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A new 3D-printed customized insole uses integrated sensors to measure the pressure on the sole of the foot directly in the shoe during various activities.
In elite sports, fractions of a second sometimes make the difference between victory and defeat. To optimize their performance, athletes use custom-made insoles. But people with musculoskeletal pain also turn to insoles to combat their discomfort.
Before specialists can accurately fit such insoles, they must first create a pressure profile of the feet. To this end, athletes or patients have to walk barefoot over pressure-sensitive mats, where they leave their individual footprints.
Based on this pressure profile, orthopedists then create customized insoles by hand. The problem with this approach is that optimizations and adjustments take time. Another disadvantage is that the pressure-sensitive mats allow measurements only in a confined space, but not during workouts or outdoor activities.
The new invention, described in the journal Scientific Reports, addresses these issues.
“You can tell from the pressure patterns detected whether someone is walking, running, climbing stairs, or even carrying a heavy load on their back—in which case the pressure shifts more to the heel,” explains co-project leader Gilberto Siqueira, senior assistant at Empa and at the ETH Zurich Complex Materials Laboratory. This makes tedious mat tests a thing of the past.
These insoles aren’t just easy to use, they’re also easy to make. They are produced in just one step—including the integrated sensors and conductors—using a single 3D printer, called an extruder.
For printing, the researchers use various inks developed specifically for this application. As the basis for the insole, the materials scientists use a mixture of silicone and cellulose nanoparticles.
Next, they print the conductors on this first layer using a conductive ink containing silver. They then print the sensors on the conductors in individual places using ink that contains carbon black. The sensors aren’t distributed at random: they are placed exactly where the foot sole pressure is greatest. To protect the sensors and conductors, the researchers coat them with another layer of silicone.
An initial difficulty was to achieve good adhesion between the different material layers. The researchers resolved this by treating the surface of the silicone layers with hot plasma.
As sensors for measuring normal and shear forces, they use piezo components, which convert mechanical pressure into electrical signals. In addition, the researchers have built an interface into the sole for reading out the generated data.
Tests showed the researchers that the additively manufactured insole works well.
“So with data analysis, we can actually identify different activities based on which sensors responded and how strong that response was,” Siqueira says.
At the moment, Siqueira and his colleagues still need a cable connection to read out the data; to this end, they have installed a contact on the side of the insole.
One of the next development steps, he says, will be to create a wireless connection. “However, reading out the data hasn’t been the main focus of our work so far.”
In the future, 3D-printed insoles with integrated sensors could be used by athletes or in physiotherapy, for example to measure training or therapy progress. Based on such measurement data, training plans can then be adjusted and permanent shoe insoles with different hard and soft zones can be produced using 3D printing.
Although Siqueira believes there is strong market potential for their product, especially in elite sports, his team hasn’t yet taken any steps towards commercialization.
Additional coauthors are from Lausanne University Hospital, the orthopedics company Numo, and ETH Zurich.
The ETH Domain’s Strategic Focus Areas program funded the project.
Source: ETH Zurich
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A new wearable sensor is so cheap and simple to produce it can be hand-drawn with a pencil onto paper treated with sodium chloride.
The sensor could clear the way for wearable, self-powered monitors to predict major health concerns like cardiac arrest and pneumonia. And it could even let you know when your baby’s diaper needs a change.
“Our team has been focused on developing devices that can capture vital information for human health,” says Huanyu “Larry” Cheng, associate professor of engineering science and mechanics at Penn State and lead author of the study in the journal Nano Letters. “The goal is early prediction for disease conditions and health situations, to spot problems before it is too late.”
The paper describes the design and fabrication process for a reliable, hand-drawn electrode sensor created using a pencil, drawn on paper treated with a sodium chloride solution. The hydration sensor is highly sensitive to changes in humidity and provides accurate readings over a wide range of relative humidity levels, from 5.6% to 90%.
Research into wearable sensors has been gaining momentum because of their wide-ranging applications in medical health, disaster warning, and military defense, Cheng explains.
Flexible humidity sensors have become increasingly necessary in health care, for uses such as respiratory monitoring and skin humidity detection, but it is still challenging to achieve high sensitivity and easy disposal with simple, low-cost fabrication processes, he adds.
“We wanted to develop something low-cost that people would understand how to make and use—and you can’t get more accessible than pencil and paper,” says Li Yang, professor in the School of Artificial Intelligence at Hebei University of Technology in China.
“You don’t need to have some piece of multi-million-dollar equipment for fabrication. You just need to be able to draw within the lines of a pre-drawn electrode on a treated piece of paper. It can be done simply and quickly.”
The device takes advantage of the way paper naturally reacts to changes in humidity and uses the graphite in the pencil to interact with water molecules and the sodium chloride solution. As water molecules are absorbed by the paper, the solution becomes ionized and electrons begin to flow to the graphite in the pencil, setting off the sensor, which detects those changes in humidity in the environment and sends a signal to a smartphone, which displays and records the data.
Essentially, drawing on the pre-treated paper within pre-treated lines creates a miniaturized paper circuit board. The paper can be connected to a computer with copper wires and conductive silver paste to act as an environmental humidity detector.
For wireless application, such as “smart diapers” and mask-based respiration monitoring, the drawing is connected to a tiny lithium battery which powers data transmission to a smartphone via Bluetooth.
For the respiration monitor, the team drew the electrode directly on a solution-treated face mask. The sensor easily differentiated mouth breathing from nose breathing and was able to classify three breathing states: deep, regular, and rapid.
Cheng explains that the data collected could be used to detect the onset of various disease conditions, such as respiratory arrest and shortness of breath and provide opportunities in the smart internet of things and telemedicine.
He adds that respiratory rate is a fundamental vital sign and research has shown it to be an early indicator of a variety of pathological conditions such as cardiac events, pneumonia, and clinical deterioration. It can also indicate emotional stressors like cognitive load, heat, cold, physical effort, and exercise-induced fatigue.
Compared with breath, the human skin exhibits a smaller change in humidity, but the researchers were still able to detect changes using their pencil-on-paper humidity sensor, even after test subjects applied lotion or exercised. Skin is the body’s largest organ, Cheng says, so if it is not processing moisture correctly, that could indicate that some other health issue is going on.
“Different types of disease conditions result in different rates of water loss on our skin,” he says. “The skin will function differently based on those underlying conditions, which we will be able to flag and possibly characterize using the sensor.”
The team also integrated four humidity sensors between the absorbent layers of a diaper to create a “smart diaper,” capable of detecting wetness and alerting for a change.
“That application was actually born out of personal experience,” says Cheng, who is the father of two young children. “There’s no easy way to know how wet is wet, and that information could be really valuable for parents. The sensor can provide data in the short-term, to alert for diaper changes, but also in the long-term, to show patterns that can inform parents about the overall health of their child.”
The applications of the humidity sensor go beyond “smart diapers” and monitoring for respiration and perspiration, Cheng explains. The team also deployed the sensor as a noncontact switch, which could sense the humidity changes in the air from the presence of a finger without the finger touching the sensor. The team used the noncontact switch to operate a small-scale elevator, play a keyboard and light up an LED array.
“The atoms on the finger don’t need to touch the button, they only need to be near the surface to diffuse the water molecules and trigger the signal,” Cheng says. “When we think about what we learned from the pandemic about the need to limit the body’s contact with shared surfaces, a sensor like this could be an important tool to stop potential contamination.”
Additional coauthors are from Hebei University of Technology, Tianjin Tianzhong Yimai Technology Development Co. Ltd., and Penn State.
The National Institutes of Health, the National Science Foundation, and Penn State funded the work.
Source: Penn State
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A new biopolymer sensor that detects bacteria, toxins, and dangerous chemicals in the environment can be printed like ink on just about anything, including gloves, masks, or everyday clothing.
Using an enzyme similar to that found in fireflies, the sensor glows when it detects these otherwise invisible threats. The new technology is described in the journal Advanced Materials.
The biopolymer sensor, which is based on computationally designed proteins and silk fibroin extracted from the cocoons of the silk moth Bombyx Mori, can also be embedded in films, sponges, and filters, or molded like plastic to sample and detect airborne and waterborne dangers, used to signal infections, or even cancer in our bodies.
The researchers demonstrated how the sensor emits light within minutes as it detects the SARS-CoV-2 virus that causes COVID, anti-hepatitis B virus antibodies, the food-borne toxin botulinum neurotoxin B, or human epidermal growth factor receptor 2 (HER2), an indicator of the presence of breast cancer.
Currently, the sensors require a quick spray with a non-toxic chemical after being potentially exposed to bacteria, toxins, and dangerous chemicals. If the target is present, then the sensor generates light. The intensity of emitted light provides a quantitative measure of the concentration of the target.
“The combination of lab-designed proteins and silk is a sensor platform that can be adapted to detect a wide range of chemical and biological agents with a high degree of specificity and sensitivity,” says Fiorenzo Omenetto, professor of engineering and director of the Tufts University Silklab, where the bio-responsive materials were developed.
“For example, SARS-CoV-2 and anti-hepatitis B antibodies can be measured at levels that approach clinical assays.”
The sensing element is modular, so developers can swap in newly designed proteins to capture specific pathogens or molecules to measure, while the light emitting mechanism remains the same. “Using the sensor, we can pick up trace levels of airborne SARS-CoV-2, or we can imagine modifying it to adapt to whatever the next public health threat might be,” Omenetto says.
He notes that, although the sensor is in a conceptual stage, the application to detect breast cancer is particularly interesting. His team created a proof-of-concept silicone bra pad that when worn can absorb secreted fluid, report the levels of HER2 hormone, and provide an indication whether breast cancer may be present.
“While further development will be required to improve and clinically validate the assay, the opportunity for such diagnostics in everyday garments is certainly compelling,” Omenetto says.
The sensors can assume a seemingly endless variety of forms. To demonstrate this, the researchers created viral sensing drones in which their fuselage was embedded with the sensor material. During flight, the propellers direct airflow through the porous body of the drone, which can be examined after landing. The drones, which in the example reacted to airborne pathogens such as SARS-CoV-2, could enable monitoring environments from a remote, safe distance.
The active component of the biopolymer sensor, which was developed by David Baker, professor in biochemistry at the Institute for Protein Design at the University of Washington, is a molecular switch made of proteins that act like lock and key, but with a cover.
When a virus, toxin, or other target molecule comes near, it binds to the switch and opens the cover. Another part of the switch—a molecular key—can then fit into the lock, and the combination forms a complete luciferase enzyme, similar to the enzyme that lights up fireflies and glowworms. The more virus, toxin, or other chemical that binds to the sensor, the brighter the glow.
The molecular glow-switch is embedded in a mixture of protein that is derived from silk cocoons, called silk fibroin. The silk fibroin is the inactive component of the biopolymer sensor, but has unique features, including the ability to be processed and manufactured using safe, water-based methods, and a remarkable versatility to be fabricated into different materials, such as films, sponges, textiles, or dispersed onto surfaces through an inkjet printer. Additionally, the silk fibroin stabilizes the molecular glow-switch and greatly extends its shelf life.
These biopolymer sensors are a big leap from other approaches to measuring pathogens or chemicals in the environment, which often rely on biological components that degrade quickly and require careful storage. The sensors also do not depend on electronic components that can be difficult to integrate into flexible wearable materials.
The researchers tested the shelf life of materials embedded with SARS-CoV-2 sensors after storing them at 60 degrees Celsius (140 degrees Fahrenheit) for four months and found very little change in performance. The breast cancer sensor shaped into a sponge was kept on the shelf at room temperature for one year, and still performed near its original sensitivity.
“This means we can manufacture, distribute, and store these sensing interfaces for long periods of time without losing their sensitivity or accuracy and without the need for refrigerated storage, which is remarkable due to the fact that they are made of protein,” says Luciana d’Amone, a graduate student in Omenetto’s lab who co-led the project with Giusy Matzeu, a research professor at Tufts’ Silklab.
This approach could make sensors widely available in different formats. “For example, you could make surgical masks capable of detecting pathogens, package them in boxes, and use them over time just like conventional masks,” says d’Amone. “We also showed that you can print the sensor inside food packaging to track spoilage and toxins. You can modify so many products that we use every day to include sensing, and store and use them as you normally would.”
The research team envisions applications for the biopolymer sensors ranging from personal and patient monitoring and infection control in health-care settings to environmental sensing in home, workplace, military, and disaster settings.
Source: Tufts University
The post Printable sensors glow when they detect viruses or other dangers appeared first on Futurity.
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