Making Soft Optical Sensors More Wearable
- PDF / 1,294,017 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 80 Downloads / 217 Views
MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.64
Making Soft Optical Sensors More Wearable Cindy Harnett University of Louisville J.B. Speed School of Engineering, 2210 S Brook St, Louisville, KY 40208, U.S.A
ABSTRACT This paper discusses new components and approaches to make stretchable optical fiber sensors better meet the power and washability requirements of wearables. First, an allpolymer quick connector allows the light source and photosensor to be quickly detached for washing. Second, the paper investigates the possibility of driving the sensors using ambient light instead of an onboard light source. While optical strain sensors and touch sensors have advantages over electronic ones in wet environments, and the intrinsic stretchability of the fibers is useful for soft robotics and highly conformal wearables, the typical light-emitting diode (LED) light source consumes more power than an electronic resistive or capacitive strain sensor. In this work, ambient light of uniform but unknown intensity is demonstrated to drive an elastomeric optical touch sensor in a differential configuration.
INTRODUCTION Elastomeric optical fibers are a new low-cost, all-polymer sensor material for measuring human activity in textile-borne and wearable formats. Researchers have recently demonstrated coating [1], molding [2], and extrusion-based [3] methods for making stretchable optical fibers. These fibers have a high refractive index core and low refractive index cladding. They transmit less light when stretched thanks to the increased length of the optical path, which includes total internal reflection events at the corecladding interface (Fig. 1). The resulting optical loss coefficient (dB/cm) is a function of core-cladding interface smoothness as well as each material’s intrinsic optical absorbance. Threadlike fibers constructed as in Fig.1 can be applied to fabrics by sewing or adhesives, and cast waveguides can be bonded to finished garments. After their light intensity signals are transformed into electronic signals using optoelectronic sensors, the activity data can be
Figure 1: Optical fiber construction.
Downloaded from https://www.cambridge.org/core. Columbia University - Law Library, on 11 Mar 2020 at 10:29:37, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2020.64
sent over a wireless link for analysis. However, for wearables, practical requirements must be taken into account.
The rest of this manuscript deals with two approaches to improving wearability: a quick connector and an investigation of ambient light as a signal source. The quick connector is briefly introduced in this section, while ambient light sensing is investigated in more detail throughout the rest of the paper.
Quick Connector Wearables with integrated electronics, such as resistive strain sensors and conductivefiber electrodes for sensing the electrical activity of skeletal muscles (electromyography or EMG) commonly transmit analog signal
Data Loading...
