Microfluidics has brought diverse advantages to chemical processes, allowing higher control of reactions and economy of reagents and energy. Low temperature co-fired ceramics (LTCC) have additional advantages as material for fabrication of microfluidic devices, such as high compatibility with chemical reagents with typical average surface roughness of 0.3154 μm, easy scaling, and microfabrication. The conjugation of LTCC technology with microfluidics allows the development of micrometric-sized channels and reactors exploiting the advantages of fast and controlled mixing and heat transfer processes, essential for the synthesis and surface functionalization of nanoparticles. Since the chemical process area is evolving toward miniaturization and continuous flow processing, we verify that microfluidic devices based on LTCC technology have a relevant role in implementing several chemical processes. The present work reviews various LTCC microfluidic devices, developed in our laboratory, applied to chemical process miniaturization, with different geometries to implement processes such as ionic gelation, emulsification, nanoprecipitation, solvent extraction, nanoparticle synthesis and functionalization, and emulsion-diffusion/solvent extraction process. All fabricated microfluidics structures can operate in a flow range of mL/min, indicating that LTCC technology provides a means to enhance micro- and nanoparticle production yield.
We propose a novel platform for detecting as well as measuring the size of individual droplets in microfluidic channels using microstrip transmission lines. The most outstanding feature of our platform is that, as opposed to previous related works, its design allows for the droplet to flow in a microfluidic channel fabricated between the top strip and the ground plane of a microstrip transmission line. This provides enhanced interaction of the electromagnetic field with the detected droplets. The proposed design allows us to measure droplet size directly from the phase of the microwave signal, without the need for a resonator. The platform is based on low temperature co-fired ceramic (LTCC), which makes it more compatible with Radiofrequency (RF) and microwave technology than platforms used in previous works. With this platform, we are able to measure droplets as small as 150 µm in radius. It is worth pointing out that our device could also be used for detection, counting and measurement of other microscopic objects.
Dedico este trabalho à minha família, em especial aos meus pais, Carlos e Zulmira. AGRADECIMENTOSAo Prof.º Dr. Marcelo Nelson Pàez Carreño, pela orientação e pelo constante estímulo transmitido durante todo trabalho.A todos os membros do grupo GNMD, pelo apoio, pelas sugestões e críticas ao longo do trabalho.Aos meus pais, Carlos Roberto Schianti e Zulmira Novais Schianti, e também a minha irmã Elizandra Novais Schianti, pelo apoio e estímulos dados no decorrer deste trabalho e ao longo de toda minha vida estudantil.Ao Daniel Orquiza de Carvalho, meu namorado, pela dedicação, paciência e compreensão, que sem dúvida nenhuma foram imprescindíveis para a conclusão deste trabalho.A minha amiga Taís Aparecida Garcia Moreira, pelo apoio a este trabalho e pela amizade desde os tempos do IFUSP.A minha amiga Patrícia Gomes do Amaral, pela amizade de longa data e pela orientação com sobre o uso dos scalps e cateteres. ABSTRACTIn this work, a process for the fabrication of microchannels over borlosilicate 7059 Corning Glass is presented. The main objective is to develop a simple and complete process for the fabrication of microfluidic systems over glass, that can be further improved in the future, with the integration of optical, electronic and active microfluidic devices such as valves and micropumps, for sensing and flow control.The fabrication process has three main parts. The first part is the microchannel production, which is achieved through contact-lithography and wet etching. In the etching studies, a solution that led to the fabrication of channels with uniform and smooth surfaces, without residue formation was sought. The best results were attained with a HF + HCl + H 2 O (1:2:3), which allow for the production of channels with depths of up to 150 μm.The second part of the fabrication process is the microchannels encapsulation, which is achieved through direct (glass-glass) bonding at room temperature, with applied pressure ranging from 0.1 to 1.0 MPa. The best results were obtained with pressure values above 0.5 MPa, which allowed for the bonding of up to 95 -100% of the glass sufaces.The third part of the fabrication process concerns the interconnection with the outside environment, which involves hole production and the introduction of tubes, to allow external access of liquids. For the hole production, a computer controlled positioning system was developed, for accurate positioning of the glass substrate in the x, y and z directions, with a precision of a few micrometers. This system guaranteed the necessary alignment of the upper and lower glass substrates, which were bonded for the encapsulation of the microchannels. The holes were made with diamond burs with a common drill. Medical catheters and scalps were used as access tubes, with epoxy resin.The characterization of the fabricated microfluidic systems was achieved by monitoring the flow of aniline aqueous solutions, which was maintained through a peristaltic pump. Reproducible results were obtained, with the production smooth and residue free microcha...
Dielectric barrier discharge (DBD) plasma was used to change the wettability of a SU-8 photoresist, reducing the contact angle and improving the surface smoothness. As most polymers, SU-8 has hydrophobic surfaces which prevents the adhesion of biological samples when used to fabricate biochemical sensors. Here, DBD Plasma treatment was conducted over the SU-8 surface, reducing the contact angle from 78° to 12°. The advantage of this treatment is that the SU-8 surface maintains the hydrophilic surface behavior over 24 h time period. DBD plasma modified the SU-8 surface wettability under low temperature variation and does not cause great irregularities on the surface. The highest value of root mean square surface roughness after 10 min exposure was 2.9 ± 0.3 nm.
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