This application claims priority of Taiwanese application no. 099110881, filed on Apr. 8, 2010.
1. Field of the Invention
This invention relates to a microfluidic chip device and a method of making the same, more particularly to a microfluidic chip device made using a shape memory polymer and a method of making the same.
2. Description of the Related Art
A conventional microfluidic device includes a micropump that is able to transport a fluid and control the same, and a microvalve that is capable of regulating a flow direction and a flow rate of the fluid in a channel of the microfluidic device. The micropump generally falls in to one of two categories: a displacement rump and a dynamic pump. The displacement pump can be further classified as a peristaltic type or a reciprocating type. The microvalve may be active or passive, and may include a mechanical moving part or a non-mechanical moving part.
M. Koch et al. proposed a microfluidic system including a reciprocal it a micropump based on a piezoelectric material (M. Koch, N., Harris, Alan G. R. Ivans, Neil M. White and Arthur Brunnschweiler, A Novel Micromachined Pump Based On Thick-Film Piezoelectric Actuation, Sensors and Actuators A: Physical, vol. 70, pp. 98-103, 1998). Specifically, the piezoelectric material is disposed on a unit of three silicon layers that are stacked together. A cantilever beam structure capable of vibrating is used to induce a unidirectional flow of a fluid. When voltage is applied, the piezoelectric material and a membrane reciprocate, thereby being able to transport the fluid.
Zengerle et al. proposed a microfluidic system that includes an electrostatic micropump made from a silicon material (Optoelectronics and Photonics: Principles and Practices. 1st ed., Prentice Hall, 2001). The electrostatic micropump employs a cantilever beam structure as a flap valve.
Compared to the structures of the aforementioned conventional microfluidic systems, a microfluidic system made from a polymer can be easily produced, is more biologically compatible, and can be made using a process that does not have limitations of a semiconductor manufacturing process. Consequently, polymeric materials, which are able to partially integrate a microvalve and a microfluidic driving source, have been continuously developed.
R. Liu et al. used an acrylic acid-hydroxyethyl methacrylate (AA/HFMA) hydrogel subjected to an ultraviolet curing process to construct a microvalve (Liu R, Yu Q and Beebe D J, “Fabrication and Characterization of Hydrogel-Based Microvalves” J. Microelectromech. Syst., vol. 11, pp. 45-53, 2002). The hydrogel changes in volume at different pH. Therefore, by virtue of volume changes of the hydrogel in buffer solutions having different pH values, a polydimethylsiloxane (POMS) membrane can be pushed. David T. Eddington et al. utilised an array of pH-responsive hydrogels and a PDMS membrane to produce a microfluidic device (David T. Eddington and David J. Beebe, “A Valved Responsive Hydrogel Microdispensing Device With Integrated Pressure Source”, Journal of Microelectro-mechanical Systems, vol. 13, no. 4, 2004). In the aforesaid two literatures, an external syringe pump is required to inject a buffer solution.
However, the aforementioned conventional partially integrated microfluidic systems require a pressure controlling device and pipes to serve as a driving source for the fluid. Even though a microfluidic chip has a small size, an external driving source having a large size is necessary for the aforementioned conventional partially integrated microfluidic systems. Accordingly, the aforementioned conventional partially integrated microfluidic systems are not convenient to use.
C. C. Hong et al. sealed a pressurized gas in a microcavity with a thermoplastic membrane, utilized electroplated nickel as a heater material, and packaged the aforementioned elements and a microfluidic chip together (J. Microtech, Micrceng. 17 (2007:410-417). When the sealing membrane is heated and melted by the heater, the pressurized gas in the microcavity is released and serves as a driving scarce to push a fluid to flow into the microfluidic chip.
Kuo-Yao Weng et al. encapsulated vacuum capillaries in a flexible and elastic film (The Royal Society of Chemistry 2008, Lab Chip, 2008, 8, 1216-1219). When the vacuum capillaries in the film are broken by an external force, pneumatic forces are generated to suck a fluid into a microfluidic system. A vacuum capillary pneumatic pump serves as a driving source.
Nevertheless, a driving source, which can induce actuation of a fluid by creating a positive pressure or a negative pressure, is generally made via a complicated process, must be precisely controlled to successfully accomplish the actuation of the fluid, and is normally not reusable. Thus, how to provide a simple method of integrating a microfluidic system and a driving source is the subject of endeavor in the present invention.
The object of the present invention is to provide a microfluidic chip device that can overcome the aforesaid drawbacks of the prior art, and a method of making the same.
According to one aspect of this invention, a method of making a microfluidic chip device is provided. The method comprises: forming a shape memory polymer into a substrate layer having a transformative portion with a memory shape; processing the substrate layer to change the transformative portion into a temporary shape; and laminating the substrate layer with a microfluidic layer so that a microchannel of the microfluidic layer is connected fluidly to the transformative portion having the temporary shape. The memory shape is recovered when the transformative portion is activated by an external stimulus, and a fluid driving pressure is produced within the microchannel when the memory shape is recovered.
According to another aspect of this invention, a microfluidic chip device is provided. The microfluidic chip device includes a substrate layer and a microfluidic layer. The substrate layer is made from a shape memory polymer, and includes a transformative portion that can change in volume when changing in shape between a memory shape and a temporary shape. The microfluidic layer is laminated with the substrate layer and has a microchannel that is in fluid communication with the transformative portion. The transformative portion produces a fluid driving pressure within the microchannel when changing between the memory shape and the temporary shape.
Other features and advantages of the present invention will become an parent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which:
As shown in step (a) of
The SMP produced from the monomer composition may fall into one of the following four categories: a SMP composed of a covalently cross-linked glassy thermoset network, a SMP composed of a covalently cross-linked semi-crystalline network, a SMP composed of a physically cross-linked glassy copolymer, and a SMP composed of a physically cross-linked semi-crystalline block copolymer. Since the SMP composed of the covalently cross-linked glassy thermoset network has a sharp glass transition temperature (Tg) curve and has a structure of a cross-linked network, the same is able to repress molecular motion between chains. Accordingly, the SMP composed of the covalently cross-linked glassy thermoset network is capable of accomplishing shape-fixing and rapid shape-recovery, and is preferably used in the method of the present invention. In this embodiment, the monomer in the monomer composition is selected from the group consisting of methyl methacrylate (MMA) and butyl metharylate (BMA).
The monomer composition may further contain polyhedral oligosilsesquioxane (POSS) that is an inorganic/organic hybrid molecule, and that contains corn an inorganic silicon-oxygen cage and compatibilizing organic groups pendant to each silicon corner of the cage. Thermal stability and melt flowability of the SMP can be increased by virtue of POSS, and a mechanical property of the SMP is not adversely affected by POSS.
As shown in steps (b) and (c) of
Referring to
In this embodiment, the microfluidic layer 3 is made by drilling a substrate made from a cyclic olefin copolymer (COC). Accordingly, the microchannel 31, and the first and second holes 311,312 are formed. A UV curable adhesive 4 is spin-coated onto the second surface of the microfluidic layer 3, which has the second hole 312. The microfluidic layer 3 is disposed on the substrate layer 2 with the second surface thereof facing the transformative portion 21, and with the second hole 312 disposed at a location of the transformative portion 21 with the temporary shape, which corresponds in positron to the indentation 21a of the transformative portion 21 with the memory shape. The assembly of the microfluidic layer 3 and the substrate layer 2 is placed in a UV exposure box and is exposed to UV light such that the microfluidic layer 3 and the transformative portion 21 are bonded to each other (see step (d) of
The memory shape of the transformative portion 21 is recovered when the transformative portion 21 is activated by an external stimulus, and a fluid driving pressure is produced within the microchannel 31 when the memory shape is recovered. Specifically, when the transformative portion 21 is activated by the external stimulus and hence changes from the temporary shape to the memory shape, a volume of the transformative portion 21 (i.e., a volume of the SMP) changes such that the fluid driving pressure is produced within the microchannel 31. Namely, a pressure change is induced by the volume change of the transformative portion 21.
When a SMP has a low POSS content, thermal stability and melt flowablility of the SMP are low. Accordingly, the memory shape of the transformative portion 21 made from the SMP having the low POSS content may deform before the hot-pressing process such that the volume change of the transformative portion 21 between the temporary shape and the memory shape may be insufficient. Hence, the fluid driving pressure for the pressure change) produced by the insufficient volume change of the transformative portion 21 may be deficient. Preferably, an amount of POSS is not less than 10 wt % based en a total weight of the monomer composition. More preferably, the amount of POSS is not less than 15 wt % based on the total weight of the monomer composition.
In this embodiment, the external stimulus is heat, and the fluid driving pressure is a negative pressure that is produced in the microchannel 31 when the indentation 21a of the transformative portion 21 is recovered. It should be noted that the transformative portion 21 could be designed to produce a positive pressure in the microchannel 31 in other embodiments.
Referring to
It should be noted that the microfluidic layer 3 and the transformative portion 21 could be detachably connected to each other in other embodiments. Consequently, the substrate layer 2 having the transformative portion 21 with the memory shape may be detached from the microfluidic layer 3, and may be subjected to a hot-pressing process so as to change the transformative portion 21 from the memory shape to the temporary shape. As a result, the substrate layer 2 may be attached to a new microfluidic layer 3 and is considered reusable.
The method of this invention is simple and convenient, and can be easily conducted. A production cost of the microfluidic chip device of this invention is also low.
While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements.
Number | Date | Country | Kind |
---|---|---|---|
099110881 | Apr 2010 | TW | national |