Soft Electronic Block Copolymer Elastomer Composites for Multi‐Material Printing of Stretchable Physiological Sensors on Textiles

Abstract

Soft and stretchable electronic materials have a number of unique applications, not least within sensors for monitoring human health. Through development of appropriate inks, micro‐extrusion 3D printing offers an appealing route for integrating soft electronic materials within wearable garments. Toward this objective, here a series of conductive inks based on soft thermoplastic styrene–ethylene–butylene–styrene elastomers combined with silver micro‐flakes, carbon black nanoparticles, or poly(3,4‐ethylenedioxythiophene) (PEDOT) conducting polymer additives, is developed. Their electrical and mechanical properties are systematically compared and found to be highly dependent on additive amount and type. Thus, while silver composites offer the highest conductivity, their stretchability is far inferior to carbon black composites, which can maintain conductivity beyond 400% strain. The PEDOT composites are the least conductive and stretchable but display unique properties due to their propensity for ionic conductivity. To integrate these inks, as well as insulating counterparts, into functional designs, a multi‐material micro‐extrusion 3D printing routine for direct deposition onto stretchable, elastic fabrics is established. As demonstration, prototypes are produced for sensing common health markers including strain, physiological temperatures, and electrocardiograms. Collectively, this work demonstrates multi‐material 3D printing of soft styrene–ethylene–butylene–styrene elastomer composites as a versatile method for fabricating soft bio‐sensors.

Stretchable Organohydrogel with Adhesion, Self-Healing, and Environment-Tolerance for Wearable Strain Sensors

“…The overlap of wearable healthcare applications and flexible electronic engineering is guiding the development direction of functional soft materials , and device design integration. , Recently, hydrogel-based wearable sensors with high hydration, tunable functionality, and high sensitivity have shone in fields such as medical devices, − human–machine interfaces, − and flexible electrodes. − For example, Fu et al developed a super-stretchable conductive hydrogel based on triple crosslinking for sensitive monitoring of human physiological motions . Nevertheless, due to the lack of adhesion properties, the conventional hydrogel-based strain sensor required additional assistance to achieve close contact between the sensor and the substrate during usage, which largely impair the accuracy and durability of signal detection. − Meanwhile, these hydrogels were easily damaged during the complex and continuous movement of the human body, which limited their application especially in human health care monitoring.…”

“…The overlap of wearable healthcare applications and flexible electronic engineering is guiding the development direction of functional soft materials 1,2 and device design integration. 3,4 Recently, hydrogel-based wearable sensors with high hydration, tunable functionality, and high sensitivity have shone in fields such as medical devices, 5−8 human−machine interfaces, 9−12 and flexible electrodes.…”