Automated SEM Image Analysis of the Sphere Diameter, Sphere-Sphere Separation, and Opening Size Distributions of Nanosphere Lithography Masks

Colloidal nanosphere monolayers—used as a lithography mask for site-controlled material deposition or removal—offer the possibility of cost-effective patterning of large surface areas. In the present study, an automated analysis of scanning electron microscopy (SEM) images is described, which enables the recognition of the individual nanospheres in densely packed monolayers in order to perform a statistical quantification of the sphere size, mask opening size, and sphere-sphere separation distributions. Search algorithms based on Fourier transformation, cross-correlation, multiple-angle intensity profiling, and sphere edge point detection techniques allow for a sphere detection efficiency of at least 99.8%, even in the case of considerable sphere size variations. While the sphere positions and diameters are determined by fitting circles to the spheres edge points, the openings between sphere triples are detected by intensity thresholding. For the analyzed polystyrene sphere monolayers with sphere sizes between 220 and 600 nm and a diameter spread of around 3% coefficients of variation of 6.8–8.1% for the opening size are found. By correlating the mentioned size distributions, it is shown that, in this case, the dominant contribution to the opening size variation stems from nanometer-scale positional variations of the spheres.

Size, shape, and orientation of macro-sized substrate protrusions affect the toe and foot adhesion of geckos

Geckos are excellent climbers using compliant, hierarchically-arranged adhesive toes to negotiate diverse terrains varying in roughness at multiple size scales. Here, we complement advancements at smaller size scales with measurements at the macro-scale. We studied the attachment of a single toe and whole foot of geckos on macro-scale rough substrates by pulling them along, across, and off smooth rods and spheres mimicking different geometric protrusions of substrates. When we pulled a single toe along rods, the force increased with the rod diameter. Whereas, the attachment force of dragging toes across rods increased from about 60% on small diameter rods relative to a flat surface to approximately 100% on larger diameter rods, but showed no further increase as rod diameter doubled. Toe force also increased as the pulling changed from along-rod loading to across-rod loading. When pulled off from spheres, toe force increased continuously with sphere diameter as observed in along-rod pulling. For feet with separated toes, attachment on spheres was stronger than that on rods with the same diameter. Attachment force of a foot decreased as rod and sphere size increased, but remained sufficient to support the body weight of geckos. These results provide a bridge to the macro-scale roughness seen in nature by revealing the importance of the dimension, shape, and orientation of macro-sized substrate features for compliant toe and foot function of geckos. Our data not only enhances our understanding of geckos’ environmental adaptive adhesion, but can also provide inspiration for novel robot feet in development.

The Role of Sphere Size in the Context of Pancreatin Therapy for Exocrine Pancreatic Insufficiency: A Systematic Review

While lipase content and appropriate acid protection of pancreatin preparations (PP) are well defined determinants of an effective therapy of exocrine pancreatic insufficiency, the optimal sphere size of PP has remained a matter of discussion. We performed a systematic review to assess the optimal sphere size of enteric coated pancreatin products that may best guarantee coordinated delivery of PP and food to the duodenum. PubMed was searched for studies on gastric emptying of indigestible spheres in the digestive phase, using overlapping search algorithms; identified sources were searched for further leads, extending the investigation to Google Scholar. Of 739 screened publications, 26 were included in the final assessment. Contrary to current guideline recommendations, no scientific evidence was found to support a 2 mm diameter threshold for gastric emptying of indigestible particles. There is no documented advantage of ≤2 mm spheres regarding duodenal delivery and restoring maldigestion. The evolving picture is that of a gradation of sizes, over which gastric emptying becomes slower and more variable as particle size increases. Even 7 mm particles may be emptied from the stomach in conjunction with nutrient uptake. In conclusion sphere size of PP is not the essential parameter for selecting an effective PP fitting all patients. A variety of brands offer different lipase contents and sphere sizes that allow the physician to tailor treatment to the individual patient`s needs.