Application Note | Biological Surface Topography
Seed Surface Topography Measurement Using 3D Profilometry
Roughness, Texture Direction and Groove Height on Tomato and Lettuce Seeds
Research & Experimental Testing
Andrea Novitsky
Visual Design & Editorial
Andrew Shore
Introduction
The surface topography and overall surface features present on common seeds provide a great visual example of the capabilities of the NANOVEA 3D Non-Contact Profilometer. Seeds are small, and most of their intricate surface features are not discernible by eye, but this is no problem for the resolution and accuracy of the profilometer. The profilometer’s analysis software also offers a wide range of studies applicable to these unique surfaces.
Importance of 3D Non-Contact Profilometry for Surface Topography
Unlike other techniques such as touch probes or interferometry, the 3D Non-Contact Profilometer, using axial chromatism, can measure nearly any surface; sample sizes can vary widely due to open staging and there is no sample preparation needed. Nano through macro range is obtained during surface profile measurement with zero influence from sample reflectivity or absorption, with advanced ability to measure high surface angles and no software manipulation of results. It easily measures any material: transparent, opaque, specular, diffusive, polished, rough, etc. The technique of the non-contact profilometer provides an ideal, broad and user friendly capability to maximize surface studies, along with the benefits of combined 2D and 3D capability.
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Measurement Objective
In this application, the NANOVEA ST400 Profilometer is used to measure the surface of a tomato seed and a romaine lettuce seed. The entire surface of each seed was scanned with a high resolution. Various analyses are used to characterize the surfaces, including surface roughness, contour analysis and texture direction.
NANOVEA ST400 Standard
Optical 3D Profilometer
Results
3D Surface
The 3D view and false color view of the seeds show a complex surface structure. They provide users a straightforward tool to directly observe the morphology of the surface from different angles. The overall form was then removed from the surface in order to calculate the local surface roughness of the seeds, and the texture direction of the lettuce seed.
2D Surface Analysis
Line profiles can also be extracted from the surface to show a cross-sectional view of the seed surface. The contour analysis and step height studies were used to measure precise dimensions of the seeds’ surface features.
Conclusion
In this application, we have shown how the NANOVEA 3D Non-Contact Profilometer can precisely characterize a wide range of surface features. The tomato and lettuce seeds had a local surface roughness of 4.858 µm and 11.03 µm, respectively. Texture direction analysis was also used to determine the most significant angle of the lettuce seed grooves, 0.234°. From the profile view, the lettuce seed grooves were found to be between 19 and 30 µm high. The data shown here represents only a portion of the calculations available in the analysis software.
Frequently Asked Questions About Seed Surface Measurement
Why scan seeds with a 3D profilometer?
Seeds are small, with intricate surface features that are not discernible by eye; the non-contact profilometer resolves them with high resolution and accuracy, and its software offers a wide range of analyses.
How rough are the seed surfaces?
After form removal, the local roughness Sa was 4.858 µm for the tomato seed and 11.03 µm for the lettuce seed (ISO 25178).
Do the lettuce seed grooves have a direction?
Yes. Texture direction analysis gave a most significant angle of 0.234°, along the length of the seed, with a texture isotropy of 15.63%.
How high are the lettuce seed grooves?
Step height analysis on a cross-section found the grooves to be between 19 and 30 µm high.
Does the sample need preparation?
No. Axial chromatism measures without contact or sample preparation, with zero influence from reflectivity or absorption.
What other analyses are possible?
Contour analysis of cross-section profiles gives precise dimensions of surface features, alongside 3D views, form removal, roughness and texture direction.
