Polymethylmethacrylate Microfluidic Devices Research Articles

Особенности неразъемного клеевого соединения деталей микрофлюидных устройств из полиметилметакрилата

Особенности неразъемного клеевого соединения деталей микрофлюидных устройств из полиметилметакрилата

EFFECTS OF SURFACE PROPERTIES ON FLUID ENGINEERING GENERATED BY THE SURFACE-DRIVEN CAPILLARY FLOW OF WATER IN MICROFLUIDIC LAB-ON-A-CHIP SYSTEMS FOR BIOENGINEERING APPLICATIONS

In this research paper, in total 212 individual leakage-free Polymethylmethacrylate (PMMA) microfluidic devices are fabricated by maskless lithography, hot embossing lithography and direct bonding technique. The effect of channel aspect ratio on dyed water flow is investigated using these microfluidic devices. Experimental studies show that the dyed water flow is faster on the surface of higher wettability. The effect of capillary pressure on dyed water flow is studied in the fabricated PMMA microfluidic devices. According to the experimental observations, the centrifugal force has prominent effect on the dyed water flow. Also, the effect of bend angle is investigated on the surface-driven capillary flow of water. The polystyrene microparticles have been separated in the microfluidic lab-on-a-chip systems using the investigated flow features. A 100% separation efficiency is achieved in these lab-on-a-chip systems. These microfluidic lab-on-a-chip systems can be used to separate blood cells from human whole blood for further clinical tests. These experimental studies are important in bioengineering applications. The effect of bend angle as channel geometry to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems. Also, the effect of surface wettability as surface property to control the surface-driven capillary flow is investigated as a novel approach to control the separation time in microfluidic lab-on-a-chip systems.

Protein immobilization on the surface of polydimethylsiloxane and polymethyl methacrylate microfluidic devices.

PDMS and PMMA are two of the most used polymers in the fabrication of lab-on-chip or microfluidic devices. In order to use these polymers in biological applications, it is sometimes essential to be able to bind biomolecules such as proteins and DNA to the surface of these materials. In this work, we have evaluated a number of processes that have been developed to bind protein to PDMS surfaces which include passive adsorption, passive adsorption with glutaraldehyde cross-linking, (3-aminopropyl) triethoxysilane functionalization followed by glutaraldehyde or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride cross-linkers. It has been shown that the latter technique--using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride--results in more than twice the bonding of protein to the surface of PDMS microchannels than proteins binding passively. We have also evaluated a few techniques that have been tested for the functionalization of PMMA microchannels where we have found that the use of polyethyleneimine (PEI) has led to the strongest protein-PMMA microchannel bond. We finally demonstrated the effect of PDMS curing methodology on protein adsorption to its surface, and showed that increased curing time is the factor that reduces passive adsorption the most.

EXPERIMENTAL STUDIES OF SURFACE-DRIVEN CAPILLARY FLOW IN PMMA MICROFLUIDIC DEVICES PREPARED BY DIRECT BONDING TECHNIQUE AND PASSIVE SEPARATION OF MICROPARTICLES IN MICROFLUIDIC LABORATORY-ON-A-CHIP SYSTEMS

Proper bonding technique is investigated to achieve leakage-free surface-driven capillary flow in polymethylmethacrylate (PMMA) microfluidic devices. SU-8-based silicon stamp is fabricated by maskless lithography. This stamp is used to produce PMMA microchannel structure by hot embossing lithography. A direct bonding technique is mainly employed for leakage-free sealing inside PMMA microfluidic devices. The effect of surface wettability on surface-driven capillary flow is also investigated in PMMA microfluidic devices. The separation of polystyrene microparticles in PMMA laboratory-on-a-chip systems is investigated with the reduction of separation time by air dielectric barrier discharge (DBD) plasma processing of channel surfaces. This study is useful to fabricate the microfluidic laboratory-on-a-chip systems and to understand the surface-driven capillary flow.

Ultrasonic bonding for thermoplastic microfluidic devices without energy director

Thermal assisted ultrasonic bonding and solvent assisted ultrasonic bonding for thermoplastic microfluidic devices are proposed in this paper. Both of these two methods are non-molten bonding, energy director is not employed and thus avoided the problem of controlling the molten polymer flow along the microstructure during bonding process. Ultrasonic bonding system and interfacial temperature testing system were established. The critical amplitude for bonding was chosen by interfacial temperature tests to keep the bonding interface below glass transition temperature ( T g) of the polymer. Polymethylmethacrylate (PMMA) microfluidic devices were bonded by both thermal assisted ultrasonic bonding and solvent assisted ultrasonic bonding with the bonding time of 30 s and 20 s, respectively, while the tensile strength of 0.95 MPa and 2.25 MPa, respectively. The bonding area was 27 mm × 51 mm, the maximum dimension loss for the microstructure was 0.66% ± 0.60. A four-layer PMMA microfluidic device was also bonded using thermal assisted ultrasonic bonding, demonstrated the advantage of localized heating character of ultrasonic bonding and did some preliminary work in multilayer polymer MEMS device bonding. This paper provided the potential high throughput bonding methods for mass production of polymer microfluidic devices.

Microwave-induced, thermally assisted solvent bonding for low-cost PMMA microfluidic devices

We present a low-cost bonding method for polymethylmethacrylate (PMMA) microfluidics that combines elements of solvent bonding, thermal bonding and microwave bonding. Rather than using specialized equipment, we take household equipment and combine it to produce an effective bonding method that borrows from food packaging technologies for selective heating in a microwave. A poor solvent for PMMA is applied between two halves of a microfluidic system and clamped together using miniature binder clips. Excess solvent from the channels is then drawn out via capillary action and avoids channel clogging during the bonding process. Placing the whole apparatus in a commercial microwave will heat up the thin metal clips and cause the solvent to dissolve and bond the PMMA interface. The whole bonding process takes only a few minutes, and results in high bond strengths.

Characterisation of PMMA microfluidic channels and devices fabricated by hot embossing and sealed by direct bonding

In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp micro-structure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU-8) stamp includes microchannel arrays of approximately 30 μm in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 μm wide and 6 μm in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 °C embossing temperature were optimum for transferring the micro-structure to the PMMA substrate.

PMMA microfluidic devices with three-dimensional features for blood cell filtration

In this paper, a PMMA (polymethylmethacrylate) microfluidic device with filtration features fabricated by hot embossing and thermal bonding was used to separate RBCs (red blood cells) from whole rat blood. The filtration features are composed of 20 µm deep and 300 µm wide main channels, 15 µm high and 25 µm wide micro-dams which were fabricated in main channels and an array of orthogonal side channels for perfusion flow to collect RBCs. As rat blood advances through the main channels, a perfusion flow through the side channels washes away RBCs which are sufficiently small to enter the gaps between the micro-dams and the cover plate. A silicon mold fabricated by dry etching was used to produce three-dimensional filtration features on PMMA substrates. Oxygen plasma treatment was used to increase the adhesive ability of PMMA surfaces, which enables thermal bonding at 86 °C and 0.75 MPa. The distortion of microchannels and micro-dams has been minimized, which makes the value of the gap between the micro-dam and the cover plate appropriate for cell filtration.