Micro-Actuated Tunable Hierarchical Silver Nanostructures to Measure Tensile Force for Biomedical Wearable Sensing Applications.

Yong Ho Kwon,Jayer Fernandes,Jae-Jun Kim,Hongrui Jiang,Jiangang Chen

doi:10.3390/mi12050476

Abstract

Commercially available biomedical wearable sensors to measure tensile force/strain still struggle with miniaturization in terms of weight, size, and conformability. Flexible and epidermal electronic devices have been utilized in these applications to overcome these issues. However, current sensors still require a power supply and some form of powered data transfer, which present challenges to miniaturization and to applications. Here, we report on the development of flexible, passive (thus zero power consumption), and biocompatible nanostructured photonic devices that can measure tensile strain in real time by providing an optical readout instead of an electronic readout. Hierarchical silver (Ag) nanostructures in various thicknesses of 20–60 nm were fabricated and embedded on a stretchable substrate using e-beam lithography and a low-temperature dewetting process. The hierarchical Ag nanostructures offer more design flexibility through a two-level design approach. A tensional force applied in one lateral (x- or y-) direction of the stretchable substrate causes a Poisson contraction in the other, and as a result, a shift in the reflected light of the nanostructures. A clear blue shift of more than 100 nm in peak reflectance in the visible spectrum was observed in the reflected color, making the devices applicable in a variety of biomedical photonic sensing applications.

Highlights

The requirement of electronic accessories such as power supplies and data transfer modules for wireless communication further increases the overall weight of the flexible sensors, hindering many of their potential wearable applications
AgAg nanoisland structures thatthat we developed can be Thethin thinfilm filmwith with dewetted nanoisland structures we developed canapbe plied to biomedical photonic sensingsensing applications, in which in thewhich tunability the nanoisland applied to biomedical photonic applications, the of tunability of the structure is key
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Summary

Introduction

The potential causes of these disorders are closely related to continuously applied strains in joints, ligaments, and muscles that hold the internal organs [11,12,13,14,15,16,17]; monitoring the changes of tension forces in real time via flexible sensors could provide much needed data on these strains. Current flexible sensors are not suitable for directly and accurately monitoring such tension forces. Their relatively large sizes make it challenging to attach them to the structural surfaces of the joints, ligaments, and muscles.

Methods

Results

Conclusion