Two-photon polymerization with a visible micro-laser is used to polymerize several resists in a microfluidic channel. The minimum resolution that is achievable, named voxel, is estimated using an ...ascending scan method for different photosensitive polymers: standard microelectronics resists such as SU8 and AZ1512HS – construction resists such as PEG based and 3015 – electrically movable resist based on 4-HBA. Once extracted the polymerization parameters for creating and overlapping voxels, complex 3D structures are built inside the microfluidic channel. Thanks to microfluidics, the resist flow is stabilized during the microfabrication process. Finally, an electro-sensible arm is created with both PEG and 4-HBA based resists. A micrometer-range displacement of this arm is observed under electrical field actuation normal to the arm axe.
Precise spatial localization of colloids is required to fully exploit the potential of colloidal handling in a microfluidic channel. In this work, we present the fabrication and integration of a new ...type of microfluidic chip that can provide such tools. With the use of photopatternable silicones, two levels of metal deposited electrodes are sandwiching a microchannel layer, whom height is precisely control. The microfabrication process does not require extra etching step for eventual residual layer, thus making electrical contact between the fluid in the channel and electrodes on the upper and lower slices. The chip is integrated in an experimental bench that addresses up to 120 electrodes immerged and aligned into the channel itself. This high level of integration makes colloidal handling with dielectrophoresis possible thanks to the introduction of several key functions such as focus, defocus, stop or vectorial path. Finally, first results are presented with the quantification of the influences of the applied potential frequency and peak-to-peak voltage for the stop function with 1
μm polystyrene colloids under a 600
μl/min flow, highlighting optimal frequency for this function.
•Three-dimensional particle structures were built from a multi-color (red, green and blue) colloidal suspension using capillary for assembly.•Optical response was studied under UV irradiation after ...transfer on a silicon surface.•Particle structures exhibit a polychromatic visible light emission.•Spectrum and color can be controlled by varying the red, green and blue particle ratio.•We report color coordinates very closed to the ideal pure white.
This work presents the fabrication of on-chip polychromatic light source from a colloidal suspension. Capillary force assembly of the colloidal mixture composed from red, blue and green fluorescent dye doped 100nm particles is performed on a patterned substrate to create particles structure composed of ∼10,000 nanoparticles with a natural hexagonal close-packed arrangement. Under UV excitation, the particle structure exhibit a white light emission closed to the CIE characteristics of the ideal pure white.
Resist pull-off during mold-substrate separation is one of the major limiting factor for high resolution replication using nanoimprint lithography (NIL). Adhesion properties of anti-sticking layers ...(ASLs) are generally obtained using contact angle measurements; however, this technique does not take into account mold penetration into the polymer and interactions between the mold and resist that can affect the demolding step. In this paper, we present results on adhesion properties of different ASLs used for NIL, measured using AFM nano-indentation tests. AFM tips were coated with two different ASLs and nano-indentations were performed on three different polymers (NEB22A2, PMMA, and polycarbonate). The total force necessary to remove the AFM tip from the indented resist surface was measured for both ASL-coated and uncoated tips to more quantitatively analyse the importance of adhesion forces in NIL. Results show important influence of both ASL and polymer used on adhesion properties.
With the rise of microfluidics for the past decade, there has come an ever more pressing need for a low-cost and rapid prototyping technology, especially for research and education purposes. In this ...article, we report a rapid prototyping process of chromed masks for various microfluidic applications. The process takes place out of a clean room, uses a commercially available video-projector, and can be completed in less than half an hour. We quantify the ranges of fields of view and of resolutions accessible through this video-projection system and report the fabrication of critical microfluidic components (junctions, straight channels, and curved channels). To exemplify the process, three common devices are produced using this method: a droplet generation device, a gradient generation device, and a neuro-engineering oriented device. The neuro-engineering oriented device is a compartmentalized microfluidic chip, and therefore, required the production and the precise alignment of two different masks.
Janus particles have proven to be original particles to sense protein–cell interactions or to organize cell on a substrate. This work presents a covalent coupling strategy to graft fibronectin on a ...specific side of Au/PS or Au/SiO2 1μm Janus particles. By studying several buffers that could limit adsorption of protein on plain particles of PS, SiO2 and Au, fibronectin is covalently grafted on those particles. We demonstrate two ways of grafting proteins on one side of the Janus particles, either on the Au side functionalized with thiols or on the PS/SiO2 side activated with carboxylate groups.
Microcavities consisting of two identical tapered mirrors etched into silicon-on-insulator ridge waveguides are investigated for operation at telecommunication wavelengths. They offer very small ...modal volumes of approximately 0.6 (λ/n)3 and calculated intrinsic Q factors of 400 000. We have measured a Q factor of 8900 for a loaded cavity, in agreement with the theoretical value. In contrast to recent works performed on suspended membranes, the buried SiO2 layer is not removed. The cavities possess strong mechanical robustness, thus making them attractive from the viewpoint of integration in large systems. The cavity Q factor is much larger than those previously obtained for similar geometries on a substrate.
Micromagnets have been reported to successfully levitate picoliter water droplets in air. Manipulation of levitating water droplets is a contamination-free alternative to digital-microfluidic ...labs-on-chip where droplets are handled in channels or on a substrate. An integrated electromagnetic hybrid device combining dielectrophoretic (DEP) forces to control the position of levitating droplets along a magnetic groove, is proposed. Diamagnetic forces are analytically computed with CADES while Comsol Multiphysics™ (FEM) is used for the DEP forces. Approximations of the `point dipole model' are compared to the Maxwell Stress Tensor method applied on the 3-D model. Based on these results, an electric sequence for polarizing planar parallel Indium Tin Oxide (ITO) electrodes is proposed in order to provide a stable and accurate control of the droplet microposition along the gap. The use of these electrodes as micro-conductors to produce variable magnetic fields for magnetophoretic droplet actuation is considered and compared to DEP actuation.
Convective-capillary force assembly (CFA)
1 and the capillary separation effect
2 are combined in order to fabricate Au colloidal dimers with modulated edge-to-edge inter-particle spacings. A study ...of the assembly process demonstrates the effect of temperature and air-suction flow rate on contact-line speed and receding contact-angle. Finally, the dark-field spectroscopy of the polarized light scattered by the dimers shows evidence of plasmonic coupling.
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