Temperature measurement of aqueous solution in miniature sample chamber in microscopic system based on near-infrared spectrum

Measurement of the sample temperature in biophysics research is challenging, as the samples are commonly placed in a miniature sample chamber under a microscope. In this study, we proposed a method to measure the temperature of an aqueous solution in miniature sample chambers in a microscopic system. Existing studies show that the absorption coefficient spectrum of water shifts with temperature, especially in the near-infrared (NIR) band. We measured the absorption spectra of water with different temperatures and analyzed them, to build a mathematical model relating the temperature and the spectrum. A setup for temperature measurement in a microscopic system was designed and implemented by coupling a spectrometer and a light source to a microscope. The temperature could be calculated by the spectral data and the mathematical model while simultaneously observing the micro-image of the sample. A series of liquid samples at different temperatures were tested using the setup, and the root mean square error of the calculated temperature is less than 0.5 degrees C. The results demonstrate that the method based on the NIR spectrum can be used for noncontact and quick measurement of the liquid sample temperature in a microscopic system.