wearable
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Attachable Skin Monitors that Wick the Sweat Away
- A silicone membrane for wearable devices is more comfortable and breathable thanks to better-sized pores made with the help of citric acid crystals. -
A new preparation technique fabricates thin, silicone-based patches that rapidly wick water away from the skin. The technique could reduce the redness and itching caused by wearable biosensors that trap sweat beneath them. The technique was developed by bioengineer and professor Young-Ho Cho and his colleagues at KAIST and reported in the journal Scientific Reports last month.
“Wearable bioelectronics are becoming more attractive for the day-to-day monitoring of biological compounds found in sweat, like hormones or glucose, as well as body temperature, heart rate, and energy expenditure,” Professor Cho explained. “But currently available materials can cause skin irritation, so scientists are looking for ways to improve them,” he added.
Attachable biosensors often use a silicone-based compound called polydimethylsiloxane (PDMS), as it has a relatively high water vapour transmission rate compared to other materials. Still, this rate is only two-thirds that of skin’s water evaporation rate, meaning sweat still gets trapped underneath it.
Current fabrication approaches mix PDMS with beads or solutes, such as sugars or salts, and then remove them to leave pores in their place. Another technique uses gas to form pores in the material. Each technique has its disadvantages, from being expensive and complex to leaving pores of different sizes.
A team of researchers led by Professor Cho from the KAIST Department of Bio and Brain Engineering was able to form small, uniform pores by crystallizing citric acid in PDMS and then removing the crystals using ethanol. The approach is significantly cheaper than using beads, and leads to 93.2% smaller and 425% more uniformly-sized pores compared to using sugar. Importantly, the membrane transmits water vapour 2.2 times faster than human skin.
The team tested their membrane on human skin for seven days and found that it caused only minor redness and no itching, whereas a non-porous PDMS membrane did.
Professor Cho said, “Our method could be used to fabricate porous PDMS membranes for skin-attachable devices used for daily monitoring of physiological signals.”
“We next plan to modify our membrane so it can be more readily attached to and removed from skin,” he added.
This work was supported by the Ministry of Trade, Industry and Energy (MOTIE) of Korea under the Alchemist Project.
Image description:
Smaller, more uniformly-sized pores are made in the PDMS membrane by mixing PDMS, toluene, citric acid, and ethanol. Toluene dilutes PDMS so it can easily mix with the other two constituents. Toluene and ethanol are then evaporated, which causes the citric acid to crystallize within the PDMS material. The mixture is placed in a mould where it solidifies into a thin film. The crystals are then removed using ethanol, leaving pores in their place.
Image credit:
Professor Young-Ho Cho, KAIST
Image usage restrictions:
News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only.
Publication:
Yoon, S, et al. (2021) Wearable porous PDMS layer of high moisture permeability for skin trouble reduction. Scientific Reports 11, Article No. 938. Available online at https://doi.org/10.1038/s41598-020-78580-z
Profile:
Young-Ho Cho, Ph.D
Professor
mems@kaist.ac.kr
https://mems.kaist.ac.kr
NanoSentuating Systems Laboratory
Department of Bio and Brain Engineering
https://kaist.ac.kr
Korea Advanced Institute of Science and Technology (KAIST)
Daejeon, Republic of Korea
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2021.02.22 View 10887 -
‘WalkON Suit 4’ Releases Paraplegics from Wheelchairs
- KAIST Athletes in ‘WalkON Suit 4’ Dominated the Cybathlon 2020 Global Edition. -
Paraplegic athletes Byeong-Uk Kim and Joohyun Lee from KAIST’s Team Angel Robotics won a gold and a bronze medal respectively at the Cybathlon 2020 Global Edition last week. ‘WalkON Suit 4,’ a wearable robot developed by the Professor Kyoungchul Kong’s team from the Department of Mechanical Engineering topped the standings at the event with double medal success.
Kim, the former bronze medallist, clinched his gold medal by finishing all six tasks in 3 minutes and 47 seconds, whereas Lee came in third with a time of 5 minutes and 51 seconds. TWIICE, a Swiss team, lagged 53 seconds behind Kim’s winning time to be the runner-up.
Cybathlon is a global championship, organized by ETH Zurich, which brings together people with physical disabilities to compete using state-of-the-art assistive technologies to perform everyday tasks. The first championship was held in 2016 in Zurich, Switzerland.
Due to the COVID-19 pandemic, the second championship was postponed twice and held in a new format in a decentralized setting. A total of 51 teams from 20 countries across the world performed the events in their home bases in different time zones instead of traveling to Zurich. Under the supervision of a referee and timekeeper, all races were filmed and then reviewed by judges.
KAIST’s Team Angel Robotics participated in the Powered Exoskeleton Race category, where nine pilots representing five nations including Korea, Switzerland, the US, Russia, and France competed against each other.
The team installed their own arena and raced at the KAIST Main Campus in Daejeon according to the framework, tasks, and rules defined by the competition committee. The two paraplegic pilots were each equipped with exoskeletal devices, the WalkON Suit 4, and undertook six tasks related to daily activities.
The WalkON Suit 4 recorded the fastest walking speed for a complete paraplegic ever reported. For a continuous walk, it achieved a maximum speed of 40 meters per minute. This is comparable to the average walking pace of a non-disabled person, which is around two to four kilometers per hour.
The research team raised the functionality of the robot by adding technology that can observe the user’s level of anxiety and external factors like the state of the walking surface, so it can control itself intelligently. The assistive functions a robot should provide vary greatly with the environment, and the WalkON Suit 4 made it possible to analyze the pace of the user within 30 steps and provide a personally optimized walking pattern, enabling a high walking speed.
The six tasks that Kim and Lee had to complete were:1) sitting and standing back up, 2) navigating around obstacles while avoiding collisions, 3) stepping over obstacles on the ground, 4) going up and down stairs, 5) walking across a tilted path, and 6) climbing a steep slope, opening and closing a door, and descending a steep slope.
Points were given based on the accuracy of each completed task, and the final scores were calculated by adding all of the points that were gained in each attempt, which lasted 10 minutes. Each pilot was given three opportunities and used his/her highest score. Should pilots have the same final score, the pilot who completed the race in the shortest amount of time would win.
Kim said in his victory speech that he was so thrilled to see all his and fellow researchers’ years of hard work paying off. “This will be a good opportunity to show how outstanding Korean wearable robot technologies are,” he added.
Lee, who participated in the competition for the first time, said, “By showing that I can overcome my physical disabilities with robot technology, I’d like to send out a message of hope to everyone who is tired because of COVID-19”.
Professor Kong’s team collaborated in technology development and pilot training with their colleagues from Angel Robotics Co., Ltd., Severance Rehabilitation Hospital, Yeungnam University, Stalks, and the Institute of Rehabilitation Technology.
Footage from the competition is available at the Cybathlon’s official website.
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2020.11.20 View 7526 -
Sturdy Fabric-Based Piezoelectric Energy Harvester Takes Us One Step Closer to Wearable Electronics
KAIST researchers presented a highly flexible but sturdy wearable piezoelectric harvester using the simple and easy fabrication process of hot pressing and tape casting. This energy harvester, which has record high interfacial adhesion strength, will take us one step closer to being able to manufacture embedded wearable electronics.
A research team led by Professor Seungbum Hong said that the novelty of this result lies in its simplicity, applicability, durability, and its new characterization of wearable electronic devices.
Wearable devices are increasingly being used in a wide array of applications from small electronics to embedded devices such as sensors, actuators, displays, and energy harvesters.
Despite their many advantages, high costs and complex fabrication processes remained challenges for reaching commercialization. In addition, their durability was frequently questioned. To address these issues, Professor Hong’s team developed a new fabrication process and analysis technology for testing the mechanical properties of affordable wearable devices.
For this process, the research team used a hot pressing and tape casting procedure to connect the fabric structures of polyester and a polymer film. Hot pressing has usually been used when making batteries and fuel cells due to its high adhesiveness. Above all, the process takes only two to three minutes.
The newly developed fabrication process will enable the direct application of a device into general garments using hot pressing just as graphic patches can be attached to garments using a heat press.
In particular, when the polymer film is hot pressed onto a fabric below its crystallization temperature, it transforms into an amorphous state. In this state, it compactly attaches to the concave surface of the fabric and infiltrates into the gaps between the transverse wefts and longitudinal warps. These features result in high interfacial adhesion strength. For this reason, hot pressing has the potential to reduce the cost of fabrication through the direct application of fabric-based wearable devices to common garments.
In addition to the conventional durability test of bending cycles, the newly introduced surface and interfacial cutting analysis system proved the high mechanical durability of the fabric-based wearable device by measuring the high interfacial adhesion strength between the fabric and the polymer film. Professor Hong said the study lays a new foundation for the manufacturing process and analysis of wearable devices using fabrics and polymers.
He added that his team first used the surface and interfacial cutting analysis system (SAICAS) in the field of wearable electronics to test the mechanical properties of polymer-based wearable devices. Their surface and interfacial cutting analysis system is more precise than conventional methods (peel test, tape test, and microstretch test) because it qualitatively and quantitatively measures the adhesion strength.
Professor Hong explained, “This study could enable the commercialization of highly durable wearable devices based on the analysis of their interfacial adhesion strength. Our study lays a new foundation for the manufacturing process and analysis of other devices using fabrics and polymers. We look forward to fabric-based wearable electronics hitting the market very soon.”
The results of this study were registered as a domestic patent in Korea last year, and published in Nano Energy this month. This study has been conducted through collaboration with Professor Yong Min Lee in the Department of Energy Science and Engineering at DGIST, Professor Kwangsoo No in the Department of Materials Science and Engineering at KAIST, and Professor Seunghwa Ryu in the Department of Mechanical Engineering at KAIST.
This study was supported by the High-Risk High-Return Project and the Global Singularity Research Project at KAIST, the National Research Foundation, and the Ministry of Science and ICT in Korea.
-Publication:
Jaegyu Kim, Seoungwoo Byun, Sangryun Lee, Jeongjae Ryu, Seongwoo Cho, Chungik Oh, Hongjun Kim, Kwangsoo No, Seunghwa Ryu, Yong Min Lee, Seungbum Hong*, Nano Energy 75 (2020), 104992.
https://doi.org/10.1016/j.nanoen.2020.104992
-Profile: Professor Seungbum Hong
seungbum@kaist.ac.kr
http://mii.kaist.ac.kr/
Department of Materials Science and Engineering
KAIST
2020.09.17 View 11803 -
‘SoundWear’ a Heads-Up Sound Augmentation Gadget Helps Expand Children’s Play Experience
In this digital era, there has been growing concern that children spend most of their playtime watching TV, playing computer games, and staring at mobile phones with ‘head-down’ posture even outdoors.
To counter such concerns, KAIST researchers designed a wearable bracelet using sound augmentation to leverage play benefits by employing digital technology. The research team also investigated how sound influences children’s play experiences according to their physical, social, and imaginative aspects.
Playing is a large part of enjoyable and rewarding lives, especially for children. Previously, a large part of children’s playtime used to take place outdoors, and playing outdoors has long been praised for playing an essential role in providing opportunities to perform physical activity, improve social skills, and boost imaginative thinking.
Motivated by these concerns, a KAIST research team led by Professor Woohun Lee and his researcher Jiwoo Hong from the Department of Industrial Design made use of sound augmentation, which is beneficial for motivating playful experiences by facilitating imagination and enhancing social awareness with its ambient and omnidirectional characteristics.
Despite the beneficial characteristics of sound augmentation, only a few studies have explored sound interaction as a technology to augment outdoor play due to its abstractness when conveying information in an open space outdoors. There is also a lack of empirical evidence regarding its effect on children's play experiences.
Professor Lee’s team designed and implemented an original bracelet-type wearable device called SoundWear. This device uses non-speech sound as a core digital feature for children to broaden their imaginations and improvise their outdoor games.
Children equipped with SoundWear were allowed to explore multiple sounds (i.e., everyday and instrumental sounds) on SoundPalette, pick a desired sound, generate the sound with a swinging movement, and transfer the sound between multiple devices for their outdoor play.
Both the quantitative and qualitative results of a user study indicated that augmenting playtime with everyday sounds triggered children’s imagination and resulted in distinct play behaviors, whereas instrumental sounds were transparently integrated with existing outdoor games while fully preserving play benefits in physical, social, and imaginative ways.
The team also found that the gestural interaction of SoundWear and the free sound choice on SoundPalette helped children to gain a sense of achievement and ownership toward sound. This led children to be physically and socially active while playing.
PhD candidate Hong said, “Our work can encourage the discussion on using digital technology that entails sound augmentation and gestural interactions for understanding and cultivating creative improvisations, social pretenses, and ownership of digital materials in digitally augmented play experiences.”
Professor Lee also envisioned that the findings being helpful to parents and educators saying, “I hope the verified effect of digital technology on children’s play informs parents and educators to help them make more informed decisions and incorporate the playful and creative usage of new media, such as mobile phones and smart toys, for young children.”
This research titled “SoundWear: Effect of Non-speech Sound Augmentation on the Outdoor Play Experience of Children” was presented at DIS 2020 (the ACM Conference on Designing Interactive Systems) taking place virtually in Eindhoven, Netherlands, from July 6 to 20. This work received an Honorable Mention Award for being in the top 5% of all the submissions to the conference.
Publication:
Hong, J., et al. (2020) ‘SoundWear: Effect of Non-speech Sound Augmentation on the Outdoor Play Experience of Children’. Proceedings of the 2020 ACM Designing Interactive Systems Conference (DIS'20), Pages 2201-2213. Available online at https://doi.org/10.1145/3357236.3395541
Profile: Professor Woohun Leewoohun.lee@kaist.ac.krhttp://wonderlab.kaist.ac.kr
Department of Industrial Design (ID) KAIST
2020.07.28 View 7437 -
Wearable Strain Sensor Using Light Transmittance Helps Measure Physical Signals Better
KAIST researchers have developed a novel wearable strain sensor based on the modulation of optical transmittance of a carbon nanotube (CNT)-embedded elastomer. The sensor is capable of sensitive, stable, and continuous measurement of physical signals. This technology, featured in the March 4th issue of ACS Applied Materials & Interfaces as a front cover article, shows great potential for the detection of subtle human motions and the real-time monitoring of body postures for healthcare applications.
A wearable strain sensor must have high sensitivity, flexibility, and stretchability, as well as low cost. Those used especially for health monitoring should also be tied to long-term solid performance, and be environmentally stable. Various stretchable strain sensors based on piezo-resistive and capacitive principles have been developed to meet all these requirements.
Conventional piezo-resistive strain sensors using functional nanomaterials, including CNTs as the most common example, have shown high sensitivity and great sensing performance. However, they suffer from poor long-term stability and linearity, as well as considerable signal hysteresis. As an alternative, piezo-capacitive strain sensors with better stability, lower hysteresis, and higher stretchability have been suggested. But due to the fact that piezo-capacitive strain sensors exhibit limited sensitivity and strong electromagnetic interference caused by the conductive objects in the surrounding environment, these conventional stretchable strain sensors are still facing limitations that are yet to be resolved.
A KAIST research team led by Professor Inkyu Park from the Department of Mechanical Engineering suggested that an optical-type stretchable strain sensor can be a good alternative to resolve the limitations of conventional piezo-resistive and piezo-capacitive strain sensors, because they have high stability and are less affected by environmental disturbances. The team then introduced an optical wearable strain sensor based on the light transmittance changes of a CNT-embedded elastomer, which further addresses the low sensitivity problem of conventional optical stretchable strain sensors.
In order to achieve a large dynamic range for the sensor, Professor Park and his researchers chose Ecoflex as an elastomeric substrate with good mechanical durability, flexibility, and attachability on human skin, and the new optical wearable strain sensor developed by the research group actually shows a wide dynamic range of 0 to 400%.
In addition, the researchers propagated the microcracks under tensile strain within the film of multi-walled CNTs embedded in the Ecoflex substrate, changing the optical transmittance of the film. By doing so, it was possible for them to develop a wearable strain sensor having a sensitivity 10 times higher than conventional optical stretchable strain sensors.
The proposed sensor has also passed the durability test with excellent results. The sensor’s response after 13,000 sets of cyclic loading was stable without any noticeable drift. This suggests that the sensor response can be used without degradation, even if the sensor is repeatedly used for a long time and in various environmental conditions.
Using the developed sensor, the research team could measure the finger bending motion and used it for robot control. They also developed a three-axes sensor array for body posture monitoring. The sensor was able to monitor human motions with small strains such as a pulse near the carotid artery and muscle movement around the mouth during pronunciation.
Professor Park said, “In this study, our group developed a new wearable strain sensor platform that overcomes many limitations of previously developed resistive, capacitive, and optical-type stretchable strain sensors. Our sensor could be widely used in a variety of fields including soft robotics, wearable electronics, electronic skin, healthcare, and even entertainment.”
This work was supported by the National Research Foundation (NRF) of Korea.
Publication:
Jimin Gu, Donguk Kwon, Junseong Ahn, and Inkyu Park. (2020) “Wearable Strain sensors Using Light Transmittance Change of Carbon Nanotube-Embedded Elastomers with Microcracks” ACS Applied Materials & Interfaces. Volume 12. Issue 9. Available online at https://doi.org/10.1021/acsami.9b18069
Profile:
Inkyu Park
Professor
inkyu@kaist.ac.kr
http://mintlab1.kaist.ac.kr
Micro/Nano Transducers Laboratory (MINT Lab)
Department of Mechanical Engineering (ME)Korea Advanced Institute of Science and Technology (KAIST)
Profile:
Jimin Gu
Ph.D. Candidate
mint9411@kaist.ac.kr
http://mintlab1.kaist.ac.kr
MINT Lab
KAIST ME
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2020.03.20 View 15592 -
Transformative Electronics Systems to Broaden Wearable Applications
Imagine a handheld electronic gadget that can soften and deform when attached to our skin. This will be the future of electronics we all dreamed of. A research team at KAIST says their new platform called 'Transformative Electronics Systems' will open a new class of electronics, allowing reconfigurable electronic interfaces to be optimized for a variety of applications.
A team working under Professor Jae-Woong Jeong from the School of Electrical Engineering at KAIST has invented a multifunctional electronic platform that can mechanically transform its shape, flexibility, and stretchability. This platform, which was reported in Science Advances, allows users to seamlessly and precisely tune its stiffness and shape.
"This new class of electronics will not only offer robust, convenient interfaces for use in both tabletop or handheld setups, but also allow seamless integration with the skin when applied onto our bodies," said Professor Jeong.
The transformative electronics consist of a special gallium metal structure, hermetically encapsulated and sealed within a soft silicone material, combined with electronics that are designed to be flexible and stretchable. The mechanical transformation of the electronic systems is specifically triggered by temperature change events controlled by the user.
"Gallium is an interesting key material. It is biocompatible, has high rigidity in solid form, and melts at a temperature comparable to the skin's temperature," said lead author Sang-Hyuk Byun, a researcher at KAIST.
Once the transformative electronic platform comes in contact with a human body, the gallium metal encapsulated inside the silicone changes to a liquid state and softens the whole electronic structure, making it stretchable, flexible, and wearable. The gallium metal then solidifies again once the structure is peeled off the skin, making the electronic circuits stiff and stable. When flexible electronic circuits were integrated onto these transformative platforms, it empowered them with the ability to become either flexible and stretchable or rigid.
"This technology could not have been achieved without interdisciplinary efforts," said co-lead author Joo Yong Sim, who is a researcher with ETRI. "We worked together with electrical, mechanical, and biomedical engineers, as well as material scientists and neuroscientists to make this breakthrough."
This universal electronics platform allowed researchers to demonstrate applications that were highly adaptable and customizable, such as a multi-purpose personal electronics with variable stiffness and stretchability, a pressure sensor with tuneable bandwidth and sensitivity, and a neural probe that softens upon implantation into brain tissue.
Applicable for both traditional and emerging electronics technologies, this breakthrough can potentially reshape the consumer electronics industry, especially in the biomedical and robotic domains. The researchers believe that with further development, this novel electronics technology can significantly impact the way we use electronics in our daily life.
< Transformative electronics in soft mode,which becomes wearable for outdoor applications.>
Video Material:
https://youtu.be/im0J18TfShk
Publication: Sang-Hyuk Byun, Joo Yong Sim, Zhanan Zhou, Juhyun Lee, Raza Qazi, Marie C. Walicki, Kyle E. Parker, Matthew P. Haney, Su Hwan Choi, Ahnsei Shon, Graydon B. Gereau, John Bilbily, Shuo Li, Yuhao Liu, Woon-Hong Yeo, Jordan G. McCall, Jianliang Xiao, and Jae-Woong Jeong. 2019. Mechanically transformative electronics, sensors, and implantable devices. Science Advances. Volume 5. No. 11. 12 pages. https://doi.org/10.1126/sciadv.aay0418
Link to download the full-text paper: https://advances.sciencemag.org/content/advances/5/11/eaay0418.full.pdf
Profile: Prof. Jae-Woong Jeong, PhD jjeong1@kaist.ac.kr
https://www.jeongresearch.org/
Professor
Bio-Integrated Electronics and Systems Laboratory
School of Electrical Engineering
Korea Advanced Institute of Science and Technology (KAIST) https://www.kaist.ac.kr
Daejeon 34141, Korea
Profile: Sang-Hyuk Byun, PhD Candidate
shbun95@kaist.ac.kr
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2020.01.31 View 6263 -
KAIST Showcases Advanced Technologies at CES 2020
< President Sung-Chul Shin experiencing cooling gaming headset developed by TEGWAY >
KAIST Pavilion showcased 12 KAIST startups and alumni companies’ technologies at the International Consumer Electronics Show (CES) 2020 held in Las Vegas last month. Especially four companies, TEGWAY, THE.WAVE.TALK, Sherpa Space, and LiBEST won the CES 2020 Innovation Awards presented by the Consumer Technology Association (CTA). The CTA selects the most innovative items from among all submissions.
TEGWAY spinned off by KAIST Professor Byung Jin Cho already made international headlines for their flexible, wearable, and temperature immersive thermoelectric device. The device was selected as one of the top ten most promising digital technologies by the Netexplo Forum in 2015, and has been expanded into VR, AR, and games.
THE.WAVE.TALK has developed their first home appliance product in collaboration with ID+IM Design Laboratory of KAIST in which Professor Sang-Min Bae heads as creative director. Their real-time bacteria analysis with smart IoT sensor won the home appliances section.
Sherpa Space and LiBEST are the alumni companies. Sherpa Space’s lighting for plants won the sustainability, eco-design, and smart energy section, and LiBEST’s full-range flexible battery won the section for technology for a better world.
KAIST’s Alumni Association, Development Foundation, and the Office of University-Industry Cooperation (OUIC) made every effort to present KAIST technologies to the global market. President Sung-Chul Shin led the delegation comprising of 70 faculty, researchers, and young entrepreneurs. The KAIST Alumni Association fully funded the traveling costs of 30 alumni entrepreneurs and students, establishing scholarship for the CES participation. Ten young entrepreneurs were selected through the KAIST Startup Awards, and 20 current students preparing to start their own companies were selected via recommendation from the respective departments.
Associate Vice President of the OUIC Kyung Cheol Choi said in excitement, “We received many offers for joint research and investment from leading companies around the world,” adding, “We will continue doing our best to generate global value by developing the innovative technologies obtained from education and research into businesses.”
The KAIST pavilion at CES 2020 showcased:
1. flexible thermoelectric device ThermoReal and cooling gaming headset from TEGWAY,
2. wearable flexible battery from LiBEST,
3. applications such as conductive transparent electrode film and transparent heating film from J-Micro,
4. on-device AI solution based on deep learning model compression technology from Nota,
5. portable high resolution brain imaging device from OBELAB,
6. real-time bacteria analysis technology from THE.WAVE.TALK,
7. conversation-based AI-1 radio service platform from Timecode Archive,
8. light source solutions for different stages in a plant’s life cycle from Sherpa Space,
9. skin attached micro-LED patch and flexible piezoelectric acoustic sensor from FRONICS,
10. real-time cardiovascular measurement device from Healthrian,
11. block chain based mobile research documentation system from ReDWit, and
12. student-developed comprehensive healthcare device using a smart mirror.
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2020.01.13 View 9940 -
New Liquid Metal Wearable Pressure Sensor Created for Health Monitoring Applications
Soft pressure sensors have received significant research attention in a variety of fields, including soft robotics, electronic skin, and wearable electronics. Wearable soft pressure sensors have great potential for the real-time health monitoring and for the early diagnosis of diseases.
A KAIST research team led by Professor Inkyu Park from the Department of Mechanical Engineering developed a highly sensitive wearable pressure sensor for health monitoring applications. This work was reported in Advanced Healthcare Materials on November 21 as a front cover article.
This technology is capable of sensitive, precise, and continuous measurement of physiological and physical signals and shows great potential for health monitoring applications and the early diagnosis of diseases.
A soft pressure sensor is required to have high compliance, high sensitivity, low cost, long-term performance stability, and environmental stability in order to be employed for continuous health monitoring. Conventional solid-state soft pressure sensors using functional materials including carbon nanotubes and graphene have showed great sensing performance. However, these sensors suffer from limited stretchability, signal drifting, and long-term instability due to the distance between the stretchable substrate and the functional materials.
To overcome these issues, liquid-state electronics using liquid metal have been introduced for various wearable applications. Of these materials, Galinstan, a eutectic metal alloy of gallium, indium, and tin, has great mechanical and electrical properties that can be employed in wearable applications. But today’s liquid metal-based pressure sensors have low-pressure sensitivity, limiting their applicability for health monitoring devices.
The research team developed a 3D-printed rigid microbump array-integrated, liquid metal-based soft pressure sensor. With the help of 3D printing, the integration of a rigid microbump array and the master mold for a liquid metal microchannel could be achieved simultaneously, reducing the complexity of the manufacturing process. Through the integration of the rigid microbump and the microchannel, the new pressure sensor has an extremely low detection limit and enhanced pressure sensitivity compared to previously reported liquid metal-based pressure sensors. The proposed sensor also has a negligible signal drift over 10,000 cycles of pressure, bending, and stretching and exhibited excellent stability when subjected to various environmental conditions.
These performance outcomes make it an excellent sensor for various health monitoring devices. First, the research team demonstrated a wearable wristband device that can continuously monitor one’s pulse during exercise and be employed in a noninvasive cuffless BP monitoring system based on PTT calculations. Then, they introduced a wireless wearable heel pressure monitoring system that integrates three 3D-BLiPS with a wireless communication module.
Professor Park said, “It was possible to measure health indicators including pulse and blood pressure continuously as well as pressure of body parts using our proposed soft pressure sensor. We expect it to be used in health care applications, such as the prevention and the monitoring of the pressure-driven diseases such as pressure ulcers in the near future. There will be more opportunities for future research including a whole-body pressure monitoring system related to other physical parameters.”
This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT.
< Figure 1. The front cover image of Advanced Healthcare Materials, Volume 8, Issue 22. >
< Figure 2. Highly sensitive liquid metal-based soft pressure sensor integrated with 3D-printed microbump array. >
< Figure 3. High pressure sensitivity and reliable sensing performances of the proposed sensor and wireless heel pressure monitoring application. >
-ProfileProfessor Inkyu ParkMicro/Nano Transducers Laboratoryhttp://mintlab1.kaist.ac.kr/
Department of Mechanical EngineeringKAIST
2019.12.20 View 11890 -
Wearable Robot 'WalkON Suit' Off to Cybathlon 2020
Standing upright and walking alone are very simple but noble motions that separate humans from many other creatures. Wearable and prosthetic technologies have emerged to augment human function in locomotion and manipulation. However, advances in wearable robot technology have been especially momentous to Byoung-Wook Kim, a triplegic for 22 years following a devastating car accident.
Kim rejoiced after standing upright and walking again by putting on the ‘WalkON Suit,’ the wearable robot developed by Professor Kyoungchul Kong’s team. Even more, Kim won third prize in the powered exoskeleton race at Cybathlon 2016, an international cyborg Olympics hosted by ETH Zurich.
Now Kim and Professor Kong’s team are all geared up for the Cybathlon Championship 2020. Professor Kong and his startup, Angel Robotics, held a kickoff ceremony for Cybathlon 2020 at KAIST on June 24. The 2020 championship will take place in Switzerland.
Only pilots with complete paralysis of the legs resulting from spinal cord injuries are eligible to participate in the Cybathlon, which takes place every four years. Pilots compete against each other while completing everyday tasks using technical assistance systems in six different disciplines: a brain-computer interface race, a functional electrical stimulation bike race, a powered arm prosthesis race, a powered leg prosthesis race, a powered exoskeleton race, and a powered wheelchair race. The 2016 championship drew 66 pilots from 56 teams representing 25 countries.
In the powered exoskeleton race, pilots complete everyday activities such as getting up from a sofa and overcoming obstacles such as stairs, ramps, or slopes and up to four pilots compete simultaneously on tracks to solve six tasks; and the pilot that solves the most tasks in the least amount of time wins the race.
(Kim, a triplegic for 22 years demonstrates walking and climbing the stairs (below photo) wearing the WalkOn Suit during the media day on June 21 at KAIST.)
Kim, who demonstrated walking and climbing the stairs wearing the WalkON Suit during the media day for the Cybathlon 2020 kickoff ceremony on June 21 at KAIST, said, “I have been confined to a wheelchair for more than 20 years. I am used to it so I feel like the wheelchair is one of my body parts. Actually, I don’t feel any big difficulties in doing everyday tasks in wheelchair. But whenever I face the fact that I will never be able to stand up with my own two legs again, I am so devastated.” He continued, “I still remember the day when I stood up with my own two legs by myself after 22 years. It was beyond description.”
The market for wearable robots, especially for exoskeleton robots, is continuing to grow as the aging population has been a major challenge in almost every advanced country. The global market for these robots expects to see annual growth of 41.2% to 8.3 billion US dollars by 2025. Healthcare wearable robots for the elderly and rehabilitation take up the half of the market share followed by wearable robots for industrial and defense purposes.
Professor Kong from the Department of Mechanical Engineering and his colleagues have developed two wearable robot systems in 2014: The "WalkON Suit" for complete paraplegics and “Angel Suit” for those with partial impairment in walking ability such as the elderly and rehabilitation patients.
Professor Kong said after 15 years of basic research, the team is now able to develop its own distinct technologies. He said their robots are powered by non-resistant precision drives with algorithms recognizing the user’s moving intention. Incorporated with prosthetic devices technology from the Severance Rehabilitation Hospital, their control technology has led to the production of a customizable robot suit optimized for each user’s physical condition.
The WalkON Suit, which boasts a maximum force of 250 Nm and maximum rotation speed of 45 RPM, gives the user high-energy efficiency modeled after the physiology of the human leg. It allows users to walk on flat ground and down stairs, climb up and down inclines, and sit and lie down. Currently the battery lasts five to six hours for locomotion and the approximate 25 kg of robot weight still remains a technical challenge to upgrade.
Professor Kong’s team has grafted AR glass technology into the WalkOn Suit that one of his pilots put on for the torch relay of the PyongChang Paralympics in 2018. His team is now upgrading the WalkON Suit 4.0 for next year’s competition. Severance Rehabilitation Hospital will help the seven pilots with their training.
Professor Kong said his goal is to make robots that can make people with disabilities much more independent. He stressed, “Wearable robots should be designed for each single user. We provide a very good graphical user interface so that we can design, check, and also verify our optimized design for users’ best performance.”
(Seven pilots and Professor Kong (fifth from left in second row) pose with guests who joined the Cybathlon 2020 kickoff ceremony. President Shin (fifth from right) made a congratulatory remarks during the ceremony.)
2019.06.25 View 38115 -
Improving Silver Nanowires for FTCEs with Flash Light Interactions
Flexible transparent conducting electrodes (FTCEs) are an essential element of flexible optoelectronics for next-generation wearable displays, augmented reality (AR), and the Internet of Things (IoTs). Silver nanowires (Ag NWs) have received a great deal of attention as future FTCEs due to their great flexibility, material stability, and large-scale productivity. Despite these advantages, Ag NWs have drawbacks such as high wire-to-wire contact resistance and poor adhesion to substrates, resulting in severe power consumption and the delamination of FTCEs.
A research team led by Professor Keon Jae Lee of the Materials Science and Engineering Department at KAIST and Dr. Hong-Jin Park from BSP Inc., has developed high-performance Ag NWs (sheet resistance ~ 5 Ω/sq, transmittance 90 % at λ = 550 nm) with strong adhesion on plastic (interfacial energy of 30.7 J∙m-2) using flash light-material interactions.
The broad ultraviolet (UV) spectrum of a flash light enables the localized heating at the junctions of nanowires (NWs), which results in the fast and complete welding of Ag NWs. Consequently, the Ag NWs demonstrate six times higher conductivity than that of the pristine NWs. In addition, the near-infrared (NIR) of the flash lamp melted the interface between the Ag NWs and a polyethylene terephthalate (PET) substrate, dramatically enhancing the adhesion force of the Ag NWs to the PET by 310 %.
Professor Lee said, “Light interaction with nanomaterials is an important field for future flexible electronics since it can overcome thermal limit of plastics, and we are currently expanding our research into light-inorganic interactions.”
Meanwhile, BSP Inc., a laser manufacturing company and a collaborator of this work, has launched new flash lamp equipment for flexible applications based on the Professor Lee’s research.
The results of this work entitled “Flash-Induced Self-Limited Plasmonic Welding of Ag NW Network for Transparent Flexible Energy Harvester (DOI: 10.1002/adma.201603473)” were published in the February 2, 2017 issue of Advanced Materials as the cover article.
Professor Lee also contributed an invited review in the same journal of the April 3, 2017 online issue, “Laser-Material Interactions for Flexible Applications (DOI:10.1002/adma.201606586),” overviewing the recent advances in light interactions with flexible nanomaterials.
References
[1] Advanced Materials, February 2, 2017, Flash-Induced Self-Limited Plasmonic Welding of Ag NW network for Transparent Flexible Energy Harvester http://onlinelibrary.wiley.com/doi/10.1002/adma.201603473/epdf
[2] Advanced Materials, April 3, 2017, Laser-Material Interactions for Flexible Applications
http://onlinelibrary.wiley.com/doi/10.1002/adma.201606586/abstract
For further inquiries on research:
keonlee@kaist.ac.kr (Keon Jae Lee), hjpark@bsptech.co.kr (Hong-Jin Park)
Picture 1: Artistic Rendtition of Light Interaction with Nanomaterials
(This image shows flash-induced plasmonic interactions with nanowires to improve silver nanowires (Ag NWs).)
Picture 2: Ag NW/PET Film
(This picture shows the Ag NWs on a polyethylene terephthalate (PET) film after the flash-induced plasmonic thermal process.)
2017.04.05 View 9507 -
KAIST and Four Science and Technology Universities Host a Start-up Competition
KAIST and four other science and technology universities, such as Gwangju Institute of Science and Technology (GIST), Ulsan National Institute of Science and Technology (UNIST), Daegu Gyeongbuk Institute of Science and Technology (DGIST), and Pohang University of Science and Technology (POSTECH), hosted a startup competition on November 27, 2015 at the Dongdaemun Design Plaza in Seoul.
Approximately 150 participants including students from the five universities, "angel" investors, and entrepreneurs attended the competition.
The competition was held to promote startups that are based on research achievements in science and technology and to foster entrepreneurs with great potential.
Two hundred and sixty applicants from 81 teams competed this year. Only ten teams made it to the finals.
KAIST students presented two business plans: an experience-centered education platform and mobile taxi-pooling service. Students from other universities presented a brain-stimulating simulation software (GIST), handy smart health trainer (GIST), real-time reporting system for luggage (DGIST), a flower delivery system (UNIST), surveillance and alarm system for stock-related events via machinery studies (UNIST), augmented emotion toys using augmented reality (POSTECH), and a nasal spray for fine dust prevention (POSTECH).
KAIST also displayed an exhibition of “wearable haptic device for multimedia contents” and “next generation recommendation service platform based on one-on-one matching system with high expandability and improved user experience system.”
The winning team received an award from the Minister of Science, ICT and Future Planning of Korea, as well as an opportunity to participate in overseas startup programs over the course of ten days.
Joongmyeon Bae, Director of the KAIST Industry and University Cooperation, who organized the contest, said, “The alumni of Stanford University (USA) has annually created over 5.4 million jobs through startup activities. Likewise, we hope that our event will contribute to job creation by fostering innovative entrepreneurs.”
2015.11.26 View 9434 -
KAIST Hosts the Wearable Computer Contest 2015
“What you see is a compact electronic system on a dust mask, which monitors the amount of dust taken in by a worker and lets other workers know if the person is injured in an industrial site,” said Bum Taek Jung, a Master’s candidate from Sungkyunkwan University during the Wearable Computer Contest 2015 held in KI building of KAIST on November 5, 2015.
He explained his interest in developing this system, “Dust-related respiratory diseases and falling accidents are still prevalent in industrial sites.” He added, “Using the smart dust mask helps monitoring workers’ physical condition in real time, allowing us to cope with accidents in a much more timely manner.” A smart dust mask is a portable device that alerts the user with orange or red light signs when the amount of dust inhaled by the user is higher than the threshold. Its application on a smartphone can also allow project managers to alert the risk of falling accidents to workers by employing a gyroscope and an accelerometer on the mask.
The Wearable Computer Contest 2015 met for the eleventh time at KAIST on November 5-6, 2015. A wearable computer refers to a portable device which users can wear directly on the body or on their clothes while moving. Products that can provide various services by connecting to a smartphone have become increasingly popular. The contest is an excellent opportunity for university students to design creative wearable systems similar to those often depicted in movies and comics.
This year 102 teams from universities all over the nation participated. After screening and evaluation of their presentations, only 8 teams in the product section and 3 teams in the ideas section were selected for the finals. Of the many entries to the contest, the ECG security system caught many people’s attention. The wearable, which attaches to a shirt, acts like an electrocardiogram. By comparing the ECG reading with the one stored in the data server, the wearable can authenticate the user. The system could be widely used by enterprises and financial companies where tight security and authentication are crucial.
The winners of the product and the ideas sections received USD 4,300 and usd 860 respectively along with Minister Prizes from the Minister of Science, ICT and Future Planning of Korea. The Chairman of the contest, Professor Hoi-Jun Yoo from the Electrical Engineering Department of KAIST said, “The contest will be a great opportunity for anyone to have a look at advanced wearable devices developed through close integration of state-of-the-art technologies and creative ideas from young minds.”
2015.11.05 View 7064