Abstract
This study introduces a thermophoretic lab-on-a-chip device to measure the Soret coefficient. We use resistive heating of a microwire on the chip to induce a temperature gradient, which is measured by fluorescence lifetime imaging microscopy (FLIM). To verify the functionality of the device, we used dyed polystyrene particles with a diameter of 25 nm. A confocal microscope is utilized to monitor the concentration profile of colloidal particles in the temperature field. Based on the measured temperature and concentration differences, we calculate the corresponding Soret coefficient. The same particles have been recently investigated with thermal diffusion forced Rayleigh scattering (TDFRS) and we find that the obtained Soret coefficients agree with literature results. This chip offers a simple way to study the thermophoretic behavior of biological systems in multicomponent buffer solutions quantitatively, which are difficult to study with optical methods solely relying on the refractive index contrast.Graphic abstract
Highlights
Soret coefficients quantitatively in systems containing proteins, ligands and buffer compounds
Compared to the temperature distribution, the concentration profile is sharpened near the heated microwire, due to the logarithmic relation between concentration and temperature given by Eq 3
We introduced a thermophoretic chip for measuring Soret coefficients with a confocal microscope including a fluorescence lifetime imaging microscopy (FLIM) unit
Summary
Soret coefficients quantitatively in systems containing proteins, ligands and buffer compounds. Most experimental methods probe the concentration change optically by measuring the refractive index contrast Since these methods are limited to measure thermophoretic properties of binary and specific ternary mixtures, they are not appropriate for proteins in buffer solutions. It turned out that thermophoretic measurements of a protein–ligand system with an established method are difficult to analyze as it is not always possible to separate signal contributions stemming from buffer, ligand and protein simultaneously [24]. Those difficulties could certainly be avoided, if the thermophoretic motion of a protein could be monitored directly using a thermophoretic chip. The results are compared to a recent study of the same particles using a validated optical method referred to as thermal diffusion forced Rayleigh scattering (TDFRS) [23,27]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
