Method for microfluidic whole-chip temperature measurement using thin-film poly(dimethylsiloxane)/rhodamine B

Area of Science:

• Microfluidics
• Materials Science
• Optical Measurement Techniques

Background:

• Accurate on-chip temperature monitoring is crucial for microfluidic applications.
• Traditional methods using Rhodamine B dye in microchannels suffer from adsorption/absorption issues and electrophoresis effects.
• A need exists for a robust and reliable temperature sensing method in microfluidic systems.

Purpose of the Study:

• To develop and validate a novel on-chip temperature measurement method using a Rhodamine B-doped poly(dimethylsiloxane) (PDMS) thin film.
• To demonstrate the advantages of this thin film method over traditional in-channel dye injection techniques.
• To enable accurate, whole-chip temperature mapping in microfluidic devices.

Main Methods:

• Fabrication of a PDMS thin film doped with Rhodamine B dye, sandwiched between glass substrates.
• Integration of the thin film with a microchannel molded in a PDMS substrate.
• Utilizing fluorescent intensity visualization for whole-chip temperature measurements.
• Verification through Joule heating experiments in a tapered microchannel and comparison with numerical simulations.

Main Results:

• The PDMS thin film method successfully measured axial temperature gradients, showing good agreement with numerical simulations.
• Errors due to film thickness were analyzed and accounted for.
• The thin film approach eliminated false intensity readings caused by Rhodamine B adsorption into PDMS channels.
• Whole-chip temperature measurements were achieved, and potential electrophoresis effects were mitigated.

Conclusions:

• The novel Rhodamine B-doped PDMS thin film provides a superior method for on-chip temperature measurements in microfluidic systems.
• This technique overcomes limitations of traditional methods, offering enhanced accuracy and reliability.
• The developed method facilitates precise thermal characterization of microfluidic devices.