Abstract:We present a new size-selective detection method for integrated optical interferometric biosensors that can strongly enhance their performance. We demonstrate that by launching multiple wavelengths into a Young interferometer waveguide sensor it is feasible to derive refractive index changes from different regions above the waveguide surface, enabling one to distinguish between bound particles (e.g. proteins, viruses, bacteria) based on their differences in size and simultaneously eliminating interference from bulk refractive index changes. Therefore it is anticipated that this new method will be ideally suited for the detection of viruses in complex media. Numerical calculations are used to optimize sensor design and the detection method. Furthermore the specific case of virus detection is analyzed theoretically showing a minimum detectable virus mass coverage of 4 × 10 2 fg/mm 2 (typically corresponding to 5 × 10 1 particles/ml).

The prmclple of measurmg pressure by means of a resonant diaphragm has been studled An oscillator conslstmg of an integrated amphfler with a plezoelectrlcally driven diaphragm m its feedback loop has been bullt The oscillator frequency 1s accurately proportional to the square of the pressure m the range 60 to 130 Torr The frequency range 1s 1324 to 1336 Hz (this range being limited by a spurious mode which could be suppressed by better processing) for a 25 mm diameter diaphragm made of a slhcon wafer and with PZT ceramics as driver and receptor We have made an mtegrated version (1 X 1 mm2) of a square resonant diaphragm pressure gauge by selective etchmg of (1 0 0) planes with ethylenedlamme The plezoelectrlc drlvmg maternal was sputtered zmc oxide A driver was deposited midway between the bending point and the point of greatest curvature A receptor was located at a symmetrlcal posltlon to give an optimum transfer condltlon The integrated current amplifier had a low impedance differential mput stage, two gam cells and a high Impedance output stage These electrical conditions ensured maximum elastic freedom of the diaphragm A dlgltal clrcult m 12L technology has been designed and made with eight-bit parallel read out of the frequency This clrcult may be directly connected to a mlcroprocessor The whole system contams the sensor chip, the analog amphfler chip and the digital chip, all m compatible technology *Based on a Paper presented at Solid-State Transducers

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Equipment has been designed for the study of the energy distribution and mass composition of particles, particularly positive ions, emitted from solids upon irradiation with laser pulses from a TEA CO 2 laser (power densities in the order of 10 8 W /cm 2 ). The equipment for the mass/energy analysis consists of a quadrupole mass spectrometer (QMS) and a modified cylindrical mirror analyzer (CMA) which can measure parallel ion beams. This paper describes the equipment, the basic construction, and the operation principles of the experimental setup. The system performance and experimental procedures are described on the basis of some preliminary experimental results. The results indicate that the analyzer described in this paper is capable of measuring the mass composition and the energy distribution of particles, particularly positive ions, supplied either in a pulsed or in a continuous manner. It is useful in studying charged particles in processes involving muItispecies plasmas, like those occurring in thin film deposition through evaporation of targets by means of a pulsed laser.