Namib Beetle Inspired Self-Decontaminating Surface from Polyelectrolyte Multilayer

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FIGS. 1A and 1B are scanning electron microscope images of porous polyelectrolyte multilayers.FIG. 6 is an AFM image of a superhydrophilic surface.FIGS. 13C-D are atomic force micrographs of surfaces with extreme wetting properties; FIGS. 14A is a video image showing wetting behavior of surfaces.
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Inventors
Professor Robert Cohen
Department of Chemical Engineering, MIT
External Link (cohengroup.mit.edu)
Professor Michael Rubner
Department of Materials Science and Engineering, MIT
External Link (web.mit.edu)
Xiaoxia Sheng
Department of Materials Science and Engineering, MIT
Lei Zhai
Department of Materials Science and Engineering, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Patterned coatings having extreme wetting properties and methods of making

US Patent 8,153,233
Publications
Patterned Superhydrophobic Surfaces:  Toward a Synthetic Mimic of the Namib Desert Beetle
Nano Lett., May 2 2006, 6 (6), pp. 1213-1217

Applications

Self-decontaminating coatings have applications in the medical, sanitation, architectural, and military industries. In addition, the solution-based process can produce patterns of differing wettability on surfaces that can be used to direct and control the flow of fluids, with potential applications in the creation of microfluidic devices.

Problem Addressed

Superhydrophobic coatings exhibit self-cleaning properties by allowing water droplets to roll across the surface and carry away contaminants without leaving liquid traces. However, existing superhydrophobic coatings lack a mechanism to neutralize bacteria on their surfaces, limiting their utility in environments subject to such contamination. This invention describes a class of patterned surfaces that overcome this limitation by releasing bactericidal agents through localized superhydrophilic regions and defects in the superhydrophobic coating.

Technology

This invention comprises a superhydrophobic coating based on a multilayer microporous polyelectrolyte film covered with several layers of silica or silver nanoparticles chemically modified to confer hydrophobicity. The combination of micron-scale pores and nanometer-scale particles provide the surface texture needed to recreate the Lotus Effect, a naturally occurring superhydrophobic cleaning phenomenon. The pores of the polyelectrolyte film are filled with antibacterial silver nanoparticles.

A pattern of superhydrophilic regions is created by selectively wetting the surface with an alcohol solution containing a superhydrophilic molecule. When bacteria-containing water droplets contact the surface, they accumulate in the hydrophilic regions where they are subject to the antibacterial action of silver ions released by the reservoir of silver nanoparticles in the underlying porous polyelectrolyte film. Since silver nanoparticles are present throughout the polyelectrolyte film, any droplets that accumulate at defects in the superhydrophobic coating are also subject to this antibacterial action.

Antibacterial action at the hydrophilic regions can be further increased by covalently attaching additional antibacterial agents such as quaternary amines.

Advantages

  • Solution-based deposition process can conform to substrate materials of arbitrary shape
  • Combination of releasable and non-releasable biocidal agents provide multi-level antibacterial capability
  • Reservoir of antibacterial nanoparticles provide long-term antibacterial activity