Papers by Keyword: Microfluidic Channels

Abstract: Additive manufacturing of microfluidic devices is a field of increasing interest due to the great variety of fields where they can be used, especially in physicochemical, biological and medical ones. These devices include internal channels whose manufacture can be challenging as it takes place close to or into the micro geometric scale. On the other hand, the use of low-cost techniques can provide access to certain services in depopulated areas in different fields, so this approach can be of interest in the development of new products under new production and living contexts. In this work, the geometrical ranges of practical application for the manufacture of microfluidic channels by two of the most common additive manufacturing techniques for polymeric materials (Fused Filament Fabrication and the Stereolithography) are analyzed by means of an evaluation of the dimensional accuracy obtained in samples with channels of circular section. The circular channels present diameters that vary from 2 mm to the minimal size feasible which each printer (a Markforged Onyx One, a Ultimaker S5 and a Formlabs Form3). The Ultimaker S5 (FFF) equipment is the one that presents the best results, being the dimensional deviations around 0.2 mm in a wide range 1 < d_nom (mm) < 2; and contrary to the expectations, the SLA system provides the worst results, with a growing trend starting from deviations of 0.6 mm. An obturation effect in the channels has been also detected, being critical in the case of nominal diameters lower than 0.8 mm for the Ultimaker S5 system. In general, it can be concluded that the FFF technology is a more reliable option compared to SLA under the printing parameters considered in this work and for the materials used in this study.

Abstract: Spin rinse drying (SRD) and surface tension gradient drying (STG) are used to clean and dry wafers after wet processing. These methods are effective at removing surface fluid and fluid trapped by capillary forces in small (<1um) features. SRD and STG processes combine driven fluid flows with controlled evaporation of thin water films to leave a dry wafer with low defect density (i.e. a low number of physical particle process adders, or areas of haze or oxidation).

Abstract: AC electrokinetics is one of many methods used to move particles in microfluidic channels. This paper presents single cell trapping efficacy using dielectrophoresis (DEP) force of two biochip designs; a planar biochip and the new sandwiched-insulation with back contact (SIBC) biochip. The new biochip, is structured on a glass slide, consists of microelectrode arrays patterned on top of Nickel-Chromium (NiCr) and Gold (Au) layers. Prior to the microelectrode patterning, a back contact layer of NiCr and Au was coated with SU-8 2005. Then, the SU-8 2005 or the insulation layer was patterned with arrays of microcavities. In contrast, the planar biochip consists of 2 layers; an SU-8 2005 insulation layer and NiCr and Au metal layers constructed on a Silicon Nitride (Si₃N₄) substrate. The electric field intensity results simulated using Comsol v3.5a software indicated that DEP force generated from the SIBC biochip are greater than the planar biochip design. Results from experiment with polystyrene microbeads and Ishikawa cancer cells also showed that the SIBC biochip has higher trapping efficiency than the planar biochip. These promising results indicate that the SIBC biochip is capable of trapping single cells and can be used to facilitate studies on intracellular activities using surface the replicating technique known as the Bioimprint technique.

Abstract: The lithographic exposure characteristic of amorphous silica (SiO₂) was investigated for 6.8 MeV ¹⁶O³⁺ ions. A programmable proximity aperture lithography (PPAL) technique was used for the ion beam exposure. After exposure, the exposed pattern was developed by selective etching in 4% v/v HF. Here, we report on the development of SiO₂ in term of the etch depth dependence on the ion fluence. This showed an exponential approach towards a constant asymptotic etch depth with increasing ion fluence. An example of microfluidic channels produced by this technique is demonstrated.

Abstract: In this paper, a new approach for controllable bio-fabrication of patterened cellulose nano-fibers has been proposed by micro-fluidic techniques, via the combination of biological technology and nanotechnology. We attempted to make sure whether A. xylinum can regularly move within micro-fluidic channels and further to clarify how the flow can direct and control the assembly of cellulose nano-fibers. The movement of A. xylinum within the micro-fluidic channels was observed in vivo by real time video microscopy. The well-patterned materials have great potential utility in tissue engineering.

Abstract: The gap control problem in hole-machining of Pyrex® wafer by electrochemical discharge machining (ECDM) to obtain a smooth quality and acceptable material removal rate is studied. Analysis of the pulse signals shows that the average current pulse interval is constant, and it is mainly related to the ion translation conditions, such as the electrolyte concentration and the flushing strategy. The most steady and intense average current density can be obtained if the voltage on-time is around 3 times the average current pulse interval and the voltage off-time is 1/4 of the on-time for bubble film dissipation. The utmost allowable feed rate at each depth is recorded as the reference of the feed rate in real continuous machining to avoid the damage to the wafer. By applying 80% of the extreme allowable feed rate, 99.9% quality-proved holes can be acquired. The diametric error at the entrance or exit is within 6%. Besides, there is no crater-like problem around the hole that facilitates the succeeding bonding process. This study contributes to the successful production of reusable optical biological chips with integrated micro fluidic channels.