Thermophoretic microfluidic cells for evaluating Soret coefficient of colloidal particles

Namkyu Lee, Shilpa Mohanakumar, Simone Wiegand

Research output: Contribution to journalArticlepeer-review


Thermodiffusion or thermophoresis gained much interest in bio, chemical, and energy engineering. Although there are several methods to measure thermophoresis, they consume large sample volumes, are limited to binary mixtures, and give only indirect access to the applied temperature profile. Herein, we propose a thermophoretic microfluidic cell for quantitative measurements of the Soret coefficient of colloids. The actual microscale measuring channel lies between cooling and heating channels to achieve a one-dimensional temperature gradient. Fluorescence lifetime imaging microscopy with Rhodamine B is utilized to measure the spatial temperature profile in the channel. The fluorescence intensity of fluorescently labeled polystyrene particles with a diameter of 25 nm is used to monitor the concentration profile. The observed temperature and concentration profiles are one-dimensional, as gradients in the longitudinal and height directions can be neglected. In the investigated temperature range, the averaged difference between the measured Soret coefficients with the cell and determined with the Thermal Diffusion Forced Rayleigh Scattering set-up is less than 8%.

Original languageEnglish
Article number123002
JournalInternational Journal of Heat and Mass Transfer
Publication statusPublished - 2022 Sept 15

Bibliographical note

Funding Information:
We thank the JCNS workshop and ZEA 1 for their advice and fabrication of the cells. We are grateful to Jan Dhont for inspiring ideas and his generous support of our work. NL acknowledges the support by the Humboldt foundation and SM acknowledges the support by the International Helmholtz Research School of Biophysics and Soft Matter (BioSoft).

Publisher Copyright:
© 2022 Elsevier Ltd

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes


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