Tag Archives: sensors

Neuromorphic night vision powered by quantum dots with memory

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Michael Berger’s August 27, 2025 Nanowerk Spotlight article takes us into the field of ‘brainlike’ vision (neuromorphic vision), Note: Links have been removed,

Human eyes adjust effortlessly to darkness. A few minutes after stepping into a dim room or driving through a tunnel at night, vision sharpens, objects come into focus, and movement is easier to track. This ability comes from a combination of immediate sensitivity and short-term memory built into the retina itself. Rod cells detect weak light. Neurons store patterns. Together, they let the brain build a coherent picture even in near darkness.

Artificial vision systems do none of this. Cameras capture light, but they rely on separate memory and processing units to interpret it. In dim conditions, this pipeline breaks down. Signals get noisy. Processing lags. And without a way to remember what was just seen, tracking motion or recognizing shapes becomes unreliable. The result is a major weakness in technologies that need to see in the dark, from autonomous vehicles to low-power robotics and surveillance.

Solving this problem requires more than just better sensors. It requires hardware that behaves more like a retina, adapting to weak light while storing and processing visual information locally. The field of retinomorphic vision aims to build such systems by mimicking biological principles in electronic devices. But one of the biggest technical barriers has remained unresolved.

Even the most light-sensitive materials, such as quantum dots, struggle to generate usable signals in low-light environments because the charges they produce remain locked together and don’t travel. Without charge separation, there’s no current to store, no memory to form, and no adaptation to achieve.

A study published in Advanced Materials (“Ferroelectric Quantum Dots for Retinomorphic In‐Sensor Computing”) presents a solution to this problem. The researchers developed ferroelectric quantum dots that combine strong light absorption with built-in electric fields. These fields help separate photo-generated charges, enabling a new kind of device that can detect, adapt to, and remember visual information in real time and low-light conditions.

My hat’s off to whomever produced this illustration as it is unusually accessible to someone like me, i.e., not particularly skilled at decrypting scientific illustrations,

Figure 1: Biological and artificial vision systems with adaptive and dynamic sensing capabilities. a) The human visual system receives external stimuli through photoreceptors, including cones and rods, and continuously adapts by updating synaptic connections to form visual dynamic memory. Highly photosensitive rod cells are essential for weak light detection and scotopic adaptation. b) A floating gate configuration is used to implement the LADM system. The synthesis of FE-QDs involves a ligand exchange process, where the long-chain PVDF-SH ligands replace the short-chain OA ligands. The FE-QD’s advantage is its ability to realize LADM functions within a single device, facilitated by the ferroelectric PVDF-SH ligand and the photoelectric response of QDs. c) Schematic diagram of car motion recognition under low-light conditions, using conventional sensing, adaptive sensing, and adaptive & dynamic sensing, respectively. [downloaded from https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/adma.202504117]

Back to Berger’s August 27, 2025 article,

The team started with cadmium selenide quantum dots, a well-studied material known for its efficient light absorption. They wrapped the dots in a shell of zinc cadmium sulfide and replaced the usual surface ligands with specially designed polymer chains. These polymers, made from polyvinylidene fluoride, are ferroelectric. That means they contain internal dipoles that reorient under an applied voltage, generating a small electric field. This field counteracts the force that normally holds electrons and holes together inside a quantum dot, making it easier for the charges to separate.

The researchers synthesized the ferroelectric polymer using a controlled polymerization method and modified it with sulfur-based groups that strongly attach to the surface of the dots. This chemical structure not only introduces the desired electrical behavior but also helps prevent the dots from clumping together in a film, ensuring even distribution for device fabrication. Tests confirmed that the modified quantum dots preserved their optical properties and showed stable emission under illumination. Measurements also confirmed ferroelectric switching, with clear polarization loops and reversible shifts in surface potential.

To turn the material into a functional device, the team built a synaptic phototransistor. In this structure, the quantum dot film acts as a floating gate layer between insulators and a semiconducting channel. When light strikes the device, it creates charges in the dots. The direction of the ferroelectric polarization determines how easily these charges tunnel through to the channel. Once there, the charges modulate the current in the device, which continues to flow even after the light is turned off. This persistent current functions as a kind of memory, storing information about the visual input.

The researchers showed that applying different voltages changed the behavior of the device. A positive voltage aligned the internal dipoles to help charges flow, boosting memory retention. A negative voltage did the opposite, reducing the stored current. This switchable behavior mimics synaptic plasticity in biological systems, where the strength of a signal pathway changes based on input. The device demonstrated both short-term and long-term memory effects, depending on the strength and duration of the light pulses. In tests, the photocurrent persisted for over seven hours under ambient conditions without encapsulation, a result attributed to the chemical stability of the fluorinated polymer ligands.

…

The researchers also tested a form of sensory adaptation similar to how the human eye adjusts to low light over time. They projected a target pattern onto a 3 by 3 sensor array under dim conditions, along with a distracting background signal. Without polarization, the pattern was hard to detect. But when the ferroelectric function was activated, the pattern gradually became clearer with each pulse of light. This behavior mimicked the gradual increase in contrast that occurs in the retina during scotopic adaptation. Even after the light was removed, the stored signal remained visible, demonstrating that the sensor could both adapt and remember.

…

By combining material innovation with device design, the researchers have developed a sensor that moves beyond passive detection. It responds to light like a photoreceptor, stores information like a memory cell, and adapts its behavior like a synapse. The system could provide a foundation for vision hardware that processes information where it is captured, enabling fast, energy-efficient operation in conditions that currently challenge conventional cameras and sensors.

I wonder if this work will find its way into self-driving cars. Having just read a book about some of the problems with Tesla’s self-driving cars (2025 book, “The Tesla Files: The Definitive Exposé of the World’s Most Powerful Businessman and the Rise and Fall of his Empire” by Sönke Iwersen, Michael Verfürden), this would (if feasible) seem like an improvement over what they have currently.

Getting back to the research, here’s a link to and a citation for the paper,

Ferroelectric Quantum Dots for Retinomorphic In-Sensor Computing by Tingyu Long, Huanyu Zhou, Jaewan Ko, Hongwei Tan, Jaemin Lim, Yanfei Zhao, Daehan Kang, Eojin Yoon, Gyeong-Tak Go, Somin Kim, Seung-Woo Lee, Chan-Yul Park, Hyojun Choi, Hyeran Kim, Hyung Joong Yun, Sung Hyuk Park, Kwan Sik Park, Jeong Woo Park, Mungeun Kim, Yong Soo Cho, Ho Won Jang, Wenqiang Yang, Min Hyuk Park, Wan Ki Bae, Sebastiaan van Dijken, Joona Bang, Tae-Woo Lee. Advanced Materials DOI: https://doi.org/10.1002/adma.202504117 First published: 23 August 2025

This paper is open access.

Converting body heat into electricity with smart fabric

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This bioenergy harvesting story is from the University of Waterloo (Ontario, Canada), where its researchers were part of an international collaboration. From an August 14, 2023 news item on ScienceDaily,

Imagine a coat that captures solar energy to keep you cozy on a chilly winter walk, or a shirt that can monitor your heart rate and temperature.Picture clothing athletes can wear to track their performance without the need for bulky battery packs.

University of Waterloo researchers have developed a smart fabric with these remarkable capabilities.

The fabric has the potential for energy harvesting, health monitoring, and movement tracking applications.

…

An August 14, 2024 University of Waterloo news release (also on EurekAlert), which originated the news item, provides more information about the new fabric and the research team, Note: A link has been removed,

The new fabric developed by a Waterloo research team can convert body heat and solar energy into electricity, potentially enabling continuous operation with no need for an external power source. Different sensors monitoring temperature, stress, and more can be integrated into the material.

It can detect temperature changes and a range of other sensors to monitor pressure, chemical composition, and more. One promising application is smart face masks that can track breath temperature and rate and detect chemicals in breath to help identify viruses, lung cancer, and other conditions.

“We have developed a fabric material with multifunctional sensing capabilities and self-powering potential,” said Yuning Li, a professor in the Department of Chemical Engineering. “This innovation brings us closer to practical applications for smart fabrics.”

Unlike current wearable devices that often depend on external power sources or frequent recharging, this breakthrough research has created a novel fabric which is more stable, durable, and cost-effective than other fabrics on the market. 

This research, conducted in collaboration with Professor Chaoxia Wang and PhD student Jun Peng from the College of Textile Science and Engineering at Jiangnan University, showcases the potential of integrating advanced materials such as MXene and conductive polymers with cutting-edge textile technologies to advance smart fabrics for wearable technology.

Li, director of Waterloo’s Printable Electronic Materials Lab, highlighted the significance of this advancement, which is the latest in the university’s suite of technologies disrupting health boundaries.

“AI technology is evolving rapidly, offering sophisticated signal analysis for health monitoring, food and pharmaceutical storage, environmental monitoring, and more. However, this progress relies on extensive data collection, which conventional sensors, often bulky, heavy, and costly, cannot meet,” Li said. “Printed sensors, including those embedded in smart fabrics, are ideal for continuous data collection and monitoring. This new smart fabric is a step forward in making these applications practical.”

The next phase of research will focus on further enhancing the fabric’s performance and integrating it with electronic components in collaboration with electrical and computer engineers. Future developments may include a smartphone app to track and transmit data from the fabric to healthcare professionals, enabling real-time, non-invasive health monitoring and everyday use.

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

MXene-based thermoelectric fabric integrated with temperature and strain sensing for health monitoring by Jun Peng, Fangqing Ge, Weiyi Han, Tao Wu, Jinglei Tang, Yuning Li, Chaoxia Wang. Journal of Materials Science & Technology Volume 212, 20 March 2025, Pages 272-280

This paper is behind a paywall but you will be able to read snippets in a preview.

Turn yourself into a robot

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Turning yourself into a robot is a little easier than I would have thought,

William Weir’s September 19, 2018 Yale University news release (also on EurekAlert) covers some of the same ground and fills in a few details,

When you think of robotics, you likely think of something rigid, heavy, and built for a specific purpose. New “Robotic Skins” technology developed by Yale researchers flips that notion on its head, allowing users to animate the inanimate and turn everyday objects into robots.

Developed in the lab of Rebecca Kramer-Bottiglio, assistant professor of mechanical engineering & materials science, robotic skins enable users to design their own robotic systems. Although the skins are designed with no specific task in mind, Kramer-Bottiglio said, they could be used for everything from search-and-rescue robots to wearable technologies. The results of the team’s work are published today in Science Robotics.

The skins are made from elastic sheets embedded with sensors and actuators developed in Kramer-Bottiglio’s lab. Placed on a deformable object — a stuffed animal or a foam tube, for instance — the skins animate these objects from their surfaces. The makeshift robots can perform different tasks depending on the properties of the soft objects and how the skins are applied.

“We can take the skins and wrap them around one object to perform a task — locomotion, for example — and then take them off and put them on a different object to perform a different task, such as grasping and moving an object,” she said. “We can then take those same skins off that object and put them on a shirt to make an active wearable device.”

Robots are typically built with a single purpose in mind. The robotic skins, however, allow users to create multi-functional robots on the fly. That means they can be used in settings that hadn’t even been considered when they were designed, said Kramer-Bottiglio.

Additionally, using more than one skin at a time allows for more complex movements. For instance, Kramer-Bottiglio said, you can layer the skins to get different types of motion. “Now we can get combined modes of actuation — for example, simultaneous compression and bending.”

To demonstrate the robotic skins in action, the researchers created a handful of prototypes. These include foam cylinders that move like an inchworm, a shirt-like wearable device designed to correct poor posture, and a device with a gripper that can grasp and move objects.

Kramer-Bottiglio said she came up with the idea for the devices a few years ago when NASA  [US National Aeronautics and Space Administration] put out a call for soft robotic systems. The technology was designed in partnership with NASA, and its multifunctional and reusable nature would allow astronauts to accomplish an array of tasks with the same reconfigurable material. The same skins used to make a robotic arm out of a piece of foam could be removed and applied to create a soft Mars rover that can roll over rough terrain. With the robotic skins on board, the Yale scientist said, anything from balloons to balls of crumpled paper could potentially be made into a robot with a purpose.

“One of the main things I considered was the importance of multifunctionality, especially for deep space exploration where the environment is unpredictable,” she said. “The question is: How do you prepare for the unknown unknowns?”

For the same line of research, Kramer-Bottiglio was recently awarded a $2 million grant from the National Science Foundation, as part of its Emerging Frontiers in Research and Innovation program.

Next, she said, the lab will work on streamlining the devices and explore the possibility of 3D printing the components.

Just in case the link to the paper becomes obsolete, here’s a citation for the paper,

OmniSkins: Robotic skins that turn inanimate objects into multifunctional robots by Joran W. Booth, Dylan Shah, Jennifer C. Case, Edward L. White, Michelle C. Yuen, Olivier Cyr-Choiniere, and Rebecca Kramer-Bottiglio. Science Robotics 19 Sep 2018: Vol. 3, Issue 22, eaat1853 DOI: 10.1126/scirobotics.aat1853

This paper is behind a paywall.

I am a sound speaker/loudspeaker (well, maybe one day)

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Caption: From left are Saewon Kang, Professor Hyunhyub Ko, and Seungse Cho in the School of Energy and Chemical Engineering at UNIST. Credit: UNIST

What are these scientists so happy about? A September 18, 2018 news item on ScienceDaily reveals all,

An international team of researchers, affiliated with UNIST [Ulsan National Institute of Science and Technology] has presented an innovative wearable technology that will turn your skin into a loudspeaker.

An August 6, 2018 UNIST press release (also on EurekAlert but published September 17,2018), which originated the news item, delves further into the research,

This breakthrough has been led by Professor Hyunhyub Ko in the School of Energy and Chemical Engineering at UNIST. Created in part to help the hearing and speech impaired, the new technology can be further explored for various potential applications, such as wearable IoT sensors and conformal health care devices.

In the study, the research team has developed ultrathin, transparent, and conductive hybrid nanomembranes with nanoscale thickness, consisting of an orthogonal silver nanowire array embedded in a polymer matrix. They, then, demonstrated their nanomembrane by making it into a loudspeaker that can be attached to almost anything to produce sounds. The researchers also introduced a similar device, acting as a microphone, which can be connected to smartphones and computers to unlock voice-activated security systems.

Nanomembranes (NMs) are molcularly thin seperation layers with nanoscale thickness. Polymer NMs have attracted considerable attention owing to their outstanding advantages, such as extreme flexibility, ultralight weight, and excellent adhesibility in that they can be attached directly to almost any surface. However, they tear easily and exhibit no electrical conductivity.

The research team has solved such issues by embedding a silver nanowire network within a polymer-based nanomembrane. This has enabled the demonstration of skin-attachable and imperceptible loudspeaker and microphone.

“Our ultrathin, transparent, and conductive hybrid NMs facilitate conformal contact with curvilinear and dynamic surfaces without any cracking or rupture,” says  Saewon Kang in the doctroral program of Energy and Chemical Engineering at UNIST, the first author of the study.

He adds, “These layers are capable of detecting sounds and vocal vibrations produced by the triboelectric voltage signals corresponding to sounds, which could be further explored for various potential applications, such as sound input/output devices.”

Using the hybrid NMs, the research team fabricated skin-attachable NM loudspeakers and microphones, which would be unobtrusive in appearance because of their excellent transparency and conformal contact capability. These wearable speakers and microphones are paper-thin, yet still capable of conducting sound signals.

“The biggest breakthrough of our research is the development of ultrathin, transparent, and conductive hybrid nanomembranes with nanoscale thickness, less than 100 nanometers,” says Professor Ko. “These outstanding optical, electrical, and mechanical properties of nanomembranes enable the demonstration of skin-attachable and imperceptible loudspeaker and microphone.”The skin-attachable NM loudspeakers work by emitting thermoacoustic sound by the temperature-induced oscillation of the surrounding air. The periodic Joule heating that occurs when an electric current passes through a conductor and produces heat leads to these temperature oscillations. It has attracted considerable attention for being a stretchable, transparent, and skin-attachable loudspeaker.

Wearable microphones are sensors, attached to a speaker’s neck to even sense the vibration of the vocal folds. This sensor operates by converting the frictional force generated by the oscillation of the transparent conductive nanofiber into electric energy. For the operation of the microphone, the hybrid nanomembrane is inserted between elastic films with tiny patterns to precisely detect the sound and the vibration of the vocal cords based on a triboelectric voltage that results from the contact with the elastic films.

“For the commercial applications, the mechanical durability of nanomebranes and the performance of loudspeaker and microphone should be improved further,” says Professor Ko.

Thankfully, the researchers have made video that lets us hear this sound speaker,


Paper-thin stick-on speakers, developed by Professor Hyunhyub Ko and his research team at UNIST.

Thank you to the folks at UNIST for including something with the sound. Strangely, it’s not common practice to include audio when publishing research on sound, not in my experience anyway..

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

Transparent and conductive nanomembranes with orthogonal silver nanowire arrays for skin-attachable loudspeakers and microphones by Saewon Kang, Seungse Cho, Ravi Shanker, Hochan Lee, Jonghwa Park, Doo-Seung Um, Youngoh Lee, and Hyunhyub Ko. Science Advances 03 Aug 2018: Vol. 4, no. 8, eaas8772 DOI: 10.1126/sciadv.aas8772

This paper appears to be open access.

Build nanoparticles using techniques from the ancient Egyptians

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Great Pyramid of Giza and Sphinx [downloaded from http://news.ifmo.ru/en/science/photonics/news/7731/]

Russian and German scientists have taken a closer look at the Great Pyramid as they investigate better ways of designing sensors and solar cells. From a July 30, 2018 news item on Nanowerk,

An international research group applied methods of theoretical physics to investigate the electromagnetic response of the Great Pyramid to radio waves. Scientists predicted that under resonance conditions the pyramid can concentrate electromagnetic energy in its internal chambers and under the base. The research group plans to use these theoretical results to design nanoparticles capable of reproducing similar effects in the optical range. Such nanoparticles may be used, for example, to develop sensors and highly efficient solar cells.

A July 30, 2018 ITMO University press release, which originated the news item,  expands on the theme,

While Egyptian pyramids are surrounded by many myths and legends, we have little scientifically reliable information about their physical properties. As it turns out, sometimes this information proves to be more fascinating than any fiction. This idea found confirmation in a new joint study undertaken by scientists from ITMO University and the Laser Zentrum Hannover. The physicists took an interest in how the Great Pyramid would interact with electromagnetic waves of a proportional, or resonant, length. Calculations showed that in the resonant state the pyramid can concentrate electromagnetic energy in its internal chambers as well as under its base, where the third unfinished chamber is located.

These conclusions were derived on the basis of numerical modeling and analytical methods of physics. The researchers first estimated that resonances in the pyramid can be induced by radio waves with a length ranging from 200 to 600 meters. Then they made a model of the electromagnetic response of the pyramid and calculated the extinction cross section. This value helps to estimate which part of the incident wave energy can be scattered or absorbed by the pyramid under resonant conditions. Finally, for the same conditions, the scientists obtained the electromagnetic fields distribution inside the pyramid.

3D model of the pyramid. Credit: cheops.SU
3D model of the pyramid. Credit: cheops.SU

In order to explain the results, the scientists conducted a multipole analysis. This method is widely used in physics to study the interaction between a complex object and electromagnetic field. The object scattering the field is replaced by a set of simpler sources of radiation: multipoles. The collection of multipoles radiation coincides with the field scattering by an entire object. Therefore, by knowing the type of each multipole, it is possible to predict and explain the distribution and configuration of the scattered fields in the whole system.

The Great Pyramid attracted the researchers’ attention while they were studying the interaction between light and dielectric nanoparticles. The scattering of light by nanoparticles depends on their size, shape, and refractive index of the source material. By varying these parameters, it is possible to determine the resonance scattering regimes and use them to develop devices for controlling light at the nanoscale.

“Egyptian pyramids have always attracted great attention. We as scientists were interested in them as well, and so we decided to look at the Great Pyramid as a particle resonantly dissipating radio waves. Due to the lack of information about the physical properties of the pyramid, we had to make some assumptions. For example, we assumed that there are no unknown cavities inside, and the building material has the properties of an ordinary limestone and is evenly distributed in and out of the pyramid. With these assumptions, we obtained interesting results that can have important practical applications,” says Andrey Evlyukhin, DSc, scientific supervisor and coordinator of the research.

Now the scientists plan to use the results to reproduce similar effects at the nanoscale.

Polina Kapitanova
Polina Kapitanova

“By choosing a material with suitable electromagnetic properties, we can obtain pyramidal nanoparticles with a potential for practical application in nanosensors and effective solar cells,” says Polina Kapitanova, PhD, associate at the Faculty of Physics and Engineering of ITMO University.

The research was supported by the Russian Science Foundation and the Deutsche Forschungsgemeinschaft (grants № 17-79-20379 and №16-12-10287).

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

Electromagnetic properties of the Great Pyramid: First multipole resonances and energy concentration featured by Mikhail Balezin, Kseniia V. Baryshnikova, Polina Kapitanova, and Andrey B. Evlyukhin. Journal of Applied Physics 124, 034903 (2018) https://doi.org/10.1063/1.5026556 or Journal of Applied Physics, Volume 124, Issue 3. 10.1063/1.5026556 Published Online 20 July 2018

This paper is behind a paywall..

Electrode-filled elastic fiber for wearable electronics and robots

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This work comes out of Switzerland. A May 25, 2018 École Polytechnique Fédérale de Lausanne (EPFL) press release (also on EurekAlert) announces their fibers,

EPFL scientists have found a fast and simple way to make super-elastic, multi-material, high-performance fibers. Their fibers have already been used as sensors on robotic fingers and in clothing. This breakthrough method opens the door to new kinds of smart textiles and medical implants.

It’s a whole new way of thinking about sensors. The tiny fibers developed at EPFL are made of elastomer and can incorporate materials like electrodes and nanocomposite polymers. The fibers can detect even the slightest pressure and strain and can withstand deformation of close to 500% before recovering their initial shape. All that makes them perfect for applications in smart clothing and prostheses, and for creating artificial nerves for robots.

The fibers were developed at EPFL’s Laboratory of Photonic Materials and Fiber Devices (FIMAP), headed by Fabien Sorin at the School of Engineering. The scientists came up with a fast and easy method for embedding different kinds of microstructures in super-elastic fibers. For instance, by adding electrodes at strategic locations, they turned the fibers into ultra-sensitive sensors. What’s more, their method can be used to produce hundreds of meters of fiber in a short amount of time. Their research has just been published in Advanced Materials.

Heat, then stretch
To make their fibers, the scientists used a thermal drawing process, which is the standard process for optical-fiber manufacturing. They started by creating a macroscopic preform with the various fiber components arranged in a carefully designed 3D pattern. They then heated the preform and stretched it out, like melted plastic, to make fibers of a few hundreds microns in diameter. And while this process stretched out the pattern of components lengthwise, it also contracted it crosswise, meaning the components’ relative positions stayed the same. The end result was a set of fibers with an extremely complicated microarchitecture and advanced properties.

Until now, thermal drawing could be used to make only rigid fibers. But Sorin and his team used it to make elastic fibers. With the help of a new criterion for selecting materials, they were able to identify some thermoplastic elastomers that have a high viscosity when heated. After the fibers are drawn, they can be stretched and deformed but they always return to their original shape.

Rigid materials like nanocomposite polymers, metals and thermoplastics can be introduced into the fibers, as well as liquid metals that can be easily deformed. “For instance, we can add three strings of electrodes at the top of the fibers and one at the bottom. Different electrodes will come into contact depending on how the pressure is applied to the fibers. This will cause the electrodes to transmit a signal, which can then be read to determine exactly what type of stress the fiber is exposed to – such as compression or shear stress, for example,” says Sorin.

Artificial nerves for robots

Working in association with Professor Dr. Oliver Brock (Robotics and Biology Laboratory, Technical University of Berlin), the scientists integrated their fibers into robotic fingers as artificial nerves. Whenever the fingers touch something, electrodes in the fibers transmit information about the robot’s tactile interaction with its environment. The research team also tested adding their fibers to large-mesh clothing to detect compression and stretching. “Our technology could be used to develop a touch keyboard that’s integrated directly into clothing, for instance” says Sorin.

The researchers see many other potential applications. Especially since the thermal drawing process can be easily tweaked for large-scale production. This is a real plus for the manufacturing sector. The textile sector has already expressed interest in the new technology, and patents have been filed.

There’s a video of the lead researcher discussing the work as he offers some visual aids,

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

Superelastic Multimaterial Electronic and Photonic Fibers and Devices via Thermal Drawing by Yunpeng Qu, Tung Nguyen‐Dang, Alexis Gérald Page, Wei Yan, Tapajyoti Das Gupta, Gelu Marius Rotaru, René M. Rossi, Valentine Dominique Favrod, Nicola Bartolomei, Fabien Sorin. Advanced Materials First published: 25 May 2018 https://doi.org/10.1002/adma.201707251

This paper is behind a paywall.

Canada’s National Institute of Nanotechnology and cellphone breathalyzers

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First a soap opera, of sorts and then the science.

Canada’s ‘morphing’ National Institute of Nanotechnology

It seems we in Canada no longer have a National Institute of Nanotechnology (NINT) as such. (sigh) The NINT been downsized and rebranded. Always part of Canada’s National Research Council (NRC), the NINT has been languishing for a number of years. The downsizing/rebranding has resulted in two new ‘entities’: the NRC Nanotechnology Research Centre and the NRC-UAlberta [University of Alberta] Nanotechnology Initiative. The original NINT was a joint venture between the Canadian federal government’s NRC and the province of Alberta, which was a co-funder with the institute (now initiative/research centre) itself being located at the University of Alberta. You can see the latest description of these agencies on this NRC Nanotechnology webpage.

For scandal mongers, the date the NRC Nanotechnology webpage was last updated is an interesting one:  March 14, 2018. My first posting about the ‘Montemagno affair’ was on March 5, 2018. Briefly, Carlo Montemagno was a US ressearcher and academic who was enticed to work at the University of Alberta with $100M of federal and provincial funding to be paid out over a 10-year period. His salary when he left about 1/2 way through his term was approximately $500,00 CAD per year. Departing in July/August 2017, Dr. Montemagno who headed up the “ingenuity Lab,” a kind of nanotechnology research and incubator project, moved to the Southern Illinois University (SIU) where he ran into some problems some of which seemed to stretch backwards to his time in Alberta. I did a followup two-part posting (April 26, 201 8 (part 1) after a student reporter from SIU dug up more material. This downsizing/rebranding seems to have been quite the cleanup job. By the way, Canada’s NanoPortal (mentioned in the March 5, 2018 posting) has currently ‘disappeared’.

Finally, the science

There is finally (it has been years) some sort of nanotechnology research from Alberta and the ‘initiative’. From a June 15, 2018 article by Jamie Sarkonak for the Edmonton Herald (in Alberta),

Cellphone breathalyzers may be on the horizon with the breakthrough by an Edmonton-based nanotechnology team.

The special sensors, called nano-optomechanical systems, are normally studied in airtight conditions. But the research of nanotechnologist Wayne Hiebert, published in the journal Science on Friday [June 15, 2018], has found the sensors work better in the open air — making them candidates for everyday use.

Hiebert, a researcher at the Nanotechnology Research Centre [emphasis mine] at the University of Alberta, said this means the sensors may one day run metabolic readings, cancer screenings and other tests that currently have to be done in laboratories. The sensors could also improve GPS and clock accuracy once the technology is more developed, Hiebert said.

…

Scientists have always believed that sensors on the nanoscale work better when they’re in a space sealed off from any air, Hiebert said. Readings taken in vacuums are much “sharper” than readings taken in regular air, which was always thought to be more useful in nanotechnology.

Four years of Hiebert’s work has found the opposite. The “duller” readings taken in the open gave the scientists a more accurate reading of what was in the air.

…

For the interested, there are more details in Sarkonak’s article.

For those who can read the science, here’s a link to and a citation for the paper,

Improving mechanical sensor performance through larger damping by Swapan K. Roy, Vincent T. K. Sauer, Jocelyn N. Westwood-Bachman, Anandram Venkatasubramanian, Wayne K. Hiebert. Science 15 Jun 2018: Vol. 360, Issue 6394, eaar5220 DOI: 10.1126/science.aar5220

This paper is behind a paywall.

A 3D printed ‘living’ tattoo

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MIT engineers have devised a 3-D printing technique that uses a new kind of ink made from genetically programmed living cells. Courtesy of the researchers [and MIT]

If that image isn’t enough, there’s also a video abstract (I don’t think I’ve seen one of these before) for the paper,

For those who’d still like to read the text, here’s more from a December 5, 2017 MIT (Massachusetts Institute of Technology) news release (also on EurekAlert),

MIT engineers have devised a 3-D printing technique that uses a new kind of ink made from genetically programmed living cells.

The cells are engineered to light up in response to a variety of stimuli. When mixed with a slurry of hydrogel and nutrients, the cells can be printed, layer by layer, to form three-dimensional, interactive structures and devices.

The team has then demonstrated its technique by printing a “living tattoo” — a thin, transparent patch patterned with live bacteria cells in the shape of a tree. Each branch of the tree is lined with cells sensitive to a different chemical or molecular compound. When the patch is adhered to skin that has been exposed to the same compounds, corresponding regions of the tree light up in response.

The researchers, led by Xuanhe Zhao, the Noyce Career Development Professor in MIT’s Department of Mechanical Engineering, and Timothy Lu, associate professor of biological engineering and of electrical engineering and computer science, say that their technique can be used to fabricate “active” materials for wearable sensors and interactive displays. Such materials can be patterned with live cells engineered to sense environmental chemicals and pollutants as well as changes in pH and temperature.

What’s more, the team developed a model to predict the interactions between cells within a given 3-D-printed structure, under a variety of conditions. The team says researchers can use the model as a guide in designing responsive living materials.

Zhao, Lu, and their colleagues have published their results today [December 5, 2017] in the journal Advanced Materials. The paper’s co-authors are graduate students Xinyue Liu, Hyunwoo Yuk, Shaoting Lin, German Alberto Parada, Tzu-Chieh Tang, Eléonore Tham, and postdoc Cesar de la Fuente-Nunez.

A hardy alternative

In recent years, scientists have explored a variety of responsive materials as the basis for 3D-printed inks. For instance, scientists have used inks made from temperature-sensitive polymers to print heat-responsive shape-shifting objects. Others have printed photoactivated structures from polymers that shrink and stretch in response to light.

Zhao’s team, working with bioengineers in Lu’s lab, realized that live cells might also serve as responsive materials for 3D-printed inks, particularly as they can be genetically engineered to respond to a variety of stimuli. The researchers are not the first to consider 3-D printing genetically engineered cells; others have attempted to do so using live mammalian cells, but with little success.

“It turns out those cells were dying during the printing process, because mammalian cells are basically lipid bilayer balloons,” Yuk says. “They are too weak, and they easily rupture.”

Instead, the team identified a hardier cell type in bacteria. Bacterial cells have tough cell walls that are able to survive relatively harsh conditions, such as the forces applied to ink as it is pushed through a printer’s nozzle. Furthermore, bacteria, unlike mammalian cells, are compatible with most hydrogels — gel-like materials that are made from a mix of mostly water and a bit of polymer. The group found that hydrogels can provide an aqueous environment that can support living bacteria.

The researchers carried out a screening test to identify the type of hydrogel that would best host bacterial cells. After an extensive search, a hydrogel with pluronic acid was found to be the most compatible material. The hydrogel also exhibited an ideal consistency for 3-D printing.

“This hydrogel has ideal flow characteristics for printing through a nozzle,” Zhao says. “It’s like squeezing out toothpaste. You need [the ink] to flow out of a nozzle like toothpaste, and it can maintain its shape after it’s printed.”

From tattoos to living computers

Lu provided the team with bacterial cells engineered to light up in response to a variety of chemical stimuli. The researchers then came up with a recipe for their 3-D ink, using a combination of bacteria, hydrogel, and nutrients to sustain the cells and maintain their functionality.

“We found this new ink formula works very well and can print at a high resolution of about 30 micrometers per feature,” Zhao says. “That means each line we print contains only a few cells. We can also print relatively large-scale structures, measuring several centimeters.”

They printed the ink using a custom 3-D printer that they built using standard elements combined with fixtures they machined themselves. To demonstrate the technique, the team printed a pattern of hydrogel with cells in the shape of a tree on an elastomer layer. After printing, they solidified, or cured, the patch by exposing it to ultraviolet radiation. They then adhere the transparent elastomer layer with the living patterns on it, to skin.

To test the patch, the researchers smeared several chemical compounds onto the back of a test subject’s hand, then pressed the hydrogel patch over the exposed skin. Over several hours, branches of the patch’s tree lit up when bacteria sensed their corresponding chemical stimuli.

The researchers also engineered bacteria to communicate with each other; for instance they programmed some cells to light up only when they receive a certain signal from another cell. To test this type of communication in a 3-D structure, they printed a thin sheet of hydrogel filaments with “input,” or signal-producing bacteria and chemicals, overlaid with another layer of filaments of an “output,” or signal-receiving bacteria. They found the output filaments lit up only when they overlapped and received input signals from corresponding bacteria .

Yuk says in the future, researchers may use the team’s technique to print “living computers” — structures with multiple types of cells that communicate with each other, passing signals back and forth, much like transistors on a microchip.

“This is very future work, but we expect to be able to print living computational platforms that could be wearable,” Yuk says.

For more near-term applications, the researchers are aiming to fabricate customized sensors, in the form of flexible patches and stickers that could be engineered to detect a variety of chemical and molecular compounds. They also envision their technique may be used to manufacture drug capsules and surgical implants, containing cells engineered produce compounds such as glucose, to be released therapeutically over time.

“We can use bacterial cells like workers in a 3-D factory,” Liu says. “They can be engineered to produce drugs within a 3-D scaffold, and applications should not be confined to epidermal devices. As long as the fabrication method and approach are viable, applications such as implants and ingestibles should be possible.”

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

3D Printing of Living Responsive Materials and Devices by Xinyue Liu, Hyunwoo Yuk, Shaoting Lin, German Alberto Parada, Tzu-Chieh Tang, Eléonore Tham, Cesar de la Fuente-Nunez, Timothy K. Lu, and Xuanhe Zhao. Advanced Materials DOI: 10.1002/adma.201704821 Version of Record online: 5 DEC 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Bandage with a voice (sort of)

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Researchers at Empa (Swiss Federal Laboratories for Materials Testing and Research) have not developed a talking bandage despite the title (Bandage with a Voice) for a July 4, 2017 Empa press release  (also a July 4, 2017 news item on Nanowerk),

A novel bandage alerts the nursing staff as soon as a wound starts healing badly. Sensors incorporated into the base material glow with a different intensity if the wound’s pH level changes. This way even chronic wounds could be monitored at home.

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Using a UV lamp, the pH level in the wound can be verified without removing the bandage and the healing process can continue unimpeded. Image: Empa / CSEM

All too often, changing bandages is extremely unpleasant, even for smaller, everyday injuries. It stings and pulls, and sometimes a scab will even start bleeding again. And so we prefer to wait until the bandage drops off by itself.

It’s a different story with chronic wounds, though: normally, the nursing staff has to change the dressing regularly – not just for reasons of hygiene, but also to examine the wound, take swabs and clean it. Not only does this irritate the skin unnecessarily; bacteria can also get in, the risk of infection soars. It would be much better to leave the bandage on for longer and have the nursing staff “read” the condition of the wound from outside.

The idea of being able to see through a wound dressing gave rise to the project Flusitex (Fluorescence sensing integrated into medical textiles), which is being funded by the Swiss initiative Nano-Tera. Researchers from Empa teamed up with ETH Zurich, Centre Suisse d’Electronique et de Microtechnique (CSEM) and University Hospital Zurich to develop a high-tech system that is supposed to supply the nursing staff with relevant data about the condition of a wound. As Luciano Boesel from Empa’s Laboratory for Biomimetic Membranes and Textiles, who is coordinating the project at Empa, explains: “The idea of a smart wound dressing with integrated sensors is to provide continuous information on the state of the healing process without the bandages having to be changed any more frequently than necessary.” This would mean a gentler treatment for patients, less work for the nursing staff and, therefore, lower costs: globally, around 17 billion $ were spent on treating wounds last year.

When wounds heal, the body produces specific substances in a complex sequence of biochemical processes, which leads to a significant variation in a number of metabolic parameters. For instance, the amount of glucose and oxygen rises and falls depending on the phase of the healing process; likewise does the pH level change. All these variations can be detected with specialized sensors. With this in mind, Empa teamed up with project partner CSEM to develop a portable, cheap and easy-to-use device for measuring fluorescence that is capable of monitoring several parameters at once. It should enable nursing staff to keep tabs on the pH as well as on glucose and oxygen levels while the wound heals. If these change, conclusions about other key biochemical processes involved in wound healing can be drawn.

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The bandage reveals ist measurings in UV light.
A high pH signals chronic wounds

The pH level is particularly useful for chronic wounds. If the wound heals normally, the pH rises to 8 before falling to 5 or 6. If a wound fails to close and becomes chronic, however, the pH level fluctuates between 7 and 8. Therefore, it would be helpful if a signal on the bandage could inform the nursing staff that the wound pH is permanently high. If the bandage does not need changing for reasons of hygiene and pH levels are low, on the other hand, they could afford to wait.

But how do the sensors work? The idea: if certain substances appear in the wound fluid, “customized” fluorescent sensor molecules respond with a physical signal. They start glowing and some even change color in the visible or ultra-violet (UV) range. Thanks to a color scale, weaker and stronger changes in color can be detected and the quantity of the emitted substance be deduced.

Empa chemist Guido Panzarasa from the Laboratory for Biomimetic Membranes and Textiles vividly demonstrates how a sample containing sensor molecules begins to fluoresce in the lab. He carefully drips a solution with a pH level of 7.5 into a dish. Under a UV light, the change is plain to see. He adds another solution and the luminescence fades. A glance at the little bottle confirms it: the pH level of the second solution is lower.

Luminous molecules under UV

The Empa team designed a molecule composed of benzalkonium chloride and pyranine. While benzalkonium chloride is a substance also used for conventional medical soap to combat bacteria, fungi and other microorganisms, pyranine is a dye found in highlighters that glows under UV light. “This biomarker works really well,” says Panzarasa; “especially at pH levels between 5.5 and 7.5. The colors can be visualized with simple UV lamps available in electronics stores.” The Empa team recently published their results in the journal “Sensors and Actuators”.

The designer molecule has another advantage: thanks to the benzalkonium chloride, it has an antimicrobial effect, as researchers from Empa’s Laboratory for Biointerfaces confirmed for the bacteria strain Staphylococcus aureus. Unwelcome bacteria might potentially also be combatted by selecting the right bandage material in future. As further investigations, such as on the chemical’s compatibility with cells and tissues, are currently lacking, however, the researchers do not yet know how their sensor works in a complex wound.

Keen interest from industry

In order to illustrate what a smart wound dressing might actually look like in future, Boesel places a prototype on the lab bench. “You don’t have to cover the entire surface of wound dressings with sensors,” he explains. “It’s enough for a few small areas to be impregnated with the pyranine benzalkonium molecules and integrated into the base material. This means the industrial wound dressings won’t be much pricier than they are now – only up to 20% more expensive.” Empa scientists are currently working on this in the follow-up project FlusiTex-Gateway in cooperation with industrial partners Flawa, Schöller, Kenzen and Theranoptics.
Panzarasa now drips various liquids with different pH levels onto all the little cylinders on the wound pad prototype. Sure enough, the lighter and darker dots are also clearly discernible as soon as the UV lamp is switched on. They are even visible to the naked eye and glow in bright yellow if liquids with a high pH come into contact with the sensor. The scientists are convinced: since the pH level is so easy to read and provides precise information about the acidic or alkaline state of the sample, this kind of wound dressing is just the ticket as a diagnostic tool. Using the fluorescence meter developed by CSEM, more accurate, quantitative measure-ments of the pH level can be accomplished for medical purposes.

According to Boesel, it might one day even be possible to read the signals with the aid of a smartphone camera. Combined with a simple app, nursing staff and doctors would have a tool that enables them to easily and conveniently read the wound status “from outside”, even without a UV lamp. And patients would then also have the possibility of detecting the early onset of a chronic wound at home.

I wonder how long or even if this innovation will ever make its way into medical practice. I’m guessing this stage would be described as ‘proof of concept’ and that clinical testing is still many years away.

The metaphor in the press release’s title helped to wake me up. Thank you to whoever wrote it.

Worm-inspired gel material and soft robots

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The Nereis virens worm inspired new research out of the MIT Laboratory for Atomistic and Molecular Mechanics. Its jaw is made of soft organic material, but is as strong as harder materials such as human dentin. Photo: Alexander Semenov/Wikimedia Commons

What an amazing worm! Here’s more about robots inspired by the Nereis virens worm in a March 20, 2017 news item on Nanowerk,

A new material that naturally adapts to changing environments was inspired by the strength, stability, and mechanical performance of the jaw of a marine worm. The protein material, which was designed and modeled by researchers from the Laboratory for Atomistic and Molecular Mechanics (LAMM) in the Department of Civil and Environmental Engineering (CEE) [at the Massachusetts Institute of Technology {MIT}], and synthesized in collaboration with the Air Force Research Lab (AFRL) at Wright-Patterson Air Force Base, Ohio, expands and contracts based on changing pH levels and ion concentrations. It was developed by studying how the jaw of Nereis virens, a sand worm, forms and adapts in different environments.

The resulting pH- and ion-sensitive material is able to respond and react to its environment. Understanding this naturally-occurring process can be particularly helpful for active control of the motion or deformation of actuators for soft robotics and sensors without using external power supply or complex electronic controlling devices. It could also be used to build autonomous structures.

A March 20, 2017 MIT news release, which originated the news item, provides more detail,

“The ability of dramatically altering the material properties, by changing its hierarchical structure starting at the chemical level, offers exciting new opportunities to tune the material, and to build upon the natural material design towards new engineering applications,” wrote Markus J. Buehler, the McAfee Professor of Engineering, head of CEE, and senior author of the paper.

The research, recently published in ACS Nano, shows that depending on the ions and pH levels in the environment, the protein material expands and contracts into different geometric patterns. When the conditions change again, the material reverts back to its original shape. This makes it particularly useful for smart composite materials with tunable mechanics and self-powered roboticists that use pH value and ion condition to change the material stiffness or generate functional deformations.

Finding inspiration in the strong, stable jaw of a marine worm

In order to create bio-inspired materials that can be used for soft robotics, sensors, and other uses — such as that inspired by the Nereis — engineers and scientists at LAMM and AFRL needed to first understand how these materials form in the Nereis worm, and how they ultimately behave in various environments. This understanding involved the development of a model that encompasses all different length scales from the atomic level, and is able to predict the material behavior. This model helps to fully understand the Nereis worm and its exceptional strength.

“Working with AFRL gave us the opportunity to pair our atomistic simulations with experiments,” said CEE research scientist Francisco Martin-Martinez. AFRL experimentally synthesized a hydrogel, a gel-like material made mostly of water, which is composed of recombinant Nvjp-1 protein responsible for the structural stability and impressive mechanical performance of the Nereis jaw. The hydrogel was used to test how the protein shrinks and changes behavior based on pH and ions in the environment.

The Nereis jaw is mostly made of organic matter, meaning it is a soft protein material with a consistency similar to gelatin. In spite of this, its strength, which has been reported to have a hardness ranging between 0.4 and 0.8 gigapascals (GPa), is similar to that of harder materials like human dentin. “It’s quite remarkable that this soft protein material, with a consistency akin to Jell-O, can be as strong as calcified minerals that are found in human dentin and harder materials such as bones,” Buehler said.

At MIT, the researchers looked at the makeup of the Nereis jaw on a molecular scale to see what makes the jaw so strong and adaptive. At this scale, the metal-coordinated crosslinks, the presence of metal in its molecular structure, provide a molecular network that makes the material stronger and at the same time make the molecular bond more dynamic, and ultimately able to respond to changing conditions. At the macroscopic scale, these dynamic metal-protein bonds result in an expansion/contraction behavior.

Combining the protein structural studies from AFRL with the molecular understanding from LAMM, Buehler, Martin-Martinez, CEE Research Scientist Zhao Qin, and former PhD student Chia-Ching Chou ’15, created a multiscale model that is able to predict the mechanical behavior of materials that contain this protein in various environments. “These atomistic simulations help us to visualize the atomic arrangements and molecular conformations that underlay the mechanical performance of these materials,” Martin-Martinez said.

Specifically, using this model the research team was able to design, test, and visualize how different molecular networks change and adapt to various pH levels, taking into account the biological and mechanical properties.

By looking at the molecular and biological makeup of a the Nereis virens and using the predictive model of the mechanical behavior of the resulting protein material, the LAMM researchers were able to more fully understand the protein material at different scales and provide a comprehensive understanding of how such protein materials form and behave in differing pH settings. This understanding guides new material designs for soft robots and sensors.

Identifying the link between environmental properties and movement in the material

The predictive model explained how the pH sensitive materials change shape and behavior, which the researchers used for designing new PH-changing geometric structures. Depending on the original geometric shape tested in the protein material and the properties surrounding it, the LAMM researchers found that the material either spirals or takes a Cypraea shell-like shape when the pH levels are changed. These are only some examples of the potential that this new material could have for developing soft robots, sensors, and autonomous structures.

Using the predictive model, the research team found that the material not only changes form, but it also reverts back to its original shape when the pH levels change. At the molecular level, histidine amino acids present in the protein bind strongly to the ions in the environment. This very local chemical reaction between amino acids and metal ions has an effect in the overall conformation of the protein at a larger scale. When environmental conditions change, the histidine-metal interactions change accordingly, which affect the protein conformation and in turn the material response.

“Changing the pH or changing the ions is like flipping a switch. You switch it on or off, depending on what environment you select, and the hydrogel expands or contracts” said Martin-Martinez.

LAMM found that at the molecular level, the structure of the protein material is strengthened when the environment contains zinc ions and certain pH levels. This creates more stable metal-coordinated crosslinks in the material’s molecular structure, which makes the molecules more dynamic and flexible.

This insight into the material’s design and its flexibility is extremely useful for environments with changing pH levels. Its response of changing its figure to changing acidity levels could be used for soft robotics. “Most soft robotics require power supply to drive the motion and to be controlled by complex electronic devices. Our work toward designing of multifunctional material may provide another pathway to directly control the material property and deformation without electronic devices,” said Qin.

By studying and modeling the molecular makeup and the behavior of the primary protein responsible for the mechanical properties ideal for Nereis jaw performance, the LAMM researchers are able to link environmental properties to movement in the material and have a more comprehensive understanding of the strength of the Nereis jaw.

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

Ion Effect and Metal-Coordinated Cross-Linking for Multiscale Design of Nereis Jaw Inspired Mechanomutable Materials by Chia-Ching Chou, Francisco J. Martin-Martinez, Zhao Qin, Patrick B. Dennis, Maneesh K. Gupta, Rajesh R. Naik, and Markus J. Buehler. ACS Nano, 2017, 11 (2), pp 1858–1868 DOI: 10.1021/acsnano.6b07878 Publication Date (Web): February 6, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.