Northwestern University researchers Stoyan K Smoukov, Kyle Bishop, Bartlomiej Kowalczyk, Alexander Kalsin, Bartosz Grzybowski have developed an inexpensive, single-dip method for producing antibacterial and other electrostatic metal coatings on surfaces.
The patent pending coatings are plated from aqueous solutions containing charged nanoparticles. The coatings are stable in common solvents and can be used in applications ranging from antibacterial protection to plasmonics. The nanotechnology is available for licensing from Northwestern University’s Technology Transfer Office.
The patent pending coatings are plated from aqueous solutions containing charged nanoparticles. The coatings are stable in common solvents and can be used in applications ranging from antibacterial protection to plasmonics. The nanotechnology is available for licensing from Northwestern University’s Technology Transfer Office.
This method provides an inexpensive, efficient route to applying antibacterial and other electrostatic coatings of metal nanoparticles on materials. The main advantages are the ease of deposition from aqueous solutions, wide applicability to a variety of substrates and long durability of the coatings. The production process is simple and allows coating of large areas and non-planar surfaces such as micro patterned ones. It allows flexibility in tailoring surface composition, a high degree of control over the coatings thickness, and the re-usability of the plating solutions. The environmentally friendly manufacturing process is easily scaleable and inexpensive. The materials can operate under demanding pH conditions.
The process involves depositing “patchy” coatings of metal nanoparticles (NP) with alternating charge distributions on various types of materials, including polymers, elastomers and semiconductors. Surface adsorption of the NP is driven by cooperative electrostatic interactions and does not require chemical ligation or layer-by layer schemes. The composition and the quality of the coatings can be regulated by the types, charges and the relative concentrations of the NPs used and by the pH. Irrespective of substrate the coatings were NP monolayers with surface coverages of ~65-75%.
Silver coatings are well known to confer bacteriostatic and bactericidal properties to surfaces. Traditional methods for the preparation of such coatings are often material-specific, require numerous coat-rinse steps or are incompatible with corrugated/microstructured surfaces, e.g. for lab on a chip or other micro fluidic devices. The silver nanoparticles can be deposited from a solution onto arbitrarily shaped substrates and can give very thin coatings with total silver content below the safe reference dose.
Antibacterial activity of the coating is attributed to Ag+ cations released from the nanoparticles. The slow rate of release of Ag+ cations from the nanoparticles renders these coatings effective over relatively long periods of time, at least months which is relevant to applications like food packaging. The coatings also have a characteristic hue which provides easily discernible indication of their presence and structural integrity. It can be extended to particles of different metal cores, e.g. antifungal copper NP’s. A new class of super hydrophobic (“water repellant”) coatings can be produced comprising functionalized metal nanoparticles on polymeric surfaces. This will enable nanopoarticle deposition on various types of polymers without the need for material-specific chemical attachment schemes.
Potential applications for the materials are; antibacterial coatings (both Gram positive (S.aureus) and Gram-negative (E.coli) bacteria) on PDMS, polyester, Polyethylene Terephthalate Glycol (PETG), polyethylene terephthalate copolymer (PET) and polystyrene e.g. in protective films of home-appliance products and medical devices e.g. on catheters or siloxane implants. Antibacterial films for large surfaces like ceilings and walls of hospitals, cleanrooms & food prep areas, door handles and bathroom surfaces in airports, and other public places. Other applications are in antifungal coatings; hydrophobic coatings and plasmonics-based detection systems.
STATUS: A patent application has been filed, and Northwestern University seeks to develop the invention.
LIT: Science 312, 420, 2006; Nano Lett., 6, 1896, 2006; JACS 128,15046,2006; JACS 129,6664, 2007
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