Novel full platinum nanoprobes suitable for biological SPM experiments

We present the fabrication and characterization of hybrid SPM probes with full platinum (Pt) cantilever and tip for biological SPM experiments. In recent years, SPM has shown its value in imaging and characterizing biological samples. Classic SPM sensors for biological experiments exist of Silicon (Si) or Silicon Nitride (SiN). The need however for better biocompatible materials is ever increasing. Since Pt is highly biocompatible and very inert, it makes it an excellent choice for fabrication of a bio-SPM sensor. The photopolymer SU-8 is used to make the body of the probe. The process is based on a surface moulding technique where a pyramidal mould made in KOH solution is used to form the tip. Oxidation sharpening of the mould yields very sharp tips with measured tip radius below 20 nm. Sputter deposition guarantees with its good step coverage an excellent mould filling with Pt. Stress control in the metal layer is important for straight cantilevers and is done by adjustment of deposition parameters. After a dry structuring of the cantilever, a 200-um-thick SU-8 body for the probe is formed on top of the metal. Proper surface treatment prior to SU-8 spinning ensures a good adhesion between the SU-8 and the metal. With the open honey-comb body structure, a top-side dry etch release is feasible. First imaging with the hybrid Pt probe, with a spring constant of 5-e2 Nm^-1 has been performed on a mica sample. As a reference, an image on mica by a conventional Si cantilever in dry conditions was also taken. For both images, the minimum measured stepheight is 2.5 nm. The results are promising to study cells and do force spectroscopy with the Pt probe. These measurements are carried out at present and their results will be presented in the final contribution as well.