Abstract
The advent of nanotechnology has opened the possibility of fabricating nanoscopic pillars on the surface of polymeric films mimicking the Gecko’s foot, in an attempt to increase their adhesive capabilities enhanced by van der Waals forces. However, these forces are considerably weakened in a wet physiological environment. To circumvent this loss in force, current biocompatible adhesives with nanopillars require complex multiple-step fabrication, including an extra layer of adhesive coating to stabilize tissue bonding under physiological conditions. In this report, we describe a simple one-step fabrication process of a single-layer chitosan film that has pillars with base diameter in the range of 100–600 nm and a height of ~70 nm. The nanostructured adhesive is laser-bonded to tissue and does not require pillar coating to enhance bonding in water. In comparison with a ‘flat’ adhesive (without pillars), the nanostructured adhesive bonded significantly stronger to tissue under either stress or pressure. Atomic force spectroscopy also confirmed the superior bonding capability of the nanostructured adhesive. This study demonstrates a one-step fabrication technique to produce a monolayer gecko-inspired adhesive that is biocompatible and bonds effectively to tissue. A gecko-inspired adhesive that retains its adhesion in wet environments and can be easily fabricated has been demonstrated. Gecko-inspired adhesives have strong adhesion due to nanoscale protrusions that maximize the surface area and hence Van der Waals forces, but they tend to lose their sticking power in the wet. Although biocompatible adhesives that are suitable for wet conditions have been produced, they require an extra layer and complex fabrication processes. Now, Antonio Lauto of Western Sydney University in Australia and his co-workers report a single-layer chitosan film with nanoscale pillars that can be fabricated by a simple one-step process involving dry casting. The film bonds strongly to tissue on laser irradiation, making it promising for biomedical applications such as facilitating wound sealing and tissue repair. This study describes a simple one-step fabrication process of a chitosan film that has nanoscale pillars. The adhesive is laser-bonded to tissue and does not require pillar coating to enhance bonding in water. In comparison with a ‘flat’ adhesive without pillars, the nanostructured adhesive bonded significantly stronger to tissue under either stress or pressure. This adhesive combines two mechanisms for tissue bonding: one based on the nanopatterned surface that increases the adhesion strength over short distances (van der Waals and electrostatic interactions) and another based on elastic interaction with polymer chains over much longer distances.
Highlights
Since the adhesion mechanism of the Gecko’s foot has been described,[1] researchers have designed and fabricated adhesive films mimicking the lizard’s toes, which contain arrays of keratin fibrils ~ 100 μm long and ~ 5 μm wide with a very high density (5000 mm − 2)
The advent of nanotechnology has opened the possibility of fabricating nanoscopic pillars on the surface of polymeric films mimicking the Gecko’s foot, in an attempt to increase their adhesive capabilities enhanced by van der Waals forces
Setae terminate in numerous nanosized branches named spatulae with a diameter ranging between 200 and 400 nm
Summary
Samuel J Frost[1], Damia Mawad[2,3], Michael J Higgins[4], Herleen Ruprai[1], Rhiannon Kuchel[5], Richard D Tilley[5], Simon Myers[1,6], James M Hook[5] and Antonio Lauto[1,6,7]. The advent of nanotechnology has opened the possibility of fabricating nanoscopic pillars on the surface of polymeric films mimicking the Gecko’s foot, in an attempt to increase their adhesive capabilities enhanced by van der Waals forces. These forces are considerably weakened in a wet physiological environment. To circumvent this loss in force, current biocompatible adhesives with nanopillars require complex multiple-step fabrication, including an extra layer of adhesive coating to stabilize tissue bonding under physiological conditions. NPG Asia Materials (2016) 8, e280; doi:10.1038/am.2016.73; published online 17 June 2016
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