Surface Modification of Cyclic Olefinic Copolymers for Bio-Mems Microfluidic Devices

Abstract

Cyclic Olefin copolymers (COC) are a new class of polymers that may prove to be extremely useful in injection molding of micron scale fluidic devices. In microfluidic devices it is desirable to have a hydrophilic surface such as in flow driven by capillary action. However, such hydrophilic surfaces tend to display protein deposition when contacted with blood unlike hydrophobic surfaces. Alternatives to capillary action are then needed to control fluid flow for hydrophobic surfaces. Our goal in this research is to tune the slightly hydrophobic COC surfaces through simple surface modifications that are amenable to injection molding and other processing methods. In this study, the surface of an injection molded microfluidic component made from COC was modified in order to change the surface properties important to bio-fluidic devices. Some of the techniques used in this study were plasma treatments and ASG (aerosol gel) coating. Plasma treatments were conducted by using O2, CF4 and their combination gas. O2 treated surfaces became hydrophilic with increasing time of treatment. Combining O2 and CF4 made the surfaces more hydrophobic compared to CF4 only. The structural changes after the plasma treatments were examined by ATR (Attenuated Total Reflectance) spectroscopy. Titania and silica particles from the ASG process were synthesized from titanium iso-propoxide and tetraethoxysilane, respectively. Titania coated surfaces became more hydrophilic and the silica coated surfaces did not have much change in their surface characteristics. The hydrophobicity of the plastic surfaces was measured by their contact angle with water. The implication of these treatments on bio-fluidic devices and their adaptation to the injection molding process will also be discussed.

Surface modification of thermoplastics—towards the plastic biochip for high throughput screening devices

“…For instance, plasma treatment has been employed successfully to increase the hydrophilicity of the plastics. [9][10][11][12][13] This is a rather aggressive method that generates a large number of polar groups such as hydroxyl groups. However, this technique is difficult to implement on an industrial scale since it requires expensive high vacuum systems.…”

A mass manufacturable thermoplastic based microfluidic droplet generator on cyclic olefin copolymer

“…The power and time were optimized (150 W for 120 s) to obtain a contact angle of approximately 120°. This behavior can be explained only with a surface chemical change where the CF 4 attaches to the surface giving a hydrophobic nature [45].…”

“…Since the ATR (attenuated total reflectance) spectrum of a CF 4 + O 2 plasma treated COC surface shows a strong C-F peak and a C=O peak instead of a strong CH 2 peak and a small C-H peak as shown in native COC [45], the nature of penetration of the solvent in the hydrophobic COC surface will be different. This necessitated an optimisation of the solvent bonding process.The thin COC film was cleaned in 2-propanol and was dried with Nitrogen.…”

Controlling the Wettability of Hierarchically Structured Thermoplastics

“…32 Understanding the effect of micro-and nanoroughness combined with different surface chemistries should help in the design of biomaterials, for example, in tissue engineering or microfluidics. 33,34 In this paper we describe a simple, efficient, and highly reproducible method of producing well-defined, dual scale roughened substrates on a large area to provide a surface with well-controlled and stable wettability. A surface with large (macro) scale features is combined with nanoscale features made by plasma etching together with modifications to the surface chemistry, producing a surface with controllable wettability.…”