Beyond hydrogel: Stretchy PDMS optical fibers make better biosensors
A biosensor that uses polydimethylsiloxane (PDMS) dye-doped optical fibers is more thermally and environmentally stable than when using hydrogel fibers.
Laser Focus World recently reported on the development of flexible and stretchable hydrogel optical fibers that, when injected with dye and monitored as a function of wavelength, can provide strain information that allows them to be used as biosensors in a variety of applications. Now, researchers at Tsinghua University (Beijing, China) have developed a similar biosensor using polydimethylsiloxane (PDMS) dye-doped optical fibers that works in the same manner, but is more thermally and environmentally stable than when using hydrogel fibers, which suffer from shrinkage and performance degradation unless they are used in an aqueous environment.
The PDMS fibers have a measured strain precision of <1% and optical loss of <0.25 dB/cm over a 450-850 nm wavelength range. Durability measurements for a 0.5-mm-diameter, 4-cm-long fiber loaded with repeated strains of approximately 100% saw no changes in fiber length, even after 500 repeat strain loads. In fact, strain loading improved to a maximum axial strain of 231% as the fiber diameter decreased. To demonstrate real-time monitoring of finger motion, a PDMS fiber was attached to a wearable glove and accurately recorded strain corresponding to flexion and extension of the fingers with no degradation after 12 cycles. The technology can be adapted to wearable smart devices, and for sport/function performance monitoring and body movement analysis. Reference: J. Guo et al., Optica, 4, 10, 1285-1288 (2017).