Pressure sensitive microparticle adhesion through biomimicry of the pollen–stigma interaction

Abstract

Many soft biomimetic synthetic adhesives, optimized to support macroscopic masses (∼kg), have been inspired by geckos, insects and other animals. Far less work has investigated bioinspired adhesion that is tuned to micro- and nano-scale sizes and forces. However, such adhesive forces are extremely important in the adhesion of micro- and nanoparticles to surfaces, relevant to a wide range of industrial and biological systems. Pollens, whose adhesion is critical to plant reproduction, are an evolutionary-optimized system for biomimicry to engineer tunable adhesion between particles and micro-patterned soft matter surfaces. In addition, the adhesion of pollen particles is relevant to topics as varied as pollinator ecology, transport of allergens, and atmospheric phenomena. We report the first observation of structurally-derived pressure-sensitive adhesion of a microparticle by using the sunflower pollen and stigma surfaces as a model. This strong, pressure-sensitive adhesion results from interlocking between the pollen's conical spines and the stigma's receptive papillae. Inspired by this behavior, we fabricated synthetic polymeric patterned surfaces that mimic the stigma surface's receptivity to pollen. These soft mimics allow the magnitude of the pressure-sensitive response to be tuned by adjusting the size and spacing of surface features. These results provide an important new insight for soft material adhesion based on bio-inspired principles, namely that ornamented microparticles and micro-patterned surfaces can be designed with complementarity that enable a tunable, pressure-sensitive adhesion on the microparticle size and length scale.

Safflospermidines from the bee pollen of Helianthus annuus L. exhibit a higher in vitro antityrosinase activity than kojic acid

“…The plant origin of the collected bee pollen was determined from its morphology under SEM, using known SBP as a reference material. The morphology of the bee pollen was homogeneous (Figure 2), spherical in shape with three farrows (tricolporate pollen) and spines (Figure 2), consistent with that of sunflower pollen (Lin et al, 2016).…”

Sexual and natural selection on pollen morphology in Taraxacum

“…). For example, a biomechanical analysis in Helianthus suggests that the pollen spines optimally fit around stigma papillae (Lin et al., ). Morphological matching between stigma and pollen could bring the phenomena of female choice on pollen sculpturing into play in the arena of sexual selection.…”

Attachment-based mechanisms underlying capture and release of pollen grains

“…However, immersing stigmas into liquid makes it difficult to correctly measure the initial adhesion events that are dominated by physical interactions. Since Zinkl & Preuss [10] conceived an alternative method capable of measuring pollen-stigma adhesion in a dry environment [10,11], there have been almost no studies in this topic except the very recent one from Lin et al [12]. Despite the vast diversity in morphologies and secreted liquid of stigmatic surfaces and pollen [13], to the best of our knowledge, the quantitative adhesion measurements of dry pollen have been done only on stigmatic surfaces of a few plant species: Arabidopsis thaliana [10,11] and Helianthus annuus [12].…”