Strain-Insensitive Biocompatible Temperature Sensor Based on DNA Solid Film on an Optical Microfiber

We demonstrated a biocompatible and highly sensitive temperature sensor using DNA-CTMA (DNA-Cetyl trimethyl ammonium) solid film deposited on micro-tapered fiber. The micro-tapered silica fiber provided a built-in interferometer that was inherently sensitive to the environment variation due to the enhancement of evanescent wave interaction. The tapered region was coated with DNA-CTMA film with a high thermo-optic coefficient enabling a high-temperature sensitivity higher than -0.9 nm/°C in the bio-medically important region from 35 to 80 °C in a water bath. The cross-sensitivity problem between the temperature-sensing and the strain-sensing was successfully resolved since the elastic properties of the DNA-CTMA film on the micro-tapered silica fiber resulted in a very low strain sensitivity of -7 pm/με . Detailed procedures for device fabrication and optical characterization of the proposed device were described.