Laser Induced Periodic Surface Structures (LIPSS) may have numerous applications, ranging from biomaterial applications to LCDs, microelectronic fabrication and photonics. However, in order to control the development of these structures for their particular application, it is necessary to understand how they are generated.
We report our work on investigating the melting that occurs during LIPSS formation. LIPSS were generated on three polymer surfaces - polyethylene terephthalate (PET), amorphous polycarbonate (APC) and oriented crystalline polycarbonate (OPC) - which were irradiated with a polarized ArF excimer laser (193 nm) beam with fluences between 3 and 5 mJ/cm2.
The structures were imaged using a Transmission Electron Microscope (TEM), which facilitated investigation of changes in the polymer structures and consequently the depth of the melt zone that accompanies LIPSS generation.
We also present theoretical calculations of the temperature-depth profile due to the interaction of the low fluence 193 nm laser beam with the polymer surfaces and compare these calculations with our experimental results.
Bone-bonding implants include some of the commonest biomaterials currently used. The useful lifetimes of these materials are limited in part by the capacity of the material to support an intimate bond with the tissue in which they are implanted. A number of materials currently used have either good mechanical properties but poor biological responses, or have the ability to form suitable bonds with bone but lack the requisite strength, wear resistance, etc. In particular, polymeric materials have generally been shown to be inert with respect to bone. We report on our work on developing methods to surface treat polymers to encourage colonisation by bone, either for clinical implantation or in vitro tissue engineering applications. Polymers were treated by one of two methods; either 1) using an excimer laser to machine arrays of grooves in the surface; the periodicity of the grooves was varied from a few hundred nanometers to 10 μm; or 2) using an excimer lamp to affect the chemistry of the surface layer by breaking surface bonds and incorporating atmospheric oxygen. Surface structures of samples treated by method 1 were examined using Scanning Electron Microscopy (SEM), White Light Intereferometry and Atomic Force Microscopy (AFM) and surfaces of samples treated by method 2 were examined by using contact angle measurements which indicated a higher surface energy. The difference in cellular response to the control surfaces and modified surfaces was investigated. In conclusion, these methods provide viable means for altering polymers and may generate improved polymers for bone-bonding applications.