Temperature imaging of water in a microchannel using thermal sensitivity of near-infrared absorption

Abstract

This paper presents a remote and preparation-free method of temperature imaging of aqueous solutions in microchannels of microfluidic chips. The principle of this method is based on the temperature dependency of the near-infrared (NIR) absorption band (ν(2) + ν(3) band) of water. Temperature images were constructed from absorbances in a narrow wavelength range including 1908 nm, the most sensitive to temperature in the band, measured by using an NIR camera and an optical narrow-bandpass filter. Calculation and calibration results demonstrated a linear relationship between the absorption coefficient and temperature with a temperature coefficient of 1.5 × 10(-2) K(-1) mm(-1). Temperature images of 50 μm thick water in a Y-shaped PDMS microchannel locally heated by a neighboring hot wire were obtained, in which thermal diffusion processes in the microchip were visualized. Temperature resolution was estimated to be approximately 0.2 K according to the temperature coefficient and noise level.

Noninvasive sensing of thermal treatments of Japanese seafood products using imaging spectroscopy

“…Moreover, increasing temperature leads to spectral shifts in the spectrum towards shorter wavelengths. However, such a shift in wavelengths when the temperature increased from 20 °C to 80 °C was very tiny and can be neglected (Kakuta et al ., ). As the kamaboko tissue could be modelled as an opaque medium with infinite thickness in the visible to near infrared region, this implies that all photons that are directed to the sample either experiences specular (interface) reflection or penetrates into the first layer of the samples.…”

“…Conventional infrared (IR) imaging based on sensing infrared radiation might be a good choice for noncontact measurement and profiling of temperature, but it essentially detects surface temperatures only. Therefore, an important advantage of the spectral‐based method is that it can average the influence of temperature over the light path within the medium including internal temperatures (Kakuta et al ., ). Accordingly, the underlying aim of this study was to investigate whether the imaging spectroscopy system operated in the short‐wave infrared region (900–2500 nm) can be a viable solution for rapid and noninvasive prediction of thermal treatment of seafood products by developing robust multivariate models for the prediction of core temperatures and thermal history as well as the classification of samples receiving different thermal treatments.…”

Quantitative full-colour transmitted light microscopy and dyes for concentration mapping and measurement of diffusion coefficients in microfluidic architectures

“…Previous work on absorbance imaging in transmitted light microscopy used narrow-band light sources (either via monochromators or band pass filters) in combination with monochrome cameras. 1,2,[8][9][10][11][12][13] Conventional transmitted light microscopes are readily equipped with colour RGB (red-green-blue) cameras. One goal of this work is to establish to what extent full-colour transmitted light imaging using RGB cameras can be combined with suitable dye solutions to enable the simultaneous measurement of multi-component concentration distributions.…”

Simultaneous measurement of temperature and flow field formed by a small heated sphere in water by near-infrared absorption imaging method and particle tracking velocimetry

“…10.21611/qirt.2019.038 In Fig. 1 (a), the absorption band of water, called the ν1 + ν2 + ν3 band [3], is observed and its spectrum depends on the temperature. Figure 1 (b) presents the difference spectra, ΔA, defined as:…”

“…This paper presents a near-infrared (NIR) imaging system that simultaneously measures the temperature and flow fields formed by a 1-mm-diameter steel sphere. The temperature is based on the temperature dependence of an NIR absorption band of water [2,3], Using this NIR-based technique with the Inverse Abel Transform (IAT) [4], we got absorbance difference images of water around the steel sphere and then estimated the temperature distribution. The flow visualization and velocity measurement are implemented by particle tracking velocimetry (PTV) [5].…”