J. Bastemeijer

Integrated flow-cells for novel adjustable sheath flows

In this paper two integrated flow-cells are presented that can generate novel sheath flows. The flow-cells allow for dynamic orthogonal control of the sample flow dimensions. In addition to this, the sample flow can be freely positioned inside the channel. The flow-cells are attractive, because they are very simple to fabricate and are compatible with the integration of sensors. Experiments have been carried out demonstrating that the sample flow dimensions can be controlled over a wide range; also the results show good agreement with finite element simulation results.

Near-field optical sensors for particle shape measurements

Two new optical particle shape sensors are introduced. By placing them directly in the near-field of the particle projection (Fresnel region), no lenses or additional optical components are required to obtain particle images. Besides size information, accurate shape information is also obtained. Simulations show that distortion by diffraction is limited and can be reduced even further. Both static and dynamic measurements have been performed, which show that the sensors work as predicted by theory. The sensors have been developed to be applied in a microfluidic cytometer.

Temperature-compensated Love-wave sensors on quartz substrates

Love wave-based microacoustic sensors are suitable for sensing applications in the liquid phase, where conventional Rayleigh surface acoustic wave sensors cannot be used. Typically, they yield even higher sensitivities than comparable Rayleigh SAW devices offer in gas sensing. Up to now, Love-wave devices have been realized using commercially available standard crystal orientations. The latter are optimized to provide intrinsic temperature compensation for conventional SAW or bulk wave devices; however, they yield no temperature compensation for Love modes. To overcome this, new crystal orientations have been considered. In this contribution, we present an alternative crystal cut based on theoretical considerations and its experimental verification.

DNA tracking within a nanochannel: device fabrication and experiments

Fabrication of nanochannels is drawing considerable interest due to its broad applications in nanobiotechnology (e.g. biomolecular sensing and single DNA manipulation). Nanochannels offer distinct advantages in allowing a slower translocation and multiple sensing spots along the channel, both of which improve the read-out resolution. However, implementing electrodes inside the nanochannel has rarely been demonstrated to our knowledge. The device described in this work is a Si-Glass anodically bonded Lab-on-a-Chip (LOC) device of a few millimetres in size capable of performing DNA manipulation. The LOC device structure is based on two mainstream microchannels interconnected by nanochannels. DNA, once trapped within the nanochannel, has been tracked throughout the length of the channel and the data have been recorded and analysed.

Continuous Electrodeless Dielectrophoretic Separation in a Circular Channel

We present a novel continuous electrodeless separation structure based on dielectrophoresis (DEP). The non-uniform electric field is generated by applying voltage over a circular channel. Driven by the electro-osmotic flow, the particles with different dielectric properties move continuously to the different location across the channel as they flow due to the different DEP force, thus continuously separated into the different outlets. The finite element modelling and simulation results show it can separate particles of different dielectric properties in both spatial and time domain. Compared with the previously reported dieletrophoretic separation using electrode arrays [1-10], this structure is more easily fabricated, mechanically robust and chemically inert. And compared with the previously reported electrodeless dielectrophoretic separation methods [11-14], this structure achieves higher throughput and continuous separation.

PCR array on chip - thermal characterization

This paper presents thermal analysis simulation and verification of a 50-nanoliter-reactor PCR (Polymerase Chain Reaction) well for application in silicon arrays, allowing 5/spl times/5 chamber matrix to be fitted on a 1cm/sup 2/ square. Every reactor cell is equipped with an integrated heater, temperature sensor and a photodetector. Each well forms a separate unit independently controlled and thermally insulated from the rest. Through micromachining the thermal capacity of each chamber is minimized, enabling rapid (8 - 10 cycles per minute) PCR cycling. To characterize the thermal behavior, an equivalent lumped element electrical circuit was defined and the results were compared to those obtained by Finite Element Method (FEM) analysis with CoventorWare/spl trade/. The proposed structure was implemented on a silicon substrate using a standard CMOS process and post-processing. Experiments were performed for verification of the model. Analysis shows that a temperature of about 95/spl deg/C can be reached (starting from 55/spl deg/C) by applying 1.5 W of electrical power in the integrated heater over a period of less than 2.5 seconds. The cooling (not active - self cooling) of the device is done in about 1.5 second.

Time of flight technique used for measuring position and orientation of laparoscopic surgery tools

An ultrasound wireless positioning system is developed to localize the laparoscopic instruments inside the patients body. The cross correlation method applied for measuring time of flight of ultrasound bursts yields 1 mm resolution in determining the instrument position. The 90/spl deg/ or respectively 180/spl deg/ phase-shift is introduced after the first half of the ultrasound burst.

Filter-protected photodiodes for high-throughput enzymatic analysis

This paper relates to the use of a thin film of re-crystallized (polycrystalline) silicon as a low-pass rejection filter in the ultraviolet light range and, more particularly, to the use of this layer as a protective layer for semiconductor diodes. The polycrystalline silicon filters were fabricated by laser annealing a thin film of amorphous silicon deposited by an LPCVD process. A standard component of the polysilicon-gate CMOS process is the boron phosphor silicate glass (BPSG) planarization layer. Since this layer is always applied, the possibility of using it as the isolator between the diode and the filter (and, thereby, omit one SiO/sub 2/ layer) is considered. Using scanning electron microscopy, we compared the crystallization process of the LPCVD silicon film deposited on a glass substrate and on a BPSG layer. The fabrication and the characterization of the filter-protected photodiodes are described in the paper.

Electronic baseline-suppression for liquid conductivity detection in a capillary electrophoresis microchip

Liquid conductivity detection for application in chip-based capillary electrophoresis (CE) has received attention because the sensor electrodes can be integrated in the chip and there is no loss of sensitivity when downscaling the detector. A well known disadvantage of conductivity detection is the high level of the baseline (due to the conductivity of the carrier electrolyte) that has a high influence on the measured values and deteriorates the detection limit. By using a lockin amplifier, making use of its two differential inputs and of its phase-locked sinewave output, we can generate a signal of controlled amplitude and phase, related to the level and phase of the baseline signal. By subtracting this signal from the AC output signal of the detector the baseline is significantly suppressed. Ideally, only the changes of the background signal are then measured. When applying the baseline-suppression method to real measurements, the level of the background signal was decreased 50 times. The detection limit (which is related to the signal-to-noise ratio) was found to be 10 times lower. Reproducible separations with concentrations from 1 mM down to 10 /spl mu/M of potassium, sodium, and lithium ions were obtained. For our separation and detection system, the concentration of 10 /spl mu/M could not be detected without the baseline-suppression technique described here.

Integrated sensor arrays for bioluminescence and fluorescence bio-chemical analysis

We present on-chip luminescence and fluorescence bio-chemical analysis, using integrated photodiodes. The detectors and the read-out electronics are implemented on a silicon substrate using standard CMOS processing. The photosensitive structures result from two-stacked PN junctions and an (optional) optical filter. The bioluminescent analyses are based on a light producing reaction - the conversion of ATP (adenosine triphosphate) molecules to AMP - catalyzed by the enzyme luciferase. The obtained results for three different initial concentrations of ATP molecules, in ATP consuming reactions, are presented. Initial fluorescent measurements have been conducted, based on the enzyme protein tyrosine phosphatase (PTP1B) using molecular probes DiFMUP (UV excitable). An enzyme solution (500 pg//spl mu/l) was mixed with DiFMUP. The reaction product DiFMU exhibits excitation/emission maxima of /spl sim/358/455 nm. The undesired excitation (UV) light was filtered out with. an integrated on-chip high pass filter with wavelength cut-off at 400 nm.