Soft dendritic microparticles with unusual adhesion and structuring properties

Abstract

The interplay between morphology, excluded volume and adhesivity of particles critically determines the physical properties of numerous soft materials and coatings1,2,3,4,5,6. Branched particles2 or nanofibres3, nanofibrillated cellulose4 or fumed silica5 can enhance the structure-building abilities of colloids, whose adhesion may also be increased by capillarity or binding agents6. Nonetheless, alternative mechanisms of strong adhesion found in nature involve fibrillar mats with numerous subcontacts (contact splitting)7,8,9,10,11 as seen in the feet of gecko lizards and spider webs12,13,14,15,16,17. Here, we describe the fabrication of hierarchically structured polymeric microparticles having branched nanofibre coronas with a dendritic morphology. Polymer precipitation in highly turbulent flow results in microparticles with fractal branching and nanofibrillar contact splitting that exhibit gelation at very low volume fractions, strong interparticle adhesion and binding into coatings and non-woven sheets. These soft dendritic particles also have potential advantages for food, personal care or pharmaceutical product formulations.

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Fig. 1: Fabrication and properties of soft dendritic colloidal microparticles.
Fig. 2: Conditions for dendricolloid formation.
Fig. 3: Adhesion characteristics of soft dendritic colloidal microparticles.
Fig. 4: Structuring capability of soft dendricolloids in liquid suspensions.

Data availability

All data, experimental details and supplemental analysis are available in the main text or the supplementary material. Further related raw data images and files are available on request from the authors.

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Acknowledgements

This study was supported by grants from US National Science Foundation, no. CMMI-1825476 and partially no. CBET-1604116. We also thank NC State University for support through 2017 Chancellors Innovation Fund Award and Unilever Research. We thank L. Hsiao, S. Khan and M. Dickey for discussions and generously providing their rheometer, goniometer and mechanical testing machine facilities. We thank the Cellular and Molecular Imaging Facility at NC State University for their help with confocal imaging supported by the National Science Foundation (grant no. DBI-1624613).

Author information

The initial discovery of the dendricolloid formation was made by S.R. and O.D.V. The experimental design and data analysis were done by O.D.V., S.R., A.H.W., R.S.B. and S.D.S. The experimental laboratory work on dendricolloid synthesis and characterization was performed by S.R., A.H.W., and R.S.B. S.R. and O.D.V. were primary writers of the manuscript, and O.D.V. was the principal investigator. All authors discussed the results and provided feedback on the manuscript.

Correspondence to Orlin D. Velev.

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Competing interests

S.R. and O.D.V. are inventors on a patent application submitted by NC State University, which covers synthesis and properties of fractal polymer colloids.

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Supplementary information

Supplementary Information

Supplementary text, Video 1 legend, Figs. 1–14, Table 1 and references.

Supplementary Video 1

Three-dimensional confocal reconstruction video of a soft dendritic microparticle.

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Roh, S., Williams, A.H., Bang, R.S. et al. Soft dendritic microparticles with unusual adhesion and structuring properties. Nat. Mater. 18, 1315–1320 (2019). https://doi.org/10.1038/s41563-019-0508-z

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