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North Carolina State University
17.01.2023

Embroidery as Low-Cost Solution for Making Wearable Electronics

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.”

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.

 

Source:

North Carolina State University, Rong Yin, Laura Oleniacz

A shirt that monitors breathing. Bild EMPA
28.12.2022

Wearables for healthcare: sensors to wear

Stylish sensors to wear 
With sensors that measure health parameters and can be worn on the body, we do let technology get very close to us. A collaboration between Empa and designer Laura Deschl, sponsored by the Textile and Design Alliance (TaDA) of Eastern Switzerland, shows that medical monitoring of respiratory activity, for example, can also be very stylish – as a shirt.
 
With sensors that measure health parameters and can be worn on the body, we do let technology get very close to us. A collaboration between Empa and designer Laura Deschl, sponsored by the Textile and Design Alliance (TaDA) of Eastern Switzerland, shows that medical monitoring of respiratory activity, for example, can also be very stylish – as a shirt.

Stylish sensors to wear 
With sensors that measure health parameters and can be worn on the body, we do let technology get very close to us. A collaboration between Empa and designer Laura Deschl, sponsored by the Textile and Design Alliance (TaDA) of Eastern Switzerland, shows that medical monitoring of respiratory activity, for example, can also be very stylish – as a shirt.
 
With sensors that measure health parameters and can be worn on the body, we do let technology get very close to us. A collaboration between Empa and designer Laura Deschl, sponsored by the Textile and Design Alliance (TaDA) of Eastern Switzerland, shows that medical monitoring of respiratory activity, for example, can also be very stylish – as a shirt.

The desire for a healthy lifestyle has triggered a trend towards self-tracking. Vital signs should be available at all times, for example to consistently measure training effects. At the same time, among the continuously growing group of people over 65, the desire to maintain performance into old age is stronger than ever. Preventive, health-maintaining measures must be monitored if they are to achieve the desired results. The search for measurement systems that reliably determine the corresponding health parameters is in full swing. In addition to the leisure sector, medicine needs suitable and reliable measurement systems that enable efficient and effective care for an increasing number of people in hospital and at home. After all, the increase in lifestyle diseases such as diabetes, cardiovascular problems or respiratory diseases is putting a strain on the healthcare system.

Researchers led by Simon Annaheim from Empa's Biomimetic Membranes and Textiles laboratory in St. Gallen are therefore developing sensors for monitoring health status, for example for a diagnostic belt based on flexible sensors with electrically conductive or light-conducting fibers. However, other, less technical properties can be decisive for the acceptance of continuous medical monitoring by patients. For example, the sensors must be comfortable to wear and easy to handle – and ideally also look good.

This aspect is addressed by a cooperation between the Textile and Design Alliance, or TaDA for short, in eastern Switzerland and Empa. The project showed how textile sensors can be integrated into garments. In addition to technical reliability and a high level of comfort, another focus was on the design of the garments. The interdisciplinary TaDA designer Laura Deschl worked electrically conductive fibers into a shirt that change their resistance depending on how much they are stretched. This allows the shirt to monitor how much the subjects' chest and abdomen rise and fall while they breathe, allowing conclusions to be drawn about breathing activity. Continuous monitoring of respiratory activity is of particular interest for patients during the recovery phase after surgery and for patients who are being treated with painkillers. Such a shirt could also be helpful for patients with breathing problems such as sleep apnea or asthma. Moreover, Deschl embroidered electrically conductive fibers from Empa into the shirt, which are needed to connect to the measuring device and were visually integrated into the shirt's design pattern.

The Textile and Design Alliance is a pilot program of the cultural promotion of the cantons of Appenzell Ausserrhoden, St.Gallen and Thurgau to promote cooperation between creative artists from all over the world and the textile industry. Through international calls for proposals, cultural workers from all disciplines are invited to spend three months working in the textile industry in eastern Switzerland. The TaDA network comprises 13 cooperation partners – textile companies, cultural, research and educational institutions – and thus offers the creative artists direct access to highly specialized know-how and technical means of production in order to work, research and experiment on their textile projects on site. This artistic creativity is in turn made available to the partners as innovative potential.

Image: Gaharwar Laboratory
13.12.2022

New inks for 3D-printable wearable bioelectronics

Flexible electronics have enabled the design of sensors, actuators, microfluidics and electronics on flexible, conformal and/or stretchable sublayers for wearable, implantable or ingestible applications. However, these devices have very different mechanical and biological properties when compared to human tissue and thus cannot be integrated with the human body.

A team of researchers at Texas A&M University has developed a new class of biomaterial inks that mimic native characteristics of highly conductive human tissue, much like skin, which are essential for the ink to be used in 3D printing.

This biomaterial ink leverages a new class of 2D nanomaterials known as molybdenum disulfide (MoS2). The thin-layered structure of MoS2 contains defect centers to make it chemically active and, combined with modified gelatin to obtain a flexible hydrogel, comparable to the structure of Jell-O.

Flexible electronics have enabled the design of sensors, actuators, microfluidics and electronics on flexible, conformal and/or stretchable sublayers for wearable, implantable or ingestible applications. However, these devices have very different mechanical and biological properties when compared to human tissue and thus cannot be integrated with the human body.

A team of researchers at Texas A&M University has developed a new class of biomaterial inks that mimic native characteristics of highly conductive human tissue, much like skin, which are essential for the ink to be used in 3D printing.

This biomaterial ink leverages a new class of 2D nanomaterials known as molybdenum disulfide (MoS2). The thin-layered structure of MoS2 contains defect centers to make it chemically active and, combined with modified gelatin to obtain a flexible hydrogel, comparable to the structure of Jell-O.

“The impact of this work is far-reaching in 3D printing,” said Dr. Akhilesh Gaharwar, associate professor in the Department of Biomedical Engineering and Presidential Impact Fellow. “This newly designed hydrogel ink is highly biocompatible and electrically conductive, paving the way for the next generation of wearable and implantable bioelectronics.”1 

The ink has shear-thinning properties that decrease in viscosity as force increases, so it is solid inside the tube but flows more like a liquid when squeezed, similar to ketchup or toothpaste. The team incorporated these electrically conductive nanomaterials within a modified gelatin to make a hydrogel ink with characteristics that are essential for designing ink conducive to 3D printing.

“These 3D-printed devices are extremely elastomeric and can be compressed, bent or twisted without breaking,” said Kaivalya Deo, graduate student in the biomedical engineering department and lead author of the paper. “In addition, these devices are electronically active, enabling them to monitor dynamic human motion and paving the way for continuous motion monitoring.”

In order to 3D print the ink, researchers in the Gaharwar Laboratory designed a cost-effective, open-source, multi-head 3D bioprinter that is fully functional and customizable, running on open-source tools and freeware. This also allows any researcher to build 3D bioprinters tailored to fit their own research needs.

The electrically conductive 3D-printed hydrogel ink can create complex 3D circuits and is not limited to planar designs, allowing researchers to make customizable bioelectronics tailored to patient-specific requirements.

In utilizing these 3D printers, Deo was able to print electrically active and stretchable electronic devices. These devices demonstrate extraordinary strain-sensing capabilities and can be used for engineering customizable monitoring systems. This also opens up new possibilities for designing stretchable sensors with integrated microelectronic components.

One of the potential applications of the new ink is in 3D printing electronic tattoos for patients with Parkinson’s disease. Researchers envision that this printed e-tattoo can monitor a patient’s movement, including tremors.

This project is in collaboration with Dr. Anthony Guiseppi-Elie, vice president of academic affairs and workforce development at Tri-County Technical College in South Carolina, and Dr. Limei Tian, assistant professor of biomedical engineering at Texas A&M.
This study was funded by the National Institute of Biomedical Imaging and Bioengineering, the National Institute of Neurological Disorders and Stroke and the Texas A&M University President’s Excellence Fund. A provisional patent on this technology has been filed in association with the Texas A&M Engineering Experiment Station.

1 This study was published in ACS Nano.

Source:

Alleynah Veatch Cofas, Texas A & M University