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Microfluidics integration of acoustic biosensors is an actively developing field. Despite significant progress in “passive” microfluidic technology, integration with microacoustic devices is still in its research state. The major challenge is bonding polymers with monocrystalline piezoelectrics to seal microfluidic biosensors. In this contribution, we specifically address the challenge of microfluidics integration on gallium arsenide (GaAs) acoustic biosensors. We have developed a robust plasma-assisted bonding technology, allowing strong connections between PDMS microfluidic chip and GaAs/SiO2 at low temperatures (70 °C). Mechanical and fluidic performances of fabricated device were studied. The bonding surfaces were characterized by water contact angle measurement and ATR-FTIR, AFM, and SEM analysis. The bonding strength was characterized using a tensile machine and pressure/leakage tests. The study showed that the sealed chips were able to achieve a limit of high bonding strength of 2.01 MPa. The adhesion of PDMS to GaAs was significantly improved by use of SiO2 intermediate layer, permitting the bonded chip to withstand at least 8.5 bar of burst pressure. The developed bonding approach can be a valuable solution for microfluidics integration in several types of MEMS devices.

Manipulating micro and nano-biological particles like extracellular vehicles (EVs), without extracting them from their biological media, presents a big challenge for diagnosis purposes. Here we present the design and fabrication of a sorting device based on the combination of microfluidic and electroacoustic modules that is capable of aligning and sorting submicron biological particles according to their size, compressibility or mass density, all in a tunable way. The device relies on a lithium niobate (LN) substrate to generate acoustic waves assembled with a micromachined glass layer for microfluidic circuits. The interference between the two surface acoustic waves (SAWs) generated by interdigitated transducers (IDTs) create a distribution of an acoustic radiation force (ARF). This force affects differently particles depending on their physical proprieties. The device is powered by an electronic circuit with a phase shifter to move the node of the standing surface acoustic wave (SSAW) along the channel width. When the device is powered at resonance frequency of the IDTs, experiment shows submicron particles alignment along the channel. By shifting the electrical signal between the two IDTs we can translate the pressure node at any targeted position in the channel width. The particles are then driven to one selected outlet.

The micro-conveyor is a 9 × 9 mm2 manipulation surface able to move millimeter-sized planar objects in the four cardinal directions using air flows. Thanks to a specific design, the air flow comes through a network of micro-channels connected to an array of micro-nozzles. Thus, the micro-conveyor generates an array of tilted air jets that lifts and moves the object in the required direction. In this paper, we characterize the device for transport and positioning tasks and evaluate its performances in terms of speed, resolution and repeatability. We show that the micro-conveyor is able to move the object with a speed up to 137 mm · s-1 in less than 100 ms whereas the positioning repeatability is around 17.7 μm with feedback control. The smallest step the object can do is 0.3 μm (positioning resolution). Moreover, we estimated thanks to a dynamic model that the speed could reach 456 mm· s-1 if several micro-conveyors were used to form a conveying line.

In this paper, we present an interesting method to microfabricate a tilted micro air jet generator. We used the well-know deep reactive ion etching (DRIE) technique in order to realize in a silicon substrate a double side etching. For aircraft and cars, micro air jets will take an important place for fluid control. Micro air jets are characterized by their speed, frequency and tilt. Usually, this micro air jets are produced by fluidic microsystems. We presented experimental results about micro tilted air jets. A comparison between finite element method simulation, theory and experimental results are performed to define the microsystem geometry leading a specific air jet angle.