Tag Archives: sensors

New, wearable cortisol sensor can help warn us of incoming burnout or depression

It’s no secret that life can get rough. Those who have to contend with that for too long can start feeling overwhelmed — burned out by the stress. Now, a team of researchers proposes a new approach through which we can quantify how much stress someone is under, and for how long. They hope that the new wearable device can help prevent burnout, and let us know when someone is most in need of support or a good old fashioned break from the stress.

Image via Pixabay.

The new device was designed by a team of engineers at Ecole Polytechnique Fédérale de Lausanne (EPFL) Nanoelectronic Devices Laboratory (Nanolab) and Xsensio, a Swiss-based biotech company. It takes the shape of a wearable sensor that measures the levels of stress hormone cortisol in a person’s sweat. This figure can then be used to gauge the levels of cortisol in the blood.

The sensor is placed directly on the skin and provides continuous readings of this hormone’s levels in their sweat.

Skin-deep stress

“Cortisol can be secreted on impulse — you feel fine and suddenly something happens that puts you under stress, and your body starts producing more of the hormone,” says Adrian Ionescu, head of Nanolab.

“But in people who suffer from stress-related diseases, this circadian rhythm is completely thrown off. If the body makes too much or not enough cortisol, that can seriously damage an individual’s health, potentially leading to obesity, cardiovascular disease, depression or burnout.”

Cortisol is synthesized from cholesterol in our body’s adrenal glands — these sit right on top of your kidneys. How much of it is secreted is in turn controlled by the pituitary gland in our brains through the use of the adrenocorticotropic hormone (ACTH).

It’s easy to read “stress hormone” and immediately assume cortisol is a bad guy, but that’s simply not true. As we’ve seen previously, stress is a completely natural and deeply useful response; the issue with it today is that we’re feeling much more stress than we would in our natural environment. In other words, stress isn’t the issue — too much stress, is.

In our day-to-day, cortisol has some very important functions, including keeping our metabolism, blood sugar, and blood pressure in check. It’s also deeply involved in other cardiovascular functions and the workings of the immune system. In a stressful situation, be it something life-threatening or a simple annoyance, cortisol is flooded into the body to make us ready for our ‘fight or flight’. This mostly means prepping up our brain, muscles, and heart for intense activity and possible injury.

Still, cortisol levels in the blood ebb and flow naturally throughout the day, following our circadian rhythm, to keep us functional or asleep as needed. It generally peaks between 6 am and 8 am to rouse us from sleep and then decreases gradually.

Since cortisol is such a good marker for how stressed we feel and how stressed our body actually is, it’s often used as a gold standard to gauge stress. To do that however you need a blood sample, and those aren’t something you can take just anywhere throughout your day.

That’s why the team designed a wearable sensor to measure how much cortisol an individual excretes through their skin. It contains a transistor and a graphene electrode, which the authors explain has very high sensitivity and can detect even low levels of the hormone. Aptamers, short fragments of single-stranded DNA or RNA that can bind to specific compounds, are tied to this graphene electrode, allowing it to interact with the cortisol molecule. Since the aptamers used naturally contain a negative charge, they will be electrostatically attracted to the cortisol molecule and release a charge as they bind together.

The more such molecules are present, the stronger the overall charge becomes. This allows for an accurate and direct measurement of its levels in sweat. The authors explain that this is the first device intended to continuously monitor cortisol levels throughout the circadian cycle (i.e. throughout the day).

“That’s the key advantage and innovative feature of our device. Because it can be worn, scientists can collect quantitative, objective data on certain stress-related diseases. And they can do so in a non-invasive, precise and instantaneous manner over the full range of cortisol concentrations in human sweat,” adds Ionescu.

They tested the device in the lab and found it reliable and efficient; the next step is to now make it available for healthcare workers or researchers. They’ve set up a bridge project with Prof. Nelly Pitteloud, chief of endocrinology, diabetes, and metabolism at the Lausanne University Hospital (CHUV), where the device will be tested for continuous use in a real-life hospital setting. They intend to run the test using healthy individuals as well as patients with Cushing’s syndrome (who produce too much cortisol), Addison’s disease (too little cortisol), and stress-related obesity.

As far as the psychological ramifications of stress, the team explains that they are still “assessed based only on patients’ perceptions and states of mind, which are often subjective”. A system such as this patch can help us determine quite reliably how much cortisol is running through their system, which can be used to gauge those at risk of depression or burnout. If nothing else, it will help them support their claims with cold-hard figures.

The paper “Extended gate field-effect-transistor for sensing cortisol stress hormone” has been published in the journal Communications Materials.


New sensor backpacks could turn bees into crop-monitoring drones

Drones? No thank you — I prefer backpacking bees.


Image credits Suzanne D. Williams.

Engineers from the University of Washington (UW) plans to give farmers a powerful (and adorable) alternative to drones. The team has developed tiny sensor systems that can fit on the back of a bumblebee without restricting the insects’ ability to fly. Such a package only requires a tiny battery to operate for up to seven hours at a time, and can recharge while the bees sleep in their hive at night.

BEElievable readings

“Drones can fly for maybe 10 or 20 minutes before they need to charge again, whereas our bees can collect data for hours,” said senior author Shyam Gollakota, an associate professor in the UW’s Paul G. Allen School of Computer Science & Engineering.

“We showed for the first time that it’s possible to actually do all this computation and sensing using insects in lieu of drones.”

It’s not the first time researchers have thought of ‘sensorising’ bees. The insects have one massive advantage over drones: they fly on their own power. However, they can’t carry much weight, limiting the range of sensors they can be fitted with. This also makes GPS receivers (which require a lot of energy and, thus, heavy batteries, to run) completely out of the question. Because of that, the farthest researchers have ever gotten was to superglue simple RFID (radio-frequency identification) backpacks onto bees to follow their movement. However, such RFID packs were a proof-of-concept and of limited use — they only worked for distances of about 10 inches and didn’t carry any sensing equipment.

The UW team needed sensors that were able to both accurately tell their location and fit on the tiny backs of bees for this research to pan out. They decided on using bumblebees (genus Bombus) since they’re beefier and can handle the weight of a tiny battery, says co-author Vikram Iyer, a doctoral student at the UW. These batteries, while small, could power an array of sensors for much longer than a conventional drone could be kept operational. Furthermore, they can be wirelessly recharged every night when the bees go to sleep.

The backpack they developed weighs only 102 milligrams, which the team says is roughly the weight of seven grains of uncooked rice. Bees are placed in a cold environment for a short while to slow them down, and the packs are glued to their back. The researchers used a similar method to remove the packs.

“The rechargeable battery powering the backpack weighs about 70 milligrams, so we had a little over 30 milligrams left for everything else, like the sensors and the localization system to track the insect’s position,” said co-author Rajalakshmi Nandakumar, a doctoral student in the Allen School.

Because GPS receivers weren’t a viable option, the team developed a unique method of localizing the backpack-toting bees. They set up multiple antennas, each broadcasting signals from a base station across a specific area. A receiver installed in the backpacks could pick up on the intensity and direction of the incoming signal to triangulate its position in space.

The team tested their localization system by installing four antennas on one side of a soccer field and carried a bee-with-backpack around the field in a jar. As long as they stood within 80 meters (roughly three-quarters the length of a soccer field) of the antennas, their system could accurately triangulate the bee’s position.

Small sensors monitoring temperature, humidity, and light intensity were later added to the pack. These would allow bees to collect and log data (along with their location) as they buzzed around the farm.

“It would be interesting to see if the bees prefer one region of the farm and visit other areas less often,” said co-author Sawyer Fuller, an assistant professor in the UW Department of Mechanical Engineering. “Alternatively, if you want to know what’s happening in a particular area, you could also program the backpack to say: ‘Hey bees, if you visit this location, take a temperature reading.'”

The data is uploaded from the backpacks into storage via backscatter when the bees return to the hive. Backscatter is a method through which devices can share information by reflecting radio waves in the environment. Right now, the team says, their packs can store about 30 kilobytes of data (which is very little), and can only upload it once they return to the hive. Going forward, the team would like to develop backpacks with live-stream cameras so farmers can monitor plant health in real time. Such a pack, however, would require instant upload capabilities (or, at least, much larger data storage).

“Having insects carry these sensor systems could be beneficial for farms because bees can sense things that electronic objects, like drones, cannot,” Gollakota said. “With a drone, you’re just flying around randomly, while a bee is going to be drawn to specific things, like the plants it prefers to pollinate. And on top of learning about the environment, you can also learn a lot about how the bees behave.”

The team will present its findings online at the ACM MobiCom 2019 conference.

Overview of the gesture-decoding glove. Credit: Timothy O'Connor et al (2017).

Cheap but smart glove translates American Sign Language into text

Overview of the gesture-decoding glove. Credit: Timothy O'Connor et al (2017).

Overview of the gesture-decoding glove. Credit: Timothy O’Connor et al (2017).

People with speech impairments will be able to communicate better with the rest of the world thanks to an experimental glove packed with bendable electronics. The glove translates gestures corresponding to the American Sign Language alphabet and then wirelessly transmits the information in text form to electronic devices that can show it on a display. The whole cost less than $100 to build — and could become way cheaper in a series production — and has a low power requirement.

Talk to the hand

There are many ways to track the movement of the human body and most methods rely on optical systems involving cameras or infrared emitters/receivers. These yield good results but the drawback is that they consume a lot of power. Moreover, these systems can be cumbersome and even immovable. On the other hand, wearable electronics overcome these constraints, especially if the tracking system is integrated inside a glove which can be used intuitively — you just have to move the hand and digits.

Gloves that track people’s gestures are already proving very useful in applications from virtual reality to telesurgery to military applications involving piloting drones. Now, researchers from the University of California, San Diego, are toying with the idea of reading American Sign Language (ASL) gestures through a similar glove.

Their glove has nine flexible strain sensors, two for each finger and one for the thumb. These sensors are responsible for registering motion by detecting knuckle articulation. An embedded microprocessor interprets the data from the sensors to translate each gesture into ASL letters. Finally, a Bluetooth radio transmits the meaning of the gestures in text format to a device for display, such as a smartphone.

During experiments, the UCSD team proved they could determine all 26 letters of the ASL alphabet accurately. After the knuckles bend for more than 1,000 times during a session, the system loses accuracy, as reported in the journal PLOS ONE.

What’s more, the researchers demonstrated their accuracy by modeling a virtual hand that mimicked real ASL gestures made with the smart glove. Not bad for a $100 prototype.

Bio-compatible wireless sensors developed to monitor brain injury

An international research team has developed miniaturized devices to monitor living brain tissue. When no longer needed the devices can be deactivated to dissolve and be reabsorbed into the soft tissue. The wireless sensors were implanted into mice brains and successfully took intracranial pressure and temperature readings.

Dissolvable brain implant consisting of pressure and temperature sensors (bottom right) connected to a wireless transmitter. Image via theguardian

Dissolvable brain implant consisting of pressure and temperature sensors (bottom right) connected to a wireless transmitter. Kang et al, 2017

Electronic implants have long been used in the treatment of medical conditions. Ranging from the humble pacemakers and defibrillators given to cardiac patients all the way to futuristic brain-computer interfaces or injectable meshes that fuse with your brain, it’s hard to imagine today’s medical field without these devices.

Whether implanted permanently or only for short periods of time, the procedure always carries some risk — the devices can hurt surrounding tissues during implantation and their metallic components are prime real estate for bacteria, possibly leading to infections in the area. Not to mention the added risk and distress involved in removing these devices.

The novel device, developed by a research team with members from America and South Korea, is described in the journal Nature and could potentially overcome these limitations. Each device houses a pressure and a temperature sensor, each one smaller than a grain of rice. They’re housed in a biodegradable silicone chip that rests on the brain and sends data via wireless transmitters attached to the outside of the skull.

The devices were successfully tested on live rats and recorded pressure and temperature changes that occurred as the animals drifted in and out of consciousness under anesthesia. They proved to be at least as or more accurate than other devices currently available.

The team showed that by tweaking the sensors they could take measurements either from the surface of the brain up to about 5mm below it. The researchers say the device can easily be modified to monitor a wide range of other important physiological parameters of brain function, such as acidity and the motion of fluids. It could also be used to deliver drugs to the brain, and, with the incorporation of microelectrodes, to stimulate or record neuronal activity.

However, what truly makes this sensor unique is the materials that go into building them, the so-called “green electronics.” These materials are designed to be stable for a few weeks then dissolve. If immersed in watery fluids (such as cerebrospinal fluid) these fully biodegradable and bio-compatible materials take about a day to fully dissipate. When the team examined the animal’s brains after the tests, they found no indication of inflammation or scarring around the implantation site.

As well as being safer for the patient the fabrication process is also cheaper and more environmentally-friendly than that employed in existing technologies.

The next step in development is to test the devices in human clinical trials, the researchers said.

The full paper describing these devices is available online in the journal Nature.


Mixing Silly Putty with graphene creates incredibly sensitive pressure sensors, scientists find

Trinity College Dublin researchers working together with University of Manchester’s National Graphene Institute (NGI) have found that mixing graphene with polysilicone (Silly Putty) produces incredibly sensitive pressure and strain sensors — they can even pick up on the footsteps of small spiders.


Johnny Coleman investigates G-Putty with his son Oisin.
Image credits AMBER, Trinity College Dublin.

Graphene can be used to make some pretty sweet sensors. Previously, researchers from the Nanyang Technological University in China developed highly efficient light sensors using the stuff. Now, Trinity’s School of Physics Professor Jonathan Coleman along with postdoctoral researcher Conor Boland found that putty mixed with graphene (which they call G-putty) has a surprising property: its electrical resistance is extremely sensitive to the slightest deformation or impact. The discovery could potentially open the way for inexpensive devices with a wide range of applications, such as diagnostics in healthcare.

Adding graphene to plastics is a pretty common practice. Usually, it improves the materials’ electrical, mechanical, thermal, or barrier properties, but the results can generally be predicted without too much surprise. The behavior of G-putty is unique, however, and Coleman believes it will “open up major possibilities in sensor manufacturing worldwide.”

“What we are excited about is the unexpected behaviour we found when we added graphene to the polymer, a cross-linked polysilicone,” Coleman said.

“It caused [the putty] to conduct electricity, but in a very unusual way. The electrical resistance of the G-putty was very sensitive to deformation with the resistance increasing sharply on even the slightest strain or impact.”

“Unusually, the resistance slowly returned close to its original value as the putty self-healed over time.”

The two first tested the G-putty by placing it on the chest and neck of subjects, then using it to measure breathing, pulse, even blood pressure. The material proved to be hundreds of times more sensitive than current pressure and strain sensors. It can even pick up on impacts as light as a small spider’s footstep.

Following initial development at Trinity, University of Manchester NGI scientists analyzed the material to determine its structure. From this, they developed a mathematical model of how G-putty deforms, explaining how the material’s structure dictates its mechanical and electrical properties.

“These phenomena are associated with the mobility of the [graphene] nanosheets in the low-viscosity polymer matrix,” the paper reads.

“By considering both the connectivity and mobility of the nanosheets, we developed a quantitative model that completely describes the electromechanical properties.”

The full paper “Sensitive electromechanical sensors using viscoelastic graphene-polymer nanocomposites” has been published in the journal Science.

New plasma printing technique can deposit nanomaterials on flexible, 3D substrates

A new nanomaterial printing method could make it both easier and cheaper to create devices such as wearable chemical and biological sensors, data storage and integrated circuits — even on flexible surfaces such as paper or cloth. The secret? Plasma.

The nozzle firing a jet of carbon nanotubes with helium plasma off and on. When the plasma is off, the density of carbon nanotubes is small. The plasma focuses the nanotubes onto the substrate with high density and good adhesion.
Image credits NASA Ames Research Center.

Printing layers of nanoparticles of nanotubes onto a substrate doesn’t necessarily require any fancy hardware — in fact, the most common method today is to use an inkjet printer very similar to the one you might have in your home or office. Although these printers are cost efficient and have stood the test of time, they’re not without limitations. They can only print on rigid materials with liquid ink — and not all materials can be easily made into a liquid. But probably the most serious limitation is that they can only print on 2D objects.

Aerosol printing techniques solve some of these problems. They can be employed to deposit smooth, thin films of nanomaterials on flexible substrates. But because the “ink” has to be heated to several hundreds of degrees to dry, using flammable materials such as paper or cloth remains a big no-no.

A new printing method developed by researchers from NASA Ames and SLAC National Accelerator Laboratory works around this issue. The plasma-based printing system doesn’t a heat-treating phase — in fact, the whole takes place at temperatures around 40 degrees Celsius. It also doesn’t require the printing material to be liquid.

“You can use it to deposit things on paper, plastic, cotton, or any kind of textile,” said Mayya Meyyappan of NASA’s Ames Research Center.

“It’s ideal for soft substrates.”

The team demonstrated their technique by covering a sheet of paper in a layer of carbon nanotubes. To do this, they blasted a mixture of carbon nanotubes and helium-ion plasma through a nozzle directly onto the paper. Because the plasma focuses the particles onto the paper’s surface, they form a well consolidated layer without requiring further heat-treatment.

They then printed two simple chemical and biological sensors. By adding certain molecules to the nanotube-plasma cocktail, they can change the tubes’ electrical resistance and response to certain compounds. The chemical sensor was designed to detect ammonia gas and the biological one was tailored to respond to dopamine, a neurotransmitter linked to disorders like Parkinson’s and epilepsy.

But these are just simple proof-of-concept constructs, Meyyappan said.

“There’s a wide range of biosensing applications,” she added.

Applications like monitoring cholesterol levels, checking for pathogens or hormonal imbalances, to name a few.

This method is very versatile and can easily be scaled up — just add more nozzles. For example, a shower-head type system could print large surfaces at once. Alternatively, it could be designed to act like a hose, spraying nanomaterials on 3D surfaces.

“It can do things inkjet printing cannot do,” Meyyappan said. “But [it can do] anything inkjet printing can do, it can be pretty competitive.”

Meyyappan said that the method is ready for commercial applications, and should be relatively simple and inexpensive to develop. The team is now tweaking their technique to allow for other printing materials, such as copper. This would allow them to print materials used for batteries onto thin sheets of metal such as aluminum. The sheet can then be rolled up to make very tiny, very powerful batteries for cellphones or other devices.

The full paper, titled “Plasma jet printing for flexible substrate” has been published online in the journal Applied Physics Letters and can be read here.

A schematic that illustrates the various applications of a smart fiber sensing network. Image: Stepan Gorgutsa, Universite Laval

Smart fibers can turn your sweater into a medical monitoring station

The more data doctors have of their patients’ health, the better the treatments they can prescribe. Ideally, you’d want patients to be constantly monitored for key life signs like heart rhythm, glucose levels or even brain activity. Typically, this is only possible in a hospital setting, but what if you want to follow how a patient is doing in real time for long periods of time, months or even years? A non-invasive technique would be to embed both monitoring and signaling devices directly into the clothing. Canadian researchers have faith something like this is possible using so-called  “smart textiles” which they developed.

Smart fibers for smart clothing

A schematic that illustrates the various applications of a smart fiber sensing network. Image:  Stepan Gorgutsa, Universite Laval

A schematic that illustrates the various applications of a smart fiber sensing network. Image: Stepan Gorgutsa, Universite Laval

“The fiber acts as both sensor and antenna. It is durable but malleable, and can be woven with wool or cotton, and signal quality is comparable to commercial antennas,” explained Professor Younes Messaddeq at Université Laval’s Faculty of Science and Engineering and Centre for Optics, Photonics and Lasers.

Smart fabric is durable, malleable, and can be woven with cotton or wool. Horizontal lines are antennas. (Credit: Stepan Gorgutsa, Universite Laval)

Smart fabric is durable, malleable, and can be woven with cotton or wool. Horizontal lines are antennas. (Credit: Stepan Gorgutsa, Universite Laval)

The fibers are made out of a polymer-clad silica with a hollow-core. The material can easily withstand high tensile and bending stresses, meaning it can easily twist and shrug as is often the case with clothing. The fibers are also resistant to mechanical abrasion and harsh environments like humidity, high temperatures, acid or detergent exposure due to the thick polyimide polymer overcoat.

All the conducting elements are inside the fibers, which are thick enough to protect the wiring against  the environment. Various sensors can be attached to the surface to monitor key health signals, which are then relayed through 2.4 GHz wireless networks with excellent signal quality. A shirt that registers your heart rate or a cap that reads your brain activity is now possible. Medical monitoring doesn’t need to be bulky and invasive; tucked inside smart fibers and woven along with regular cotton fibers, virtually any stylish clothing could be turned into a medical station.

The findings were described in a paper published in the journal Sensors. [story via KurzweilAI]