An Interference-Assisted Thermal Bonding Method for the Fabrication of Thermoplastic Microfluidic Devices

Solutions for the bonding and sealing of micro-channels in the manufacturing process of microfluidic devices are limited; therefore, further technical developments are required to determine these solutions. In this study, a new bonding method for thermoplastic microfluidic devices was developed by combining an interference fit with a thermal treatment at low pressure. This involved a process of first injection molding thermoplastic substrates with a microchannel structure, and then performing bonding experiments at different bonding conditions. The results indicated the successful bonding of microchannels over a wide range of bonding pressures with the help of the interference fit. The study also determined additional advantages of the proposed bonding method by comparing the method with the conventional thermal bonding method

Micro-optical lens array for fluorescence detection in droplet-based microfluidics

We demonstrate the design and integration of droplet-based microfluidic devices with microoptical element arrays for enhanced detection of fluorescent signals. We show that the integration of microlenses and mirror surfaces in these devices results in an 8-fold increase in the fluorescence signal and in improved spatial resolution. Using an array of microlenses, massively parallel detection of droplets containing fluorescent dyes was achieved, leading to detection throughputs of about 2000 droplets per second and per lens, parallelized over 625 measurement points

Three-dimensional simulation of droplet dynamics in planar contraction microchannel

In droplet-based microfluidic systems, microchannel design plays a primary role in transport and manipulation of liquid droplets. The objective of this paper is to investigate dynamics of a droplet in planar contraction microchannel via three-dimensional numerical simulation and theoretical analysis. In particular, this study characterizes three regimes of the droplet dynamics, namely, trap, squeeze and breakup, depending on capillary number (Ca) and contraction ratio (C). In addition, theoretical models have been proposed to describe transitions from one to another regime as a function of Ca and C. For the transition from trap to squeeze, the critical capillary number (Ca-Ic) was found to follow Ca-Ic = a(C-M - 1), whereas the critical capillary number (Ca-IIc) of transition from squeeze to breakup corresponds to Ca-IIc = c(1)C (1). Furthermore, details of the droplet dynamics along downstream of the contraction have been explored as well to depict deformation, retraction and/or breakup of the droplet. The present results would be useful guidelines in designing contraction microfluidic channel for precise control and manipulation of droplets

The microfluidic puzzle: chip-oriented rapid prototyping

International audienceWe demonstrate a new concept for reconfigurable microfluidic devices from elementary functional units. Our approach suppresses the need for patterning, soft molding and bonding when details on a chip have to be modified. Our system has two parts, a base-platform used as a scaffold and functional modules which are combined by ‘plug-and-play’. To demonstrate that our system sustains typical pressures in microfluidic experiments, we produce droplets of different sizes using T-junction modules with three different designs assembled successively on a 3 × 3 modular scaffold

Sol–gel combustion derived novel ternary transition metal boride-anisotropic magnetic powders and their magnetic property

We investigated the auto-ignition based sol–gel approach for the synthesis of ternary transition metal boride (TTMB) powders and studied their magnetic property. The obtained TTMB powders were found to have different crystallinity and magnetic behavior, based on the boron to metal ratio and further introduction of dysprosium into one of the sample lattice. The magnetic results obtained by vibrating sample magnetometer shows that TTMB is a soft magnet which demonstrates high ferromagnetic behavior with increased magnetic saturation based on the boron content, while the dysprosium based TTMB on contrary was found to exhibit an antiferromagnetic behavior. The TTMB powder showed no impurities as observed in Raman spectroscopy. The morphology of the powders obtained microscopically displays distinctive facets in the crystalline samples. The TTMB powders can be prospectively used in different polymer matrix to fabricate novel devices for sensors, environmental catalysts, radiation shielding and contrasting agents etc., to name a few

Ultra-high throughput detection of single cell β -galactosidase activity in droplets using micro-optical lens array

We demonstrate the use of a hybrid microfluidic-micro-optical system for the screening of enzymatic activity at the single cell level. Escherichia coli beta-galactosidase activity is revealed by a fluorogenic assay in 100 pl droplets. Individual droplets containing cells are screened by measuring their fluorescence signal using a high-speed camera. The measurement is parallelized over 100 channels equipped with microlenses and analyzed by image processing. A reinjection rate of 1 ml of emulsion per minute was reached corresponding to more than 10(5) droplets per second, an analytical throughput larger than those obtained using flow cytometry

Design and Fabrication of Micro Optical Film by Ultraviolet Roll Imprinting

With increasing demand for large-scale functional optical films with microstructure in the field of flat panel displays, a technology capable of fabricating large-scale polymeric micro-patterns has received much attention. To fabricate large-area micro-optical films, we designed and constructed an ultraviolet roll imprinting system consisting of a roll stamp, a material dispensing unit, a pair of flattening rollers, a contact roller, and a releasing roller. Two methods for fabricating roll stamps were considered: direct machining of the roll base and wrapping a flat stamp around the roll base. As practical examples of the roll imprinting process, we designed and fabricated a lenticular lens array, a pyramidal pattern, and a microlens array, and measured and analyzed their geometrical and optical properties. Our results suggest that the proposed UV roll imprinting process is a feasible method for mass producing large-scale functional optical films

Fabrication of All Glass Bifurcation Microfluidic Chip for Blood Plasma Separation

An all-glass bifurcation microfluidic chip for blood plasma separation was fabricated by a cost-effective glass molding process using an amorphous carbon (AC) mold, which in turn was fabricated by the carbonization of a replicated furan precursor. To compensate for the shrinkage during AC mold fabrication, an enlarged photoresist pattern master was designed, and an AC mold with a dimensional error of 2.9% was achieved; the dimensional error of the master pattern was 1.6%. In the glass molding process, a glass microchannel plate with negligible shape errors (~1.5%) compared to AC mold was replicated. Finally, an all-glass bifurcation microfluidic chip was realized by micro drilling and thermal fusion bonding processes. A separation efficiency of 74% was obtained using the fabricated all-glass bifurcation microfluidic chip