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From virtual reality to rehabilitation and communication, haptic technology has revolutionized the way humans interact with the digital world. While early haptic devices focused on single-sensory cues like vibration-based notifications, modern advancements have paved the way for multisensory haptic devices that integrate various forms of touch-based feedback, including vibration, skin stretch, pressure and temperature.
 
Recently, a team of experts, including Rice University’s Marcia O’Malley and Daniel Preston, graduate student Joshua Fleck, alumni Zane Zook ’23 and Janelle Clark ’22 and other collaborators, published an in-depth review in Nature Reviews Bioengineering analyzing the current state of wearable multisensory haptic technology, outlining its challenges, advancements and real-world applications.
Haptic devices, which enable communication through touch, have evolved significantly since their introduction in the 1960s. Initially, they relied on rigid, grounded mechanisms acting as user interfaces, generating force-based feedback from virtual environments. But with advancements in sensing and actuation technology, haptic devices have become increasingly wearable. Today’s innovations focus on cutaneous feedback — stimulating the skin’s receptors to provide realistic touch sensations — rather than kinesthetic feedback, which mimics force exerted on the musculoskeletal system.
 
“Wearable haptic devices are now integrated into consumer products such as smartwatches and gaming accessories, and they are serving more complex roles in health care, robotics and immersive media,” said O’Malley, the Thomas Michael Panos Family Professor in Engineering and professor and chair of mechanical engineering. “A new shift toward multisensory haptic feedback, which means delivering more than one type of touch stimulus simultaneously, is enhancing user experience, but it presents new engineering and perceptual challenges. As this technology continues to evolve, we will see it move to a richer, multisensory experience — one that bridges the gap between digital interaction and human touch.”

Designing effective, wearable multisensory haptic devices requires a deep understanding of human touch perception, and the research team identified several key challenges in the field today. One of the most significant hurdles is the variability in skin contact mechanics as differences in skin elasticity, receptor distribution and external factors like humidity can alter how haptic stimuli are perceived. Another issue is tactile masking, where multiple haptic sensations such as vibration and skin stretch can interfere with one another, reducing perceptual clarity.

“Every person’s skin responds differently to stimuli due to variations in elasticity, moisture and even body hair,” said Preston, assistant professor of mechanical engineering. “This variability makes designing universally effective devices incredibly complex.”
In addition, wearability and comfort continue to be major considerations in every product. Haptic devices must be designed to fit different body locations without causing discomfort, restricting movement or disrupting daily activities. Factors such as weight, size and attachment methods all play a crucial role in ensuring long-term usability.

“True immersion in haptic technology depends not just on what users feel but on how naturally and comfortably they experience it,” Preston said.

In addition to highlighting challenges, the authors identified several emerging actuation methods that could redefine wearable haptic technology.

Electromechanical actuation, commonly used in vibrational feedback systems, remains the most widely adopted method due to its reliability and affordability. However, it often struggles to provide a diverse range of haptic cues. Polymeric actuation, which relies on smart polymers that change shape or texture when exposed to stimuli, offers a lightweight and flexible alternative for delivering haptic feedback. Fluidic actuation, which utilizes pressurized air or liquid to generate dynamic tactile sensations, is gaining traction in soft robotics and textile-based haptic wearables, offering new possibilities for comfort and adaptability. Additionally, thermal actuation is emerging as a way to enhance immersion in virtual environments or simulate real-world interactions through warming or cooling sensations.

“We expect these technologies to significantly expand the scope of haptic feedback, particularly in fields such as medical rehabilitation, prosthetic development and human-machine interaction,” O’Malley said. “Although promising, further refinement is needed to improve response time, durability and energy efficiency.”

The review also offers insight into how wearable haptic technology is poised to unlock new possibilities in human interaction with digital and physical environments. In virtual and augmented reality, multisensory haptics enhance immersion by allowing users to feel digital objects, improving experiences in gaming, training simulations and education. In health care and rehabilitation, wearable haptics assist in motor skill training, post-stroke rehabilitation and prosthetic limb feedback, enabling patients to interact more effectively with their surroundings. Assistive technology and communication applications leverage tactile interfaces to help individuals with vision or hearing impairments by translating auditory or visual information into touch-based signals. Navigation and guidance systems benefit from haptic wearables by providing intuitive directional cues, aiding visually impaired individuals and improving hands-free navigation in fields such as military and aviation. Additionally, teleoperation and robotics stand to gain significantly as remote-controlled robotic systems with haptic feedback allow users to “feel” objects from a distance, improving precision in delicate tasks like robotic surgery.

Despite significant progress, the authors emphasized the need for further exploration in multisensory haptic perception. Understanding how the brain processes simultaneous haptic cues will be crucial in refining future devices, and ensuring widespread adoption will require a balance between technological sophistication, user comfort and practical usability.

“The ultimate goal is to create haptic devices that feel as natural as real-world touch,” O’Malley said.

Rapid temperature contrast hydrotherapy, also known as contrast water therapy, involves alternating immersion in hot and cold water to aid in sports recovery. By rapidly switching between these temperature extremes, the therapy aims to invigorate the body's natural healing processes, making it a popular choice for athletes and individuals seeking relief from muscle soreness, joint pain, and stress.

As a result, contrast water therapy is an effective strategy for enhancing overall athletic performance and facilitating faster recovery after competitions. Traditionally, contrast water therapy involves using two baths filled with cold and hot water respectively at precisely controlled constant temperatures . However, the facilities and significant water consumption required restrict the application of this therapy in daily athletic training. Existing wearable cooling and heating systems often struggle with limited heat transfer rates between the device and the human body, failing to meet the requirement for practical contrast water therapy.

A study published in Advanced Science highlights a breakthrough developed by a research team led by Prof. Xiaoming TAO, Chair Professor of Textile Technology of the School of Fashion and Textiles and Vincent and Lily Woo Professor in Textile Technology at The Hong Kong Polytechnic University. The team created a novel portable system based on a wearable fluidic fabric device to facilitate rapid skin temperature modulation. The innovative system enables athletes to experience the benefits of contrast water therapy without the need for actual water immersion.

The system comprises several key components, which include wearable fluidic fabrics, a small water tank (with a volume of three litres, designed for one leg), a control machine for temperature regulation, a water pump, and a connection tube (Figure 1). The wearable fluidic fabrics are designed with multiple layers to optimise performance. These layers include an outer thermal insulation fabric layer for reducing heat transfer between fluid and the surrounding environment, a middle flexible heat transfer panel (FHTP) layer, and an ultra-thin inner fabric layer that is in contact with the skin (Figure 2). The core FHTP layer consists of two pieces of laminated fabrics that are joined together by one-step welding. To achieve a uniform and rapid cooling/heating effect, the FHTP is designed with both serpentine and network channel patterns.

The system features rapid cooling/heating transitions within ten seconds over an effective area of 0.3 square metre. Using a smartphone app, users can initiate the temperature therapy program, which allows either warm or cool water to be pumped from the tank into the channels within the fabric before being recirculated back into the tank. Each therapy cycle comprises two distinct modes: cold mode and hot mode. In the cold mode, the temperature of circulating water is set to approximately 5 °C for one minute. In this mode, the flowing water absorbs heat from the skin and the surrounding environment. In the hot mode, the water temperature is raised to 40 °C for two minutes. During this phase, heat is dissipated into the skin and the surroundings.

The wearable fluidic fabric device exhibits exceptional heat transfer properties. During cold therapy, the heat transfer coefficient measured between the skin and the fabric is 98.5 W m⁻² K⁻¹. This performance translates to an impressive 92% efficiency compared to direct water immersion, significantly surpassing that of benchmark liquid cooling garments, which typically exhibit heat transfer coefficients ranging from 13 to 37 W m⁻² K⁻¹. Overall, the FHTP demonstrates strong heat transfer capability. Specifically, the heat transfer effectiveness of the FHTP reaches up to 89% during cold therapy and approximately 55% during hot therapy.

This study marks a significant breakthrough in the development of wearable fluidic fabric capable of rapidly modulating skin temperature within a wide range—from 5 °C to 40 °C. In addition to its effectiveness in contrast water therapy, this innovative fluidic fabric presents extended potential applications in skin thermal management for medical purposes as well as in extreme situations such as encountered during fire protection activity.

The research is supported by the Sport Science and Research Funding Scheme of the Hong Kong SAR Government and Hong Kong Jockey Club Charities Trust [No. P0042455], as well as the Endowed Professorship Fund of The Hong Kong Polytechnic University [No. 847A]. The data source and code can be obtained from the corresponding authors upon request.

Prof. Tao has been recognised by Stanford University as one of the top 2% most-cited scientists worldwide (career-long) in the field of materials for six consecutive years from 2019 to 2024. In acknowledgement of her outstanding contributions and expertise in engineering, she was elected as a Fellow of the Hong Kong Academy of Engineering in 2025. Currently, Prof. Tao serves as the Director of the Research Institute for Intelligent Wearable Systems at The Hong Kong Polytechnic University.

Smart textiles are making virtual reality more immersive and enabling wearers to experience the sensation of physical touch. An ultrathin film that can transmit touch sensations is able to turn textiles into a virtual second skin. For seriously ill children in hospital isolation wards, this new technology offers them the chance to feel the physical closeness of their parents during computer-simulated visits and to experience again the feeling of being held, hugged or cuddled.

The research team led by Professors Stefan Seelecke and Paul Motzki from Saarland University will be presenting the technology behind these smart textiles at Hannover Messe from 22 to 26 April.

A hand on a shoulder, the stroke of an arm or a simple hug. Human touch can bring calm, comfort and closeness, a sense of safety and of being protected. When the nerve cells in our skin are stimulated by touch, numerous parts of our brain are triggered, causing immediate changes in our body's biochemistry. Hormones and signalling molecules are released, including oxytocin, which creates a sense of well-being and bonding. Video calls, on the other hand, tend to leave us cold. We miss the closeness and emotional connection that in-person meetings produce. But what happens when physical closeness is essential, when children are seriously ill, but their parents are unable to visit? When physical contact is not possible due to a weakened immune system?

An interdisciplinary research team at Saarland University, htw saar University of Applied Sciences, the Centre for Mechatronics and Automation Technology (ZeMA) and the German Research Center for Artificial Intelligence (DFKI) is working on a technology that will enable children in hospital isolation wards to feel in a very natural way the close physical proximity of their parents during virtual visits. The 'Multi-Immerse' project is at the interface of engineering science, neurotechnology, medicine and computer science and the members of the research team are developing ways to realize multi-sensory virtual encounters between individuals. The aim is to create new technology that will allow young patients to see, hear and feel their parents and siblings in as realistic a manner as possible so that the children experience a strong sense of close physical interaction even though they are physically separated.

The research group led by Professors Stefan Seelecke and Paul Motzki at Saarland University and ZeMA in Saarbrücken is responsible for the tactile side of the project and for creating technical systems that deliver a realistic sense of touch. The Saarbrücken engineers are experts in using thin silicone films to impart novel capabilities to surfaces. They have developed films that are a mere 50 micrometres thick and that can be worn like a second skin. Just as our skin is our body's interface to the outside world, these ultrathin films are the body's interface to the virtual world. The goal is to create a lifelike sensation of touch from interactions between people in a virtual environment.

When incorporated into textiles, these high-tech films allow the child to experience being touched when the mother or father strokes a second smart textile elsewhere. 'The films, known as dielectric elastomers, act both as sensors – detecting the tactile input from mum or dad – and as actuators – that transmit these movements to the child,' explained Professor Seelecke, who heads the Intelligent Material Systems Lab at Saarland University. When functioning as a sensor, the film is able to recognize with very high precision how a hand or finger presses or stretches the film as it brushes over it. This physical deformation caused by the parent's hand is then reproduced exactly in a second textile that is in contact with the child's skin – giving the child the realistic impression of being stroked on the arm, for example.

‘A highly flexible electrically conducting layer is printed onto each side of the ultrathin film to create what is known as a dielectric elastomer. If we apply a voltage to the elastomer film, the electrodes attract each other, compressing the polymer and causing it to expand out sideways, thus increasing its surface area,' said Professor Paul Motzki, who holds a cross-institutional professorship in smart material systems for innovative production at Saarland University and at ZeMA. Even the slightest movement of the film alters its electrical capacitance, which is a physical quantity that can be precisely measured. When a finger runs over the film, the film deforms and an exact value of the electrical capacitance can be assigned to each individual position of the film. A sequence of these measured capacitance values represents the path taken by the finger as it moves. The film is therefore its own flexible sensor that can recognize how it is being deformed.

By knowing how capacitance values and film deformations correlate, the researchers can use the smart textile to transfer the stroking motion of a parent's hand to the child's arm. The research team is able to precisely control the motion of the elastomer film. By combining the capacitance data and intelligent algorithms, the team has developed a control unit that can predict and program motion sequences and thus precisely control how the elastomer film deforms. 'We can get the film to perform continuously controlled flexing motions so that it exerts increasing pressure on the skin, or we can get it to remain in a fixed position”, explained PhD student Sipontina Croce, who is carrying out doctoral research in the project. They can also create tapping movements at a specified frequency. The amplitude and frequency of the motion can be precisely regulated.

At this year's Hannover Messe, the team will be demonstrating their technology with a “watch” that has a smart film applied to its back. 'We can create chains of these smart components so that they can transmit long stroking motions. To do this, we interconnect the components so that they can communicate and cooperate collectively within a network,' explained Paul Motzki.

This smart-textile technology is inexpensive, lightweight, noiseless and energy-efficient. By providing a tactile element to computer gaming, the novel elastomer-film technology can also be used to make the gaming experience more realistic. In related projects, the engineers have used their technology to create interactive gloves for future industrial production processes, or to create the sensation of a tactile 'button' or 'slider' on flat glass display screens, which is literally bringing a new dimension to touchscreen interactions.

At this year's Hannover Messe, the experts for intelligent materials from Saarbrücken will be showcasing other developments that make use of dielectric elastomers, such as sensory shirts or shoe soles, or industrial components like pumps, vacuum pumps and high-performance actuators.

Freezing is one of the most common and debilitating symptoms of Parkinson’s disease, a neurodegenerative disorder that affects more than 9 million people worldwide. When individuals with Parkinson’s disease freeze, they suddenly lose the ability to move their feet, often mid-stride, resulting in a series of staccato stutter steps that get shorter until the person stops altogether. These episodes are one of the biggest contributors to falls among people living with Parkinson’s disease.

Today, freezing is treated with a range of pharmacological, surgical or behavioral therapies, none of which are particularly effective. What if there was a way to stop freezing altogether?

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Boston University Sargent College of Health & Rehabilitation Sciences have used a soft, wearable robot to help a person living with Parkinson’s walk without freezing. The robotic garment, worn around the hips and thighs, gives a gentle push to the hips as the leg swings, helping the patient achieve a longer stride.

The device completely eliminated the participant’s freezing while walking indoors, allowing them to walk faster and further than they could without the garment’s help.

“We found that just a small amount of mechanical assistance from our soft robotic apparel delivered instan-taneous effects and consistently improved walking across a range of conditions for the individual in our study,” said Conor Walsh, the Paul A. Maeder Professor of Engineering and Applied Sciences at SEAS and co-corresponding author of the study.

The research demonstrates the potential of soft robotics to treat this frustrating and potentially dangerous symptom of Parkinson’s disease and could allow people living with the disease to regain not only their mobility but their independence.

For over a decade, Walsh’s Biodesign Lab at SEAS has been developing assistive and rehabilitative robotic technologies to improve mobility for individuals’ post-stroke and those living with ALS or other diseases that impact mobility. Some of that technology, specifically an exosuit for post-stroke gait retraining, received support from the Wyss Institute for Biologically Inspired Engineering, and Harvard’s Office of Technology Development coordinated a license agreement with ReWalk Robotics to commercialize the technology.

In 2022, SEAS and Sargent College received a grant from the Massachusetts Technology Collaborative to support the development and translation of next-generation robotics and wearable technologies. The research is centered at the Move Lab, whose mission is to support advances in human performance enhancement with the collaborative space, funding, R&D infrastructure, and experience necessary to turn promising research into mature technologies that can be translated through collaboration with industry partners. This research emerged from that partnership.

“Leveraging soft wearable robots to prevent freezing of gait in patients with Parkinson’s required a collaboration between engineers, rehabilitation scientists, physical therapists, biomechanists and apparel designers,” said Walsh, whose team collaborated closely with that of Terry Ellis,  Professor and Physical Therapy Department Chair and Director of the Center for Neurorehabilitation at Boston University.

Leveraging soft wearable robots to prevent freezing of gait in patients with Parkinson’s required a collaboration between engineers, rehabilitation scientists, physical therapists, biomechanists and apparel designers.

The team spent six months working with a 73-year-old man with Parkinson’s disease, who — despite using both surgical and pharmacologic treatments — endured substantial and incapacitating freezing episodes more than 10 times a day, causing him to fall frequently. These episodes prevented him from walking around his community and forced him to rely on a scooter to get around outside.

In previous research, Walsh and his team leveraged human-in-the-loop optimization to demonstrate that a soft, wearable device could be used to augment hip flexion and assist in swinging the leg forward to provide an efficient approach to reduce energy expenditure during walking in healthy individuals.

Here, the researchers used the same approach but to address freezing. The wearable device uses cable-driven actuators and sensors worn around the waist and thighs. Using motion data collected by the sensors, algorithms estimate the phase of the gait and generate assistive forces in tandem with muscle movement.

The effect was instantaneous. Without any special training, the patient was able to walk without any freezing indoors and with only occasional episodes outdoors. He was also able to walk and talk without freezing, a rarity without the device.

“Our team was really excited to see the impact of the technology on the participant’s walking,” said Jinsoo Kim, former PhD student at SEAS and co-lead author on the study.

During the study visits, the participant told researchers: “The suit helps me take longer steps and when it is not active, I notice I drag my feet much more. It has really helped me, and I feel it is a positive step forward. It could help me to walk longer and maintain the quality of my life.”

“Our study participants who volunteer their time are real partners,” said Walsh. “Because mobility is difficult, it was a real challenge for this individual to even come into the lab, but we benefited so much from his perspective and feedback.”

The device could also be used to better understand the mechanisms of gait freezing, which is poorly understood.

“Because we don’t really understand freezing, we don’t really know why this approach works so well,” said Ellis. “But this work suggests the potential benefits of a ’bottom-up’ rather than ’top-down’ solution to treating gait freezing. We see that restoring almost-normal biomechanics alters the peripheral dynamics of gait and may influence the central processing of gait control.”

The research was co-authored by Jinsoo Kim, Franchino Porciuncula, Hee Doo Yang, Nicholas Wendel, Teresa Baker and Andrew Chin. Asa Eckert-Erdheim and Dorothy Orzel also contributed to the design of the technology, as well as Ada Huang, and Sarah Sullivan managed the clinical research. It was supported by the National Science Foundation under grant CMMI-1925085; the National Institutes of Health under grant NIH U01 TR002775; and the Massachusetts Technology Collaborative, Collaborative Research and Development Matching Grant.

A single strand of fiber developed at Washington State University has the flexibility of cotton and the electric conductivity of a polymer, called polyaniline.

The newly developed material showed good potential for wearable e-textiles. The WSU researchers tested the fibers with a system that powered an LED light and another that sensed ammonia gas, detailing their findings in the journal Carbohydrate Polymers.

“We have one fiber in two sections: one section is the conventional cotton: flexible and strong enough for everyday use, and the other side is the conductive material,” said Hang Liu, WSU textile researcher and the study’s corresponding author. “The cotton can support the conductive material which can provide the needed function.”

While more development is needed, the idea is to integrate fibers like these into apparel as sensor patches with flexible circuits. These patches could be part of uniforms for firefighters, soldiers or workers who handle chemicals to detect for hazardous exposures. Other applications include health monitoring or exercise shirts that can do more than current fitness monitors.

“We have some smart wearables, like smart watches, that can track your movement and human vital signs, but we hope that in the future your everyday clothing can do these functions as well,” said Liu. “Fashion is not just color and style, as a lot of people think about it: fashion is science.”

In this study, the WSU team worked to overcome the challenges of mixing the conductive polymer with cotton cellulose. Polymers are substances with very large molecules that have repeating patterns. In this case, the researchers used polyaniline, also known as PANI, a synthetic polymer with conductive properties already used in applications such as printed circuit board manufacturing.

While intrinsically conductive, polyaniline is brittle and by itself, cannot be made into a fiber for textiles. To solve this, the WSU researchers dissolved cotton cellulose from recycled t-shirts into a solution and the conductive polymer into another separate solution. These two solutions were then merged together side-by-side, and the material was extruded to make one fiber.

The result showed good interfacial bonding, meaning the molecules from the different materials would stay together through stretching and bending.

Achieving the right mixture at the interface of cotton cellulose and polyaniline was a delicate balance, Liu said.

“We wanted these two solutions to work so that when the cotton and the conductive polymer contact each other they mix to a certain degree to kind of glue together, but we didn’t want them to mix too much, otherwise the conductivity would be reduced,” she said.

Additional WSU authors on this study included first author Wangcheng Liu as well as Zihui Zhao, Dan Liang, Wei-Hong Zhong and Jinwen Zhang. This research received support from the National Science Foundation and the Walmart Foundation Project.

What comes to mind when you think about “wearable technology?” In 2023, likely a lot, at a time when smartwatches and rings measure heart rates, track exercise and even receive text messages. Your mind might even drift to that “ugly” light-up sweater or costume you saw last Halloween or holiday season.

At the Wilson College of Textiles, though, researchers are hard at work optimizing a truly new-age form of wearable technology that can be proven useful in a wide range of settings, from fashion and sports to augmented reality, the military and medicine.

Currently in its final stages, this grant-funded project could help protect users in critical situations, such as soldiers on the battlefield and patients in hospitals, while simultaneously pushing the boundaries of what textiles research can accomplish.

“The goals set for this research are quite novel to any other literature that exists on wearable connectors” says Shourya Dhatri Lingampally, Wilson College of Textiles graduate student and research assistant involved in the project alongside Wilson College Associate Professor Minyoung Suh.

Ongoing since the fall of 2021, Suh and Lingampally’s work focuses on textile-integrated wearable connectors, a unique, high-tech sort of “bridge” between flexible textiles and external electronic devices. At its essence, the project aims to improve these connectors’ Technology Readiness Level — a key rating used by NASA and the Department of Defense used to assess a particular technology’s maturity.

To do this, Lingampally and her colleagues’ research examines problems that have, in the past, affected the performance of wearable devices.

Sure, these advances may benefit fashion, leading to eccentric shirts, jackets, or accessories — “to light up or change its color based on the wearer’s biometric data,” Lingampally offers — the research has roots in a much deeper mission.

Potential benefits to military, medicine and beyond
The project is funded through more than $200,000 in grant money from Advanced Functional Fabrics of America (AFFOA), a United States Manufacturing Innovation Institute (MII) located in Cambridge, Massachusetts. The mission of AFFOA is to support domestic manufacturing capability to support new technical textile products, such as textile-based wearable technologies.

A key purpose of the research centers around improving the functionality of wearable monitoring devices with which soldiers are sometimes outfitted to monitor the health and safety of their troops remotely.

Similar devices allow doctors and other medical personnel to remotely monitor the health of patients even while away from the bedside.

Though such technology has existed for years, it’s too often required running wires and an overall logistically-unfriendly design. That could soon change.

“We have consolidated the electronic components into a small snap or buckle, making the circuits less obtrusive to the wearer,” Lingampally says, explaining the team’s innovations, which include 3D printing the connector prototypes using stereolithography technology.

“We are trying to optimize the design parameters in order to enhance the electrical and mechanical performance of these connectors,” she adds.

To accomplish their goals, the group collaborated with NC State Department of Electrical and Computer Engineering Assistant Research Professor James Dieffenderfer. The team routed a variety of electrical connections and interconnects like conductive thread, epoxy and solder through textile materials equipped with rigid electronic devices.

They also tested the components for compatibility with standard digital device connections like USB 2.0 and I2C.

Ultimately, Lingampally hopes their work will make wearable technology not only easier and more comfortable to use, but available at a lower price, too.

“I would like to see them scaled, to be mass manufactured, so they can be cost efficient for any industry to use,” she explains.

In a bigger-picture sense, though, her team’s work is reinforcing the far-reaching boundaries of what smart textile research can accomplish; a purpose that stretches far beyond fashion or comfort.

Pushing the boundaries of textiles research
Suh and Lingampally’s work is just the latest breakthrough research originating from the Wilson College of Textiles that’s aimed at solving critical problems in the textile industry and beyond.

“The constant advancements in technology and materials present immense potential for the textile industry to drive positive change across a range of fields from fashion to healthcare and beyond,” Lingampally, a graduate student in the M.S. Textiles program, says, noting the encouragement she feels in her program to pursue innovation and creativity in selecting and advancing her research.

Additionally, in the fiber and polymer science doctoral program, which Suh does research with, candidates focus their research on a seemingly endless array of STEM topics, ranging from forensics to medical textiles, nanotechnology and, indeed, smart wearable technology (just to name a few).

In this case, Suh says, the research lent itself to “unexpected challenges” that required intriguing adaptations “at every corner.” But, ultimately, it led to breakthroughs not previously seen in the wearable technology industry, attracting interest from other researchers outside the university, and private companies, too.

“This project was quite exploratory by nature as there hasn’t been any prior research aiming to the same objectives,” Suh says.

Meanwhile, the team has completed durability and reliability testing on its textile-integrated wearable connectors. Eventually, the group would like to increase the sample size for testing to strengthen and validate the findings. The team also hopes to evaluate new, innovative interconnective techniques, as well as other 3D printing techniques and materials as they work to further advance wearable technologies.

Electronically conductive fibres are already in use in smart textiles, but in a recently published research article, ionically conductive fibres have proven to be of increasing interest. The so-called ionofibres achieve higher flexibility and durability and match the type of conduction our body uses. In the future, they may be used for such items as textile batteries, textile displays, and textile muscles.

The research project is being carried out by doctoral student Claude Huniade at the University of Borås and is a track within a larger project, Weafing, the goal of which is to develop novel, unprecedented garments for haptic stimulation comprising flexible and wearable textile actuators and sensors, including control electronics, as a new type of textile-based large area electronics.

WEAFING stands for Wearable Electroactive Fabrics Integrated in Garments. It started 1 January 2019 and ended 30 June 2023.

These wearables are based on a new kind of textile muscles which yarns are coated with electromechanically active polymers and contract when a low voltage is applied. Textile muscles offer a completely novel and very different quality of haptic sensation, accessing also receptors of our tactile sensory system that do not react on vibration, but on soft pressure or stroke.

Furthermore, being textile materials, they offer a new way of designing and fabricating wearable haptics and can be seamlessly integrated into fabrics and garments. For these novel form of textile muscles, a huge range of possible applications in haptics is foreseen: for ergonomics, movement coaching in sports, or wellness, for enhancement of virtual or augmented reality applications in gaming or for training purposes, for inclusion of visually handicapped people by providing them information about their environment, for stress reduction or social communication, adaptive furniture, automotive industry and many more.

In Claude Huniade’s project, the goal is to produce conductive yarns without conductive metals.

"My research is about producing electrically conductive textile fibres, and ultimately yarns, by coating non-metals sustainably on commercial yarns. The biggest challenge is in the balance between keeping the textile properties and adding the conductive feature," said Claude Huniade.

Currenty, the uniqueness of his research leans towards the strategies employed when coating. These strategies expand to the processes and the materials used.

Uses ionic liquid
One of the tracks he investigates is about a new kind of material as textile coating, ionic liquids in combination with commercial textile fibres. Just like salt water, they conduct electricity but without water. Ionic liquid is a more stable electrolyte than salt water as nothing evaporates.

"The processable aspect is an important requirement since textile manufacturing can be harsh on textile fibres, especially when upscaling their use. The fibres can also be manufactured into woven or knitted without damaging them mechanically while retaining their conductivity. Surprisingly, they were even smoother to process into fabrics than the commercial yarns they are made from," explained Claude Huniade.

Ionofibres could be used as sensors since ionic liquids are sensitive to their environment. For example, humidity change can be sensed by the ionofibers, but also any stretch or pressure they are subjected to.

"Ionofibres could truly shine when they are combined with other materials or devices that require electrolytes. Ionofibres enable certain phenomena currently limited to happen in liquids to be feasible in air in a lightweight fashion. The applications are multiple and unique, for example for textile batteries, textile displays or textile muscles," said Claude Huniade.

Needs further research
Yet more research is needed to combine the ionofibres with other functional fibres and to produce the unique textile devices.

How do they stand out compared to common electronically conductive fibres?

"In comparison to electronically conductive fibres, ionofibers are different in how they conduct electricity. They are less conductive, but they bring other properties that electronically conductive fibers often lack. Ionofibres achieve higher flexibility and durability and match the type of conduction that our body uses. They actually match better than electronically conductive fibres with how electricity is present in nature," he concluded.

Embroidering power-generating yarns onto fabric allowed researchers to embed a self-powered, numerical touch-pad and movement sensors into clothing. The technique offers a low-cost, scalable potential method for making wearable devices.

“Our technique uses embroidery, which is pretty simple – you can stitch our yarns directly on the fabric,” said the study’s lead author Rong Yin, assistant professor of textile engineering, chemistry and science at North Carolina State University. “During fabric production, you don’t need to consider anything about the wearable devices. You can integrate the power-generating yarns after the clothing item has been made.”

In the study published in Nano Energy, researchers tested multiple designs for power-generating yarns. To make them durable enough to withstand the tension and bending of the embroidery stitching process, they ultimately used five commercially available copper wires, which had a thin polyurethane coating, together. Then, they stitched them onto cotton fabric with another material called PTFE.

“This is a low-cost method for making wearable electronics using commercially available products,” Yin said. “The electrical properties of our prototypes were comparable to other designs that relied on the same power generation mechanism.”

The researchers relied on a method of generating electricity called the “triboelectric effect,” which involves harnessing electrons exchanged by two different materials, like static electricity. They found the PTFE fabric had the best performance in terms of voltage and current when in contact with the polyurethane-coated copper wires, as compared to other types of fabric that they tested, including cotton and silk. They also tested coating the embroidery samples in plasma to increase the effect.

“In our design, you have two layers – one is your conductive, polyurethane-coated copper wires, and the other is PTFE, and they have a gap between them,” Yin said. “When the two non-conductive materials come into contact with each other, one material will lose some electrons, and some will get some electrons. When you link them together, there will be a current.”
Researchers tested their yarns as motion sensors by embroidering them with the PTFE fabric on denim. They placed the embroidery patches on the palm, under the arm, at the elbow and at the knee to track electrical signals generated as a person moves. They also attached fabric with their embroidery on the insole of a shoe to test its use as a pedometer, finding their electrical signals varied depending on whether the person was walking, running or jumping.

Lastly, they tested their yarns in a textile-based numeric keypad on the arm, which they made by embroidering numbers on a piece of cotton fabric, and attaching them to a piece of PTFE fabric. Depending on the number that the person pushed on the keypad, they saw different electrical signals generated for each number.

“You can embroider our yarns onto clothes, and when you move, it generates an electrical signal, and those signals can be used as a sensor,” Yin said. “When we put the embroidery in a shoe, if you are running, it generates a higher voltage than if you were just walking. When we stitched numbers onto fabric, and press them, it generates a different voltage for each number. It could be used as an interface.”

Since textile products will inevitably be washed, they tested the durability of their embroidery design in a series of washing and rubbing tests. After hand washing and rinsing the embroidery with detergent, and drying it in an oven, they found no difference or a slight increase in voltage. For the prototype coated in plasma, they found weakened but still superior performance compared with the original sample. After an abrasion test, they found that there was no significant change in electrical output performance of their designs after 10,000 rubbing cycles.

In future work, they plan to integrate their sensors with other devices to add more functions.
“The next step is to integrate these sensors into a wearable system,” Yin said.

The study, “Flexible, durable and washable triboelectric yarn and embroidery for self-powered sensing and human-machine interaction,” was published online in Nano Energy. Co-authors included Yu Chen, Erdong Chen, Zihao Wang, Yali Ling, Rosie Fisher, Mengjiao Li, Jacob Hart, Weilei Mu, Wei Gao, Xiaoming Tao and Bao Yang. Funding was provided by North Carolina State University through the NC State Faculty Research & Professional Development Fund and the NC State Summer REU program.

Patients with severe respiratory or lung diseases require intensive treatment and their lung function needs to be monitored on a continuous basis. As part of the Pneumo.Vest project, Fraunhofer researchers have developed a technology whereby noises in the lungs are recorded using a textile vest with integrated acoustic sensors. The signals are then converted and displayed visually using software. In this way, patients outside of intensive care units can still be monitored continuously. The technology increases the options for diagnosis and improves the patient’s quality of life.

For over 200 years, the stethoscope has been a standard tool for doctors and, as such, is a symbol of the medical profession. In television hospital dramas, doctors are seen rushing through the halls with a stethoscope around their neck. Experienced doctors do indeed use them to listen very accurately to heartbeats and the lungs and, as a result, to diagnose illnesses.

Now, the stethoscope is getting some help. As part of the Pneumo.Vest project, researchers of the Fraunhofer Institute for Ceramic Technologies and Systems IKTS at the Berlin office have developed a textile vest with integrated acoustic sensors, presenting a high-performance addition to the traditional stethoscope. Piezoceramic acoustic sensors have been incorporated into the front and back of the vest to register any noise produced by the lungs in the thorax, no matter how small. A software program records the signals and electronically amplifies them, while the lungs are depicted visually on a display. As the software knows the position of each individual sensor, it can attribute the data to its precise location. This produces a detailed acoustic and optical picture of the ventilation situation of all parts of the lungs. Here is what makes it so special: As the system collects and stores the data permanently, examinations can take place at any given time and in the absence of hospital staff. Pneumo.Vest also indicates the status of the lungs over a period of time, for example over the previous 24 hours. Needless to say, traditional auscultation can also be carried out directly on the patients. However, instead of carrying out auscultation manually at different points with a stethoscope, a number of sensors are used simultaneously.

“Pneumo.Vest is not looking to make the stethoscope redundant and does not replace the skills of experienced pneumologists. However, auscultation or even CT scans of the lungs only ever present a snapshot at the time of the examination. Our technology provides added value because it allows for the lungs to be monitored continuously in the same way as a long-term ECG, even if the patient is not attached to machines in the ICU but has instead been admitted to the general ward,” explains Ralf Schallert, project manager at Fraunhofer IKTS.

Machine learning algorithms aid with diagnosis
Alongside the acoustic sensors, the software is at the core of the vest. It is responsible for storing, depicting and analyzing the data. It can be used by the doctor to view the acoustic events in specific individual areas of the lungs on the display. The use of algorithms in digital signal processing enables a targeted evaluation of acoustic signals. This means it is possible, for example, to filter out heartbeats or to amplify characteristic frequency ranges, making lung sounds, such as rustling or wheezing, much easier to hear.

On top of this, the researchers at Fraunhofer IKTS are developing machine learning algorithms. In the future, these will be able to structure and classify complex ambient noises in the thorax. Then, the pneumologist will carry out the final assessment and diagnosis.

Discharge from the ICU
Patients can also benefit from the digital sensor alternative. When wearing the vest, they can recover without requiring constant observation from medical staff. They can transfer to the general ward and possibly even be sent home and move about more or less freely. Despite this, the lungs are monitored continuously, and any sudden deterioration can be reported to medical personnel straight away.

The first tests with staff at the University Clinic for Anesthesiology and Intensive Therapy at the University of Magdeburg have shown that the concept is successful in practice. “The feedback from doctors was overwhelmingly positive. The combination of acoustic sensors, visualization and machine learning algorithms will be able to reliably distinguish a range of different lung sounds,” explains Schallert. Dr. Alexander Uhrig from Charité – Universitätsmedizin Berlin is also pleased with the technology. The specialist in infectiology and pneumology at the renowned Charité hospital was one of those who initiated the idea: “Pneumo.Vest addresses exactly what we need. It serves as an instrument that expands our diagnostic options, relieves the burden on our hospital staff and makes hospital stays more pleasant for patients.”

The technology was initially designed for respiratory patients, but it also works well for people in care facilities and for use in sleep laboratories. It can also be used to train young doctors in auscultation.

Increased need for clinical-grade wearables
With Pneumo.Vest, the researchers at Fraunhofer IKTS have developed a product that is cut out for the increasingly strained situation at hospitals. In Germany, 385,000 patients with respiratory or lung diseases require inpatient treatment every year. Over 60 percent are connected to a ventilator for more than 24 hours. This figure does not account for the current increase in respiratory patients due to the COVID-19 pandemic. As a result of increasing life expectancy, the medical industry also expects the number of older patients with breathing problems to increase. With the help of technology from Fraunhofer IKTS, the burden on hospitals and, in particular, costly ICUs can be relieved as their beds will no longer be occupied for quite as long.

It should be added that the market for such clinical-grade wearables is growing rapidly. These are compact medical devices that can be worn directly on the body to measure vital signs such as heartbeat, blood oxygen saturation, respiratory rate or skin temperature. As a medical device that can be used flexibly, Pneumo.Vest fits in perfectly with this development. But do not worry: Doctors will still be using the beloved stethoscope in the future.

Fraunhofer “M³ Infekt” cluster project
Pneumo.Vest is just one part of the extensive M³ Infekt cluster project. Its objective is to develop monitoring systems for the decentralized monitoring of patients. The current basis of the project is the treatment of COVID-19 patients. With the SARS-CoV2 virus, it is common for even mild cases to suddenly deteriorate significantly. By continuously monitoring vital signs, any deterioration in condition can be quickly identified and prompt measures for treatment can be taken.

M3 Infekt can also be used for a number of other symptoms and scenarios. The systems have been designed to be modular and multimodal so that biosignals such as heart rate, ECG, oxygen saturation, or respiratory rate and volume can be measured, depending on the patient and illness.

A total of ten Fraunhofer institutes are working on the cluster project under the leadership of the Fraunhofer Institute for Integrated Circuits IIS in Dresden. Klinikum Magdeburg, Charité – Universitätsmedizin Berlin and the University Hospitals of Erlangen and Dresden are involved as clinical partners.

Whether biodegradable geotextiles, wearables from thermoplastic elastomers or functional textiles from 3D printers - the scope of plastics developed at the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT is wide.

Insights into these projects were provided from October 16th - 23rd  in Düsseldorf: At the K, scientists presented their work on thermally and electrically conductive, biodegradable, bio-based compounds as well as compounds suitable for additive production.
 
Textile composites from the 3D printer
In the "AddiTex" project, plastics were developed that are applied to textiles in layers using 3D printing and give them functional properties. A special challenge in the development was the permanent adhesion: The printed plastic had to be both a strong bond with the textile and sufficiently flexible to be able to participate in movements and twists.

A flexible and flame-retardant compound was developed, which is particularly suitable for use in the field of textile sun and sound insulation, as well as a rigid compound, which is used, among other things, for reinforcing the shape of protective and functional clothing.

Geotextile filter for technical-biological bank protection
Geotextile filters for technical-biological bank protection are the focus of the "Bioshoreline" project. It stands for gradually biodegradable nonwovens, which allow a near-natural bank design of inland waterways with plants. They consist of renewable raw materials and are intended to stabilize the soil in the shore area until the plant roots have grown sufficiently and take over both filter and retention functions. The ageing and biodegradation of the fleeces begin immediately after installation, until the fleeces are gradually completely degraded.

Prototypes of the geotextile filters are currently being tested. Female scientists evaluate the plant mass formed above and below ground with and without geotextile filters as well as the influence of the soil type on plant growth and the biological degradation of the filter.

Wearables made of thermoplastic elastomers
In addition, Fraunhofer UMSICHT is developing novel, electrically conductive and flexible compounds that can be processed into thermoplastic-based bipolar plates. These plastics are highly electrically conductive, flexible, mechanically stable, gas-tight and chemically resistant and - depending on the degree of filling of electrically conductive additives - can be used in many different ways. For example, in electrochemical storage tanks (batteries), in energy converters (fuel cells), in chemical-resistant heat exchangers or as resistance heating elements.

Another possible field of application for these plastics: Wearables. These portable materials can be produced easily and cheaply with the new compounds. It is conceivable, for example, to form garments such as a vest by means of resistance heating elements. The idea behind this is called Power-to-Heat and enables the direct conversion of energy into heat.

FUNDING NOTES

"AddiTex" is funded with a grant from the State of North Rhine-Westphalia using funds from the European Regional Development Fund (ERDF) 2014-2020 "Investments in growth and employment". Project Management Agency: LeitmarktAgentur.NRW – Projektmanagement Jülich.

The "Bioshoreline" project (funding reference: 22000815) is funded by the Federal Ministry of Food and Agriculture (BMEL) on the basis of a resolution of the German Bundestag.