RESUMEN

Cell culture assays for therapeutic drug screening today are fully automated. Vitality of the cells is monitored by different sensors. For such a system, we propose a new reader unit, which is capable of reading two different fluorescent sensors and electrical impedance in 24-well-plates. Main goals are to reduce cost, complexity and size while achieving a similar performance as the existing reader unit. To achieve this, measurement electronics and signal paths for frequency domain fluorescence and bio-impedance measurement are combined. Central component is an integrated circuit for impedance spectroscopy. A new compact and economic optical setup is developed to read two different sensor spots on the bottom of the well. Measurement errors introduced by different components like DFT leakage, and frequency dependent signal delays are evaluated and compensated. A set of commercially available fluorescence sensor spots is used to verify the read out performance. The results are usable, with noise slightly higher than commercial readers. To verify the impedance measurement accuracy, measurements of known resistances are conducted. In the relevant impedance and frequency range for biological applications a suitable accuracy is achieved. Due to the higher sampling rate of the new reader, the higher noise can be reduced through averaging. The new system is significantly smaller and cheaper to manufacture than commercially available devices.

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RESUMEN

Over the past 30 years electronic applications have been dominated by complementary metal oxide semiconductor (CMOS) devices. These combine p- and n-type field effect transistors (FETs) to reduce static power consumption. However, CMOS transistors are limited to static electrical functions, i.e., electrical characteristics that cannot be changed. Here we present the concept and a demonstrator of a universal transistor that can be reversely configured as p-FET or n-FET simply by the application of an electric signal. This concept is enabled by employing an axial nanowire heterostructure (metal/intrinsic-silicon/metal) with independent gating of the Schottky junctions. In contrast to conventional FETs, charge carrier polarity and concentration are determined by selective and sensitive control of charge carrier injections at each Schottky junction, explicitly avoiding the use of dopants as shown by measurements and calculations. Besides the additional functionality, the fabricated nanoscale devices exhibit enhanced electrical characteristics, e.g., record on/off ratio of up to 1 × 10(9) for Schottky transistors. This novel nanotransistor technology makes way for a simple and compact hardware platform that can be flexibly reconfigured during operation to perform different logic computations yielding unprecedented circuit design flexibility.

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Schottky barrier field effect transistors based on individual catalytically-grown and undoped Si-nanowires (NW) have been fabricated and characterized with respect to their gate lengths. The gate length was shortened by the axial, self-aligned formation of nickel-silicide source and drain segments along the NW. The transistors with 10-30 nm NW diameters displayed p-type behaviour, sustained current densities of up to 0.5 MA/cm2, and exhibited on/off current ratios of up to 10(7). The on-currents were limited and kept constant by the Schottky contacts for gate lengths below 1 microm, and decreased exponentially for gate lengths exceeding 1 microm.

RESUMEN

Despite all prophecies of its end, silicon-based microelectronics still follows Moore's Law and continues to develop rapidly. However, the inherent physical limits will eventually be reached. Carbon nanotubes offer the potential for further miniaturization as long as it is possible to selectively deposit them with defined properties.

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