Characterization of Surfacesthat Generate Structural Colorby Total Internal Reflection

Our research involves the design of microstructures that generate interferencecolors. Our first report of this optical mechanism appeared in Goodling, A.
E., et al. (2019). “Colouration by total internal reflection and interference at
microscale concave interfaces.” Nature 566(7745): 523-527. Light bounces bytotal internal reflection within the microstructures and optical interference
occurs between light rays undergoing different paths of reflection.
We design microstructured surfaces to control the reflection of the light andthe colors produced. We need to measure the surface topography to be able
to correlate optical properties with the surface geometries. The geometries ofthe microstructures, such as their depth, width, angles, and surface roughness
impact the optical properties. We use the optical profilometer to characterize
the surface profiles of the microstructures and the uniformity across thesurface. Sometimes our structures have steep angles, so being able to use
different modes of surface profiling is important to get the most accurate
determination of the microstructure geometry.
CASE STUDY CHARACTERIZATION OF SURFACES THAT GENERATE STRUCTURAL COLOR BY TOTALINTERNAL REFLECTION

Penn State University,Department of Chemistryand Department of Materials
Science and Engineering. TheDepartment of Chemistry atPenn State offers excellence inthe chemical sciences througha vibrant and collaborative
academic community.
Authors: Lauren Zarzar, Nate
Sturniolo, Caleb Meredith, andAmy Goodling.

1■ Measurements

2CASE STUDY CHARACTERIZATION OF SURFACES THAT GENERATE STRUCTURAL COLOR BY TOTALINTERNAL REFLECTION

■ Conclusions
Using the profilometer, we have been able to image our microstructured
surfaces with high spatial resolution in XYZ to yield important information
regarding the surface roughness of our samples, reproducibility after structural
replication, and variation across the surface that may impact the opticalproperties. Sensofar’ S lynx profilometer was the best option for us because of
the versatility in imaging modes available. Sometimes we need high accuracy
in the height distribution across the surface and choose to use white lightinterference. Other times we need to get information on the sidewalls of themicrostructures that have relatively steep angles, so confocal imaging is better.
By choosing to use Sensofar’ S lynx, we have access to both of these imaging
modalities which means we can get even more information about our sample
than just using a confocal profiler or white light interferometer on its own.
Sensofar worked closely with us to choose the specific profilometer and addon options that worked best for specific samples and imaging needs.

■ References
1.		 Goodling, A. E., et al. (2019). Colouration by total internal reflection andinterference at microscale concave interfaces. Nature 566(7745): 523-527.
2.		 Goodling, A. E., et al. (2020). Tunable and Responsive Structural Color fromPolymeric Microstructured Surfaces Enabled by Interference of Totally
Internally Reflected Light. ACS Materials Letters 2(7): 754-763.

CASE STUDY CHARACTERIZATION OF SURFACES THAT GENERATE STRUCTURAL COLOR BY TOTALINTERNAL REFLECTION

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