  We have experimentally demonstrated an on-chip all-silk fibroin whispering
gallery mode microresonator by using a simple molding and solution-casting
technique. The quality factors of the fabricated silk protein microresonators
are up to 10^5. A high-sensitivity thermal sensor was realized in this silk
fibroin microtoroid with sensitivity of 1.17 nm/K, 8 times higher than previous
WGM resonator based thermal sensors. This opens the way to fabricate
biodegradable and biocompatible protein based microresonators on a flexible
chip for biophotonics applications.
