Materials for Microfluidic Chips Fabrication

Through manipulating fluids using microfabricated channeland chamber structures, microfluidics is a powerful tool to realize high sensitive, high speed, high throughput, and low cost analysis. In addition, the method can establish a well-controlled microenivroment for manipulating fluids and particles. It also has rapid growing implementations in both sophisticated chemical/biological analysis and low-cost point-of-care assays. Some unique phenomena emerge at the micrometer scale. For example, reactions are completed in a shorter amount of time as the travel distances of mass and heat are relatively small; the flows are usually laminar; and the capillary effect becomes dominant owing to large surface-to-volume ratios. In the meantime, the surface properties of the device material are greatly amplified, which can lead to either unique functions or problems that we would not encounter at the macroscale. Also, each material inherently corresponds with specific microfabrication strategies and certain native properties of the device. Therefore, the material for making the device plays a dominating role in microfluidic technologies. In this Account, we address the evolution of materials used for fabricating microfluidic chips, and discuss the application-oriented pros and cons of different materials.

This generally follows the order of the materials introduced to microfluidics. Glass and silicon, the first generation microfluidic device materials, are perfect for capillary electrophoresis and solvent-involved applications but expensive for microfabriaction. Elastomers enable low-cost rapid prototyping and high density integration of valves on chip, allowing complicated and parallel fluid manipulation and in-channel cell culture. Plastics, as competitive alternatives to elastomers, are also rapid and inexpensive to microfabricate. Their broad variety provides flexible choices for different needs. For example, some thermosets support in-situ fabrication of arbitrary 3D structures, while some perfluoropolymers are extremely inert and antifouling. Chemists can use hydrogels as highly permeable structural material, which allows diffusion of molecules without bulk fluid flows. They are used to support 3D cell culture, to form diffusion gradient, and to serve as actuators. Researchers have recently introduced paper-based devices, which are extremely low-cost to prepare and easy to use, thereby promising in commercial point-of-care assays.

In general, the evolution of chip materials reflects the two major trends of microfluidic technology: powerful microscale research platforms and low-cost portable analyses. For laboratory research, chemists choosing materials generally need to compromise the ease in prototyping and the performance of the device. However, in commercialization, the major concerns are the cost of production and the ease and reliability in use. There may be new growth in the combination of surface engineering, functional materials, and microfluidics, which is possibly accomplished by the utilization of composite materials or hybrids for advanced device functions. Also, significant expanding of commercial applications can be predicted.

Understanding More What is PDMS

Polydimethylsiloxane or shortly known as PDMS belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological or flow properties. PDMS is optically clear, and, in general, inert, non-toxic, and non-flammable. It is also called dimethicone and is one of several types of silicone oil (polymerized siloxane). Its applications range from contact lenses and medical devices to elastomers; it is also present in shampoos as dimethicone makes hair shiny and slippery, food antifoaming agent, caulking, lubricants, kinetic sand , and heat-resistant tiles.

PDMS is viscoelastic, meaning that at long flow times (or high temperatures), it acts like a viscous liquid, similar to honey. However, at short flow times (or low temperatures), it acts like an elastic solid, similar to rubber. In other words, if some PDMS is left on a surface overnight (long flow time), it will flow to cover the surface and mold to any surface imperfections. However, if the same PDMS is rolled into a sphere and thrown onto the same surface (short flow time), it will bounce like a rubber ball.

Although the viscoelastic properties of PDMS can be intuitively observed using the simple experiment described above, they can be more accurately measured using dynamic mechanical analysis. This method requires determination of the material's flow characteristics over a wide range of temperatures, flow rates, and deformations. Because of PDMS's chemical stability, it is often used as a calibration fluid for this type of experiment.

PDMS can be used to fabricate a myriad of structures through soft lithography. The process of soft lithography consists of creating an elastic stamp which enables the transfer of patterns only a few nanometers in size. Furthermore a single master mold can be used to fabricate numerous PDMS devices.

The process of fabricating a microfluidic device from PDMS is relatively simple. To start, the PDMS two-part kit, consisting of the base and the cross-linking agent are mixed. The mixing ratios and curing procedures used determine the mechanical, chemical and optical properties of the final device. Upon mixing, the PDMS must be degassed under vacuum. Next the liquid pre-polymer is poured over a previously fabricated master mold. The master molds used to fabricate PDMS devices are most commonly made from SU-8. However metal, plastic and even 3D printed maters are now gaining popularity. Once the PDMS is poured into the mold, the liquid pre-polymer conforms to the shape of the mold, replicating the features.

Knowing Corsolutions Microfuidic Connectors

Understanding the word itself connectors are used in connecting two objects to join or fasten (two things together, or one thing with or to another). Corsolutions is one of the new company that built and design your prototype microfluidics devices that you need.

If you are looking for connectors why choose Corsolutions Connectors?

Rapidly established, user-friendly connections Connections are non-permanent Allows for tighter density of microchip ports Wide variety of fittings or adapters can be used As the approach does NOT use adhesion, fittings are reusable Connections are compatible with all substrate materials including PDMS, glass, silicon and plastics Connections remain leak-tight at greater than 500 psi Highly reproducible connections Can seal at any location on the surface or side of the device Top-side and back-side alignment Connections are lower dead-volume than conventional approaches Can be used for final performance assessment, and for chemistry treatment of devices during fabrication

How it Works Mount The connectors mount to a flat surface with either a screw (1/4-20 or M6) or a magnet.

End Attachment The end attachment portion of the connector is specific for a tubing or adapter size. This attachment is removable and can be easily exchanged. Please see below for example end attachments.

Compression Seal The connector makes a compression seal between a gasket, held by the connector arm, and the microdevice. The amount of compressive force applied can be adjusted. Depending on the microdevice substrate material, the compression seal can remain leak tight at greater than 500 psi. Watch the video below to understand more about the product.