Research on reversible bonding of microfluidic chips based on stretch release adhesive strips

According to the "elastic bonding" concept, a thick intermediate layer of flexible resin has been suggested to absorb part of the polymerization shrinkage stress and to absorb shocks during function. In this study, the effect of an additional intermediate layer of a low-viscosity resin on the microrotary fatigue resistance (microRFR) of a hybrid composite bonded to dentin was evaluated. The hypotheses tested were that an intermediate layer of a low-viscosity resin (i) increases the microRFR to dentin, but (ii) has no effect on the static bond strength. Microtensile bond strength (microTBS) samples were loaded until failure or inserted in a microrotary fatigue testing device. Specimens were tested at 4 Hz until failure or until 10(5) cycles were reached. An additional intermediate elastic layer had no effect on the static microTBS, but significantly lowered the median microRFR from 28.4 MPa to 21.6 MPa. However, the application of an intermediate flexible layer had, no effect on the static microTBS. In conclusion, an additional elastic intermediate layer did decrease significantly the microRFR (rejection of hypothesis i), but did not alter the microTBS (acceptance of hypothesis ii). The decrease in microRFR most likely may be explained by the lower mechanical properties of the intermediary layer.

Low Distortion Solvent Bonding of Microfluidic Chips

In this thesis, nanometer scale semiconductor lasers and micrometer scale polymer based dye lasers are our focus in bringing the miniaturized lasers to applications in data transmission; ultra-small chemical / biological sensors; and ultra-compact spectroscopic sources. Combining the advantage of electrically driven semiconductor lasers and the advantage of a broad emission spectrum of dye molecules would utilize the highly dense multi-functional lab-on-a-chip by integrating microfluidic PCR, microfluidic fluorescent detection system, and compact visible and NIR detectors which are commercially available. On the other hand, in the meantime of pushing the size limit of the laser cavities, new phenomena with the nanoscale lasers enable further exploration and understanding in fundamental physics. In the first part of this thesis, two sub-micron scale semiconductor lasers are presented. The smallest lasers utilizing the disk structures—with diameters of approximately 600 nm—were realized in the InGaP/InGaAlP quantum well material system at room temperature, featuring ultra-small mode volumes of approximately 0.03 cubic?microns, and exhibiting single-mode operation at low threshold powers. And the first visible photonic crystal ultra-small mode volume lasers, with cavity volumes of approximately 0.01 cubic?microns, are realized in the same material system. They are ideally suited for use as spectroscopic sources and both of them can be lithographically tuned from 650 – 690 nm. In the second part of this thesis, two sub-millimeter-scale polymer-based dye lasers—a poly(dimethylsiloxane) (PDMS)-based mechanically tunable DFB dye laser and a poly(methylmethacrylate) (PMMA)-based second-order circular grating distributed feedback dye laser—are presented. Both of them are compatible with microfluidic technology, which gives freedom in integrating the lasers with the microfluidic chips. Compared to the soft lithography used in the PDMS-based dye laser, the nanoimprint lithography used in the PMMA-based dye laser would be more useful for fabricating ultra-small dye lasers and enabling mass production in the near future. At the end of the thesis, a nano-linewidth metal grating mask pattern transferred transient grating (MPT-TG) technique is described as a potential technique using the ultra-small lasers for molecular-dynamics study in solutions.

A RT wafer bonding method for waveguide applications was investigated using an ultrathin Fe intermediate adhesive layer between LiNbO3 (LN) and SiO2 wafers. Here we focus on the optimal amounts of Fe in this layer to minimize the propagation losses of the resultant LN on-insulator (LNOI) waveguide. A sub-nanometer-thick Fe-containing intermediate layer exhibited strong bonding strength (surface energy: >1 J m−2) at RT, which may be sufficient for device applications. The influence of the Fe intermediate layer on the propagation loss of light through the LNOI waveguide was also investigated using numerical calculations. The present study is expected to be a significant contribution to the development of fabrication techniques for waveguides composed of various materials to be bonded by this RT bonding method using a metal intermediate adhesive layer.

This report describes the preliminary study on plastic microfluidic chips with pre-loaded reagents for detecting homocysteine (Hcy). All reagents needed in an Hcy immunoassay were included in a microfluidic chip to remove tedious assay steps. A simple and cost-effective bonding method was developed to realize reagent-loaded microfluidic chips. This technique uses an intermediate layer between two plastic substrates by selectively patterning polydimethylsiloxane (PDMS) on the embossed surface of microchannels and fixing the substrates under pressure. Using this bonding method, the competitive immunoassay for SAH, a converted form of Hcy, was performed without any damage to reagents in chips, and the results showed that the fluorescent signal from antibody antigen binding decreased as the SAH concentration increased. Based on the SAH immunoassay, whole immunoassay steps for Hcy detection were carried out in plastic microfluidic chips with all necessary reagents. These experiments demonstrated the feasibility of the Hcy immunoassay in microfluidic devices.

The use of copper and its alloys to create parts for metallurgical equipment is associated with an increase in abrasive wear and high-temperature corrosion. In this regard, there is a need to apply a protective coating. In particular, to prevent wear and premature chipping of the metal of copper tuyeres, the surface is hardened with a coating of zirconium dioxide stabilized with yttria oxide by thermal spraying in an air atmosphere. Due to the difference in the coefficient of thermal expansion of copper (at T = 300 K: 16.7 µm/m оС and at T = 750 K: 19.7 µm/m оС) and its low resistance to gas corrosion, the application of zirconium oxide (produced by a preapplied intermediate layer that plays a role in matching the coefficient of thermal expansion (CTE) between the copper base and the ceramic coating. In addition, the intermediate layer protects copper from gas corrosion. In this case, The use of copper and its alloys to create parts for metallurgical equipment is associated with an increase in abrasive wear and high-temperature corrosion. In this regard, there is a need to apply a protective coating. In particular, to prevent wear and premature chipping of the metal of copper tuyeres, the surface is hardened with a coating of zirconium dioxide stabilized with yttria oxide by thermal spraying in an air atmosphere. Due to the difference in the coefficient of thermal expansion of copper (at T = 300 K: 16.7 pm/m °G and at T = 750 K: 19.7 pm/m оG) and its low resistance to gas corrosion, the application of zirconium oxide (produced by a pre-applied intermediate layer that plays a role in matching the coefficient of thermal expansion (CTE) between the copper base and the ceramic coating. In addition, the intermediate layer protects copper from gas corrosion. In this case, nickel-based alloys were used as intermediate layers. The use of nickel as the basis of intermediate layers is due to the fact that copper and nickel form a continuous series of solid solutions, such as cupronickel or monel metal-like structures. This, in turn, assumes a smooth transition of thermophysical properties from copper to nickel alloy. To ensure increased adhesion of the transition layer to copper by increasing the area of mutual contact between copper and the sublayer (dagger penetration) and significantly increasing the homogeneity of the material of the intermediate layer made of a nickel alloy, laser melting of the intermediate sublayer (Ni–B–Si system) was used on a laser complex based on laser LS-5 with a power of 5 kW with a KUKA KR-60HA robot in an argon atmosphere. To test the modes, experiments were carried out on copper samples of a flat shape and a body of rotation. The optimal parameters for the process of melting flat samples were: processing speed 33 mm/s, power from 400 to 3900 W, focal length from 200 to 230 mm, pitch between tracks: 0.25, 0.5 and 1 mm. The optimal parameters for the process of melting rotating samples were: laser radiation power 400–450 W, processing step 0.125; 0.5, focal length from 200 to 210 mm.

Porous Si(1 1 1) and Si(1 0 0) as an intermediate buffer layer for nanocrystalline InN films

Petroleum-based binders used in traditional wood composites are neither eco-friendly nor sustainable, highlighting the significant potential for biobased alternatives. However, traditional biobased wood adhesives often have drawbacks such as low bonding strength, low reactivity, poor water resistance, and the inability to be reused. To address these limitations, this study first prepared quinonized lignin (QSL) via a one-step oxidation method. Subsequently, a hyperbranched amino oligosiloxane nanocluster cross-linker (HAC) was synthesized by incomplete hydrolysis. The HAC enhances the adhesive’s comprehensive performance through its strong hydrophobicity, high density of reactive amino groups, and a balanced toughness–strength profile attributed to its hyperbranched structure. The resulting cured adhesive, QSLH, exhibits a high dry bond strength (≈5.30 MPa) and a wet bond strength (≈3.00 MPa) on wood. Furthermore, this lignin-based adhesive demonstrates high reactivity and reusable and mildew-resistant characteristics. The high-performance, eco-friendly, formaldehyde-free lignin-based adhesive developed in this work alleviates dependence on petrochemical resources in conventional adhesives, providing a reference for the development of biomass adhesives.

A passive microfluidic device using SU-8 photoresist has been developed for detection and analysis of viruses. Due to its high aspect ratio with almost vertical sidewalls and its chemical stability, SU-8 offers a wide variety of applications in the fabrication of microfluidic systems. This photoresist is transparent allowing optical detection and thus, identification of biomolecules. Additionally, SU-8 shows a good biocompatibility offering the possibility to develop assay on the surface that allows the specific binding of biomolecules for analytical applications. In this work, the performance of the microfluidic device has been successfully demonstrated by detection of specific contaminants in test solutions. The microfluidic chip is composed of SU-8 microstructures which have been fabricated by means of photolithography, using glass and silicon as substrate materials. Beside the fabrication of microchannels by means of SU8, we have also used SU-8 as adhesive layer. Introduction Microfluidic chips are nowadays a concept widely used in different fields like biology, pharmacy, medicine and other biotechnologies. Microfluidic or lab-on-a-chip technology promises significant advantages for carrying out rapid, efficient and specific analysis of microorganisms, which could be found in chemical substances. The cost and reagent consumption required for analysis will be reduced by using microfluidic devices due to their small size that is very useful for μTAS (Micro Total Analysis Systems) [1]. Furthermore, analysis time is reduced diffusion paths are shorter and reactions occur with higher efficiency. Depending on the design and complexity of the microstructures, such fluidic systems can provide all necessary functions as well as to identify or quantify specific pathogens. These functions include cell handling, sample mixing [2], sorting [3], transport and measurement of biomolecules [4]. IMSAS develops multichannel microfluidic systems (see figure 1) by using the negative photoresist SU-8. With this photoresist, microstructures up to 2mm of thickness and aspect ratios up to 20 can be constructed [5]. Besides, the SU-8 is a favourable material for fabrication of microchannels because of its excellent chemical stability against several acids and bases and its thermal stability. These properties make SU-8 a very attractive material for a wide range of applications like micro optics, micro machining, packaging and analytical microfluidic applications, as described in this paper. Figure 1: Picture showing one of several microfluidic devices which have been developed and fabricated at IMSAS. It is a microchannel with integrated columns. This paper presents a method for the fabrication of microchannels, which are composed completely of SU-8 for biological applications. The microstructures were fabricated by using a soft lithography process, which involves the negative resist and utilizes SU-8 itself as adhesive bonding, under low temperatures. B3.3 SENSOR+TEST Conference 2009 SENSOR 2009 Proceedings I 193 Borosilicate glass and silicon were selected as substrate material, because processing techniques of the silicon are well developed and SU-8 provides good adhesion to both materials.

This paper presents a room temperature bonding technique of glass substrates with a transparent bonding interface. As a room temperature bonding method, surface activated bonding (SAB) is applied for the bonding of glass using Si intermediate layer. However, the bonding interface is colored by the deposited Si layers, which leads to lower applicability to optical devices. In this study, a new concept of SAB is developed using aluminum oxide intermediate layer. Glass substrates are successfully bonded at room temperature via the aluminum oxide intermediate layers activated by Ar ion beam irradiation, showing a bond strength of 1.32 J m−2. It is also shown that the optical characteristics at the interface such as transparency and reflectance are not degraded, while the bonding interface of the SAB using Si intermediate layer deteriorates. The XPS and STEM‐EDX analyses indicate that the bonding is achieved through the amorphous and O‐deficient aluminum oxide interface. This technique will provide a transparent interface for glass bonding by a room temperature process, which is highly desired in optical device fabrication.

Adherent diamond-like carbon films were deposited on silicon substrates by the pulsed laser deposition method under a magnetic field. A composition-graded intermediate layer with a composition gradient from the substrate to the film was used to enhance the adhesion. It was found that adhesion was dependent on the thickness and composition gradient of the intermediate layer. For diamond-like carbon films deposited at room temperature, intrinsic stress in the interlayer played a key role. When an intermediate layer with a thickness of about 103 nm was used, the intrinsic stress was maximum and adhesion was poor. For films deposited at 60 °C and 100 °C, thermal stress and intrinsic stress should be considered together. Very thin intermediate layers ( 34 nm) were not suitable for good adhesion due to the presence of thermal stress. Adhesion was poor when the thickness of the intermediate layer was about 178 nm owing to imposition of the intrinsic stress. A composition profile with an exponent greater than 1 (silicon-riched) was beneficial to good adhesion.

An improved, laser-induced fluorescence-based micro-optical biosensor was designed and fabricated, with cyclic olefin copolymer (COC) optical waveguides, a poly(methyl methacrylate) (PMMA) fluidic substrate with an array of microlenses, and a COC coupling prism integrated with the waveguide substrate or cover plate. The double-sided hot embossed fluidic substrate had sampling zone microchannels on the bottom and microlenses on the top. Dissolved COC injected into polydimethylsiloxane (PDMS) lost molds embedded the waveguides in the PMMA cover plate and formed the integrated coupling prism. The embedded COC waveguide was flycut down to 50 μm. The cover plate and shallow, 1:20 aspect ratio, microchannels were thermal fusion bonded using a pressure-assisted boiling point control system, without sagging. The large COC prism coupled better to the waveguide. The highest intensity evanescent excitation of the waveguide was obtained near the critical angle. The maximum signal-to-noise ratio (SNR) was 119 and the lowest detection limit was 7.34 × 10-20 mol at a SNR of 2 for a 100 μm wide by 50 μm deep waveguide. The microlenses highly focused the fluorescent radiation in the sampling zone. The microfabricated waveguide enables rapid, low-cost detection of fluorescent samples with high SNR, a low detection limit, and high sampling efficiency.

The fabrication of polymer microchips allows inexpensive, durable, high-throughput and disposable devices to be made. Poly(methylmethacrylate) (PMMA) microchips have been fabricated by hot embossing microstructures into the substrate followed by bonding a cover plate. Different surface modifications have been examined to enhance substrate and cover plate adhesion, including: air plasma treatment, and both acid catalyzed hydrolysis and aminolysis of the acrylate to yield carboxyl and amine-terminated PMMA surfaces. Unmodified PMMA surfaces were also studied. The substrate and cover plate adhesion strengths were found to increase with the hydrophilicity of the PMMA surface and reached a peak at 600 kN m(-2) for plasma treated PMMA. A solvent assisted system has also been designed to soften less than 50 nm of the surface of PMMA during bonding, while still maintaining microchannel integrity. The extent to which both surface modifications and solvent treatment affected the adhesion of the substrate to the cover plate was examined using nanoindentation methods. The solvent bonding system greatly increased the adhesion strengths for both unmodified and modified PMMA, with a maximum adhesion force of 5500 kN m(-2) achieved for unmodified PMMA substrates. The bond strength decreased with increasing surface hydrophilicity after solvent bonding, a trend that was opposite to what was observed for non-solvent thermal bonding.

Aim: To assess the bonding strength of the Equia Forte resin modified glass ionomer cement to the hybrid composite material by applying different surface treatments. Methodology: 140 samples as 70 Equia Forte and 70 G-eanial composites were produced as 8 mm diameter 3 mm high cylindrical standardized samples. The samples were divided into 7 groups to treat surfaces. G-eanial composite resins as 4 mm diameter 3 mm high was placed onto the samples and polymerized. Then 1000 thermal cycle was applied and samples were mounted in the universal testing machine. Obtained bond strength values were recorded as Newton. One way Anova and Scheffe post hoc tests were performed for statistics. Results: In the G-aenial group, the highest bond strength was obtained with laser-bond method (N=17.71, P<0.05) and the lowest bonding strength was obtained with only laser-treated method (N=3.45, P<0.05). In the Equia group, the highest bond strength was obtained with air abrasion-bond method (N=9.29, P<0.05) and the lowest bonding strength was obtained with only laser-treated method (N=0.00, P<0.05). Conclusion: The fact that sufficient bond strength could not be reached by any surface treatment in Equia Forte may suggest that replacing the Equia Forte instead of repairs may be a better choice.

Objectives:Micromechanical retention of resin cements to alloys is an important factor affecting the longevity of metal base restorations. This study aimed to compare the bond strength and etching pattern of a newly introduced experimental etchant gel namely Nano Met Etch with those of conventional surface treatment techniques for nickel-chrome (Ni-Cr) and high noble alloys.Materials and Methods:A total of 120 discs (8×10×15 mm) were cast with Ni-Cr (n=20), high noble BegoStar (n=50) and gold coin alloys (n=50). Their Surfaces were ground with abrasive papers. Ni-Cr specimens received sandblasting and etching. High noble alloy specimens (BegoStar and gold coin) received sandblasting, sandblasting-alloy primer, etching, etch-alloy primer and alloy primer alone. Cylindrical specimens of Panavia were bonded to surfaces using Tygon tubes. Specimens were subjected to micro-shear bond strength testing after storing at 37°C for 24 hours.Results:In gold coin group, the highest bond strength was achieved after sandblasting (25.82±1.37MPa, P<0.001) and etching+alloy primer (26.60 ± 5.47 MPa, P<0.01). The lowest bond strength belonged to sandblasting+alloy primer (17.79±2.96MPa, P<0.01). In BegoStar group, the highest bond strength was obtained in the sandblasted group (38.40±3.29MPa, P<0.001) while the lowest bond strength was detected in the sandblast+ alloy primer group (15.38±2.92MPa, P<0.001). For the Ni-Cr alloy, bond strength in the etched group (20.79±2.01MPa) was higher than that in the sandblasted group (18.25±1.82MPa) (P<0.01).Conclusions:For the Ni-Cr alloy, etching was more efficient than sandblasting but for the high noble alloys, higher Au content increased the efficacy of etching.