Natural spider silk as a photonics component for humidity sensing

Area of Science:

• Biomaterials Science
• Photonics
• Sensing Technology

Background:

• Biological microfibers offer diverse functionalities for photonic applications.
• Spider silk, a natural biomaterial, presents unique properties for advanced material development.

Purpose of the Study:

• To demonstrate a humidity detection technique utilizing spectral tuning of whispering gallery modes (WGMs).
• To explore the application of spider egg sac silk (SpEss) as a microresonator for humidity sensing.

Main Methods:

• Excitation of WGMs in a cylindrical SpEss microresonator using a supercontinuum laser and tapered single-mode fiber.
• Monitoring shifts in WGM resonant dips in response to changes in ambient relative humidity (RH).

Main Results:

• The SpEss-based sensor exhibited average and maximum testing sensitivities of 389.1 pm/%RH and 606.7 pm/%RH, respectively, within the 20%-75% RH range.
• A fast response time of 494 ms and good repeatability with <8% fluctuations were observed.
• Humidity-induced changes in SpEss diameter and refractive index were correlated with WGM spectral shifts.

Conclusions:

• Spider egg sac silk is a viable material for developing high-performance humidity sensors.
• The SpEss-based sensor demonstrates potential for biodegradable and biocompatible biochemical sensing applications.
• This technique expands the utility of natural silk materials in optical sensing.