This paper reports on the fabrication and development of a surface acoustic waves (SAW) platform dedicated to digital micro fluidics for biological applications. SAW at about 20MHz are generated by InterDigital Transducers (IDT) laid on a LiNbO3 piezoelectric substrate. An electrical characterization of the IDT is reported and first results related to droplet handling with the SAW platform are given. We show that accurate droplet displacement is the result of both a radio frequency (RF) pulsed excitation and a chemical pre-treatment of the platform surface. For biological applications the droplet carrying the biomaterial is squeezed between the platform and a cover to increase the surface exchange between the droplet and hydrophilic functionalized areas. Out of such areas the free displacement is significantly improved by a surface hydrophobic pre-treatment. Moreover, the fabrication of additional hydrophilic micro tracks is shown to be a solution for crossing these areas without droplet splitting. This result is a key point to validate the structure of the novel micro fluidic platform proposed in this paper.

Porous polymer monoliths were prepared by UV- or EB-induced polymerization of hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) as network precursors dissolved in porogenic solvent mixtures composed of methanol and n-hexane. The fluidic properties and the pressure resistance of porous monoliths synthesized into 1mm i.d. capillaries and in 100μm-wide microchannels were investigated. The influence of photopolymerization time (or electron beam dose) and monomer content on flow properties is discussed on the basis of morphological features. The two types of radiation can be used to achieve the in situ fabrication of monolith inside microsystems. The permeability of the porous monoliths can be adjusted by tuning compositional and processing parameters.

We show that a Surface Acoustic Waves (SAW) platform can be dedicated to liquid microdroplet transport. SAW are generated centred around 20 MHz by interdigited transducers (IDT) laid on a LiNbO3 piezoelectric substrate. We show that a modulation of the surface wetting properties treatment significantly improves the transport of droplets and chemical design of hydrophilic tracks provides trajectory control. First results related to droplet handling and mixing with the SAW platform are given. In particular a RF pulsed excitation is experimentally demonstrated to be efficient for the transport of droplets inserted between two planes. Such a situation is especially interesting when functionalized areas are patterned on one of these two planes. Thus a moving droplet brought sequentially into contact with them could undergo biochemical modifications.

The design, fabrication and testing of a novel interface resembling a micro-nib for nano-electrospray ionisation–mass spectrometry (ESI–MS) applications is reported in this paper. The micro-nibs are fabricated in a planar topology using the negative photoresist SU-8 deposited onto silicon substrates. In order to direct the liquids to the nib tip, capillary slots with dimensions of 8μm×35μm and 16μm×35μm are included in the micro-nib design. The micro-nibs are fabricated so that they overhang from the edge of a silicon substrate in order to provide a reliable free-standing planar interface from a micro-fluidic circuit to a mass spectrometer. The micro-nib sources are tested on an ion trap mass spectrometer using standard peptide samples at concentrations down to 1 μM and with a typical ionisation voltage of around 1 kV. In addition, the nibs function well when the voltage supply was decreased to a value of 0.8 kV. The resulting mass spectra are seen to have a good signal-to-noise ratio (S/N) comparable to those observed using classical emitter tips. The micro-nibs demonstrate state-of-the-art performances with respect to current micro-machined electrospray interfaces and are comparable to those obtained for stand-alone fused-silica-based emitter tips.

We formulate microfluidic design principles for electrospray ionization sources based on a rectangular capillary slot formed by two triangular cantilevers. Spontaneous imbibition of the test liquids into the slot by capillary action provides a robust mechanism for liquid transport from a reservoir to the cantilever tip where an electrospray is generated upon application of a voltage. The correct functioning of the source requires the liquid bridging the slot to have a negative Laplace pressure. Imbibition is controlled by the ratio of slot width to height w∕h and the intrinsic contact angles θw, θs of the liquid with the slot walls and the cantilever faces, respectively. Based on these parameters we derive a simple criterion for the complete filling of the slot.

We present a design for integrated lab-on-chip microsystems dedicated to mass spectrometry analysis based on the fabrication of watertight microchannels for the circulation of liquids. In this paper, we demonstrate how to fabricate complete polymer microchannels using the negative photoresist SU-8 which has the advantage of being compatible with protein analysis by mass spectrometry. Our method of fabrication requires novel technological steps involving SU-8 multi-layer processing, improved SU-8 adhesion and the use of SU-8 wafer bonding for the watertight closing of the microchannels with a Pyrex wafer. This technique also encompasses the design of various microfluidic elements such as tapered recesses for the housing of capillary tubes allowing the connection of the channels to external systems. Following this, the capillary tubes were used to test the hydrodynamic behaviour of the channels and consequently the efficiency of our technological process in achieving fully watertight structures within our flow rate and pressure specifications.

We present a novel nanoelectrospray emitter tip based on the principle of a nib rather than a nozzle for nano-electrospray ionization–mass spectrometry (ESI–MS) applications. The fabrication of the micro-nibs relies on micromachining techniques using the epoxy-based negative photoresist SU-8. A double exposure photolithographic process has been employed to form a nib in a membrane-like structure. The nibs contained a capillary slot measuring 20 µm at the tip end. The nib sources were successfully tested on an ion trap mass spectrometer using standard peptide samples at low concentrations, down to 1 µM. High voltage (HV) supply was achieved using platinum wire inserted in a liquid reservoir. A Taylor cone was clearly seen protruding from the nib tip and was determined by the dimensions of the capillary slot.

This work concerns the design of microsystems for the travelling of liquid droplets under an electric field. The driving electrodes laid on glass are sealed at some tens of mum. The achieved demonstrators allow basic manipulations: cutting of a droplet from an inlet reservoir and its transporting over a few electrode network but also joining two droplets. Finally the concept of dielectrophoretic transport is examined in view to handle conducting biological liquids which can recover a dielectric behaviour under a high frequency electric field.

We report here on the fabrication of a novel silicon microfluidic system dedicated to protein sample preparation prior to their on-line analysis by electrospray and mass spectrometry (ESI-MS). The microsystem includes several main module, such as a digestion cell, an elution column, a pumping system as well as an integrated nano-ESI source, whose realization reflects our technological choice. After a brief presentation on microsystems, we describe our work in microfluidics, the conception and the description of the different modules, the accounting for the retained technological alternatives and the first realizations.

A novel 2D nanoelectrospray emitter for mass spectrometry has been micromachined using photoresist SU-8 on silicon substrates using one-step photomasking. The design contains a reservoir, a capillary slot and an emitter tip. The emitters were successfully tested on an ion trap mass spectrometer. A nanoelectrospray was observed at voltages as low as 0.8 kV.

We report here on the fabrication of a novel silicon microfluidic system dedicated to protein sample preparation prior to their on-line analysis by electrospray and mass spectrometry (ESI-MS). The microsystem includes several main modules such as a digestion cell, an elution column, a pumping system as well as an integrated nano-ESI source, whose realization reflects our technological choice. After a brief introduction on the overall microsystem, we describe the conception of the different modules including the description and the accounting for the retained technological alternatives, their development and the first realizations.

In this paper we present, to our knowledge, the first low frequency noise characterization of two NbNx thin films deposited on a silicon substrate. Using a transmission line model (TLM) test structure, it is checked that the noise of the contacts is negligible. From 77 K to 300 K no generation-recombination (g-r) noise is observed and both samples exhibit only 1/f noise. By referring to noise studies in semiconductor materials, a first interpretation is suggested.

In this paper we present a comparison of DC and electrical noise characteristics of high-temperature superconducting thin films. Two YBaCuO thin films deposited on MgO substrates were studied and compared. The R-T, I-V and electrical noise properties were studied for each film. Noise measurements show that they are more sensitive than the DC ones. They can give evidence of physical phenomena such as "pre-transitional superconducting effect".

We describe here our proposal for a microfluidic lab-on-chip devoted to protein identification by ESI/MS/MS. As a starting point we have realized silicon etched microchannels (10 mum depth) connected to a standard silicon needle. This elementary prototype ready for the sample mass spectrometer (MS) screening can be viewed as a first step before implementing basic functions as fluid actuation, Solid Phase Extraction (SPE) column, nanoemitter, necessary to cope with the nanospray problems.

We present a new characterization technique applicable to ferroelectric liquid crystals. This non perturbative technique allows the determination of the real and imaginary parts of the complex permittivity from current and voltage noise measurements. A current noise measurement set-up is described. The method is validate on an anti ferroelectric liquid crystal from simultaneous dielectric and noise measurements.