Morphological and chemical characterization of microfabricated fibres for biological applications.

Monodisperse fibres and particulates of different materials with controllable three-dimensional shape, size and chemical composition are of interest in research on toxic respirable fibres as well as wear debris around orthopaedic implants. We have previously demonstrated the production of well-controlled, metal and oxide microfabricated fibres having dimensions 0.1 to 10 microm. While our previous results focused on how controlled fibres can be prepared by microfabrication methods, this paper evaluates property-production relationships for microfabricated fibres. Here we have briefly reviewed the production of 0.1 microm x 0.5 microm x 10 microm microfabricated fibres made by electron beam lithography from evaporated titanium or silicon oxide films using a double lift-off method. We have also analysed the properties of these fibres with respect to morphology and chemical composition, and how they are affected by variations in the production process. Two different solution types have been used to place fibres into liquid suspension and to clean and sterilize them for biological testing. One method involves the use of organic solvents; the other a hydroxide solution and water. While fibre dimensions appear to be material-specific, differences can be corrected for by compensation of the size of the lithographic pattern. Similarly the crystallinity of fibres is material-specific, as is to be expected of evaporated thin films, but should be possible to modify by varying deposition parameters or heat treating, for example. Of the cleaning methods used, the one using an aqueous hydroxide solution is preferred over solvent cleaning, as it is easier to perform and appears to be more effective at removing resist from the fibre suspension.