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.
Subscribe to Journal
Get full journal access for 1 year
only $16.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
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.
Alargova, R. G., Bhatt, K. H., Paunov, V. N. & Velev, O. D. Scalable synthesis of a new class of polymer microrods by a liquid–liquid dispersion technique. Adv. Mater. 16, 1653–1657 (2004).
Bahng, J. H. et al. Anomalous dispersions of ‘hedgehog’ particles. Nature 517, 596–599 (2015).
Zhu, J. Brached aramid nanofibers. Angew. Chem. Int. Ed. 56, 11744–11748 (2017).
Pääkkö, M. et al. Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels. Biomacromolecules 8, 1934–1941 (2007).
Khan, S. A. & Zoeller, N. J. Dynamic rheological behavior of flocculated fumed silica suspensions. J. Rheol. 37, 1225–1235 (1993).
Koos, E. & Willenbacher, N. Capillary forces in suspension rheology. Science 331, 897–900 (2011).
Cadirov, N., Booth, J. A., Turner, K. L. & Israelachvili, J. N. Influence of humidity on grip and release adhesion mechanisms for gecko-inspired microfibrillar surfaces. ACS Appl. Mater. Interfaces 9, 14497–14505 (2017).
King, D. R., Bartlett, M. D., Gilman, C. A., Irschick, D. J. & Crosby, A. J. Creating gecko-like adhesives for ‘real world’ surfaces. Adv. Mater. 26, 4345–4351 (2014).
Ge, L., Sethi, S., Ci, L., Ajayan, P. M. & Dhinojwala, A. Carbon nanotube-based synthetic gecko tapes. Proc. Natl Acad. Sci. USA 104, 10792–10795 (2007).
Kwak, M. K., Jeong, H. E. & Suh, K. Y. Rational design and enhanced biocompatibility of a dry adhesive medical skin patch. Adv. Mater. 23, 3949–3953 (2011).
Qu, L., Dai, L., Stone, M., Xia, Z. & Wang, Z. L. Carbon nanotube arrays with strong shear binding-on and easy normal lifting-off. Science 322, 238–243 (2008).
Autumn, K. et al. Adhesive force of a single gecko foot-hair. Nature 405, 681–685 (2000).
Autumn, K. et al. Evidence for van der Waals adhesion in gecko setae. Proc. Natl Acad. Sci. USA 99, 12252–12256 (2002).
Tian, Y. et al. Adhesion and friction in gecko toe attachment and detachment. Proc. Natl Acad. Sci. USA 103, 19320–19325 (2006).
Sahni, V., Harris, J., Blackledge, T. A. & Dhinojwala, A. Cobweb-weaving spiders produce different attachment discs for locomotion and prey capture. Nat. Commun. 3, 1106 (2012).
Kamperman, M., Kroner, E., Del Campo, A., McMeeking, R. M. & Arzt, E. Functional adhesive surfaces with ‘Gecko’ effect: the concept of contact splitting. Adv. Eng. Mater. 12, 335–348 (2010).
Hawthorn, A. C. & Opell, B. D. van der waals and hygroscopic forces of adhesion generated by spider capture threads. J. Exp. Biol. 206, 3905–3911 (2003).
Smoukov, S. K. et al. Scalable liquid shear-driven fabrication of polymer nanofibers. Adv. Mater. 27, 2642–2647 (2015).
Haase, M. F., Stebe, K. J. & Lee, D. Continuous fabrication of hierarchical and asymmetric bijel microparticles, fibers, and membranes by solvent transfer-induced phase separation (STRIPS). Adv. Mater. 27, 7065–7071 (2015).
Procaccia, I. Fractal structures in turbulence. J. Stat. Phys. 36, 649–663 (1984).
Bhushan, B. Adhesion of multi-level hierarchical attachment systems in gecko feet. J. Adhes. Sci. Technol. 21, 1213–1258 (2007).
Arzt, E., Gorb, S. & Spolenak, R. From micro to nano contacts in biological attachment devices. Proc. Natl Acad. Sci. USA 100, 10603–10606 (2003).
Raut, H. K. et al. Gecko-inspired dry adhesive based on micro-nanoscale hierarchical arrays for application in climbing devices. ACS Appl. Mater. Interfaces 10, 1288–1296 (2018).
Huber, G. et al. Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements. Proc. Natl Acad. Sci. USA 102, 16293–16296 (2005).
Israelachvili, J. N. Intermolecular and Surface Forces (Elsevier, 2011).
Johnson, K. L., Kendall, K. & Roberts, A. D. Surface energy and the contact of elastic solids. Proc. R. Soc. A 324, 301–313 (1971).
Lau, K. K. S. et al. Superhydrophobic carbon nanotube forests. Nano Lett. 3, 1701–1705 (2003).
Buhleier, E., Wehner, W. & Vögtle, F. ‘Cascade’- and ‘nonskid-chain-like’ syntheses of molecular cavity topologies. Synthesis 1978, 155–158 (1978).
Hawker, C. J. & Fréchet, J. M. J. Preparation of polymers with controlled molecular architecture. a new convergent approach to dendritic macromolecules. J. Am. Chem. Soc. 112, 7638–7647 (1990).
Astruc, D., Boisselier, E. & Ornelas, C. Dendrimers designed for functions: from physical, photophysical, and supramolecular properties to applications in sensing, catalysis, molecular electronics, photonics, and nanomedicine. Chem. Rev. 110, 1857–1959 (2010).
Butt, H. & Kappl, M. Surface and Interfacial Forces. (John Wiley & Sons, Weinheim, 2009).
Chaudhury, M. K., Weaver, T., Hui, C. Y. & Kramer, E. J. Adhesive contact of cylindrical lens and a flat sheet. J. Appl. Phys. 80, 30–37 (1996).
Spolenak, R., Gorb, S., Gao, H. & Arzt, E. Effects of contact shape on the scaling of biological attachments. Proc. R. Soc. A 461, 305–319 (2005).
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).
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.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
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
Nature Materials (2019)