A silicon based chip device with a regular array of more than 100,000 cylindrical sub-microelectrodes has been developed for the dielectrophoretic (DEP) manipulation of nanoparticles and molecules in solution. It was fabricated by a standard CMOS (complementary metal oxide semiconductor) compatible process. The distribution of the electrical field gradient was calculated to predict the applicability of the setup. Heating due to field application was determined microscopically using a temperature sensitive fluorescent dye. Depending on voltage and frequency, temperature increase was found to be compatible with protein function. Successful field controlled immobilisation of biomolecules from solution was demonstrated with the autofluorescent protein R-phycoerythrin (RPE) and with fluorescently labelled IgG antibodies. Biological activity after DEP application was proven by immobilisation of an anti-RPE antibody and subsequent binding of RPE. These results demonstrate that the developed chip system allows the directed immobilisation of proteins onto microelectrodes by dielectrophoresis without the need for any chemical modification and that protein function is preserved. Being based on standard lithographical methods, further miniaturisation and on-chip integration of electronics towards a multiparameter single cell analysis system appear near at hand.

The enzyme horseradish peroxidase has been immobilized on nanoelectrode arrays by alternating current dielectrophoresis (DEP). Preservation of its enzymatic function after field application was demonstrated by oxidizing dihydrorhodamine 123 with hydrogen peroxide as co-oxidant to create its fluorescent form, rhodamine 123 (Rh123). Localization of the fluorescently labeled enzyme and its product was conducted by fluorescence microscopy. Nanoelectrodes were prepared as tungsten pins arranged in square arrays. Experimental parameters for dielectrophoretic immobilization were optimized for even enzyme distribution and for enzymatic efficiency. Enzyme activity was quantified by determination of fluorescence intensities of immobilized enzyme molecules and of Rh123 produced. These results demonstrate that DEP can be applied to immobilize enzyme molecules while retaining their activity and rendering any chemical modifications unnecessary. This introduces a novel way for the preparation of bioactive surfaces for processes such as biosensing.

Integrated AlN/SiO 2 /Si (1 0 0) delay lines for Rayleigh surface acoustic waves (SAWs) with resonant frequencies up to 3.4 GHz were fabricated using a new CMOS compatible concept. Different thicknesses of textured AlN films with wurtzite structure were deposited on tungsten-based interdigital transducers embedded in a SiO 2 layer by reactive pulse dc-sputtering at a temperature of 200 • C. Rocking curves of the films indicate c-axis (0 0 0 1) oriented, textured piezoelectric AlN films with a full-width at half-maximum of 1.88 • . The determined propagation loss and coupling factor K 2 of these SAW devices are 0.07 dB/λ and 0.78%, respectively. Different Rayleigh modes with acoustic velocities up to 5770 m s −1 are observed. By varying the wavelength, number of fingers as well as the length (i.e., the separation between the transducers) of the delay lines, the impact of several physical parameters on the frequency responses (S 11 , S 21 ) was studied. The influence of the AlN thickness and of the orientation of the delay lines on the silicon (1 0 0) wafers was also investigated. Finite element method simulations were applied to model the resonant frequencies, giving resonant frequencies in reasonable agreement with the experimental data.

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Aluminum nitride (AlN) based high frequency surface acoustic wave (SAW) devices are produced by using a new CMOS compatible concept. Textured c‐axis oriented AlN films have been deposited on tungsten based embedded interdigital transducers (IDTs) by the reactive pulse DC‐sputter technique within the thermal budget of back end of line (BEOL) processes. Two SAW Rayleigh modes with different acoustic velocities were measured and identified by finite element method (FEM) simulation (Kaletta and Wenger, FEM Simulation of Rayleigh waves for CMOS compatible SAW devices based on AlN/SiO2/Si(100) (Elsevier Ultrasonics, available online 18 April 2013, ISSN 0041‐624X, 10.1016/j.ultras.2013.04.009) [1]). Electromagnetic crosstalk between in‐ and output IDTs via low resistive Silicon substrates is one of the most troublesome sources of integrated SAW devices. The impact of several device parameters like the acoustic aperture, the number of fingers and the delay line length on the electromagnetic crosstalk was studied and routes for optimizing SAW filter designs on low resistive Si(100) will be presented. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)