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We have fabricated nanometer-sized interdigitated electrode patterns using electron beam lithography and liftoff techniques. The aim of the investigation was to find out whether the dimensions ͑i.e., the electrode separations͒ of the pattern would affect the admittance signal of the biomolecules in between the electrodes. Since the admittance signal scales with the geometrical factor A/d, where A is the electrode area and d is the separation, we chose to keep A/d constant when changing the electrode separation in order to eliminate this trivial effect on the admittance signal. An interdigitated electrode structure having an interelectrode spacing in the nanometer regime makes it possible to reach high nonstationary as well as stationary electric field strengths while having a low applied voltage level. Hence, electrode reactions will be as small as possible, while a high signal to noise ratio is obtained. We have been able to experimentally study the response of the impedance behavior to high electric fields exhibiting either a positive or a negative shift of the permittivity as a function of the field being a high alternating-current or a direct-current field, respectively.

Articles you may be interested inLow temperature direct bonding mechanisms of tetraethyl orthosilicate based silicon oxide films deposited by plasma enhanced chemical vapor deposition In this study we will report on the development of a process to establish antisticking layers on nickel-based stamps, which are used in several industrial applications of nanoimprint lithography or related methods. The fluorinated alkyl silane films have been deposited onto different Ni-based stamp surfaces in order to minimize the adhesion tendency at the stamp/polymer interface. Film thickness, chemical composition, purity, and binding mechanisms of the silane groups to different stamp surface materials have been determined by photoelectron spectroscopy ͑XPS͒. In the case of electroplated nickel stamps-where low imprint qualities are observed-multilayer thick films cover the stamp surfaces, consisting of polymerized, cross-linked alkyl silanes, which are poorly bound to the surface. In order to overcome these restrictions a 100 Å thick polycrystalline titanium layer has been established in a sandwich position between the nickel substrate and the silane film.Here, silane film thicknesses in the monomolecular region together with evidences for strong covalent linkage between the silane groups and the oxidized Ti surface can be concluded from the XPS results, leading to film properties and imprint qualities, which are comparable to those formerly observed for silicon stamps.

The method for purification of biomolecules by a combination of affinity interactions and membrane filtration for separation of unwanted material has been found to be of interest for large-scale work. This study examines the suitability of silica nanoparticles as carriers in the process. Alcohol dehydrogenase and lactate dehydrogenases were chosen as target molecules to be purified. The binding capacity was found to be comparative to what is obtained for high-performance liquid chromatography (HPLC) packing material. Both binding and desorption of the enzymes were found to be effective. The limiting factor of the process was the filtration flow rate.

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