Molecular modification

A UK company has developed a technology that is claimed to be able to modify a wide range of materials by changing their surface properties at the molecular level.

The Onto (just about anything) platform, developed by Oxford Advanced Surfaces (OAS), involves coating the surface of a substrate with a solution of a reactive molecule via dip or spray, then curing the agent under thermal or photo-irradiation conditions to create a molecular layer that bonds permanently to the substrate. The process could be used to make a hydrophobic material, such as Teflon, hydrophilic.

OAS said that the technology has generated interest from a number of companies wishing to enhance their materials to expand application possibilities, including DuPont Advanced Fiber Systems — the company responsible for Kevlar.

‘In essence, what we do is develop advanced materials by modifying existing materials with specific tailored properties at the surface. We developed a formulation that will carry the chemistry you need to coat the material — that can be anything, a fibre, particle, a roll of film or a tiny diamond.

‘The molecules have a latent reactivant and when exposed to energy in the curing stage — it can be anything, heat, UV, IR — you basically dry it out and carry out the reaction and create ion bonds. It [Onto] will react with anything it sees to create a permanent covalent bond — so if it is looking at the surface it will react with the surface, if it is looking at itself it is going to react with itself,’ said Marcelo Bravo, chief executive of OAS.

According to OAS the coating can be applied to many types of substrates, including synthetic polymers, natural polymers such as cotton and wool, inorganic surfaces such as graphite and glass, and metal surfaces. The company also claims that because the technology can be controlled at the micron level, the modification of a surface can be carried out very precisely, so that two or more sets of functionalities can be applied to a surface either homogenously or with patterning.

‘We have a library of reactivants with a library of functions. Typical examples of stuff we are working on are a lot of wetting [the degree to which a liquid maintains contact with a surface] properties. Take a substrate like Teflon. It’s a very hydrophobic, inert material, and if you are trying to use it, for example in a dielectric in an electronic device, you need to make it wettable if you want to put something such as a dye on top. So we will modify the Teflon so it is hydrophilic.

‘Or, let’s say you have something you need to make hydrophobic, such as trying to control patterns on an electronic device, and you do not want your ink to spread over. We can trace very precise patterns of hydrophobicity or hydrophilicity, or both,’ said Bravo.

In addition to applying wetting properties, the Onto technology can be used for adhesion and biocidal (pathogen destroying) applications.

To achieve adhesion of two incompatible materials, OAS can make them more like each other by changing both surfaces or making changes to just one surface, for example, by applying a coating that acts as a primer for an adhesive.

Acrylate adhesives, for example, do not interact well with some polymers, so the Onto technology could be used to prime the polymer so that it becomes more like acrylate and therefore interact with the acrylate adhesive to create a bond.

In another adhesion application, it may be necessary to create a rough surface on a material, such as glass, which would conventionally be done by etching.

‘We can do a nano-rough coating that puts on the roughness, as an alternative to etching. Sometimes you do not want to do etching because you cannot control it very well, or because you are using an environmentally- troublesome chemical such as chromium,’ said Bravo.

OAS has also developed a regenerable biocidal coating, which would be useful particularly in hospital applications.

‘This is where we put down an anchor that will grab hydrogen peroxide and release it when a bioagent or bug comes in contact with it, but then you can wash that surface with a dilute solution [of hydrogen peroxide] and it [the biocidal capability] will recharge,’ said Bravo.

Anh Nguyen