Surface characterisation of PEO-like microstructures by means of ToF-SIMS, XPS and SPR M. Perez-Roldan, P. Colpo, D. Gilliland, G. Ceccone* and F. Rossi In this work, we present a method to produce micro and nanostructured surfaces containing bioadhesive features embedded in an antifouling matrix. These surfaces are fabricated by combining plasma polymerization and electron beam lithography. This combination allows the fabrication of structured surfaces in just two steps and without the use of solvents. ToF-SIMS analysis demonstrates that the e-beam treatment induces a chemical change at the surface depending upon the radiation dose employed. In particular, a decrease of peaks characteristic of the PEO-like fragments (e.g. CH 3 O + ,C 3 H 7 O + ,C 3 H 5 O 2 + ) and a correspondent increase of hydrocarbon moieties such as C 2 H 3 + and C 3 H 3 + is observed in the irradiated zones. These results are supported by XPS analysis that indicate a slight reduction of the intensity of the C–O component in the C1s core level spectrum after irradiation similar to that observed in UV-treated PEO-like films. Experiments with proteins show a pref- erential adhesion of the biomolecules to the irradiated zone indicating the good potential of this technique for the development of nanostructured biosensing platforms. Copyright © 2012 John Wiley & Sons, Ltd. Keywords: PEO-like; ToF-SIMS; e-beam treatment; antifouling surfaces; plasma polymerization; SPRi Introduction The fabrication of patterns allowing immobilization of biomolecules at the micro and nanometer scale is of a paramount importance for the study of the fundamental aspects of cell adhesion and for engi- neering a new generation of biological and chemical sensors. The combination of fouling and non-fouling material for the creation of chemical patterns at sub-micro and nanometer scale is becom- ing more and more popular, due to their possible applications in biomolecular detection. [1] The techniques employed for the pattern fabrication are varied , [2] and among them, electron beam lithogra- phy is considered the most suitable because of the high spatial res- olution achievable. [3] In this work, we present the combination of plasma polymerization and electron beam lithography techniques for the functionalization and patterning of surfaces with a chemical contrast. The functionalization of the surfaces was carried out by plasma deposition of PEO-like films which have excellent anti- fouling properties, [4–6] and the pattern creation was performed by direct writing on the PEO-like film with the electron beam. Such exposure to the electrons turns the antifouling PEO-like film into a bio-adhesive film, as was reported by Brétagnol et al. [7] In this work, they produced bio-adhesive patterns applying an electron beam at 20 KeV, while in the present paper, lower fabrication energy (2 KeV) has been explored in order to reduce the exposure time in the fabrication process. In fact, reducing the electron energy applied in the lithographic process decreases the penetration of the elec- trons into the substrate thus resulting in a higher deposited electron energy near the surface; as a consequence, the dose required to make a pattern is also reduced, Therefore, an accelera- tion voltage of 2 KeV can significantly decrease the exposure time. Micro patterned areas have been analyzed by means of XPS, ToF-SIMS and SPRi to evaluate the chemical modification of the exposed areas and their ability to act as biointerfaces in bio- sensing platforms. Experimental Silicon wafers (Resistivity: < 20 Ωcm, Thickness = 150 mm, Orien- tation (100)) were used as substrates for the process characterisa- tion, while SPRi-Biochips ™ purchased from Horiba were used for SPRi experiments. Human serum albumin (HSA) and anti-HSA (Ab-HSA) were purchased from Sigma-Aldrich, and ubiquitin enriched with 15 N (Ub- 15 N) was purchased from ProtEra. The deposition of PEO-like films was carried out in pulsed mode in a homemade stainless steel reactor (300 Â 300 Â 150 mm 3 ) equipped with two symmetrical parallel plate electrodes (diameter 140 mm, electrode distance 5 cm). An RF generator was connected to the upper electrode, while the other electrode was grounded and used as a sample holder. Pure diethylene glycol dimethyl ether (DEGDME) from Sigma Aldrich (CH 3 –OCH 2 CH 2 ) 2 O) mixed with argon (15% DEGDME in Ar) was injected into the chamber by a feeding tube placed at a side of the chamber. A MKS mass flow controller controlled gas and precursor flow rates. The working pressure, monitored by a MKS baratron, was kept constant at 20 mTorr. The patterning process was carried out using an external beam controller (Elphy Quantum, Raith GmbH) connected to a scanning electron microscope FEI W Nova ™ NanoLab ™ 600i DualBeam ™ working in electron mode at 2 KeV. The substrates used in this study were ultrasonically cleaned for 5 min in ethanol. Then, a film of approximately 15 nm of plasma- polymerized PEO-like film was deposited on the substrate. Finally, * Correspondence to: Dr. G. Ceccone, EC-JRC- IHCP, Via E. Fermi 2749, 21027, Ispra (VA), Italy. E-mail: giacomo.ceccone@jrc.ec.europa.eu EC-JRC- IHCP, Via E. Fermi 2749, 21027, Ispra (VA), Italy Surf. Interface Anal. 2013, 45, 240–243 Copyright © 2012 John Wiley & Sons, Ltd. SIMS proceedings paper Received: 10 October 2011 Revised: 3 May 2012 Accepted: 18 May 2012 Published online in Wiley Online Library: 15 June 2012 (wileyonlinelibrary.com) DOI 10.1002/sia.5070 240