Bonding of PMMA to silicon by femtosecond laser pulses

Sensors and Actuators B: Chemical, 2013

Here, we introduce an instantaneous and robust strategy for bonding poly(methylmethacrylate) (PMMA) substrates via ethanol treatment combined with subsequent UV irradiation under ambient conditions, and examine the bonding reversibility by varying the percentage of the ethanolic solution manufactured. Organic solvent such as ethanol can activate the surface of PMMA without sacrificing the optical property of the PMMA substrate, and a subsequent exposure to UV recrosslinks the diffused monomers of acrylate functionalities to realize permanent bonding of two PMMA substrates under mild and ambient experimental conditions, which minimizes the deformation of channel profiles. To achieve robust sealing, two PMMA substrates were immediately placed in direct contact with each other after the treatment with ethanolic solution, and were irradiated under UV. Permanent sealing was realized in less than 1 min. Various bonding analyses were conducted by performing tensile strength measurement, high-throughput leakage test, burst test, and peel test. The highest bonding strength was determined to be approximately 6.17 MPa when 90% ethanolic solution was employed, and the bonding was sufficiently robust to endure intense introduction of liquid whose per-minute injection volume was almost 1200-fold higher than the total internal volume of the microchannel adopted. We also investigated the potential in the manipulation of bonding reversibility, and the critical percentage of ethanolic solution to realize irreversible bonding for PMMA assemblies based on the proposed strategy was determined to be just over 50%.

Micromachines

We present a rapid and highly reliable glass (fused silica) microfluidic device fabrication process using various laser processes, including maskless microchannel formation and packaging. Femtosecond laser assisted selective etching was adopted to pattern microfluidic channels on a glass substrate and direct welding was applied for local melting of the glass interface in the vicinity of the microchannels. To pattern channels, a pulse energy of 10 μJ was used with a scanning speed of 100 mm/s at a pulse repetition rate of 500 kHz. After 20–30 min of etching in hydrofluoric acid (HF), the glass was welded with a pulse energy of 2.7 μJ and a speed of 20 mm/s. The developed process was as simple as drawing, but powerful enough to reduce the entire production time to an hour. To investigate the welding strength of the fabricated glass device, we increased the hydraulic pressure inside the microchannel of the glass device integrated into a custom-built pressure measurement system and moni...

2012

Abstract. We have investigated femtosecond-laser-induced microstructures (on the surface and within the bulk), gratings, and craters in four different polymers: polymethyl methacrylate, polydimethylsiloxane, polystyrene, and polyvinyl alcohol. The structures were achieved using a Ti: sapphire laser delivering 100-fs pulses at 800 nm with a repetition rate of 1 kHz and a maximum pulse energy of 1 mJ.

2010

Abstract Laser direct writing technique is employed to fabricate microstructures, including gratings (buried and surface) and two-dimensional photonic crystal-like structures, in bulk poly (methylmethacrylate)(PMMA) and poly (dimethylsiloxane)(PDMS) using∼ 100 femtosecond (fs) pulses. The variation of structure size with different writing conditions (focussing, speed and energy) was investigated in detail.

Biosensors, 2021

This review summarizes and compares the available surface treatment and bonding techniques (e.g., corona triggered surface activation, oxygen plasma surface activation, chemical gluing, and mixed techniques) and quality/bond-strength testing methods (e.g., pulling test, shear test, peel test, leakage test) for bonding PDMS (polydimethylsiloxane) with other materials, such as PDMS, glass, silicon, PET (polyethylene terephthalate), PI (polyimide), PMMA (poly(methyl methacrylate)), PVC (polyvinyl chloride), PC (polycarbonate), COC (cyclic olefin copolymer), PS (polystyrene) and PEN (polyethylene naphthalate). The optimized process parameters for the best achievable bond strengths are collected for each substrate, and the advantages and disadvantages of each method are discussed in detail.

Procedia Technology, 2015

Laser micro-machining offers a versatile tool for the rapid manufacturing of polymeric microfluidics systems, with a typical turnaround-time in the order of minutes. However, the chaotic nature of the thermal evaporative ablation process can yield a significant number of defects in the surface of the manufactured microchannels, in the form of residual condensed material. In this work we have investigated the use of solvent evaporation by which to not only laminate bond the laser machined structures but to remove a significant number of the defect formed by the condensation of residual polymer. Results are presented of the surface profiling of the bonded channel structures and demonstrations of the bonding of the microchips to produce autonomous capillary microchannels.

Informacije Midem-journal of Microelectronics Electronic Components and Materials, 2017

Two room-temperature bonding processes for thermoplastic PDMS polymer covalent bonding based on the organic substrate surface functionalization by means of organofunctional silanes APTES and amine-PDMS linker were developed and applied. The efficiency of covalent bonding was evaluated by measuring water contact angles on oxygen plasma pretreated surfaces and by measuring burst pressure on fabricated test devices. Developed amine-PDMS linker bonding process resulted in bond strength of 5 bar and 2 bar on continuous pressure of air and water respectively, while water initiated the hydrolysis of covalent bonds established via the modified APTES bonding process. Both bonding processes were applied on piezoelectric micropumps where glass substrate was replaced by thermoplastic substrate. Micropumps employing amine-PDMS linker exhibit no deterioration in their performance after eight weeks of continuous operation.

Sensors and Actuators B: Chemical, 2010

This paper reports on the development and application of a surface modification technique as an improved method for bonding polymer microfluidic substrates. This technique readily produced complete microfluidic chips via plasma oxidation followed by silane reagent treatment on the polymer surface. Characterization of the bonded chips was performed using scanning electron microscopy (SEM), water contact angle measurement, and tensile strength measurement. SEM images showed that the integrity of the channel features was successfully preserved. A bond strength approaching that of solvent welding was demonstrated. This technique has been successfully applied to bond dissimilar polymer substrates (polymethylmethacrylate (PMMA), amorphous polyethylene terephthalate (APET), polycarbonate (PC)), and is also applicable to bonding a hard polymer substrate to polydimethylsiloxane (PDMS) or glass.

Applied Surface Science

Large-scale microstructures were imprinted on the surface of silicon with dimensions of 1 mm × 1 mm by femtosecond laser line-by-line scanning irradiation. The scanning was made under air and under chlor/hydrogen based liquid layers. Scanning electron microscope investigations evidenced homogeneous surface microstructures, such as: ripples with sub-wavelengths dimensions, Si pillars and directional oriented bacilliform structures. The dependence of the surface morphology on laser energy, scanning speed and irradiation media was analyzed. In air, the microstructure changes from directionalarranged bacilliform structures to well-known ripple structures with a width of about 525 nm. When using the liquid media, we observe ripple structures with a width of about 370 nm and an overlapping of those that evolve in certain regions into Si pillars. The surfaces show interesting gradient topography behaviour which could be used as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth. By using chlor and hydrogen based liquids we were able to explore the microstructuring of the silicon by line-by-line irradiation process using the femtosecond laser.

IEEE Transactions on Components, Packaging and Manufacturing Technology, 2012

A novel sealing method is proposed for encapsulating devices comprised of glass substrates. This sealing method is based on applying a glass frit paste cord onto the substrate and then using a laser beam to locally supply the necessary energy to allow the formation of a hermetic bonding layer. A detailed description of the laser bonding technique, the necessary equipment and method, and a preliminary study is carried out. The need to apply mechanical pressure during the bonding step is averted, thus facilitating the manufacturing process. The glass bonding cord obtained by the laser-assisted process was found to have an excellent contact with both substrates and no gas inclusions or voids were detected, indicating that an effective sealing was achieved. Preliminary hermeticity tests of the laserbonded cells yielded encouraging results. The developed laserassisted glass frit bonding process is a promising technique for obtaining hermetic sealing of photoelectronic and electrochemical devices, as it allows temperature-sensitive materials to be used inside them.