the size of the Sun. The exoplanet itself appears to be about the same size as Earth, but is expected to have a surface temperature of about 180 °C. That is about the right temperature for baking a pie. But that is not why K2-315b has been dubbed the “π planet” – it takes just 3.14 Earth days to orbit its star.

K2-315b was studied by Prajwal Niraula and colleagues using the NASA Kepler Space Telescope’s K2 mission and the SPECULOOS network of ground-based telescopes. They described their observations in The Astronomical Journal.

Science is a human endeavour, so it is not surprising that the scientific literature can sometimes reflect social attitudes that were prevalent when the papers were written. In “Science journals are purging racist, sexist work. Finally”, Adam Marcus and Ivan Oransky of Retraction Watch applaud the removal of papers published less than a decade ago “that have been called out for both their content and their lack of scientific rigour”. They also call for the more aggressive retraction of papers that although not based on repugnant ideas, are nonetheless wrong and pose threats to the credibility of the scientific literature.

Ultrasound signals are converted directly to visible images by new device

The first ultrasound imaging device that converts acoustic signals directly into light has been created by Hyeonggeun Yu and colleagues at North Carolina State University in the US. The device was fabricated by depositing an organic LED onto a piezoelectric crystal and it can produce real-time images without the need for signal processing. This approach could significantly reduce the costs of advanced ultrasound imaging techniques, making them far more accessible in applications including engineering and medicine.

Ultrasound is an increasingly popular technique for imaging the interiors of objects – animate and inanimate. It works by transmitting sound waves into an object using a piezoelectric transducer, then using the same transducer to pick up sound reflected from structures within the object. The resulting voltages in the transducer are then converted into electrical signals, from which images can be reconstructed by a computer. Since ultrasound achieves low-cost, real-time imaging without the need for powerful magnets or ionizing radiation, it offers significant advantages over approaches such as magnetic resonance imaging and X-ray scans.

Recently, improvements to ultrasound technology have replaced single, moveable transducers with large arrays of more than 10,000 devices, allowing for scans with far higher resolutions and image-production speeds. However, these newer techniques involve far more sophisticated hardware, and require far more complex approaches to signal processing compared with previous approaches. This significantly drives up the cost of ultrasound imaging, making it inaccessible to many groups that would benefit from the technology.

OLED on PZT

In their study, Yu’s team found a way of avoiding signal processing by fabricating a layered organic LED (OLED) on top of a lead zirconate titanate (PZT) piezoelectric crystal. In the resulting “p-OLED”, the voltages induced by ultrasonic waves are converted directly into light, which is displayed on a screen built into the transducer itself – eliminating the need for signal processing.

Yu and colleagues demonstrated this concept with an 8×8 array of p-OLED transducers immersed in water – each of which produced a 1×1 cm pixel in the final ultrasound image. With a total thickness of just 120 nm, the organic LED screen had a high luminescence and low turn-on voltage, while demonstrating a high conversion efficiency between mechanical and optical energy.

The team now hopes that through relatively simple improvements to their setup, they will be able to produce images with resolutions as high as 500×500 pixels. They also believe that they will soon be able to manufacture their p-OLED for just around $100 – a remarkable improvement on the price tags of previous transducer arrays, which could exceed $100,000. Ultimately, these improvements could make advanced ultrasound imaging accessible for those providing high-demand medical services such as foetus imaging, drug delivery, and early cancer detection. Elsewhere, it could lead to far more cost-effective ways for engineers to monitor the structural health of buildings and infrastructure.

The new device is described in ACS Applied Materials & Interfaces.

Ask me anything: Deji Akinwande

What skills do you use every day in your job?

Communication is very important, as are other “soft” skills such as networking and collaboration with peers, students and leaders in the field. I think that basically every student (and indeed everybody involved in research) will eventually need to become skilled in project management. Knowing when to end a project, when to pivot it in a different direction and how to manage risk are all really important. Failure is an option – and often the experience when you’re doing research – so individuals have to be resilient. They have to embrace failure, learn from it and move on.

Knowing when to end a project, when to pivot it in a different direction and how to manage risk are all really important

Of course, technical skills are also very important. We use statistics frequently to analyse our data, and we also use ideas from algebra, calculus (curvature, slopes and vectors) and matrix mathematics. Those skill sets are often needed because we’re constantly dealing with data. And then there are specific physics skills, like an understanding of electromagnetics and (especially) solid-state physics. Because we work on devices, we deal with concepts in solid-state physics on a day-to-day basis in order to understand the materials the devices are made from and what we should expect from them. All those technical skills are very prominent.

One of the most challenging aspects of my work is that the materials we’ve known about historically are bulk materials – steel, copper, gold, iron. These materials have been well studied for 50 or 100 years, maybe more. But the atomically thin materials that I work with are not well studied. There are a lot of unknowns. We have to learn the basics of their materials science: their kinetics and thermal dynamics, what their phase diagrams look like, and so on. These are not things that I was privy to in my undergraduate degree or even my graduate education, but they are necessary, and you also need to know how to characterize these materials with advanced tools.

What do you like best and least about your job?

For me, and perhaps for many of my kind, what we like best is discovery. The whole point of doing research, to some extent, is to discover things that haven’t been discovered before. That’s always a thrill for us.

With every career, there will be things that you doesn’t necessarily like. I don’t really enjoy the paperwork and bureaucratic bottlenecks that are abundant in our field, but those are things that we have to deal with. They’re not fun, but they are necessary, so we accept them.

What do you know today, that you wish you knew when you were starting out in your career?

In retrospect, there are many things that I wish I knew, but I think I would go back and emphasize the soft skills. Of course, I had an idea when I was younger that they were important, but I wish I had become more involved and acquainted with skills such as networking and communication. Those skills are very important and often they are not adequately taught, or opportunities to get this experience are not abundant when one is an undergraduate or postgraduate student.

Fractionated heating could improve cancer therapy with thermosensitive drugs

Thermosensitive liposomes release encapsulated drugs when heated with focused ultrasound. (Courtesy: Kullervo Hynynen)

Improving the delivery of chemotherapy drugs to solid tumours while minimizing harmful side effects is key to optimizing cancer treatments. One promising approach lies in the use of thermosensitive liposomes (TSLs) that release encapsulated drugs upon heating, such as doxorubicin-loaded TSL (TSL-Dox), for example. TSL-Dox has shown encouraging outcomes in some patients, but its widespread clinical adoption is hindered by a lack of effective temperature control.

MRI-guided focused ultrasound (MRgFUS) could provide such control, enabling non-invasive heating of tissues to the hyperthermia regime of 41–43 °C. Previous preclinical studies of MRgFUS with TSL-Dox showed that raising tissue temperatures for tens of minutes to hours led to drug release and anti-tumour effects. But respiratory motion and cooling by blood make it difficult to maintain hyperthermia effectively. Instead, researchers in Canada propose a novel new approach: using MRgFUS to create fractionated ultrashort thermal exposures that release the encapsulated drug.

“It is very difficult to induce uniform temperature elevation and maintain it over long periods of time in a clinical setting, and even more difficult in an organ that moves with breathing, such as the liver,” explains lead author Kullervo Hynynen from Sunnybrook Research Institute and the University of Toronto. “Our aim was to use short ultrasound exposures that are short enough to be delivered during a patient breath-hold, thus eliminating the motion problem.”

Reducing each burst of heating to just 30 s also means that the temperature elevation is not highly dependent on the tissue’s blood perfusion rate, which is unknown and heterogenous throughout the tumour. As such, it should allow uniform thermal exposure over the entire tumour volume.

In vivo assessments

To determine whether the proposed ultrashort FUS exposures can release doxorubicin from TSL-Dox, the researchers first tested the approach using a dorsal skinfold chamber on a mouse with implanted tumour cells. After injecting TSL-Dox, they exposed the tumours to ten 30 s FUS thermal exposures, using thermocouple-based temperature-based feedback to heat the tissue to 41°, 42°, 43° or 45°C.

The experiment showed that the ultrashort thermal exposures could effectively release the doxorubicin and that the drug was subsequently taken up by tumour cells. Heating to 42 °C appeared to give the most consistent increases in drug delivery to the mouse tumours. Thus the team chose this temperature to evaluate the therapeutic efficacy of fractionated ultrashort MRgFUS heating with TSL-Dox in rabbit thigh tumours.

For the studies on rabbits, the researchers employed a custom MRI-compatible FUS system to deliver short-duration heating, with MR thermometry providing real-time temperature feedback during the treatment. They used MRI to identify the tumours and define discrete regions-of-interest (ROIs) to encompass the tumour. After administering either TSL-Dox or a control dextrose, each ROI was heated 10 times, to 42 °C for 30 s. The FUS was delivered via a single-focus transducer translated through a series of discrete locations to achieve tumour coverage.

Temperature profiles in one of the ROIs in the rabbit thigh tumour, during 10 FUS thermal exposures. (Courtesy: Kullervo Hynynen)

Examining drug delivery to excised bilateral tumours (one heated, one not heated) demonstrated that the level of doxorubicin fluorescence was markedly increased in the heated versus the unheated tumour sections – indicating the release of drug, which does not fluoresce when in liposomal form.

The researchers also evaluated the anti-tumour efficacy of the treatment. They saw a significant improvement in survival for rabbits receiving MRgFUS plus TSL-Dox compared with animals receiving MRgFUS alone or TSL-Dox alone. Of six rabbits treated with MRgFUS plus TSL-Dox, three survived to 120 days following treatment, four showed complete tumour destruction and only one reached the tumour size-related endpoint.

Follow-up MR images showed a marked decrease in tumour size in rabbits treated with MRgFUS plus TSL-Dox. Conversely, all 11 rabbits that received either MRgFUS or TSL-Dox alone showed tumour growth, and all reached the tumour size-related endpoint within 28 days.

One week after treatment, tumours in the group that received MRgFUS alone were significantly larger than in the group receiving MRgFUS plus TSL-Dox. Two weeks after treatment, rabbits in both the MRgFUS alone and the TSL-Dox alone groups had significantly larger tumours than those treated with MRgFUS plus TSL-Dox.

The researchers conclude that these results have considerable implications for the widespread clinical adoption of thermosensitive drugs in oncology. Hynynen tells Physics World that the team is now working on translating the method for clinical testing.

The findings are published in Science Advances.

History and fundamentals of tip-enhanced Raman spectroscopy (TERS)

Want to learn more on this subject?

Watch now

TERS gives the vibrational information of a sample with nanometric resolution. Obtaining physico-chemical information with such resolution opens up possibilities to characterize materials at unprecedented levels, which allows research findings unsuspected until recently.

This webinar introduces the fundamentals of TERS through the history of near-field spectroscopic optics. From the great idea of Synge more than 90 years ago to the technical progress of scanning probe microscopy, the history of near-field optics crosses the emerging plasmonics field and the discovery of the amplification of the Raman signal by Richard Van Duyne.

During this webinar, Marc Chaigneau will also briefly introduce this nanospectroscopic technique for 2D materials and other semiconductors, but also present the current applications of this for biological samples such as viruses and DNA.

Want to learn more on this subject?

Watch now

Marc Chaigneau received his PhD in solid-state physics from the University of Nantes in 2007. He joined the Laboratory of Physics of Interfaces and Thin Films (PICM) at Ecole Polytechnique in 2008 and was appointed tenured researcher in 2010. His research activities were concentrated on the development and applications of Tip-Enhanced Raman spectroscopy (TERS).

Marc is the author of three patents, one book chapter and more than 50 articles in peer-reviewed journals.

He joined HORIBA France in 2015 to oversee global R&D, applications and marketing of Raman spectroscopy products coupled with Scanning Probe Microscopy (SPM). He received the IP Award from the HORIBA group for innovative intellectual property in 2016.

Martian buildings could be made of chitin-based material

Early settlers on Mars could build their homes using a material that includes chitin, which is a a fibrous substance made by a wide variety of living organisms from fish to fungi. The versatile new material was developed by Javier Fernandez and colleagues at Singapore University of Technology and Design. They used it to create objects ranging from cartoon figures and basic tools, to scale models of sturdy Martian shelters.

Crewed missions to Mars have been discussed for decades, but NASA has now expressed hopes that a long-term settlement on the Red Planet could be achieved by the late 2030s. Among the immense challenges that colonizers will face is the scarcity of basic resources on the Martian surface. This is also becoming an issue here on Earth, where certain resources are being rapidly consumed and there is a movement towards sustainable and circular manufacturing processes.

One promising solution is to create materials using chitin – an abundant biological polymer that is made by a wide range of living things. While it is highly unlikely that chitin-producing organisms currently live on Mars, they could easily be part of an artificial ecosystem created on the planet.

Obtainable on Mars

Fernandez’s team created their new material by extracting a form of chitin from shrimp exoskeletons, through treatment with sodium hydroxide. This chemical would be easily obtainable on Mars through the simple chemical process of electrolytic hydrolysis.

The researchers then dissolved the chitin in a low concentration of acetic acid – a common product of fermentation, which would be crucial to the food supply on an early Martian settlement. Finally, they mixed the chitin solution with a powdered material simulating Martian soil, forming a thick sediment. The only other ingredient necessary for the process is water – which can be readily found in Mars’ subsurface ice.

After fine-tuning the ratios of these ingredients to optimize the structural properties of their material, Fernandez’s team demonstrated a wide variety of manufacturing methods. These included casting techniques for producing cartoon figures and basic tools, including a functional wrench strong enough to tighten a hexagonal bolt. The team also used the material as a mortar to repair holes. Finally, they exploited the sediment’s self-adhesive properties to 3D print a 5 m scale model of a proposed Mars habitat called MARSHA.

Fernandez and colleagues have shown that their chitinous material not only requires minimal energy to produce; its ingredients are also readily available on Mars, and do not compete with food production. These advantages avoid the need for complex polymer synthesis and the shipping of expensive equipment – enabling the earliest Martian settlements to operate independently from Earth’s resources. With some adaptation, these techniques could inspire new routes towards a circular, sustainable economy on Earth – which would operate without unleashing further damage on natural ecosystems.

The new material is described in PLOS One.

Machine learning and Doppler vibrometer monitor household appliances

A way of monitoring household appliances by using machine learning to analyse vibrations on a wall or ceiling has been developed by researchers in the US. Their system could be used to create centralized smart home systems without the need for individual sensors in each object. What is more, the technology could help track energy use, identify electrical faults and even remind people to empty the dishwasher.

“Recognizing home activities can help computers better understand human behaviours and needs, with the hope of developing a better human-machine interface,” says team member and information scientist Cheng Zhang of Cornell University.

The system, dubbed VibroSense, comprises two core parts: a laser Doppler vibrometer and a deep learning model, which is a type of machine learning system.

Wall or ceiling

The vibrometer detects tiny vibrations by measuring the distortion of a laser beam reflected from a surface. For single-story houses, VibroSense’s laser is targeted at a central interior wall within the home, whereas in two-story residences, the researchers aim it at a ceiling. The researchers’ prototype device is cable of detecting vibration velocities of up to 1.25 m/s with a resolution of around 0.2 µm/s.

The deep learning model learns how to identify individual appliances based on their characteristic noises and distinct paths that these vibrations follow through the building. Training the model involves using samples of individual vibration patterns for each target appliance. It takes around 1-2 h, depending on the number of vibration sources being monitored.

In tests undertaken across five households over two days, the VibroSense prototype could identify the activities of 18 different common household objects with a 96% accuracy rate – even when the appliances were spread across different rooms and floors. This included picking out the signals generated by an electric kettle, a range hood, a microwave, a washing machine, an exhaust fan and even a dripping tap. In addition, the device was capable of distinguishing between different stages of individual appliance use with an average accuracy of more than 97%.

Energy-saving advice

“Since our system can detect both the occurrence of an indoor event, as well as the time of an event, it could be used to estimate electricity and water-usage rates, and provide energy-saving advice for homeowners,” says Zhang.

In addition, VibroSense may even be able to help homeowners detect electrical faults before they become critical. “The theory is that if there is any abnormal condition to certain appliance, their vibration pattern would change, which VibroSense probably can pick up and detect with appropriate training,” Zhang explains.

In the future, Zhang believes that it may be possible to create a more advanced version of the machine learning system that uses vibration data for assorted appliances to accommodate the addition of new appliances to a home without needing additional training.

Privacy issues

The concept is not without some inherent issues, however – specifically as regards to the privacy implications of the device being able to “spy” on the activities going on in neighbouring flats, should it be used within an apartment complex. For this reason, the researchers say, the design is perhaps best suited for implementation within detached dwellings.

Commercial development of VibroSense, Zhang commented, “would definitely require collaboration between researches, industry practitioners and government – to make sure this was used for the right purposes.”

Michael Connelly, an engineer at Ireland’s University of Limerick comments, “The VibroSense technology has the potential to greatly enhance the understanding of the complex home environment and find applications in other areas of vibration measurement”. However, Connelly, who was not involved in the development of VibroSense adds, “laser vibrometers are expensive thereby it will be challenging to commercially exploit the VibroSense system, particularly as the deployment of the Internet of Things in the home increases.”

This is an issue that the researchers are aware of. According to Zhang, the current version of VibroSense would cost around $1000–$2000. However, he adds that similar results may be possible using cheaper sensors such as accelerometers or geophones.

With their initial study complete, the researchers are now moving to explore the potential of using similar, minimally intrusive sensing devices to monitor human activities within broader settings – with the goal of using the data gathered to both enhance human–computer interactions and also to explore potential diagnostic medical applications.

The research is described in the Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies.

The promises and pitfalls of peer review

This week’s podcast focuses on Peer Review Week, an annual event honouring the vital role that peer review plays in maintaining the quality of published scientific papers. But while peer review is important, it’s certainly not perfect. The quality of reviews is not always up to scratch – as the darkly comic website Shit My Reviewers Say demonstrates. The pool of peer reviewers is nowhere near as diverse as the scientific community itself. And the many helpful, conscientious reviewers aren’t getting the rewards and recognition they deserve.

Joining us to talk about these challenges (and strategies for addressing them) are Kim Eggleton, the Research Integrity and Inclusion Manager at IOP Publishing (which publishes Physics World), and Bahar Mehmani, who is Reviewer Experience Lead at the scientific publishing giant Elsevier. Kim and Bahar also discuss how the coronavirus pandemic is affecting peer review. With so much at stake for public health, the need for published scientific research to be as accurate, robust and transparent as possible has never been greater.

Browse articles by content type