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Abstract

For the purpose of biochip miniaturization, we developed a liquid spotter-based on silicon microcantilevers incorporating in-plane nanotips as a MEMS nanopatterning tool. We present new fabricated cantilevers with added piezoresistors for the contact force control during deposition. Matrices of droplets of 1 ¼m in diameter were achieved with a 10 ¼m interspot distance with high uniformity and high reproducibility by the nanotip cantilever with piezoresistive force controller.

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Abstract

The methods presented can be used for non-photostructurable polymers and where spin-coating cannot be performed. As demonstrator of the viability of the proposed fabrication process, they have been applied for the definition of hydrophobic barriers on a microfluidics network, which is dedicated to selectively dispense liquid to a spotting device consisting of 12 silicon microcantilevers.

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Abstract

A microspotting tool, consisting of an array of micromachined silicon cantilevers with integrated microfluidic channels is introduced. This spotter, called Bioplume, is able to address on active surfaces and in a time-contact controlled manner picoliter of liquid solutions, leading to arrays of 5 to 20-¼m diameter spots. In this paper, this device is used for the successive addressing of liquid solutions at the same location. Prior to exploit this principle in a biological context, it is demonstrated that: (1) a simple wash in water of the microcantilevers is enough to reduce by >96% the cross-contamination between the successive spotted solutions, and (2) the spatial resolution of the Bioplume spotter is high enough to deposit biomolecules at the same location. The methodology is validated through the immobilization of a 35mer oligonucleotide probe on an activated glass slide, showing specific hybridization only with the complementary strand spotted on top of the probe using the same microcantilevers. Similarly, this methodology is also used for the interaction of a protein with its antibody. Finally, a specifically developed external microfluidics cartridge is utilized to allow parallel deposition of three different biomolecules in a single run.

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Abstract

The focus of this work is a liquid dispensing system relying on the use of piezoresistive silicon microcantilevers. Experimental calibration of newly developed devices, required for global characterisation of their mechanical, electromechanical properties and other performance characteristics, is usually complicated due to structures small size as well as cost- and time-consumption. On the other hand, closed-form analytical solutions to nonlinear behaviour of devices of non-canonical geometry incorporating residual stresses are not commonly available either. Therefore, virtual calibration by means of computational modelling and simulation is not only adequate, but highly desirable. The finite element method has repeatedly proven its worth as a useful and efficient technique for the investigation of various mechanical and multiphysical systems, and has been extensively used in the design and analysis of MEMS. In the present work, the method is employed for virtual calibration of mechanical and electromechanical properties of novel liquid dispensing cantilevers. Separately, mechanical and electromechanical simulation results are in good agreement with experiment. Combined, these simulation data provide the ultimate calibration tool allowing control over the force applied by depositing devices onto the substrate and therefore preventing stiction problems and damage of fragile depositing surfaces.

Abstract

Electrowetting is used to assist the delivery of droplets by a contact method. The electro-assisted liquid dispensing technique enables to monitor the drop size via the voltage applied between the tool, i.e. silicon cantilevers, and the deposition surface. Voltages ranging from 0 to 210 V are used to deposit water-glycerol drops with diameters and volumes in the range of 5µm-40µm and 20fL-13pL. The presented results demonstrate that electrowetting-assisted deposition is of special interest for patterning applications requiring large features to be directly and quickly written using a minimum volume of reagents.

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Abstract

The methods presented can be used for non-photostructurable polymers and where spin-coating cannot be performed. As demonstrator of the viability of the proposed fabrication process, they have been applied for the definition of hydrophobic barriers on a microfluidics network, which is dedicated to selectively dispense liquid to a spotting device consisting of 12 silicon microcantilevers.

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Mots-Clés / Keywords