Spider silk-based humidity sensor

We select a section of spider egg sac silk (SESS) from an Araneus ventricosus for humidity sensing. SESSs are composed of tubiliform fibers, which suggests that the silk fibroin is more sensitive to ambient humidity. We employ a section of single mode fiber (SMF) and a section of SESS to configure an interference-cavity structure. The change of ambient humidity will cause a change in the SESS diameter, which will change the length of the interference-cavity. The change of the interference-cavity length will cause the interference spectrum to redshift, and the SESS-based sensor will perform the humidity-sensing characteristic. The testing results indicate that the higher the ambient humidity, the higher the sensitivity. The maximum value of the sensitivity is 0.99 nm/%RH in the humidity range of 90%–99%. The sensor is protected from temperature disturbance, and the temperature sensitivity is 33 pm/°C. Spider silk is a kind of natural moisture-sensitive material, which is environmentally friendly and does not demand additional sensitization. Therefore, the spider silk is very promising candidates for optical-based chemical and biological sensors that are biocompatible, biodegradable, and highly sensitive.