Integrated microfluidic and electronic components

Details Integrated microfluidic and electronic components Integrated microfluidic and electronic components

2000-06-22

2003-10-14

Soderquist, Arlen (Department: 1743)

Chemical apparatus and process disinfecting, deodorizing, preser

Analyzer, structured indicator, or manipulative laboratory...

Means for analyzing liquid or solid sample

C422S091000, C422S098000, C422S105000, C422S105000, C204S600000, C204S601000, C204S602000, C204S603000, C204S452000

Reexamination Certificate

active

06632400

ABSTRACT:

TECHNICAL FIELD
The invention relates to microfabricated devices for chemical and biological analysis, and more particularly to the integration of microfluidic and electronic components.
BACKGROUND ART
Microfluidic technology is utilized to create systems that can perform chemical and biological analysis on a much smaller scale than previous techniques. A popular use of microfluidic systems is in the analysis of DNA molecules. Microfluidic systems for analysis, chemical and biological processing, and sample preparation may include some combination of the following elements: pre- and post-processing fluidic handling components, microfluidic components, microfluidic-to-system interface components, electrical and electronics components, environmental control components, and data analysis components.
As microfluidic systems reduce in size and increase in complexity, there is a growing need for electronic and electrical processing support to enhance the analysis capabilities. Known microfluidic systems provide electronic and electrical processing support by performing operations such as voltage/current sourcing, signal sourcing, signal detection, signal processing, signal feedback, and data processing separately from the microfluidic system. In some instances separation of the electronic processing and microfluidic functions is desirable. For example, a relatively large power supply is required in order to apply a high voltage to a microfluidic channel for electrophoresis, and it is best to locate the power supply separate from the microfluidic system. As another example, data analysis is best performed using a computer that is separate from the microfluidic system.
However, some electrical processes have requirements that are difficult to meet utilizing electrical components that are separate from the microfluidic system. For example, very low energy signals which are detected from microfluidic systems tend to degrade as they are conducted away from the microfluidic system to a separate signal processing component. As a result of the tendency for signal degradation, it is preferable to amplify the detected signals before they degrade. On-system electrical processing is also desired in cases where information gathered from many sensors on a microfluidic system must be used to control processes on the microfluidic chip. For example, a temperature system input might be used to control heaters of a microfluidic system.
One technique for providing signal detection for a microfluidic system involves a single photodiode which is bonded onto a microfluidics chip as disclosed in the article entitled “An Optical MEMS-based Fluorescence Detection Scheme with Applications to Capillary Electrophoresis,” by K. D. Kramer et al. (
SPIE Conference on Microfluidic Devices and Systems
, September 1998, SPIE Vol. 3515, pages 7-85.) Although a single photodiode is bonded onto the microfluidics chip, the photodiode is simply an electrical transducer and has no electronics signal processing or system control capability.
As described in the article entitled “Microfabricated Devices for Genetic Diagnostics,” by Carlos H. Mastrangelo et al. (
Proceedings of the IEEE
, Vol. 86, No. 8, August 1998, pages 1769-1787), electronics have also been integrated directly onto the same substrate as a microfluidic system. Mastrangelo et al. have included the following devices on a silicon substrate: fluidic components, electrical driving components, diode detection components, and fluidic control elements (e.g., thermal valving). Although Mastrangelo et al. disclose integrated microfluidic and electronic components, the microfluidic and electronic components are fabricated on the same substrate. Fabricating both microfluidic and electronic components on the same substrate is not only more costly and difficult than fabricating microfluidic components, but also limits the selection of materials and processes available to fabricate the components. Further, the quality of the fabricated components is more easily controlled when the components are fabricated separately using known techniques.
Microfluidic systems have been fabricated in polymer, glass, silicon, and ceramic substrates. A microfluidic component fabricated on or in silicon can have electrical and data analysis components fabricated directly onto the silicon substrate as described by Mastrangelo, et al. However, this is not easily achieved on polymer or glass substrates. Polymer and glass substrates are the most useful substrates for microfluidic applications and therefore it is desirable to integrate polymer or glass substrates with electronics components. In view of the need to have electronics components in close proximity with microfluidic components and in view of the preference for polymer or glass microfluidic substrates, what is needed is a microfluidic system having a microfluidic component, ideally formed of polymer or glass, that is integrated with an electronics component.
SUMMARY OF THE INVENTION
A microfluidic component having a microfluidic channel is bonded to an electronics component having a circuit for processing signals related to the microfluidic component. In one embodiment, the electronics component is a prefabricated integrated circuit chip that includes signal processing and/or process control circuits that provide a substantially higher degree of functionality than a mere photodiode. The microfluidic component of the invention is preferably made of polymer and the integrated circuit chip is preferably bonded to the microfluidic component using a flip chip type process, common to the integrated circuit industry. The bonding of the microfluidic component to the electronics component provides a modular architecture in which different combinations of microfluidic components and electronics components can be used to create customized processing and analysis tools.
In a preferred embodiment, the microfluidic component includes a substrate that has features such as microfluidic channels, microfluidic compartments, and microfluidic flow control elements. Therefore, the microfluidic component may include known features such as capillary channels, separation channels, detection channels, valves and pumps.
The microfluidic component may be fabricated by direct means such as photolithographic processes, wet or dry chemical etching, laser ablation, or traditional machining. The microfluidic component may also be fabricated by indirect means such as injection molding, hot embossing, casting, or other processes that utilize a mold or patterned tool to form the features of the microfluidic component. The microfluidic substrate is made of a material such as polymer, glass, silicon, metal, or ceramic. A polymer such as polyimide or polymethylmethacrylate (PMMA) is preferred. The microfluidic component is substantially fabricated before the electronic component is bonded to it.
In addition to the microfluidic features, the microfluidic component may include conductive traces that are formed within the substrate and/or on the surface of the substrate. The conductive traces provide electrical connection between the electronics component and various electrical features on or in the microfluidic component. These electrical features may include: (1) direct contacts to the fluid; (2) elements which, either in contact with or not in contact with the fluid, control the flow or the operation of the fluid or its contents; (3) sensors in direct contact with the fluid; (4) sensors that do not directly contact the fluid; (5) electrical heating or cooling elements integrated in or on the microfluidic component; (6) elements that can affect surface change within the microfluidic component; and (7) active microfluidic control elements such as valves, pumps, and mixers. Conductive traces may also lead to contact pads on the microfluidic component that provide electrical connections to off-component systems such as signal processors, signal readout devices, power supplies, and/or data storage systems. Providing contact pads on the microfluidic component for connection to

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