Inter-Laboratory Research Exchange: Baker Lab Visits Temple University for TIR Dark-Field Microscopy demonstration

Inter-laboratory research exchanges are a key component to the advancement of science within CSENND and beyond, as they play a pivotal role in the educational and professional development of our members.

Graduate students from the Baker lab (Texas A&M University) visited Temple University (Willets’ Lab) at the end of 2025, for a demonstration and hands on-experience with total internal reflection (TIR) dark-field microscopy. Their goal was to learn microscopy techniques that could help improve the location of particles in scanning electrochemical cell microscopy measurement (SECCM) experiments. The demonstration included an overview of optical microscopy fundamentals, including how dark-field imaging is achieved using a white-light source on an inverted optical microscope, an explanation of the differences between epi-illumination and TIR, and how epi-illumination aligns the laser to directly illuminate the entire sample, whereas TIR relies on high angle incident light to selectively excite the sample with the remaining evanescent wave.

Following the demonstration, the Baker lab was able to practice basic laser safety, aligning the laser using various optics on an optical breadboard, and making fine optical adjustments. They then returned to the microscope to image a rhodamine 6G fluorescent sample under TIR conditions, where they learned how to properly load and bring a sample into focus, and see how fluorescence can be used to fine-tune the optics to confirm TIR alignment. Once fluorescence TIR was achieved, they transitioned to dark-field TIR imaging. To conclude the visit, they examined samples containing particles of different shapes in both air and water, to observe how scattering behavior and TIR conditions changed.

On a fun note, Josselyn De León saw snow for the first time!
(Pictured: Zac O’Dell, Kathleen Bailey, Josselyn De León, & Sanjay Sridhar)