Flexible, stretchable electronics that can change size and shape dynamically are poised to open doors to innovation

Medical implants of the future may feature reconfigurable electronic platforms that can morph in shape and size dynamically as bodies change or transform to relocate from one area to monitor another within our bodies. In Applied Physics Letters, a group of researchers reports a silicon honeycomb-serpentine reconfigurable electronic platform that can dynamically morph into three different shapes: quatrefoils (four lobes), stars and irregular ones. This image shows: (a) the serpentine-honeycomb reconfigurable platform. (b) The design with the eight reconfiguring nodes highlighted. (c) The irregular configuration. (d) The quatrefoil configuration. (e) The star configuration. CREDIT Muhammad Hussain

Reconfigurable electronics show promise for wearable, implantable devices

Medical implants of the future may feature reconfigurable electronic platforms that can morph in shape and size dynamically as bodies change or transform to relocate from one area to monitor another within our bodies.

In Applied Physics Letters, from AIP Publishing, a group of researchers from King Abdullah University of Science and Technology and University of California, Berkeley reports a silicon honeycomb-serpentine reconfigurable electronic platform that can dynamically morph into three different shapes: quatrefoils (four lobes), stars and irregular ones.

“Quatrefoils can be used for rectangular object-based operation, while stars are for more intricate architectures, and irregular-shaped ones are specifically for implanted bioelectronics,” said Muhammad Hussain, co-author and a visiting professor at the University of California, Berkeley.

With their work, the researchers are introducing a new branch of flexible, stretchable electronics — opening the door to new engineering challenges and providing opportunities for innovation in biomedical technologies that can be used for drug delivery, health monitoring, diagnosis, therapeutic healing, implants and soft robotics.

Inspiration for the group’s honeycomb-shaped platform comes from nature. “Think of how flowers bloom. Based on the same principle, we gathered many videos of flowers blossoming, analyzed their geometric pattern and used them for our first set of designs,” Hussain said. “In particular, we analyzed their stress distribution in an iterative manner, taking design architecture, materials and their properties into consideration. It’s a tedious process to reach the optimal balance, but this is where engineering helps.”

Reconfigurable electronic platforms are designed to undergo physical deformation, such as stretching, bending, folding or twisting to morph into another shape. “Imagine that a lab-on-chip platform is implanted within your body to monitor the growth of a tumor in the shoulder area,” said Hussain. “While it is implanted, if we observe some abnormality in lung function, a platform that is equipped enough can change its shape and size, and relocate or expand to go monitor lung function.”

Another idea the researchers are actively pursuing is a wearable heart sleeve to monitor heart activity with the ability to mechanically pump the heart by repeated expansion and contraction when needed.

“We still have a long way to go to integrate soft robotics with embedded high-performance flexible complementary metal-oxide semiconductor (CMOS) electronics on a variety of reconfigurable electronic platforms, which will be of immense importance,” Hussain said. “It offers wonderful engineering challenges, requires true multidisciplinary efforts and has the ability to bind a variety of disciplines into applications that are simply not possible with the existing electronics infrastructure.”

Learn more: Reconfigurable electronics show promise for wearable, implantable devices

 

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Liquid metal printing has taken a key step toward the rapid manufacture of flexible computer screens and other stretchable electronic devices

via Oregon State University

Researchers in Oregon State University’s College of Engineering have taken a key step toward the rapid manufacture of flexible computer screens and other stretchable electronic devices, including soft robots.

The advance by a team within the college’s Collaborative Robotics and Intelligent Systems Institute paves the way toward the 3D printing of tall, complicated structures with a highly conductive gallium alloy.

Researchers put nickel nanoparticles into the liquid metal, galinstan, to thicken it into a paste with a consistency suitable for additive manufacturing.

“The runny alloy was impossible to layer into tall structures,” said Yi?it Mengüç, assistant professor of mechanical engineering and co-corresponding author on the study. “With the paste-like texture, it can be layered while maintaining its capacity to flow, and to stretch inside of rubber tubes. We demonstrated the potential of our discovery by 3D printing a very stretchy two-layered circuit whose layers weave in and out of each other without touching.”

Findings were recently published in Advanced Materials Technologies.

Gallium alloys are already being used as the conductive material in flexible electronics; the alloys have low toxicity and good conductivity, plus they’re inexpensive and “self-healing” – able to attach back together at break points.

But prior to the modification developed at OSU, which used sonication – the energy of sound – to mix the nickel particles and the oxidized gallium into the liquid metal, the alloys’ printability was restricted to 2-dimensional.

For this study, researchers printed structures up to 10 millimeters high and 20 millimeters wide.

“Liquid metal printing is integral to the flexible electronics field,” said co-author Do?an Yirmibe?o?lu, a robotics Ph.D. student at OSU. “Additive manufacturing enables fast fabrication of intricate designs and circuitry.”

The field features a range of products including electrically conductive textiles; bendable displays; sensors for torque, pressure and other types of strain; wearable sensor suits, such as those used in the development of video games; antennae; and biomedical sensors.

“The future is very bright,” Yirmibe?o?lu said. “It’s easy to imagine making soft robots that are ready for operation, that will just walk out of the printer.”

The gallium alloy paste demonstrates several features new to the field of flexible electronics, added co-corresponding author Uranbileg Daalkhaijav, Ph.D. candidate in chemical engineering.

“It can be made easily and quickly,” Daalkhaijav said. “The structural change is permanent, the electrical properties of the paste are comparable to pure liquid metal, and the paste retains self-healing characteristics.”

Future work will explore the exact structure of the paste, how the nickel particles are stabilized, and how the structure changes as the paste ages.

Learn more: Modified, 3D-printable alloy shows promise for flexible electronics, soft robots

 

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Stroke treatment could be revolutionized by stretchable electronics

The throat sensor is designed to minimize irritation on sensitive skin. It measures patients’ swallowing ability and patterns of speech.

New wearable device for the throat presented at AAAS annual meeting

A groundbreaking new wearable designed to be worn on the throat could be a game changer in the field of stroke rehabilitation.

Developed in the lab of Northwestern University engineering professor John A. Rogers, in partnership with Shirley Ryan AbilityLab, the sensor is the latest in Rogers’ growing portfolio of stretchable electronics that are precise enough for use in advanced medical care and portable enough to be worn outside the hospital, even during extreme exercise.

Related: Interactive press kit

Rogers presented research on the implications of stretchable electronics for stroke recovery treatment Saturday, Feb. 17, at the American Association for the Advancement of Science (AAAS) annual meeting in Austin, Texas.

Rogers’ sensors stick directly to the skin, moving with the body and providing detailed health metrics including heart function, muscle activity and quality of sleep.

“Stretchable electronics allow us to see what is going on inside patients’ bodies at a level traditional wearables simply cannot achieve,” Rogers said. “The key is to make them as integrated as possible with the human body.”

Rogers’ new bandage-like throat sensor measures patients’ swallowing ability and patterns of speech. The sensors aid in the diagnosis and treatment of aphasia, a communication disorder associated with stroke.

<span>Bandage-like sensors on man's legs</span>
Sensors on the arms, legs and chest track patients’ movements with a level of precision traditional wearables cannot achieve.

The tools that speech-language pathologists have traditionally used to monitor patients’ speech function – such as microphones – cannot distinguish between patients’ voices and ambient noise.

“Our sensors solve that problem by measuring vibrations of the vocal cords,” Rogers said. “But they only work when worn directly on the throat, which is a very sensitive area of the skin. We developed novel materials for this sensor that bend and stretch with the body, minimizing discomfort to patients.”

Shirley Ryan AbilityLab, a research hospital in Chicago, uses the throat sensor in conjunction with electronic biosensors – also developed in Rogers’ lab – on the legs, arms and chest to monitor stroke patients’ recovery progress. The intermodal system of sensors streams data wirelessly to clinicians’ phones and computers, providing a quantitative, full-body picture of patients’ advanced physical and physiological responses in real time.

“One of the biggest problems we face with stroke patients is that their gains tend to drop off when they leave the hospital,” said Arun Jayaraman, research scientist at the Shirley Ryan AbilityLab and a wearable technology expert. “With the home monitoring enabled by these sensors, we can intervene at the right time, which could lead to better, faster recoveries for patients.”

Because the sensors are wireless, they eliminate barriers posed by traditional health monitoring devices in clinical settings. Patients can wear them even after they leave the hospital, allowing doctors to understand how their patients are functioning in the real world.

Stretchable electronics allow us to see what is going on inside patients’ bodies at a level traditional wearables simply cannot achieve.”
John Rogers
McCormick School of Engineering

“Talking with friends and family at home is a completely different dimension from what we do in therapy,” said Leora Cherney, research scientist at the Shirley Ryan AbilityLab and an expert in aphasia treatment. “Having a detailed understanding of patients’ communication habits outside of the clinic helps us develop better strategies with our patients to improve their speaking skills and speed up their recovery process.”

Jayaraman describes the platform’s mobility as a “game changer” in rehabilitation outcomes measurement.

iPad with graphical data
The sensors wirelessly stream data to clinicians’ phones and computers, allowing them to react to patients’ changing metrics in real time. 

Data from the sensors will be presented in a dashboard that is easy for both clinicians and patients to understand. It will send alerts when patients are underperforming on a certain metric and allow them to set and track progress toward their goals.

Learn more: Stretchable electronics a ‘game changer’ for stroke recovery treatment

 

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New metal printing technology for low-cost, flexible and stretchable electronics

This prototype demonstrates the potential of the new technique for printing flexible, stretchable circuits.

Researchers from North Carolina State University have developed a new technique for directly printing metal circuits, creating flexible, stretchable electronics. The technique can use multiple metals and substrates and is compatible with existing manufacturing systems that employ direct printing technologies.

“Flexible electronics hold promise for use in many fields, but there are significant manufacturing costs involved – which poses a challenge in making them practical for commercial use,” says Jingyan Dong, corresponding author of a paper on the work and an associate professor in NC State’s Edward P. Fitts Department of Industrial & Systems Engineering.

“Our approach should reduce cost and offer an efficient means of producing circuits with high resolution, making them viable for integrating into commercial devices,” Dong says.

The technique uses existing electrohydrodynamic printing technology, which is already used in many manufacturing processes that use functional inks. But instead of ink, Dong’s team uses molten metal alloys with melting points as low as 60 degrees Celsius. The researchers have demonstrated their technique using three different alloys, printing on four different substrates: one glass, one paper and two stretchable polymers.

“This is direct printing,” Dong says. “There is no mask, no etching and no molds, making the process much more straightforward.”

The researchers tested the resilience of the circuits on a polymer substrate and found that the circuit’s conductivity was unaffected even after being bent 1,000 times. The circuits were still electrically stable even when stretched to 70 percent of tensile strain.

The researchers also found that the circuits are capable of “healing” themselves if they are broken by being bent or stretched too far.

“Because of the low melting point, you can simply heat the affected area up to around 70 degrees Celsius and the metal flows back together, repairing the relevant damage,” Dong says.

The researchers demonstrated the functionality of the printing technique by creating a high-density touch sensor, fitting a 400-pixel array into one square centimeter.

“We’ve demonstrated the resilience and functionality of our approach, and we’re open to working with the industry sector to implement the technique in manufacturing wearable sensors or other electronic devices,” Dong says.

Learn more: Metal Printing Offers Low-Cost Way to Make Flexible, Stretchable Electronics

 

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New form of stretchable electronics could give robots a sense of touch

Research led by Cunjiang Yu, Bill D. Cook Assistant Professor of mechanical engineering, has created an artificial skin that allows a robotic hand to sense hot and cold.

UH Researchers Discover New Form of Stretchable Electronics, Sensors and Skins

A team of researchers from the University of Houston has reported a breakthrough in stretchable electronics that can serve as an artificial skin, allowing a robotic hand to sense the difference between hot and cold, while also offering advantages for a wide range of biomedical devices.

The work, reported in the journal Science Advances, describes a new mechanism for producing stretchable electronics, a process that relies upon readily available materials and could be scaled up for commercial production.

Cunjiang Yu, Bill D. Cook Assistant Professor of mechanical engineering and lead author for the paper, said the work is the first to create a semiconductor in a rubber composite format, designed to allow the electronic components to retain functionality even after the material is stretched by 50 percent.

The work is the first semiconductor in rubber composite format that enables stretchability without any special mechanical structure, Yu said.

He noted that traditional semiconductors are brittle and using them in otherwise stretchable materials has required a complicated system of mechanical accommodations. That’s both more complex and less stable than the new discovery, as well as more expensive, he said.

“Our strategy has advantages for simple fabrication, scalable manufacturing, high-density integration, large strain tolerance and low cost,” he said.

Yu and the rest of the team – co-authors include first author Hae-Jin Kim, Kyoseung Sim and Anish Thukral, all with the UH Cullen College of Engineering – created the electronic skin and used it to demonstrate that a robotic hand could sense the temperature of hot and iced water in a cup. The skin also was able to interpret computer signals sent to the hand and reproduce the signals as American Sign Language.

“The robotic skin can translate the gesture to readable letters that a person like me can understand and read,” Yu said.

The artificial skin is just one application. Researchers said the discovery of a material that is soft, bendable, stretchable and twistable will impact future development in soft wearable electronics, including health monitors, medical implants and human-machine interfaces.

The stretchable composite semiconductor was prepared by using a silicon-based polymer known as polydimethylsiloxane, or PDMS, and tiny nanowires to create a solution that hardened into a material which used the nanowires to transport electric current.

“We foresee that this strategy of enabling elastomeric semiconductors by percolating semiconductor nanofibrils into a rubber will advance the development of stretchable semiconductors, and … will move forward the advancement of stretchable electronics for a wide range of applications, such as artificial skins, biomedical implants and surgical gloves,” they wrote.

Learn more: Artificial ‘Skin’ Gives Robotic Hand a Sense of Touch

 

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