Michal Marek Mielnik

First fabrication of full 3D-detectors at SINTEF

3D-detectors, with electrodes penetrating through the entire substrates have drawn great interests for high energy physics and medical imaging applications. Since its introduction by C. Kenney et al in 1995, many laboratories have begun research on different 3D-detector structures to simplify and industrialise the fabrication process. SINTEF MiNaLab joined the 3D collaboration in 2006 and started the first 3D fabrication run in 2007. This is the first step in an effort to fabricate affordable 3D-detectors in small to medium size production volumes. The first run was fully completed in February 2008 and preliminary results are promising. Good p-n junction characteristics have been shown on selected devices at the chip level with a leakage current of less than 0.5 nA per pixel. Thus SINTEF is the second laboratory in the world after the Stanford Nanofabrication Facility that has succeeded in demonstrating full 3D-detectors with active edge. A full 3D-stacked detector system were formed by bump-bonding the detectors to the ATLAS readout electronics, and successful particle hit maps using an Am-241 source were recorded. Most modules, however, showed largely increased leakage currents after assembly, which is due to the active edge and p-spray acting as part of the total chip pn-junction and not as a depletion stop. This paper describes the first fabrication and the encountered processing issues. The preliminary measurements on both the individual detector chips and the integrated 3D-stacked modules are discussed. A new lot has now been started on p-type wafers, which offers a more robust configuration with the active edge acting as depletion stop instead of part of the pn-junction.

Towards a “Sample-In, Answer-Out” Point-of-Care Platform for Nucleic Acid Extraction and Amplification: Using an HPV E6/E7 mRNA Model System

The paper presents the development of a “proof-of-principle” hands-free and self-contained diagnostic platform for detection of human papillomavirus (HPV) E6/E7 mRNA in clinical specimens. The automated platform performs chip-based sample preconcentration, nucleic acid extraction, amplification, and real-time fluorescent detection with minimal user interfacing. It consists of two modular prototypes, one for sample preparation and one for amplification and detection; however, a common interface is available to facilitate later integration into one single module. Nucleic acid extracts (n = 28) from cervical cytology specimens extracted on the sample preparation chip were tested using the PreTect HPV-Proofer and achieved an overall detection rate for HPV across all dilutions of 50%–85.7%. A subset of 6 clinical samples extracted on the sample preparation chip module was chosen for complete validation on the NASBA chip module. For 4 of the samples, a 100% amplification for HPV 16 or 33 was obtained at the 1 : 10 dilution for microfluidic channels that filled correctly. The modules of a “sample-in, answer-out” diagnostic platform have been demonstrated from clinical sample input through sample preparation, amplification and final detection.

High aspect ratio deep RIE for novel 3D radiation sensors in high energy physics applications

3D detectors with electrodes penetrating through the entire silicon substrate have many advantages over conventional planar silicon technology, for example, high radiation tolerance. High aspect ratio through-wafer holes are essential in such fabrication, and deep reactive ion etching (DRIE) is used. A series of DRIE processes were tested and optimised to achieve the required aspect ratio, and in 5-¿m wide trenches, aspect ratios of 58:1 were achieved.

Visualization and measurements of flows in micro silicon Y-channels

Velocities and accelerations are measured and visualized in silicon microchannels using particle tracking velocimetry (PTV). Both pulsatile and stationary flows are generated in channels with different geometry. Distinct differences between flow regimes and geometries are shown. Flow separation occurred at Re = 84 for the channel with an expanded bifurcation shown by streamlines from long exposed images. Moving least squares are used to find the ensemble-averaged positions of the measured velocities from tracking. This is needed to find the local and convective accelerations.Graphical abstract

Characteristics of Hydrodynamically Focused Streams for Use in Microscale Particle Image Velocimetry (Micro-PIV)

This paper presents the characteristics of hydrodynamically focused streams to be used in Microscale Particle Image Velocimetry (micro-PIV). The investigation was done by means of Confocal Laser Scanning Microscopy (CLSM) in channels of cross-sections 260 × 200 μ m and 1040 × 800 μ m, within the downstream velocities range from 0.1 to 2.5 cm/s. The formulation of a curvature of the sheet, its dependence on the side stream ratio, and the overall downstream velocity are discussed qualitatively and quantitatively. The results show that the curvature is highly dependent on the velocities of the system. Sheet characteristics such as curvature and observed sheet width variation become amplified with higher velocities. This leads to the conclusion that hydrodynamic focusing is promising as a selective seeding technique for use in micro-PIV up to velocities of few cm/s. However, the fact that this is the upper velocity range in microfluidics renders the SeS-PIV technique as a very suitable tool for complicated flows visualization.

Interconnects and substrates for thermal considerations

Novel and emerging packaging technologies expand the designers toolbox. Metal coated polymer spheres (MPS) for ball grid array (BGA) assembly is a promising interconnect technology improving reliability, while high thermal conductivity substrates, e.g. AlSiC and AlN, is interesting for enhanced thermal performance. But new tools bring along new challenges in the design phase of innovative packaging solutions. Knowledge of how these tools influence the system characteristics is therefore key; e.g. electrical, mechanical and thermal performance. This study reports on the thermal performance of several novel and more traditional interconnect and substrate technologies. It comprises a relative thermal impact study of individual technologies. The system consists of a power dissipating silicon die assembled onto different substrates with varying interconnect technologies. The study was performed with finite element analysis (FEA) assisted with a compact model and is scheduled for comparison with identical fabricated systems. The results show that it is possible to utilize FEA efficiently on a system scale during the design process with sufficient accuracy. It also reveals that the combination of interconnect and substrate technology should be chosen with care, especially regarding the systems thermal performance, disclosing potential reliability issues and illustrating cost-benefit tradeoffs.

Teflon-carbon black as new material for the hydrophobic patterning of polymer labs-on-a-chip

We provide a new method for the selective surface patterning of microfluidic chips with hydrophobic fluoropolymers which is demonstrated by the fabrication of hydrophobic valves. It enables efficient optical quality control for the surface patterning thus permitting the low-cost production of highly reproducible hydrophobic valves. Specifically, a fluoropolymer-solvent-dye solution based on carbon black (CB) is presented which creates superhydrophobic surfaces (contact angle = 157.9°) on chips made from cyclic olefin copolymer (COC). It further provides good visibility for the quality control (QC) in polymer labs-on-a-chip and increases the burst pressure of hydrophobic valves. Finally, an application which aims for the amplification of mRNA on-chip and relies on the defined flow control by hydrophobic valves is presented. Here, the QC in combination with the Teflon-CB coating improves the average standard deviation of the burst pressures from 14.5% down to 6.1 % compared to solely Teflon-coated valves.

Improvement of Micro-PIV Resolution by Selective Seeding

A novel seeding method, permitting high out-of-plane resolution and instantaneous (time-resolved) velocity field measurements using a standard Microscale Particle Image Velocimetry (micro-PIV) setup, is presented. The method relies on selective seeding of a thin fluid layer within an otherwise particle-free flow. The generated particle sheet defines the depth and position of the measurement plane, independently of the details of the optical setup. Therefore, for low magnification objectives in particular, considerable improvement in the measurement depth is possible. Selectively seeded micro-PIV (SeS-PIV) is applied to a microchannel flow, and the measured instantaneous velocity fields are in excellent agreement with the theoretical solution for the flowfield. The currently presented measurements have a depth-wise resolution 20% below the estimated optical measurement depth of the micro-PIV system. In principle, a measurement depth corresponding to the diameter of the tracer particles may be achieved.Copyright

BioMEMS meets lab-on-a-chip: Heterogeneous integration of silicon MEMS and NEMS in polymer microfluidics

We present a new heterogeneous integration method which enables direct incorporation of silicon-based microfluidic components in an injection-moulded polymer lab-on-a-chip (LOC). The integration is performed as part of the injection moulding process, forming direct fluidic junctions between the polymer and the silicon chip while embedding the silicon chip in the polymer chip. We have demonstrated that such fluidic junctions can withstand at least 3 bars of liquid pressure. With this integration method, the fluidic interface between the silicon chip and the polymer chip can be made compact and free of dead-volume. The method opens for mass fabrication of highly functional, heterogeneous LOC systems containing MEMS and NEMS components such as biosensors and actuators integrated in the polymer chip.

The MicroActive project : automatic detection of disease-related molecular cell activity

The aim of the MicroActive project is to develop an instrument for molecular diagnostics. The instrument will first be tested for patient screening for a group of viruses causing cervical cancer. Two disposable polymer chips with reagents stored on-chip will be inserted into the instrument for each patient sample. The first chip performs sample preparation of the epithelial cervical cells while mRNA amplification and fluorescent detection takes place in the second chip. More than 10 different virus markers will be analysed in one chip. We report results on sub-functions of the amplification chip. The sample is split into smaller droplets, and the droplets move in parallel channels containing different dried reagents for the different analyses. We report experimental results on parallel droplet movement control using one external pump only, combined with hydrophobic valves. Valve burst pressures are controlled by geometry. We show droplet control using valves with burst pressures between 800 and 4500 Pa. We also monitored the re-hydration times for two necessary dried reagents. After sample insertion, uniform concentration of the reagents in the droplet was reached after respectively 60 s and 10 min. These times are acceptable for successful amplification. Finally we have shown positive amplification of HPV type 16 using dried enzymes stored in micro chambers.