3D printed sensors enable the production of flexible e-textiles

Traditional military training often relies on standardized methods, which limits the provision of optimized training tailored to individual combatants’ characteristics or specific combat situations. To address this, a research team from Korea Advanced Institute of Science and Technology (KAIST) has developed an e-textile platform, securing core technology that can reflect the unique traits of individual combatants and various combat scenarios. This technology has proven robust enough for battlefield use and is economical enough for widespread distribution to a large number of troops.

Professor Steve Park’s research team at KAIST’s Department of Materials Science and Engineering has developed a flexible, wearable electronic textile (e-textile) platform using 3D printing technology that ‘draws’ electronic circuits directly onto fabric. The research is published in the journal npj Flexible Electronics.

The wearable e-textile platform developed by the research team combines 3D printing with new materials engineering design to directly print flexible and highly durable sensors and electrodes onto textile substrates. This enables the collection of precise movement and human body data from individual combatants, which can then be used to propose customized training models.

Existing e-textile fabrication methods are often complex or limited in their ability to provide personalized customization. To overcome these challenges, the research team adopted Direct Ink Writing (DIW) 3D printing.

This technology involves directly dispensing and printing special ink, which functions as sensors and electrodes, onto textile substrates in desired patterns. This allows for the flexible implementation of various designs without the complex process of mask fabrication. This is expected to be an effective technology that can be easily supplied to hundreds of thousands of military personnel.

The core of this technology lies in the development of high-performance functional inks based on advanced materials engineering design. The research team combined styrene-butadiene-styrene (SBS) polymer, which provides flexibility, with multi-walled carbon nanotubes (MWCNT) for electrical conductivity.

They developed a tensile/bending sensor ink that can stretch up to 102% and maintain stable performance even after 10,000 repetitive tests. This means that accurate data can be consistently obtained even during the strenuous movements of combatants.

Furthermore, new material technology was applied to implement ‘interconnected electrodes’ that electrically connect the upper and lower layers of the fabric. The team developed an electrode ink combining silver (Ag) flakes with rigid polystyrene (PS) polymer, precisely controlling the impregnation level (how much the ink penetrates the fabric) to effectively connect both sides or multiple layers of the fabric. This secures the technology for producing multi-layered wearable electronic systems integrating sensors and electrodes.

The research team then proved the platform’s performance through actual human movement monitoring experiments. They printed the e-textile on major joint areas of clothing (shoulders, elbows, and knees) and measured movements and posture changes during various exercises such as running, jumping jacks, and push-ups in real-time.

Additionally, they demonstrated the potential for applications such as monitoring breathing patterns using a smart mask and recognizing objects through machine learning, and perceiving complex tactile information by printing multiple sensors and electrodes on gloves. These results show that the developed e-textile platform is effective in precisely understanding the movement dynamics of combatants.

This research is an important example demonstrating how cutting-edge new material technology can contribute to the advancement of the defense sector. Major Kyusoon Pak of the Army, who participated in this research, considered required objectives such as military applicability and economic feasibility for practical distribution from the research design stage. “Our military is currently facing both a crisis and an opportunity due to the decrease in military personnel resources caused by the demographic cliff and the advancement of science and technology. Also, respect for life on the battlefield is emerging as a significant issue,” he said. “This research aims to secure original technology that can provide customized training according to military branch/duty and type of combat, thereby enhancing the combat power and ensuring the survivability of our soldiers. I hope this research will be evaluated as a case that achieved both scientific contribution and military applicability.”