Patrick Pittet

Fast prototyping using a dry film photoresist : microfabrication of soft-lithography masters for microfluidic structures

Etertec HQ-6100 dry film photoresist was used in this work to fabricate soft-lithography masters applied to microfluidic applications. We demonstrated that the use of this photoresist was a convenient alternative to conventional microfabrication approaches based on DRIE and liquid photoresists for fast-prototyping of microfluidic structures. Our method was at least two times faster than conventional processes and required limited investment for equipments. Finally, this approach was applied to the design and fabrication of microfluidic networks used for gradient generation in bulk solution.

Wide-linear-range subthreshold OTA for low-power, low-Voltage, and low-frequency applications

We propose a novel configuration of linearized subthreshold operational transconductance amplifier (OTA) for low-power, low-voltage, and low-frequency applications. By using multiple input floating-gate (MIFG) MOS devices and implementing a cubic-distortion-term-canceling technique, the linear range of the OTA is up to 1.1 Vpp under a 1.5-V supply for less than 1% of transconductance variation, according to testing results from a circuit designed in a double-poly, 0.8-/spl mu/m, CMOS process. The power consumption of the OTA remains below 1 /spl mu/W for biasing currents in the range between 1-200 nA. The offset voltage due to secondary effects (contributed by parasitic capacitances, errors and mismatches of parameters, charge entrapment, etc.) is of the order of a few ten millivolts, and can be canceled by adjusting biasing voltages of input MIFG MOS transistors.

Radiotherapy quality insurance by individualized in vivo dosimetry: State of the art

The quality insurance in radiotherapy in the frame of highly complex technical process as Intensity modulated radiotherapy (IMRT) needs independent control of the delivered dose to the patient. Actually, up to now, most of the radiotherapy treatments rely only on computed dosimetry through a rather complicated series of linked simulation tool. This dosimetry approach requires also qualified treatment means based on cautious quality insurance procedures. However, erroneous parameters could be difficult to detect and systematical errors could happen leading to radiotherapy accidents. In this context, in vivo dosimetry has a critical role of final control of the delivered dose. As many beam incidences and ports are used for any photontherapy treatment, external control could be very tedious and time consuming. Therefore, innovations are needed for in vivo dosimetry to provide ergonomic and efficient tools for these controls. This paper presents a review of technologies and products that can be used for in vivo dosimetry. It proposes also a reflection on the concepts to develop future devices suitable for this purpose. The technical means with their physical principles are reviewed, the clinical experiences demonstrating the feasibility of new techniques are then summarized and finally, the early clinical use and its impact on clinical practice is review.

CMOS buried Quad p-n junction photodetector for multi-wavelength analysis

This paper presents a buried quad p-n junction (BQJ) photodetector fabricated with a HV (high-voltage) CMOS process. Multiple buried junction photodetectors are wavelength-sensitive devices developed for spectral analysis applications where a compact integrated solution is preferred over systems involving bulk optics or a spectrometer due to physical size limitations. The BQJ device presented here is designed for chip-based biochemical analyses using simultaneous fluorescence labeling of multiple analytes such as with advanced labs-on-chip or miniaturized photonics-based biosensors. Modeling and experimental measurements of the spectral response of the device are presented. A matrix-based method for estimating individual spectral components in a compound spectrum is described. The device and analysis method are validated via a test setup using individually modulated LEDs to simulate light from 4-component fluorescence emission.

A Novel Approach to Implementing On-Chip Synchronous Detection for CMOS Optical Detector Systems

A phase-switching approach suppresses the need to employ a precise multiplier for synchronous demodulation. An improved solution for implementing on-chip synchronous detection consists of using a switched-phase amplifier, which combines pre-amplification and phase-switching operations. This enables circuit simplification, voltage lowering, and power and surface savings. A detector-associated circuit realising pre-amplification and synchronous demodulation is proposed. It includes a transimpedance amplifier, a switched-phase amplifier and a low-pass filter. All these building blocks are designed to operate under a minimum supply of 2 V, using a double-poly, 0.8-μm CMOS process. The designed circuit is to be integrated with a CMOS optical detector for portable applications. System-level simulations (including the detector model) are performed to validate the system operation, and to estimate performances. The sensitivity of the system in terms of minimum detectable optical signal (which is synchronously modulated) is evaluated to be 2.2 10−14 W/mm2 in normal measuring conditions.

A wide-linear range subthreshold OTA based on FGMOS transistor

This paper presents a new configuration of linear CMOS subthreshold operational transconductance amplifier (LSOTA) working at 1.5 V with very low power consumption. Based on FGMOS technique, the developed OTA has a wide input range and small Gm, suitable for implementing low frequency analog and monolithic continuous-time filters. For demonstration a low pass second order filter was designed and simulated. The power consumption of the filter is less than 2 /spl mu/W and the topology achieves 76 dB linearity for fully balanced input dynamic range up to 1 Vpp at 1.5 V supply voltage.

A new method to enhance frequency operation of CMOS ring oscillators

This article proposes a frequency-boosting method for CMOS ring oscillators. It consists of adding RC-based differentiators in delay cells to speed up their transient responses. Two novel delay cells for simple and differential versions are presented. On using MOS transistor components to implement the differentiators, the resulting increase of surface area is observed to be moderate, and this allows frequency tuning by voltage control, without inducing additional phase noise. The presented circuits are suitable for low-voltage operation. Simulation results on the proposed circuits have shown significant frequency enhancement with a competitive factor of merit.

PCB-based integration of electrochemiluminescence detection for microfluidic systems.

This communication presents an instrumental development based on the printed circuit board (PCB) technology to integrate electrochemiluminescence (ECL) analysis in microfluidic systems. PCB gold macro- (10 mm2) and micro- (0.09 mm2) electrodes and two ECL microfluidic devices are designed, fabricated and tested via luminol ECL detection. Potential modulation is performed between 0.7 and 0 V vs. Ag/AgCl for luminol oxidation, thus giving rise to on/off ECL responses in the presence of hydrogen peroxide. Synchronous detection is adopted to allow weak ECL signal recovery at a very low signal-to-noise ratio (SNR). The detection limit obtained with the two ECL microfluidic devices is 50 nM and 100 nM H2O2 for macroelectrodes and microelectrodes, respectively.

Investigation of the Mixing Efficiency of a Chaotic Micromixer Using Thermal Lens Spectrometry

This work investigates the efficiency of a chaotic micromixer using thermal lens spectrometry. The outlet of the mixing device was connected to a thermal lens detection head integrating the probe beam optical fibers and the sample capillary. The chaotic micromixer consisted of a Y-shaped poly(dimethylsiloxane) (PDMS) microchip in which ribbed herringbone microstructures were etched on the floor of the main channel. Due to the solvent composition dependence of the thermal lens response, the photothermal method was shown to be highly sensitive to nonhomogeneous mixing compared to fluorescence detection. The apparatus was applied to the determination of Fe2+ with 1,10-phenanthroline using flow injection analysis; a limit of detection of 11 μg L−1 of iron was obtained.

A low-frequency, sub 1.5-V micropower G/sub m/-C filter based on subthreshold MIFG MOS transistors

We present a sub-1.5V and micropower filter with very low and tunable cut off frequency. It consists of low-G/sub m/ and wide-linear-range OTA using subthreshold MIFG (multiple input floating gate) MOS transistors. A linearization technique based on cancellation of cubic distortion term is implemented. The filter designed in a 0.8-/spl mu/m CMOS process can operate under a supply voltage V/sub dd/ as low as 1.2V. For V/sub dd/ = 1.5V, the filter has a linear range of 1.1 Vpp (with THD < 1%) and a tuning range from 0.5 to 200Hz, with power dissipation below 2/spl mu/W.