New smart textiles boost connectivity for wearable technologies

From left: PhD student Mr Tian Xi, Research Fellow Dr Lee Pui Mun and Assistant Professor John Ho, together with seven NUS researchers, took a year to develop the ‘smart’ textiles

Over the past decade, a major trend in electronics has been the development of sensors, displays and smart devices which are seamlessly integrated onto the human body. Most of these wearable devices are singularly connected to a user’s smart phone and transmit all data via Bluetooth or Wi-Fi signals. But as consumers wear increasing numbers of wearable devices, and as the data they transmit increases in sophistication, more innovative connection methods are being sought after.

Now, NUS researchers have invented a completely new way for wearable devices to interconnect. They incorporated conductive textiles into clothing to dynamically connect several wearable devices at once. This ‘wireless body sensor network’ allows devices to transmit data with 1,000 times stronger signal than conventional technologies, meaning the battery life of all devices is dramatically improved. Wireless networks of these wearable devices on a body have future applications in health monitoring, medical interventions and human–machine interfaces.

This technological breakthrough, which took the 10-member team a year to achieve, was published as the cover of Nature Electronics on 17 June 2019.

Better data transmission, greater privacy

Currently, almost all body sensors like smart watches connect to smartphones and other wearable electronics via radio-waves like Bluetooth and Wi-Fi. These waves radiate outwards in all directions, meaning that most of the energy is lost to the surrounding area. This method of connectivity drastically reduces the efficiency of the wearable technology as most of its battery life is consumed in attempting the connection.

As such, Assistant Professor John Ho and his team from the Institute for Health Innovation & Technology (NUS iHealthtech) and NUS Engineering wanted to confine the signals between the sensors closer to the body to improve efficiency.

Their solution was to enhance regular clothing with conductive textiles known as metamaterials. Rather than sending waves into surrounding space, these metamaterials are able to create ‘surface waves’ which can glide wirelessly around the body on the clothes. This means that the energy of the signal between devices is held close to the body rather than spread in all directions. Hence, the wearable electronics use much less power than normal, and the devices can detect much weaker signals.

“This innovation allows for the perfect transmission of data between devices at power levels that are 1,000 times reduced. Or, alternatively, these metamaterial textiles could boost the received signal by 1,000 times which could give you dramatically higher data rates for the same power,” Asst Prof Ho stated. In fact, the signal between devices is so strong that it is possible to wirelessly transmit power from a smartphone to the device itself — opening the door for battery-free wearable devices.

Crucially, this signal boost does not require any changes to either the smartphone or the Bluetooth device — the metamaterial works with any existing wireless device in the designed frequency band.

This inventive way of networking devices also provides more privacy than conventional methods. Currently, radio-waves transmit signals several metres outwards from the person wearing the device, meaning that personal and sensitive information could be vulnerable to potential eavesdroppers. By confining the wireless communication signal to within 10 centimetres of the body, Asst Prof Ho and his team have created a network which is more secure.

Intelligent design, enhanced capabilities

The team has a first-year provisional patent on the metamaterial textile design, which consists of a comb-shaped strip of metamaterial on top of the clothing with an unpatterned conductor layer underneath. These strips can then be arranged on clothing in any pattern necessary to connect all areas of the body. The metamaterial itself is cost-effective, in the range of a few dollars per metre, and can be bought readily in rolls.

“We started with a specific metamaterial that was both flat and could support surface waves. We had to redesign the structure so that it could work at the frequencies used for Bluetooth and Wi-Fi, perform well even when close to the human body, and could be mass produced by cutting sheets of conductive textile,” Asst Prof Ho explained.

The team’s particular design was created with the aid of a computer model to ensure successful communication in the radio frequency range and to optimise overall efficacy. The smart clothing is then fabricated by laser-cutting the conductive metamaterial and attaching the strips with fabric adhesive.

Once made, the ‘smart’ clothes are highly robust. They can be folded and bent with minimal loss to the signal strength, and the conductive strips can even be cut or torn, without inhibiting the wireless capabilities. The garments can also be washed, dried, and ironed just like normal clothing.

Next steps

The team is talking to potential partners to commercialise this technology, and in the near future Asst Prof Ho is hoping to test the ‘smart’ textiles as specialised athletic clothing and for hospital patients to monitor performances and health. Potential applications could range dramatically — from measuring a patient’s vital signs without inhibiting their freedom of motion, to adjusting the volume in an athlete’s wireless headphones with a single hand motion.

“We envision that endowing athletic wear, medical clothing and other apparel with such advanced electromagnetic capabilities can enhance our ability to perceive and interact with the world around us,” Asst Prof Ho said.

Learn more: NUS innovation boosts wireless connectivity 1,000 times

 

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A new metamaterial that can improve MRI quality and cut scan time in half

This array of helical resonators stands at three centimeters tall and is constructed from 3-D-printed plastic and coils of thin copper wire. Photos by Jackie Ricciardi

BU researchers have developed a new metamaterial that can improve MRI quality and cut scan time in half

Could a small ringlike structure made of plastic and copper amplify the already powerful imaging capabilities of a magnetic resonance imaging (MRI) machine? Xin Zhang, Stephan Anderson, and their team at the Boston University Photonics Center can clearly picture such a feat. With their combined expertise in engineering, materials science, and medical imaging, Zhang and Anderson, along with Guangwu Duan and Xiaoguang Zhao, designed a new magnetic metamaterial, reported in Communications Physics, capable of boosting the performance of MRI in more ways than one.

MRI uses magnetic fields and radio waves to create images of organs and tissues in the human body, helping doctors diagnose potential problems or diseases. Doctors use MRI to identify abnormalities or diseases in vital organs, as well as many other types of body tissue, including the spinal cord and joints. “[MRI] is one of the most complex systems invented by human beings,” says Zhang, a College of Engineering professor of mechanical engineering, electrical and computer engineering, biomedical engineering, materials science and engineering, and a professor at the Photonics Center.

Depending on what part of the body is being analyzed and how many images are required, an MRI scan can take up to an hour or more. Patients can face long wait times when scheduling an examination and, for the healthcare system, operating the machines is time-consuming and costly. Strengthening MRI from 1.5 T (the symbol for tesla, the measurement for magnetic field strength) to 7.0 T can definitely “turn up the volume” of images, as Anderson and Zhang describe. But although higher-power MRIs can be done using stronger magnetic fields, they come with a host of safety risks and even higher costs to medical clinics. The magnetic field of an MRI machine is so strong that chairs and objects from across the room can be sucked toward the machine—posing dangers to operators and patients alike.

In contrast, Zhang and Anderson say that their magnetic metamaterial could be used as an additive technology to increase the imaging power of lower-strength MRI machines, increasing the number of patients seen by clinics and decreasing associated costs, without any of the risks that come with using higher-strength magnetic fields. They even envision the metamaterial being used with ultra–low field MRI, which uses magnetic fields that are thousands of times lower than the standard machines currently in use. This would open the door for MRI technology to become widely available around the world.

“This [magnetic metamaterial] creates a clearer image that may be produced at more than double the speed” of a current MRI scan, says Anderson, a School of Medicine professor of radiology and vice chairman of research in Boston Medical Center’s radiology department.

 

The magnetic metamaterial is made up of an array of units called helical resonators—three-centimeter-tall structures created from 3-D-printed plastic and coils of thin copper wire—materials that aren’t too fancy on their own. But put together, helical resonators can be grouped in a flexible array, pliable enough to cover a person’s kneecap, abdomen, head, or any part of the body in need of imaging. When the array is placed near the body, the resonators interact with the magnetic field of the machine, boosting the signal-to-noise ratio (SNR) of the MRI, “turning up the volume of the image” as Anderson says.

“A lot of people are surprised by its simplicity,” says Zhang. “It’s not some magic material. The ‘magical’ part is the design and the idea.”

To test the magnetic array, the team scanned chicken legs, tomatoes, and grapes using a 1.5 T machine. They found that the magnetic metamaterial yielded a 4.2 fold increase in the SNR, a radical improvement, which could mean that lower magnetic fields could be used to take clearer images than currently possible.

Now, Zhang and Anderson hope to partner with industry collaborators so that their magnetic metamaterial can be smoothly adapted for real-world clinical applications.

“If you are able to deliver something that can increase SNR by a significant margin, we can start to think about possibilities that didn’t exist before,” says Anderson, such as the possibility of having MRI near battlefields or in other remote locations. “Being able to simplify this advanced technology is very appealing,” he says.

Learn more: Magnetic Metamaterial Can “Turn Up the Volume” of MRI

 

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Origami-inspired metamaterial softens impact forces for potential use in spacecraft, cars and beyond

Inspired by the paper folding art of origami, a University of Washington team created a paper model of a metamaterial that uses “folding creases” to soften impact forces for potential applications in spacecraft, cars and beyond.Kiyomi Taguchi/University of Washington

Space vehicles like SpaceX’s Falcon 9 are designed to be reusable. But this means that, like Olympic gymnasts hoping for a gold medal, they have to stick their landings.

Landing is stressful on a rocket’s legs because they must handle the force from the impact with the landing pad. One way to combat this is to build legs out of materials that absorb some of the force and soften the blow.

University of Washington researchers have developed a novel solution to help reduce impact forces — for potential applications in spacecraft, cars and beyond. Inspired by the paper folding art of origami, the team created a paper model of a metamaterial that uses “folding creases” to soften impact forces and instead promote forces that relax stresses in the chain. The team published its results May 24 in Science Advances.

“If you were wearing a football helmet made of this material and something hit the helmet, you’d never feel that hit on your head. By the time the energy reaches you, it’s no longer pushing. It’s pulling,” said corresponding author Jinkyu Yang, a UW associate professor of aeronautics and astronautics.

Yang and his team designed this new metamaterial to have the properties they wanted.

“Metamaterials are like Legos. You can make all types of structures by repeating a single type of building block, or unit cell as we call it,” he said. “Depending on how you design your unit cell, you can create a material with unique mechanical properties that are unprecedented in nature.”

The researchers turned to the art of origami to create this particular unit cell.

Previously the team created a variety of origami unit cells that had different folding patterns and stiffness.

“Origami is great for realizing the unit cell,” said co-author Yasuhiro Miyazawa, a UW aeronautics and astronautics doctoral student. “By changing where we introduce creases into flat materials, we can design materials that exhibit different degrees of stiffness when they fold and unfold. Here we’ve created a unit cell that softens the force it feels when someone pushes on it, and it accentuates the tension that follows as the cell returns to its normal shape.”

Just like origami, these unit cell prototypes are made out of paper. The researchers used a laser cutter to cut dotted lines into paper to designate where to fold. The team folded the paper along the lines to form a cylindrical structure, and then glued acrylic caps on either end to connect the cells into a long chain.

The researchers lined up 20 cells and connected one end to a device that pushed and set off a reaction throughout the chain. Using six GoPro cameras, the team tracked the initial compression wave and the following tension wave as the unit cells returned to normal.

The chain composed of the origami cells showed the counterintuitive wave motion: Even though the compressive pushing force from the device started the whole reaction, that force never made it to the other end of the chain. Instead, it was replaced by the tension force that started as the first unit cells returned to normal and propagated faster and faster down the chain. So the unit cells at the end of the chain only felt the tension force pulling them back.

“Impact is a problem we encounter on a daily basis, and our system provides a completely new approach to reducing its effects. For example, we’d like to use it to help both people and cars fare better in car accidents,” Yang said. “Right now it’s made out of paper, but we plan to make it out of a composite material. Ideally, we could optimize the material for each specific application.”

Learn more: Origami-inspired materials could soften the blow for reusable spacecraft

 

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A new and improved snake-inspired soft robot uses programmable kirigami metamaterials

This programmable kirigami metamaterials enable responsive surfaces and smart skins (Image courtesy of Harvard SEAS)

Programmable kirigami metamaterials enable responsive surfaces and smart skins

Bad news for ophiophobes: Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new and improved snake-inspired soft robot that is faster and more precise than its predecessor.

The robot is made using kirigami — a Japanese paper craft that relies on cuts to change the properties of a material.  As the robot stretches, the kirigami surface “pops up” into a 3D-textured surface, which grips the ground just like snake skin.

The first-generation robot used a flat kirigami sheet, which transformed uniformly when stretched. The new robot has a programmable shell, meaning the kirigami cuts can pop up as desired, improving the robot’s speed and accuracy.

The research was published in the Proceedings of the National Academy of Sciences.

“This is a first example of a kirigami structure with non-uniform pop-up deformations,” said Ahmad Rafsanjani, a postdoctoral fellow at SEAS and first author of the paper. “In flat kirigami, the pop-up is continuous, meaning everything pops at once.  But in the kirigami shell, pop up is discontinuous. This kind of control of the shape-transformation could be used to design responsive surfaces and smart skins with on-demand changes in their texture and morphology.”

The new research combined two properties of the material — the size of the cuts and the curvature of the sheet. By controlling these features, the researchers were able to program dynamic propagation of pop ups from one end to another, or  control localized pop-ups.

In previous research, a flat kirigami sheet was wrapped around an elastomer actuator. In this research, the kirigami surface is rolled into a cylinder, with an actuator applying force at two ends. If the cuts are a consistent size, the deformation propagates from one end of the cylinder to the other. However, if the size of the cuts are chosen carefully, the skin can be programmed to deform at desired sequences.

“By borrowing ideas from phase-transforming materials and applying them to kirigami-inspired architected materials, we demonstrated that both popped and unpopped phases can coexists at the same time on the cylinder,” said Katia Bertoldi, the William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS and senior author of the paper. “By simply combining cuts and curvature, we can program remarkably different behavior.”

Next, the researchers aim to develop an inverse design model for more complex deformations.

“The idea is, if you know how you’d like the skin to transform, you can just cut, roll and go,” said Lishuai Jin, a graduate student at SEAS and coauthor of the article.

Learn more: Snake-inspired robot slithers even better than predecessor

 

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4D printed shape programming materials can be as stiff as wood or as soft as a sponge

4D-printed metamaterials can be temporarily transformed into any deformed shape and then returned to their original shape on demand when heated. The scale bar is 2 millimeters.
Image: Chen Yang/Rutgers University-New Brunswick

Rutgers engineers’ unique smart materials change shape as temperatures change

Rutgers University–New Brunswick engineers have created flexible, lightweight materials with 4D printing that could lead to better shock absorption, morphing airplane or drone wings, soft robotics and tiny implantable biomedical devices. Their research is published in the journal Materials Horizons.

3D printing, also known as additive manufacturing, turns digital blueprints to physical objects by building them layer by layer. 4D printing is based on this technology, with one big difference: it uses special materials and sophisticated designs to print objects that change shape with environmental conditions such as temperature acting as a trigger, said senior author Howon Lee, an assistant professor in the Department of Mechanical and Aerospace Engineering. Time is the fourth dimension that allows them to morph into a new shape.

“We believe this unprecedented interplay of materials science, mechanics and 3D printing will create a new pathway to a wide range of exciting applications that will improve technology, health, safety and quality of life,” Lee said.

The engineers created a new class of “metamaterials” – materials engineered to have unusual and counterintuitive properties that are not found in nature. The word metamaterials is derived from the Greek word “meta,” which means “higher” or “beyond.”

Previously, the shape and properties of metamaterials were irreversible once they were manufactured. But the Rutgers engineers can tune their plastic-like materials with heat, so they stay rigid when struck or become soft as a sponge to absorb shock.

The stiffness can be adjusted more than 100-fold in temperatures between room temperature (73 degrees) and 194 degrees Fahrenheit, allowing great control of shock absorption. The materials can be reshaped for a wide variety of purposes. They can be temporarily transformed into any deformed shape and then returned to their original shape on demand when heated.

This YouTube video shows how 4D-printed smart materials can morph from stiff to soft and also change shape. Video by Chen Yang/Rutgers University–New Brunswick.

The materials could be used in airplane or drone wings that change shape to improve performance, and in lightweight structures that are collapsed for space launches and reformed in space for a larger structure, such as a solar panel.

Soft robots made of soft, flexible and rubbery materials inspired by the octopus could have variable flexibility or stiffness that is tailored to the environment and task at hand. Tiny devices inserted or implanted in people for diagnosis or treatment could be temporarily made soft and flexible for minimally invasive and less painful insertion into the body, Lee said.

Learn more: 4D-Printed Materials Can Be Stiff as Wood or Soft as Sponge

 

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