3D optical surface profiler for quantifying leaf surface roughness

Abstract

Biological efficiency of pesticide droplets is affected by leaf surface fine structures; however, few reliable methods exist to physically measure and quantify surface roughness. A 3D optical surface profiler was evaluated for its effectiveness as a novel and reliable method to measure and quantify leaf surface roughness in terms of areal roughness parameters. Evaluations included its accuracy for measuring 3D roughness parameters relating mean roughness length, S a , skewness, S sk , and kurtosis, S ku . Their values were compared with the wettability of seven leaf types ranging from easy-to-wet to very difficult-to-wet. Measurement accuracy was validated by a qualitative visual analysis comparing 3D surface renderings of measured leaf surfaces generated by the profiler and micrographs taken with a scanning electron microscope (SEM). The accuracy was also validated by measuring and comparing the micrometer and sub-micrometer scaled roughness on leaf types with hierarchical (multi-scale) structuring and smooth surfaces. Both the renderings and the SEM showed visual agreement in surface variations from waxes and trichomes. The measured roughness lengths for the multi-scale and smooth surfaces were on the same order of magnitude for micrometer scale roughness, approximately 1×10 0 μm, but different orders of magnitude for sub-micrometer scale roughness, approximately 1×10 −1 μm and 1×10 −3 μm, respectively. Comparisons for S sk and S ku to wettability were inconclusive, however, comparisons between S a and wettability showed a positive linear fit, suggesting that S a could be a viable metric for relating leaf surface roughness to wettability. The results from the micrometer and sub-micrometer scale surface roughness quantification could be used to improve pesticide spray deposition quality, leading to reductions in pesticide use and negative environmental impact.

Noncured Graphene Thermal Interface Materials for High-Power Electronics: Minimizing the Thermal Contact Resistance

“…A 50× Nikon Mirau interferometric objective lens was used to determine the surface profile of the plates. The S q roughness was defined as [ 70 ]: …”

“…The Sq roughness was defined as [65]: 𝑆 𝑞 = √ 1 𝐴 ∬ 𝑍 2 (𝑥, 𝑦) 𝑑𝑥 𝑑𝑦 𝐴 . Here, A is the area and Z(x,y)…”

Sculpting the surface: Structural patterning of plant epidermis

“…Cells apical surfaces can be smooth ( Figures 1 A and 1B) or decorated with minute structures (such as striations seen in Figure 1 D) that must be accounted for to understand epidermis properties. By deploying a 3D surface profiler to quantify precisely leaf roughness in various species, a team of engineers showed that the ability of leaves to wet is highly dependent on the height and relative spacing between the micro/nanofeatures that generate the coarseness ( Abbott and Zhu, 2019 ). Similarly, measuring accurately the geometry of conical cells from flowers displaying UV-absorbing and UV-reflecting sectors revealed that the UV-absorbing regions tend to have higher, more acute, cellular profiles.…”

Roughness measurement of leaf surface based on shape from focus

“…In the manufacturing industry, surface roughness characterization is standardized, whereas, unfortunately, a mature method for surface roughness characterization of leaves is lacking [5]. Pioneers of the field attempted to account for contact angle as a parameter in roughness coefficient [6,7] by contrasting the contact angle of rough surfaces with that of smooth surfaces, where the roughness coefficient is merely a relative and indirect assessment of roughness.…”

“…Besides, AFM can only gain access to onedimensional profile within an action cycle, and its z-range for leaves of many plant species is unacceptably narrow. Optical profiler, a profiler based on optical principles such as phase shifting interferometry, was used to render the surface of plant leaves [5,15]. Using interferometry, speckles formed by white light interferer compose optical sections, and then the leaf surface can be reconstructed from these sections.…”