Highly Skin-Conformal Laser-Induced Graphene-Based Human Motion Monitoring Sensor

Abstract

Bio-compatible strain sensors based on elastomeric conductive polymer composites play pivotal roles in human monitoring devices. However, fabricating highly sensitive and skin-like (flexible and stretchable) strain sensors with broad working range is still an enormous challenge. Herein, we report on a novel fabrication technology for building elastomeric conductive skin-like composite by mixing polymer solutions. Our e-skin substrates were fabricated according to the weight of polydimethylsiloxane (PDMS) and photosensitive polyimide (PSPI) solutions, which could control substrate color. An e-skin and 3-D flexible strain sensor was developed with the formation of laser induced graphene (LIG) on the skin-like substrates. For a one-step process, Laser direct writing (LDW) was employed to construct superior durable LIG/PDMS/PSPI composites with a closed-pore porous structure. Graphene sheets of LIG coated on the closed-porous structure constitute a deformable conductive path. The LIG integrated with the closed-porous structure intensifies the deformation of the conductive network when tensile strain is applied, which enhances the sensitivity. Our sensor can efficiently monitor not only energetic human motions but also subtle oscillation and physiological signals for intelligent sound sensing. The skin-like strain sensor showed a perfect combination of ultrawide sensing range (120% strain), large sensitivity (gauge factor of ~380), short response time (90 ms) and recovery time (140 ms), as well as superior stability. Our sensor has great potential for innovative applications in wearable health-monitoring devices, robot tactile systems, and human–machine interface systems.

CNT/Graphite/SBS Conductive Fibers for Strain Sensing in Wearable Telerehabilitation Devices

“…However, for capturing joint flexion, it is necessary to employ a tightly-fitted garment made from highly elastic synthetic fibers such as nylon or elastane to ensure textile elongations compliance with skin movement. Generally for wearable sensors, the strain associated with joint flexion is under 50% [ 66 , 67 ] with reported strains varying from ~40% for finger bending [ 68 , 69 , 70 , 71 , 72 ], 23–45% for wrist movement [ 41 , 66 , 68 , 69 , 72 ], 35–63% for elbow flexion [ 68 , 69 , 72 ], and 30–40% for bending of the knee [ 68 , 72 , 73 ]. Values measured with knee flexion sensors are congruent with the motion capture analysis conducted by Wessendorf et al, which provides a value of 44.6% as maximum skin strain (in any direction) associated with the knee joint for full flexion and the extension cycle [ 74 ].…”

Laser Synthesized Graphene and Its Applications

“…A similar app demonstrated in Ref. [61] where graphene was obtained within a polydime (PDMS) matrix and tested against different parts of the body, including facia facial expression and fingers and biceps for body movement. An LIG patter transfer-printed onto a fiberglass composite, allowing in situ structural health of components, with no need for external bonding [62].…”

Highly Sensitive and Stretchable c-MWCNTs/PPy Embedded Multidirectional Strain Sensor Based on Double Elastic Fabric for Human Motion Detection

“…In recent years, flexible strain sensors have experienced rapid development and achieved a series of progresses in many fields like soft robotics [ 1 ], artificial skin [ 2 ], human motion detection [ 3 , 4 ], personal health monitoring [ 5 ], and human-machine interface [ 6 ]. To get better sensitivity and larger workable range, which are the main parameters of the strain sensor, many conductive materials based on semiconductors, nanomaterials, and conductive polymers were used to design strain sensitive sensors, such as ZnO [ 7 , 8 ], ZnSnO 3 [ 9 ], silver nanowire [ 10 ], silver nanoparticles [ 11 ], carbon nanotube [ 12 , 13 ], graphene [ 14 , 15 , 16 ], polypyrrole [ 17 ], and polyaniline [ 18 ], have been applied and coupled to stretchable substrates.…”