Biosensor
systems for wearable continuous monitoring are desired
to be developed into conformal patch platforms. However, developing
such patches is very challenging owing to the difficulty of imparting
materials and components with both high stretchability and high performance.
Herein, we report a fully stretchable microfluidics-integrated glucose
sensor patch comprised of an omnidirectionally stretchable nanoporous
gold (NPG) electrochemical biosensor and a stretchable passive microfluidic
device. A highly electrocatalytic NPG electrode was formed on a stress-absorbing
3D micropatterned polydimethylsiloxane (PDMS) substrate to confer
mechanical stretchability, high sensitivity, and durability in non-enzymatic
glucose detection. A thin, stretchable, and tough microfluidic device
was made by embedding stretchable cotton fabric as a capillary into
a thin polyurethane nanofiber-reinforced PDMS channel, enabling collection
and passive, accurate delivery of sweat from skin to the electrode
surface, with excellent replacement capability. The integrated glucose
sensor patch demonstrated excellent ability to continuously and accurately
monitor the sweat glucose level.
Stretchable piezoelectric nanogenerators (SPENGs) for human kinematics energy harvesting have limited use due to the low stretchability or mechanical robustness and the difficulty of structural design for omnidirectional stretchability. This study reports an efficient, omnidirectionally stretchable, and robust SPENG based on a stretchable graphite electrode on a 3D micropatterned stretchable substrate and a stacked mat of piezoelectric nanofibers. The stacked mat of free‐standing nanofibers is alternatively composed of nanocomposite nanofibers of barium titanate nanoparticles embedded in polyurethane and poly(vinylidene fluoride‐trifluoroethylene) nanofibers. The nanofiber SPENG (nf‐SPENG) exhibits a high stretchability of 40% and high mechanical durability up to 9000 stretching cycles at 30% strain, which are attributed to the stress‐relieving nature of the 3D micropattern on the substrate and the free‐standing stacked hybrid nanofibers. The nf‐SPENG produces a peak open circuit voltage (Voc) and short circuit current (Isc) of 9.3 V and 189 nA, respectively. The nf‐SPENG is demonstrated to harvest the energy from human kinematics while walking when placed over the knee cap of a subject, generating a maximum Voc of 10.1 V. The omnidirectional stretchability, efficiency, facile fabrication process, mechanical durability, environmentally friendly lead‐free components, and response to multimodal straining make this device suitable for self‐powered wearable sensing systems.
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