Scientists at University College London (UCL) and the IIT (Istituto Italiano di Tecnologia) have created a temporary tattoo that contains the same light-emitting technology used in TVs and smartphone screens.
The technology uses organic light-emitting diodes (OLEDs) and is applied in the same way as simple water-transfer tattoos. The OLEDs are fabricated onto a temporary tattoo paper and then transferred to a new surface by being pressed onto it and dabbed with water.
According to the research, these OLED devices being developed are 2.3 micrometers thick in total (less than one 400th of a millimeter) and about one-third of the length of a single red blood cell. The device consists of an electroluminescent polymer (a polymer that emits light when an electric field is applied) that is placed in between electrodes. An insulating layer is then placed in between the electrodes and the commercial tattoo paper.
This process has already been successfully applied to various materials.
Once the research team had perfected the technology, they applied the tattoo-able OLEDs (which emit green light) onto various surfaces including a pane of glass, a plastic bottle, an orange, and paper packaging. The first OLEDs were used in a flatscreen television more than 20 years ago, and now, through this proof-of-concept study, "smart tattoos" may be a thing of the (very near) future.
Why “smart tattoos” could be beneficial
OLEDs are used to create digital displays in devices (such as television screens computer monitors, smartphones, etc).
Credit: Hanna on Adobe Stock
While this is perhaps the most obvious way you could use light-emitting tattoo technology, the world of tattoo art and design could see a huge surge in new exciting trends based on light-emitting tattoo technology.
It's not just about looks—this approach provides a quick and easy method of transferring OLEDs onto practically any surface.
OLEDs are used to create digital displays in devices (such as television screens computer monitors, smartphones, etc). While some may get OLED and LED confused, they are quite different, with OLED displays emitting visible light and therefore being able to be used without a backlight. The breakthrough process of being able to transfer OLEDs onto virtually any surface can be useful in many different applications and settings.
Light-emitting tattoos could be used to indicate (and potentially even treat) various health conditions in the future.
The eventual implementation or use of OLED tattoos could be combined with other tattoo electronics to, for instance, emit light when an athlete is dehydrated, or when a person is being exposed to too much sun and is prone to sunburn.
"In healthcare, they could emit light when there is a change in a patient's condition - or, if the tattoo was turned the other way into the skin, they could potentially be combined with light-sensitive therapies to target cancer cells, for instance." - Professor Franco Cacialli (UCL)
OLED tattoo devices
Credit: Barsotti - Italian Institute of Technology
Similarly, this technology could be used on the packaging of various items to give us more information about them.
For example, OLEDs could be tattooed onto the packaging of a fruit to signal when the product is passed its expiration date or will soon become inedible.
In reality, creating light-emitting tattoo technology doesn't have to be expensive.
Professor Franco Cacialli explains to Eurekalert: "The tattooable OLEDs that we have demonstrated for the first time can be made at scale and very cheaply. They can be combined with other forms of tattoo electronics for a very wide range of possible uses. These could be for fashion - for instance, providing glowing tattoos and light-emitting fingernails. In sports, they could be combined with a sweat sensor to signal dehydration."
"Our proof-of-concept study is the first step. Future challenges will include encapsulating the OLEDs as much as possible to stop them from degrading quickly through contact with air, as well as integrating the device with a battery or supercapacitor."
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While the human body is designed for decades of use, we are prone to breaking down at inopportune times. Our necks didn't evolve to hold certain head positions (like hunched over a laptop). Foot pain is commonplace. And every year, there are more than 790,000 knee replacements in America.
The knee is a complex joint. While its major function is connecting the femur to the tibia, the fibula and patella complete the bone structure. Enter ligaments: the anterior cruciate ligament (ACL) prevents the femur from sliding backward; the posterior cruciate ligament (PCL) prevents forward sliding; medial and lateral ligaments stop side to side action. The medial and lateral menisci act as shock absorbers, while a number of bursae keep the joint working smoothly.
Until, of course, everything is not running smoothly. Knee replacements are common; meniscus surgeries even more so: an estimated 850,000 per year. Throw in 100,000 ACL reconstructions for good measure. Every year, over 1.7 million Americans are getting their knees worked on.
Fortunately, our understanding of the knee has gotten better. Many of these surgeries are relatively minor. My meniscal tear was so bad that it folded under itself and required my surgeon to add an extra hole while repairing it. Yet I still walked out of the hospital without crutches, didn't need painkillers, and was in the gym three days later (with modifications).
The caveat: the surgeon had to remove almost the entire meniscus, taking out one of my shock absorbers. Bone-on-bone action increases the likelihood of osteoarthritis (which had already begun in my thirties). He said it's likely I'll need a knee replacement down the road.
The good news: a new artificial cartilage gel appears to be strong enough to work in knees.
Duke researchers have developed the first gel-based synthetic cartilage with the strength of the real thing. A quarter-sized disc of the material can withstand the weight of a 100-pound kettlebell without tearing or losing its shape.
Photo: Feichen Yang.
That's the word from a team in the Department of Chemistry and Department of Mechanical Engineering and Materials Science at Duke University. Their new paper, published in the journal Advanced Functional Materials, details this exciting evolution of this frustrating joint.
Researchers have sought materials strong and versatile enough to repair a knee since at least the 1970s. This new hydrogel, comprised of three polymers, might be it. When two of the polymers are stretched, a third keeps the entire structure intact. When pulled 100,000 times, the cartilage held up as well as materials used in bone implants. The team also rubbed the hydrogel against natural cartilage a million times and found it to be as wear-resistant as the real thing.
The hydrogel has the appearance of Jell-O and is comprised of 60 percent water. Co-author, Feichen Yang, says this network of polymers is particularly durable: "Only this combination of all three components is both flexible and stiff and therefore strong."
As with any new material, a lot of testing must be conducted. They don't foresee this hydrogel being implanted into human bodies for at least three years. The next step is to test it out in sheep.
Still, this is an exciting step forward in the rehabilitation of one of our trickiest joints. Given the potential reward, the wait is worth it.
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Stay in touch with Derek on Twitter, Facebook and Substack. His next book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
The bicycle was a key invention that doubled human-powered speed. But what if a new kind of shoe could allow people to run faster by mimicking cycling mechanics?
This is the question my students in Vanderbilt's Center for Rehabilitation Engineering & Assistive Technology and I explored as we developed a new theory of spring-driven robotic exoskeletons. We came up with a concept for a new type of lower limb exoskeleton that could allow the world's fastest human to reach a speed of 18 meters per second or about 40 miles per hour.
Robo-boots allow the legs to supply energy in the air during running, similar to the pedaling mechanism in cycling. (A. Sutrisno and D. J. Braun, CC BY-ND)
The cutting edge of today's running shoes is Nike's Vaporfly, which allows runners to use 4% less energy than standard running shoes. Three-time Olympic medalist Eliud Kipchoge recently wore them to run a marathon in under two hours. Though the Vaporfly upended the world of professional running by increasing the efficiency of standard running shoes, it doesn't provide the advantages of cycling or otherwise fundamentally alter the physics of running.
There has been a lot of research and development in robotic exoskeletons that augment human power. These use actuators and external energy: motors and batteries. But they haven't helped humans run faster. Springs have also been used to make high-tech prostheses for paralympic running, but have not been shown to provide an unfair advantage compared to legs. For human-powered speed, the bicycle has been the reigning champion for over a century.
The precursor to the modern bicycle, dubbed the hobby horse, was invented in 1817 by Baron Karl von Drais.
Canada Science and Technology Museum/Flickr, CC BY-NC-ND
Running versus cycling
The first running machine was a bicycle with no pedals. It reduced the energy cost of running by supporting the body's weight on a seat and using wheels to avoid the inevitable energy loss when runners step.
But early bicycles did not allow cyclists to move faster than runners because the rider propelled himself by pushing against the ground with his legs – just like running. What changed the game for bicycling was the invention of the pedaling mechanism, which allowed the legs to propel the rider continuously rather than only when the foot hits the ground.
The bicycle's speed advantage over running has not endured for lack of trying. People have been imagining spring legs and refining running springs for generations, but these springs are not like a bicycle with pedals because they don't allow the legs to supply energy when they're off the ground.
The robo-boot
To apply the advantage of cycling to running, we came up with a concept for a new type of robo-boot that emulates the function of bicycle pedals. Using the robo-boot, runners supply energy by compressing a spring with each leg while it's in the air. With each footstep, the spring releases its stored energy by pushing against the ground faster and stronger than the legs could otherwise do.
We found that an ideal robo-boot would allow the fastest runner on Earth to use his legs 96% of the step time to run faster than 20 meters per second, comparable to the top speed of cycling. A more practical robo-boot that is used only about 60% of the step time could still help a runner reach a top speed of 18 meters per second. That's 50% faster than the world record speed of 12 meters per second in the 100 meter sprint.
Top speed of human-powered locomotion. Adapted from A. Sutrisno, D. J. Braun, How to run 50% faster without external energy, vol. 6, no. 13, eaay1950, 2020., CC BY-ND.
The high-tech component of the robo-boot is a variable stiffness spring that can increase its stiffness without changing its stored energy. The stiffness of the spring determines how forcefully it can push against the ground to accelerate the runner's body – the stiffer the spring, the greater the force given the same spring compression.
Conventional springs like those in retractable pens have a constant stiffness based on the spring's material, shape and size. Variable stiffness springs are a special type of spring that can change shape or size. One type of variable stiffness spring increases stiffness by getting shorter. A mechanism shortens the spring by moving the spring's attachment point from its end to its middle. The mechanism in the robo-boot shortens the spring as the runner extends her leg in the air.
Running with robo-boots. Adapted from A. Sutrisno, D. J. Braun, How to run 50% faster without external energy, vol. 6, no. 13, eaay1950, 2020., CC BY-ND.
Increasing the stiffness of the spring as the runner picks up speed is analogous to switching to a higher gear on a bike as a cyclist rides faster. This allows runners to supply more energy and bypass the biomechanical limitation of supplying energy only during the short ground contact time of high-speed running.
Next steps
Modern racing bikes nearly double the top speed of running. Robo-boots that leverage bicycle mechanics could similarly allow people to run faster without hefty motors and batteries. We hope to have an initial robo-boot prototype within a year. But just as it took many years after their invention for bicycles to take full advantage of their unique mechanics, it will take some time to make a robo-boot that can achieve its full potential.
These more portable human-powered devices could enable more widespread adoption of wearable robotic technology, and could push the boundaries of search and rescue, law enforcement and sports. What would it mean for first responders to be able to move 50% faster? Would a running shoe that provides a 50% speed increase lead to a new event at the Olympics similar to ice skating and bicycle racing?
Using science and advanced robotics technology, we're able to envision next generation robo-boots that offer the first major boost to human-powered movement since the invention of the bicycle pedal in the 19th century.
David Braun, Assistant Professor of Mechanical Engineering and Computer Engineering, Vanderbilt University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
