Optothermal Control of Local Fluid Temperature in Microfluidics

Abstract

This paper outlines an optothermal approach to manipulate local fluid temperatures in microfluidic and lab-on-chip systems. The system has the ability to control the size, location and the source heat flux using an external computer and is not constrained by predefined geometries, complex fabrication or control system. The thermal performance is evaluated using a temperature-dependent fluorescent dye. Experiments demonstrate localized heating up to 35°C over ambient temperature for a heat source spanning a downstream length of 1.5 mm. Experimental results are compared with a 1D thermal analysis of the system based on the Taylor-Aris dispersion.

Optothermal Analyte Manipulation With Temperature Gradient Focusing

“…Images were projected onto the surface of the black tape using the abovementioned optical setup controlled by a laptop. We performed in situ temperature field imaging based upon the temperature-dependent quantum efficiency of rhodamine B, using the method introduced by Ross and coworkers [22] and described in our previous work [21]. Briefly, 0.1 mM rhodamine B in 900 mM Tris-borate buffer solution was prepared and introduced into the microchannel.…”

“…The corrected raw images were then normalized with the corrected cold field images. The intensity values of the treated images were then converted to temperature using the intensity vs. temperature calibration, as described by [21]. Figure 1 shows the Gaussian shape steady state temperature profile for no-flow condition along the microchannel produced by a heater size of approximately 1.5 , after taking cross-sectional averaging at each axial location.…”

“…In previous works, the required temperature profile was generated by heating/cooling blocks [4, 17, and 19], peltier elements [18 and 20], and joule heating in a variable cross-section microchannel [4,19]. Here, we use an optothermal heating method [21] to concentrate and manipulate analytes. Major advantages associated with the proposed heating method include control of the size, location and shape of the temperature profile, and also the ability to generate localized heating without need for integrated heating/cooling components, provides the ability to generate a tightly concentrated band in a very short microchannel and transport it to the point of analysis, on demand.…”

A novel fabrication technique to minimize poly(dimethylsiloxane)‐microchannels deformation under high‐pressure operation

“…. The total measured pressure drop is a summation of different effects: where is the pressure drop in the connecting, tube which was measured directly at each flow rate, is the pressure drop in the inlet region, is the pressure drop in the fully developed region of the microchannel, is the pressure drop due to the bends in the microchannel inlet, and is the pressure drop due to the electroviscous effect .…”

“…Akbari et al. showed that and are less than 1% of the pressure drop in the fully developed region, , and therefore they could be neglected. On this basis, the measured pressure drop in the microchannel was related to the pressure drop in the fully developed region of the microchannel once had been determined.…”