An all-silica steering wheel photonic crystal fiber (SW-PCF) device with real-time analysis for cellular temperature
sensing is presented. Results are provided for water-filled SW-PCF fibers experiencing cooling down near -40°C.
Cellular temperature sensors with fast response times are of interest particularly to the study of cryopreservation, which
has been influential in applications such as tissue preservation, food quality control, genetic engineering, as well as drug
discovery and in- vitro toxin testing. Results of this investigation are relevant to detection of intracellular ice formation
(IIF) and better understanding cell freezing at very low temperatures.
IIF detection is determined as a function of absorption occurring within the core of the SW-PCF. The SW-PCF has a
3.3μm core diameter, 125μm outer diameter and steering wheel-like air hole pattern with triangular symmetry, with a
20μm radius. One end of a 0.6m length of the SW-PCF is placed between two thermoelectric coolers, filled with ~0.1μL
water. This end is butt coupled to a 0.5m length of single mode fiber (SMF), the distal end of the fiber is then inserted
into an optical spectrum analyzer. A near-IR light source is guided through the fiber, such that the absorption of the
material in the core can be measured. Spectral characteristics demonstrated by the optical absorption of the water
sample were present near the 1300-1700nm window region with strongest peaks at 1350, 1410 and 1460nm, further
shifting of the absorption peaks is possible at cryogenic temperatures making this device suitable for IIF monitoring