Composite coating to control biofilm formation and effect of alternate electro-magnetic field H. Kanematsu* 1 , S. Sasaki 1 , Y. Miura 1 , T. Kogo 1 , K. Sano 2 , N. Wada 1 , M. Yoshitake 3 and T. Tanaka 4 Three kinds of composite coating (the common matrix was silane oligomer and titanium organic, tin organic and nickel organic compounds were dispersed in the matrices) specimens on glasses were immersed in a unique Laboratory Biofilm Reacter (LBR) for 12 days. In the LBR, the water was circulated, incorporating ambient germs into the system and biofilm was formed on the specimen set in the LBR. In the LBR, clean water was circulated and the weak alternative electromagnetic field was applied to the water phase. For the biofilm resistant coating (organic titanium or tin composite coating based on silane oligomer), the effect of the applied alternative electromagnetic field was remarkable. Keywords: Biofilm, Biofouling, LBR, Laboratory biofilm reactor, Composite coating, Alternative electromagnetic field, Zeta potential This paper is part of a special issue on biointerfaces and biofouling Introduction Biofilm is a film-like matter produced on materials by bacterial activity. Strictly speaking, it is not any homo- genous film such as some industrial coatings. It is rather inhomogeneous concavo–convex substances attached to the material surfaces. 1–5 The formation of biofilm on material surfaces are composed of multi-steps: 6,7 (i) the formation of conditioning film (ii) the approach and attachment of bacteria to material surface (iii) the repeat of attachment and detachment (iv) biofilm formation and growth (v) and the breakdown of biofilm. The biofilm is critical to solve various industrial problems such as corrosion, deterioration of cooling pipes, etc. However, the safety from the medical viewpoint is the foremost and more direct problem, since biofilm would make it possible for bacteria to survive against many kinds of control factors such as antibacterial agent, chemical or mechanical cleaning, flow, predation, etc. Bacteria would lead to secondary but critical cause for nosocomially acquired infection (hospital infection). Actually, almost 100 thousands patients pass away annually due to the infection acquired in hospitals in the USA, according to a statistics. 8 It means that more effective approaches to solve the problems would be needed in the future. Biofilm is mostly formed on materials surfaces. Therefore, the problem solving from the viewpoint of materials science should be investigated more. However, it has been insufficient and the progress has been delayed. In this paper, we investigated the biofilm formation behaviours and the change with the application of alternative electromagnetic field to the environment around the material by the material scientific approach. Experimental Specimens and raw materials for composite coating Commercial floating glasses were used as substrate. Composite films were formed on the glass specimens. The coating was based on silane compounds and organ- ic metallic compounds were dispersed in them. Three kinds of raw materials for the coating were used: (A) alkoxysilane oligomer including methyl and phenyl (Per- meate, D&D Cooperation, Japan), (B) N-2-(aminoethyl)- 3-aminopropyltrimethoxysilane (KBM-603, Shin-Etsu Chemical Co., Ltd.), (C) tetra-n-butoxytitanium (B-1, Nippon Soda Co., Ltd.), tin acetylacetonato (Sigma- Aldrich Co.) or nickel (II) acetylacetonato dehydrate (Waco Pure Chemical Industries Co.). Coating process Float glasses were cut down to the tiny sheets whose sizes were 1065 cm respectively. They were cleaned in an ultrasonic bath filed with clean water containing various surfactants to remove tiny glass residues and oil components. Then the specimen surfaces were cleaned by distilled water to remove tiny glass residues, oil, etc. Then the surfactant was removed by pure water com- pletely. After cleaning, glass specimens were immersed into a solution composed of hydrogen peroxide solution 1 National Institute of Technology, Suzuka College, Japan 2 D&D Corporation, Japan 3 National Institute for Materials Science, Japan 4 Osaka University, Japan *Corresponding author, email kanemats@mse.suzuka-ct.ac.jp ß 2015 W. S. Maney & Son Ltd. Received 25 July 2014; accepted 8 October 2014 DOI 10.1179/1753555714Y.0000000223 Materials Technology: Advanced Biomaterials 2015 VOL 30 NO B1 B21