Patent Application
20050065735
The present invention generally relates to microfluidics and more particularly to the design of customized microfluidic systems using a microfluidic computer aided design system. Such customized microfluidic systems may be used, for example, for fluid analysis of biological samples.
Typically microfluidic systems for processing fluid samples employ a series of chambers each configured for subjecting the fluid sample to a specific processing step. As the fluid sample flows through the system sequentially from chamber to chamber, the fluid sample undergoes the processing steps according to a specific protocol. Because different protocols require different configurations, the design and manufacturing of such microfluidic systems can be time-consuming and costly.
Conventional computer aided design tools such as AutoCAD® are inadequate for the design and layout of microfluidic systems. For instance, AutoCAD® is a general tool, and has no drawing constraints and provides no specific microfluidic design information associated with a component.
Thus there is a need for computerized design techniques which allow the quick and easy formation of microfluidic systems with different configurations and utilizing different protocols.
The present invention provides for the design of a microfluidic system, including a microfluidic chip or circuit, using a microfluidic computer aided design (CAD) system. The microfluidic CAD system, henceforth referred to as the “MCAD” system, provides the user with the tools to design, analyze, and implement a customized microfluidic system using a plurality of building block microfluidic components. The MCAD system overcomes the disadvantages of conventional CAD tools by providing, for instance, drawing constraints, design information associated with components, I/O ports, and connectivity to I/O ports, as well as easy layout and manipulation of multilayered components.
In one embodiment the microfluidic system may include a network of single or multi-layer elastomeric structures. In an alternate embodiment some or all the structures may include rigid materials (e.g., silicon-based materials). In yet another embodiment some of the structures may include a mixture of flexible materials, (e.g., elastomeric materials) with the rigid material. Utilization of such an MCAD system can lead to quick and easy implementation of simple to highly complex networks for use in general microfluidic transfer control systems, biological diagnostics systems, etc.
In one embodiment of the present invention a microfluidic device or chip is created from a plurality of microfluidic components according to a design. First a template is selected. Next, the components are placed on the template, manually or automatically, using a placement tool. The components include multilayered components. The components are then routed, manually or automatically, using a routing tool based on preset design rule constraints to achieve a physical layout. Functional analysis (e.g., logical microfluidic flow simulation) and/or physical analysis, (e.g., dynamic microfluidic flow simulation) may then be performed on the physical layout. Following the optional functional analysis and/or physical analysis, the physical layout is used to create the chip layout file, which is later used for fabricating the microfluidic device or chip. In one embodiment of the present invention a microfluidic circuit design method is provided. The method includes developing synthesizable computer code for a design. Next, a microfluidic circuit schematic, including a plurality of symbols for microfluidic components, is generated either interactively or using the synthesizable computer code. A symbol may include at least one control channel and at least one fluid channel. The microfluidic circuit schematic is then functionally simulated. The microfluidic components are placed and routed on a template to form a physical layout. Then the physical layout is physically simulated using dynamic simulation models of the microfluidic components; and the physical layout is written to a layout file.
Another embodiment of the present invention provides a microfluidic circuit design system including one or more of the following: a synthesis module for synthesizing software of a design into a schematic having a plurality of connected symbols of microfluidic components; a design capture module for displaying and manipulating the schematic; a functional analysis module for functionally simulating selected microfluidic components of the schematic; a physical implementation module for placing and routing the microfluidic components into a physical layout according to the design; and a physical analysis module for physically simulating the components in the physical layout.
Another embodiment of the present invention is directed to a method, using a physical layout system, for laying out a microfluidic circuit including a plurality of microfluidic components, where the microfluidic components include multilayered components. The method includes: placing a first component of the plurality of microfluidic components; placing a second component of the plurality of microfluidic components; and connecting the first component to the second component.
In another embodiment of the present invention a method is provided, using a computer system, for physically laying out a microfluidic circuit including a plurality of microfluidic components. The method includes: selecting a template; placing a first microfluidic component with an associated property, such as physical scaling, physical property, layer assignment, equations of motion, simulation data, macro logic functions, or functional definition, on the template; placing a second microfluidic component on the template; and connecting the first component to the second component. The connecting may include a design rule check.
In yet another embodiment of the present invention a microfluidic circuit physical layout method, using a computer, is provided. The method includes: selecting a template including an I/O port; placing a microfluidic component on the template, wherein the microfluidic component has a component control channel and a component fluid channel; and connecting the component control channel to the I/O port.
Another embodiment of the present invention includes a method for physical layout of a microfluidic system using a computer aided design tool. The microfluidic system includes a plurality of microfluidic components. First, a template is selected, including a plurality of layers. Next, a first symbol representing a first component of the plurality of microfluidic components is placed. The first symbol includes a first fluid channel symbol and a first control channel symbol. The first control channel symbol and the first fluid channel symbol are on different layers. Next, a second symbol representing a second component of the plurality of microfluidic components is placed. The second symbol includes a second fluid channel symbol. The first fluid channel symbol is connected or routed to the second fluid channel symbol.
An embodiment of the present invention provides a method for validating a physical layout of a microfluidic circuit design including a plurality of microfluidic components, the method includes placing and routing the plurality of microfluidic components on a template to form the physical layout of the microfluidic circuit design. Next, a dynamic simulation model is determined for each component of the plurality of microfluidic components on the template. Using the physical layout and dynamic simulation models for the plurality of microfluidic components, the physical layout is physically simulated.
An embodiment of the present invention provides a method for device implementation of a microfluidic circuit including a plurality of microfluidic components. The method includes placing and routing the plurality of microfluidic components on a template to form a physical layout of the microfluidic circuit design. Then the physical layout is written to a layout file to be used for manufacturing. Next, a mask is created for a die of a plurality of dies using the layout file, where the die includes the physical layout. The plurality of dies on a wafer are laid out, where the mask creates the die on the wafer.
An advantage of the present invention is the reduction in time needed to complete the design and implementation of a microfluidic circuit. For example, in one embodiment of the present invention, synthesis, schematic capture, and functional simulation allow an efficient and expedient process of creating and validating an initial design, the physical layout tool allows easy placement and routing of multilayered components on a predefined template, the physical simulation allows the reduction in errors before fabrication, and the die placement tool allows faster wafer mask generation.
The uses and results generated by the present invention include cell based assays (including micro cell sorting, genomic analysis, such as DNA sizing, hybridization, sequencing, quantification, and amplification); protein analysis, crystallization and purification; MS-interface; biochemical and electrophysiological assays, gene expressions; differential display analysis; integrated biological sample preparation; single molecule analysis; drug delivery; diagnostics; and other uses and products related to the chemical, biochemical, biological, electronic, computer, appliance, pharmaceutical, medical, or power industries.
These and other embodiments of the present invention are described in more detail in conjunction with the text below and attached figures.
a and 9b show simplified top plan view and perspective view of an on-off valve component of an embodiment of the present invention;
Embodiments of the present invention are directed to the design of customized microfluidic systems using a microfluidic computer aided design (MCAD) system. The MCAD system provides the user with the tools to design, analyze, and implement a customized microfluidic system using a plurality of building block microfluidic components.
In one embodiment of the invention, the MCAD system includes a design capture module including a schematic entry tool for selecting and connecting microfluidic components according to a design. The system further includes a functional analysis module for functionally simulating selected microfluidic components of the design, a physical implementation module for arranging the microfluidic components into a physical layout according to the design, and a physical analysis module for physically simulating the microfluidic components in the physical layout.
In some embodiments, the modules comprise computer instructions or code stored in a computer-readable medium. The computer-readable medium is operatively coupled to a network (e.g., an internal computer bus, an external Local Area Network (LAN), or the Internet) to permit access to the instructions via the network.
The microfluidic components may be selected from a library or libraries having, for example, channels, pumps, valves, chambers, and layer interconnects (or vias). The library or libraries include normalized, custom, pre-defined, and/or user-defined, microfluidic components. The microfluidic components are connected according to preset design rules. The microfluidic components may be assigned physical scaling and physical properties. The selected components are typically active fluidic components.
The microfluidic components may include conventional microfluidic structures composed of hard, inflexible materials (such as silicon) or microfluidic structures made out of various layers of elastomer bonded together. An embodiment of the present invention uses a multi-layer soft lithography process to build integrated (i.e., monolithic) microfabricated elastomeric structures. Advantages of fabricating the elastomeric structures by binding together layers of soft elastomeric materials include the fact that the resulting devices are reduced by more than two orders of magnitude in size as compared to silicon-based devices. Further advantages of rapid prototyping, ease of fabrication, and biocompatability are also achieved. Further details may be found in PCT Patent Application No. PCT/US00/17740, entitled “Microfabricated Elastomeric Valve And Pump Systems,” filed Jun. 27, 2000; Hou-Pu Chou et al., “Integrated Elastomer Fluidic Lab-on-a-chip—Surface Patterning and DNA Diagnostics,” Proceedings of the Solid State Actuator and Sensor Workshop, Hilton Head, S.C. (2000); Stephen R. Quake and Axel Scherer, “From Micro- to Nanofabrication with Soft Materials,” Science 290: 153640 (2000); and M. A. Unger et al., “Monolithic Microfabricated Valves and Pumps by Multilayer Soft Lithography,” Science 288: 113-116 (2000). These are incorporated herein by reference each in its entirety.
The selected microfabricated components of the design may be functionally simulated by applying control stimuli to the control channels of selected active fluidic components to show functional connectivity of the design. In one embodiment of the functional simulation, components of the design are represented by Boolean expressions with operands based on connection ports of the control channels of the active fluidic components. Actuation of the active fluidic components is simulated using control stimulus generated by a Boolean based language with timing constraints. The design may be modified based on results of the functional simulation.
The microfluidic components in the physical layout may be physically analyzed. The physical analysis may include, for instance, analyzing dynamic volumetric flow rates in the components, analyzing component volumes, and analyzing volumetric capacitances of interconnecting and routing channels in the physical layout. Physically simulating the components of the physical layout may include simulating actuation of dynamic fluid flow in the components using control stimulus generated by a Boolean based language. The physical layout may be modified based on results of the physical simulation. The physical layout may be written to a layout file to be used for manufacturing.
For the purposes of this application a channel, for example, a control channel or a fluid/fluidic channel, may contain either a gas or a liquid. In one embodiment the control layer has pressurized air and the fluid layer has a liquid substance. Other embodiments have other combinations of gas-gas, liquid-gas, or liquid-liquid in two or more channels.
Conception (Phase 1)
The microfluidic circuit or chip design begins with the conception 100 of the desired functionality, outputs, or results to be achieved by inputting fluids into the microfluidic circuit or chip (phase 1).
One specific embodiment employs a black box analysis in which the inputs and outputs are first determined. A computer program using a synthesis language may then be written to simulate the generation of the outputs from the inputs. The synthesis language can be run through a synthesis compiler to generate a microfluidic circuit having a plurality of interconnected microfluidic components or structures. The synthesis compiler may also optimize a part of or all of the microfluidic circuit according to some criteria, such as minimum area. In such an embodiment, the design capture (phase 2) in effect is automatically done by the synthesis tool with access to the macro library 210 and basic library 206.
A fluidic synthesis language is like a synthesis language in the electrical arts in that certain programming language constructs map to certain structures or combinations of structures. For example, in electronic circuit design, a Hardware Description Language (HDL), such as VHSIC HDL (VHDL) or Verilog, is used to simulate the behavior of a circuit design at an abstract level (e.g., at the Register Transfer Language (RTL) level). Then, the VHDL or Verilog code is used by a synthesis tool (e.g., a tool available from Synopsys Inc. of Mountain View, Calif.) to produce an optimized gate level description of the circuit. As a simple illustration the operators in Boolean logic, such as “not,” “and,” or “or,” map to an inverter, AND gate, and OR gate. Thus a Boolean expression may be mapped (and optimized) to a respective set of hardware logic gates. In a more complicated example a “case statement” in VHDL may be synthesized into a gate level implementation of a Finite State Machine (FSM).
In an embodiment of the present invention various microfluidic structures or components represent various digital and analog functions. Examples are given in U.S. Provisional Patent Application Ser. No. 60/282,253, entitled “Microfabricated Fluidic Circuit Elements and Applications,” filed Apr. 6, 2001, which is incorporated herein by reference in its entirety. Some of the microfluidic structures or components disclosed may be configured to imitate the functionality of semiconductor circuits, such as ON/OFF switches, resistors, capacitors, logic gates, latches, switching regulators, and devices that perform mathematical functions. The microfabricated fluidic logic gates include AND gates, OR gates, NOR gates, NAND gates, inverters, and numerous other Boolean and logic functions. In addition the microfluidic components may also perform analog functions such as amplification or regulation. For example, analog components include switching regulators, capacitors, pressure multipliers, and pressure sources.
Microfluidic logic gates may perform the same Boolean logic function as electronic gates, but are substantially different both structurally and in the way they perform the logic function. As an illustration,
A microfluidic ON/OFF switch is “open” during its ON state allowing fluid (liquid or gas) flow through the channel between the source and the drain. A fluidic switch is “closed” during its OFF state preventing fluid (liquid or gas) flow through the channel between the source and the drain. Microfluidic switches are opened and closed by changing the pressure in the gate of the switch either by liquid or gas pressure. The pressure in the gate of the switch does not need to be increased above or reduced below the pressure in the drain-to-source channel. This provides an advantage over prior art, because microfluidic switches of this embodiment of the present invention can be coupled together to control each other on a single chip to perform complex logic, mathematical, multiplexing, and latching functions.
An embodiment of a microfluidic switch is shown in
Layer 55 comprises a rigid material that is deposited on top of layer 52. Layer 51 may then be placed on top of layer 52 so that layer 55 is inside channel 54. Layer 55 is deposited on layer 52 so that it overlaps channel 57 and portions of chambers 56 and 58 as shown in
When the pressure P1 in channel 54 is increased above P0, the radius of channel 54 expands and rigid layer 55 moves downwardly (with respect to
The microfabricated fluidic structure of
Chambers 56 and 58 reduce the upward force that elastomer material in layer 52 applies to layer 55 when channel 54 expands so that channel 57 closes more quickly and completely. When channel 54 expands to close channel 57, fluid is displaced from the area of chambers 56 and 58 directly beneath channel 54 into adjacent portions of chambers 56 and 58. Chambers 56 and 58 allow channel 57 to be closed without having to increase the pressure in gate channel 54 above the pressure in channel 57. Therefore, switch 50 may be coupled with other microfluidic switches to perform logic functions and other functions, because switch 50 does not require a pressure drop from the gate channel 54 to the source-to-drain channel 57.
For illustrative purposes symbols representing a number of microfluidic devices are shown in
The symbol of
Some of the microfluidic devices of the present invention may be connected together to form logic gates that perform logic functions and Boolean algebra. Previously known microfluidic chips often perform logic functions off-chip using electrical circuitry and then route the output signal onto the microfluidic chip through macroscopic control lines which are cumbersome and take up a lot of space. Performing logic functions on chip using microfluidic logic gates can greatly reduce the number control lines routed onto the chip which advantageously saves space.
The bistable logic levels for the microfluidic logic gates are high pressure (HIGH) and low pressure (LOW). Each logic gate has a connection to a low pressure source (e.g., ambient pressure), and a connection to a high pressure source (e.g., higher than ambient pressure). In an alternate embodiment, each logic gate has a connection to ambient pressure and a connection to a vacuum. In this embodiment, LOW refers to the vacuum and HIGH refers to ambient pressure.
All Boolean functions can be constructed entirely from NAND gates or entirely from NOR gates. A NAND gate performs an AND function on a set of inputs and inverts the output. A NOR gate performs an OR function on a set of inputs and inverts the output.
An example of a NAND logic gate formed with microfabricated fluidic switches is shown in
When either of inputs IN168 and IN269 is at ambient pressure (LOW), one of switches 64 or 66 is open, and fluid flows from the HP terminal 67 to the ambient exhaust 61 through the open switch(es) and resistor 62. The pressure at OUT 63 increases to high pressure (HIGH), because the resistance of resistor 62 is greater than the resistance of switches 64 and 66. When both inputs IN168 and IN269 are at high pressure (HIGH), both of switches 64 and 66 are closed and fluid flow to the HP terminal 67 is blocked. The pressure at OUT 63 diffuses through resistor 62 to the ambient exhaust terminal 61 causing the pressure at OUT 63 to decrease to ambient pressure (LOW).
A microfluidic NAND gate may comprise any number of input terminals greater than one. Each input terminal is coupled to the gate of a normally open switch coupled in parallel with switches 64 and 66 between OUT and the HP terminal. Of course, other configurations for the construction of NAND logic gates known to those of skill in the semiconductor circuit design art may be used to design a microfluidic NAND gate in which transistors are replaced with microfluidic switches. The symbol for a two input NAND gate is shown in
A microfluidic structure may also be used to construct Set-Reset (S-R) latches that have the same truth table as S-R latches constructed from electronic circuits. Latch 70 in
Latch 70 operates as follows. A transitory LOW signal occurs when the {overscore (SET)} or {overscore (RESET)} input transitions from high pressure (HIGH) to ambient pressure (LOW) and then transitions back to high pressure (HIGH) again. When a transitory LOW occurs on the {overscore (SET)} input, {overscore (OUT)} goes HIGH and remains HIGH. When a transitory LOW signal occurs on the {overscore (RESET)} input, {overscore (OUT)} goes HIGH and remains HIGH. When the pressure at the {overscore (SET)} and {overscore (RESET)} inputs are both HIGH, outputs OUT and {overscore (OUT)} remain in their previous states. An unstable condition exists at outputs OUT and {overscore (OUT)} when the pressure at the {overscore (SET)} and {overscore (RESET)} inputs are both LOW.
An example of an S-R latch constructed with microfluidic cross-coupled NAND gates is shown in
When the pressure at the {overscore (RESET)} input remains HIGH and the pressure at the {overscore (SET)} input transitions from HIGH to LOW, switch 88 is closed, switch 84 opens, and the pressure at {overscore (OUT)} goes HIGH because it is coupled to the high pressure terminal HP through low resistance switch 84. Switch 90 is closed because {overscore (OUT)} is HIGH, and the pressure at {overscore (OUT )}goes LOW, because {overscore (OUT)} is decoupled from the HP terminal. Switch 87 is open, because {overscore (OUT)} is LOW. When the pressure at the {overscore (SET)} input goes HIGH again, switch 84 closes. However, the pressure at OUT remains HIGH, because OUT is coupled to the HP terminal through switch 87 which remains open. The pressure at {overscore (OUT)} remains LOW, because switch 90 remains closed.
When the pressure at the {overscore (SET)} input remains HIGH and the pressure at the {overscore (RESET)} input transitions from HIGH to LOW, switch 84 remains closed and switch 88 opens. The pressure at {overscore (OUT)} goes HIGH, because {overscore (OUT)} is coupled to the HP terminal through low resistance switch 84. Switch 87 is closed because {overscore (OUT)} is HIGH, and the pressure at OUT goes LOW, because it is decoupled from the HP terminal. When the pressure at the {overscore (RESET)} input goes HIGH again, switch 84 closes, but switch 90 remains open because OUT is LOW. Therefore, the pressure {overscore (OUT)} remains HIGH keeping switch 87 closed, so that the pressure at OUT remains LOW.
When the pressures at {overscore (RESET)} and {overscore (SET)} are both HIGH, the pressures at OUT and {overscore (OUT)} both remain at their previous logic states. The pressures at OUT and {overscore (OUT)} are both HIGH when the pressures at {overscore (RESET)} and {overscore (SET)} are both LOW, which is considered an unstable output state because OUT and {overscore (OUT)} cannot remain in that state when {overscore (RESET)} or {overscore (SET)} go HIGH. The truth table for latch .80 is shown in Table 2.
Microfluidic S-R latches can be used to provide a large number of arbitrary latched control signals from a small number of control lines that are multiplexed externally. Thus, having fluidic devices that perform the function of S-R latches on the fluidic chip also greatly reduces the number of control lines that need to be brought onto the chip from external sources, providing additional space saving.
In one embodiment of a microfluidic circuit, when it is desirable to perform logic functions on chip using microfluidic logic gates rather than conventionally using electrical circuitry and then routing the output signal onto the microfluidic chip through macroscopic control lines, the Boolean equations, which may include timing, are first determined. These Boolean equations can be simulated to test functionality (phase 3) and then can be used, either manually or automatically, to generate the circuit.
A Hardware Description Language (HDL) may be used to model both the control channels and the fluid channels of a microfluidic circuit. In one embodiment a digital HDL, such as VHDL or Verilog, is used to model (and/or synthesize) the control channels, which perform the logical control functions of the microfluidic circuit. An analog HDL such as Verilog-A or VHDL-AMS may be used to model (and/or synthesize) the fluid channels of the microfluidic circuit. Since VHDL-AMS can model mixed digital-analog designs, VHDL-AMS may be used to model (and/or synthesize) both the digital control functions of the control channels as well as the analog fluid flow of the fluid channels. Since a component includes at least one control channel and at least one fluid channel in this embodiment, VHDL-AMS can model (and/or synthesize) the control function of the control channel, for example, ON/OFF, the fluid flow through the fluid channel, and the interaction between the control channel and the fluid channel for the component.
In an embodiment VHDL or Verilog code is written which allows the testing of the control logic via simulation using a commercial VHDL or Verilog tool. Next the control logic is synthesized and optimized using a commercial VHDL or Verilog synthesis tool, but using microfluidic logic gates rather than digital logic gates.
An illustrative simple example is the synthesis of a microfluidic D-latch using VHDL, a microfluidic S-R latch (
The above VHDL code shows that if the enable line (En 114) is “1” or H, then the output Q 116 gets the input D 112, otherwise the output Q 116 remains unchanged. This code infers a D-latch and generates the network of NAND gates in
Thus the example of
Using the above fluidic D-latch (or an equivalent D-Flip Flop with the enable replaced by a clock) and fluidic NAND gate, a Finite State Machine (FSM) can be built, for example, a one-hot FSM. Thus in one embodiment of the present invention a microfluidic computer may be built. With the components made of organic rather than inorganic material a biological computer may also be constructed. Other synthesizable designs using a Hardware Description Language can be found in Douglas J. Smith, “HDL Chip Design, A Practical Guide for Designing, Synthesizing and Simulating ASIC's and FPGAs using VHDL or Verilog,” Doone Publications, Madison, Ala. 1997 which is incorporated herein by reference.
In addition to digital circuits, the above-referenced Provisional Patent Application Ser. No. 60/282,253, entitled “Microfabricated Fluidic Circuit Elements And Applications,” filed Apr. 6, 2001, discloses analog circuits, for example, switching regulators, capacitors, pressure multipliers, and pressure sources. In an embodiment techniques similar to those used for the synthesis of microwave circuits, such as given in U.S. Pat. No. 5,031,111, entitled “Automated Circuit Design Method,” by Chao, et. al, filed Aug. 8, 1988, may be used with microfluidic components in place of microcells.
In another embodiment VHDL-AMS (Analog and Mixed Signal) (i.e., IEEE Standard 1076.1-1999 (http://www.vhdl.org/analog) or Verilog AMS) may be used for the synthesis and simulation of analog, and/or mixed digital/analog systems at several abstraction levels (e.g., functional, behavioral, macrocell/RTL, and device levels). Thus with the use of microfluidic components described above, VHDL-AMS is used in one embodiment of the present invention to simulate a mixed signal or analog design for functional analysis 360 (phase 3) and to synthesize the design from the VHDL-AMS programming code to connected microfluidic components (i.e., automatically generate phase 2) displayed on a schematic entry tool.
The following example is of VHDL_AMS code for a valve (see “VHDL-AMS Code For A Electrostatically Driven Micropump,” by Feng Cao, Sep. 28, 1999, Microfluidic Operations and Network Architectural Characterizations (MONARCH) Project, Department of Electrical and Computer Engineering, Copyright 1999, Duke University):
Design Capture (Phase 2)
Once the design has been conceptually defined, it can then be captured with a schematic entry tool 202 that is used to select the components and connect between the input/output ports of components, or the schematic may be automatically generated using a synthesis language, as described above.
Examples of library components used in this embodiment of the present invention are given in the above-mentioned PCT Patent Application No. PCT/US00/17740, entitled “Microfabricated Elastomeric Valve and Pump Systems,” filed Jun. 27, 2000 and in Provisional Patent Application Ser. No.60/282,253, entitled “Microfabricated Fluidic Circuit Elements And Applications,” filed Apr. 6, 2001 which are incorporated herein by reference. Examples of microfluidic components and structures are summarized in Appendices A and B.
In one embodiment each component in the libraries 206 and 210 has a physical component specification 214. The specification may have, for example, one or more of the following: designation of the channel as a control or fluid channel, physical scaling of channels (length, width, depth), control or fluid channel attributes, such as if a channel end is open or closed, or if a channel is square or rounded, physical properties, such as, thermal, conductivity, viscosity, or magnetic properties, layer assignment, a functional description (digital or analog), a component and/or a fixed element name, and/or a design rule specification for physical layout.
a and 9b show the top plan view and perspective view of an on-off valve component of an embodiment of the present invention. The top plan view shows the control length 232 and control width 234 of the control channel 246 and the fluid width 238 and fluid length 233 of the fluid channel 242. The perspective view shows the fluid depth 244 of the fluid channel 242 and the control depth 248 of the control channel 246. The channels 242 and 246 are semi-rounded.
One example of the Physical Component Specification 214 for the on-off valve in
The On-Off valve component may be represented by a block diagram such as
As shown in
Functional Analysis (Phase 3)
After completion of the schematic design entry, a good design practice to reduce the number of design iterations is to functionally simulate the design. Functional simulation of microfluidic circuits involves application of control signals to the active components of the design and shows the functional/static behavior of the design without regard to the dynamic behavior of the fluid within the device. Examples of active fluidic components include valves and pumps which act on the fluid. A fixed channel is an example of a passive fluidic component. Functional libraries 362 for the component models are provided for each component (
In one embodiment of the present invention, the logical fluidic flow simulation 366 simulates the control logic of the active microfluidic components (
For example, a simple valve component with a single input port and a single output port and a control port can be defined as follows:
When C=H (or ‘1’), then the output O gets the input I. When C=L (or ‘0’), then O =L regardless of the value of the input I.
Logical fluidic flow simulation 366 of the logic control 364 of the testing apparatus that will actuate the active components (
In another embodiment the functional models are VHDL or Verilog models. A valve can be represented by the VHDL expression:
O<=I and C after 5 μsec;
where “and” is a Boolean operator and there is a delay of 5 μsec before the result of the and operation is assigned to O. The DCCL of the above embodiment is represented in this embodiment as a typical VHDL test bench. As seen in
In yet another embodiment VHDL-AMS or Verilog-AMS is used to represent the Functional Models 370. The inputs into the control ports 376 are typically digital, while the functional transformation of values from the input ports 372 to the output ports 374 are given by analog functions. Thus a first order dynamic analysis may be done. This allows an intermediary analysis between the static connectivity analysis and the physical analysis 800 given by phase 6 (
In a further embodiment an analysis of the fluid flow only may be performed in a way similar to that for passive microfluidics (see “Passive Microfluidics-Ultra-Low-Cost Plastic Disposable Lab-On-A-Chips,” by Bernard H. Weigl, et. al., in Proceedings of Micro Total Analysis Systems 2000, Dordrecht, Netherlands: Kluwer Academic Publishers, 2000, p. 299). Assuming the fluid is flowing through the fluid channels and the pertinent control channels are turned on, the microfluidic circuits may be represented by analog electrical components, such as capacitors, resistors, and inductors, to predict fluid flow rates. Diffusion and chemical reactions may be calculated using finite element analysis. Thus an initial analysis of the fluid flow and fluid mixing through the fluid microcircuits may be obtained. This again is neither a static nor a full dynamic analysis, but somewhere in between, i.e., an intermediary analysis.
Physical Implementation (Phase 4)
Once the schematic design has been completed and functionally tested, the physical implementation of the schematic into a physical layout takes place.
While a tool such as AutoCAD® from Autodesk, Inc. of San Rafael, Calif., may be used to physically lay out a microfluidic circuit, it has several disadvantages. AutoCAD® has no drawing constraints as it is a general tool. Hence, for example, a control channel can overlap a fluid channel causing an unwanted parasitic valve. While this tool is capable of multiple layers, components are typically drawn on one layer only. Manipulation of a multilayered component presents serious difficulties. AutoCAD® does not have the concept of an I/O port and connectivity to an I/O port. Again since AutoCAD® is a general CAD program, there is no design information associated with a component such as functional information. Embodiments of the present invention overcome these disadvantages of AutoCAD® and other similar tools, and provide a system in which a microfluidic circuit can be easily and efficiently created using multilayered microfluidic components on a physical layout. There are two primary aspects to the physical layout 410 of the microfluidic circuit or system or device. The first is component placement and the second is the routing of the interconnections between the placed components.
Components can be either manually or automatically placed in the MCAD system's placement tool. The placement tool includes one or more of the following functions: allowing the grouping of components by connectivity by layer and/or by cross layer (3D grouping); placing components based on design rule constraints (DRC) in the DRC database 424 from set mechanical properties per layer provided in the mechanical properties library 422; performing design rule checking 420; allowing for grid and gridless placement of components; highlighting DRC errors; performing layer to layer shrinkage compensation for placements; and/or reading and writing the DWG, DXF, or other appropriate file formats.
Examples of DRC's include checks on I/O placement, channel size mismatch, dangling channels, overlapping components & channels, and channel spacing.
An I/O placement rule may restrict a user to a set of pre-defined templates having pre-defined I/O ports.
A channel size mismatch rule allows checks for component channels (i.e., channels that are part of the component) to connecting channel having size mismatch and channel-to-channel size mismatch.
A dangling channel checking rule checks for two or more unconnected ports per component channel (only one end of a component channel need be connected) and for only one connected port on a user drawn channel (both ends of channels must be connected).
An overlapping channels rule allows checking for overlapping user drawn fluidic and control channels. There is an error for any overlapping channels. If there is auto-bridging then one or both channels are re-shaped at and within a predefined distance of the overlap point and no error occurs. Other overlapping components & channels rules check for overlapping channels on the same layer and overlapping components on the same layer or on another layer. Again if there is auto-bridging, two overlapping channels on the same layer may be corrected by routing one channel to another layer and back again using vias.
A channel spacing rule checks for minimum spacing between adjacent channels of a predetermined width. For example, there may be required a minimum of 30 μm between adjacent 120 μm width channels, a minimum of 50 μm between adjacent 100 μm width channels, and a minimum of 70 μm between adjacent 80 μm width channels,
Next the interconnections between the placed components can be either manually or automatically done in the MCAD system's routing tool. The routing tool includes one or more of the following functions: definition of routing cross-sectional profiles; auto-routing 430 for similarly pitched components—grid or gridless; optimization of routing corners: right angle, radius, etc.; relocation of routing to other layers; layer to layer shrinkage compensation; and/or auto-bridging either intra or inter layer, where inter-layer bridging is done using vias.
In an embodiment of the present invention there are two types of bridging performed by the auto routing 430 (
For this embodiment, phase 1 to phase 3 are not performed and the user begins with phase 4. In this embodiment, the basic library 206 and macro library 210, which together include the components for the physical layout 410, feed the layout tool 510 directly and the schematic entry 202 is bypassed. In
The component library area 512 includes the library components, represented by symbols, that are available for the layout design. To select the portion of the library desired, one simply left clicks on the title of the portion (e.g., bridges 514, channel arrays 516, or pumps 517), and the components are displayed (e.g., active area 520 of bridges 514). If more than one component is present in the active area the up or down button is used to scroll through them. Once the proper component is found, one may left click the mouse button and hold and drag the component into the active drawing area 530 and release the button to place the component in a desired location.
A library component is typically composed of channels. Some components have channels only on one layer while some have channels on two or more layers.
The layer area 520 in
The active drawing area 530 is where components from the component library area 512 are placed and connected together using the drawing tools. In one embodiment the active drawing area includes a predefined template 532. The predefined template 532 has a plurality of I/O ports, for example 534-1, 534-2, 534-3, and 534-4. the components in component library area 512 are placed and connected on this template 532. Also connections are made from the connected components to the I/O ports.
The status bar 535 has two modes for the drawing area 530. One mode for the drawing area is the select mode (shown in
In one embodiment, if a user tries to draw a control channel 598 as shown in
In one embodiment the control channels are not connected to the fluid channels. In another embodiment, although the control channels may be on different layers than the fluid channels, they may be connected to the fluid channels by vias.
The pressure oscillator structure operates as follows. Initially, pressure source 612 provides pressure along fluid channel 611 and control channel 618 through via 616. Because of the serpentine shape of flow channel 614, pressure is lower in region 614 as compared with control channel 618. At valve 620, the pressure difference between serpentine flow channel portion 614 and overlying control channel 618 eventually causes valve 620 to close. Owing to the continued operation of pressure source 612, however, pressure begins to build up in serpentine flow channel portion 614 behind closed valve 620. Eventually the pressure equalizes between control channel 618 and serpentine flow channel portion 614, and valve 620 opens. Given the continuous operation of the pressure source 612, the above-described build up and release of pressure will continue indefinitely, resulting in a regular oscillation of pressure. Such a pressure oscillation device may perform any number of possible functions, including but not limited to, timing.
An illustration of an application developed using the physical layout tool of
The microfluidic circuit of
The operation of the sorting device in accordance with one embodiment of the present invention is as follows. The sample is diluted to a level such that only a single sortable entity would be expected to be present in the narrow channel 720 at any time. Assume, for the sake of illustration, that the sortable entity is either size A or size B and that size A entities are collected at fluid output port 636 and size B entities are collected at fluid output port 638. Pump 712 (three control valves and five damping elements) is activated by flowing a fluid through control channels 642, 644, and 646 as described above. The sortable entity enters via input port 634 and moves via fluid channel 650. The sortable entity is pushed by the pump 712 into the narrow channel 722. The narrow channel width is selected such that the sortable entities can move only in a single file manner through this channel. Hence if there happen to be two sortable entities in the narrow channel 722, one must follow the other. The narrow channel 722 serves as a detection region 724, where an external detection system, such as an optical measurement system, is used to determine if the detected sortable entity is size A or size B. The bridge components 732-1 and 732-2 are used to allow crossing of the fluid lines by the control lines without creating a parasitic valve. The bridge components are also used to create an area clear of channels for the detection region 724. If the sortable entity is size A then control channel 668 is activated and control line 666 is deactivated. This turns on the valve 750 and turns off valve 752. Hence the size A entity flows to fluid output port 636. If the sortable entity is size B then control channel 666 is activated and control line 668 is deactivated. This turns on the valve 752 and turns off valve 750. Hence the size B entity flows to fluid output port 638.
Sorting in accordance with the above embodiment would avoid the disadvantages of sorting utilizing conventional electrokinetic flow, such as bubble formation, a strong dependence of flow magnitude and direction on the composition of the solution and surface chemistry effects, a differential mobility of different chemical species, and/or decreased viability of living organisms in the mobile medium. For more detailed discussions of cell sorting by microfabricated devices, see A. Y. Fu et al, “A Microfabricated Fluorescence-Activated Cell Sorter,” Nature Biotechnology 17: 1109-1111 (1999); H. P. Chou et al., “A Microfabricated Device for Sizing and Sorting DNA Molecules,” Proc. Nat'l Acad. Sci. 96: 11-13 (1999); S. Quake et al., “Disposable Microdevices for DNA Analysis and Cell Sorting,” Proc. Solid-State Sensor and Actuator Workshop,” Hilton Head, S.C., Jun. 8-11, 1998, pp. 11-14; and H. P. Chou et al., “Microfabricated Devices for Sizing DNA and Sorting Cells, Micro- and Nanofabricated Structures and Devices for Biomedical Environmental Applications,” Paul L. Gourley, Editor, Proceedings of SPIE Vol. 3258, 181-7 (1998).
Further details on the physical layout tool is given by the User's Manual in Appendix C, which is herein incorporated by reference.
Physical Analysis (Phase 5)
Once the design has been completed, placed, and routed, a simulation indicating the dynamic performance can be performed under physical analysis 800 (phase 5). As shown in
In one embodiment the dynamic fluidic flow simulation 840 is performed using ANSYS/Multiphysics (coupled field structural-fluid) and ANSYS/FLOTRAN™ (computational fluid dynamics) tools of ANSYS Inc. of Canonsburg, Pa. (www.ansys.com/products/html/multiphysics.htm and (www.ansys.com/products/flotran.htm). The ANSYS tools can perform laminar flow simulations and coupled physics simulations, such as dynamic fluidic and mechanical simulations, for microfluidic systems. Using this tool, dynamic simulation models 810 are first developed, taking into account the mechanical/structural properties of the model's associated component (mechanical properties library 820). Next using the dynamic simulation models 810 as connected and laid out in the physical layout 410, a dynamic fluidic flow simulation circuit model for the microfluidic circuit of the physical layout 410 is developed. Parasitic or coupling effects between different channels, which are typically second order effects, optionally, may be incorporated into the dynamic fluidic flow simulation circuit model. The ANSYS/Mutiphysics tool is then used to simulate the dynamic fluidic flow simulation circuit model using a variety of test inputs. Both the final outputs and intermediate test points of the circuit model are analyzed to determine if the proper results are achieved. If not, then the physical layout 410 is modified and the associated modified dynamic fluidic flow simulation circuit model is again simulated. This iterative design process is continued until the desired results are achieved.
In another embodiment the dynamic fluidic flow simulation 840 may employ the DCCL 380 used in the functional analysis 360 as shown in
Device Implementation (Phase 6)
Once the design has been placed and routed, the physical layout 410 of phase 4 will write out the desired chip layout files 902 to manufacture a prototype 904 of the microfluidic circuit as seen in
The wafer is then manufactured (step 904) and the resulting microfluidic device is ready for either one-time use (disposable) or for continuous reuse (semi-permanent test device).
The MCAD system 10 can be implemented and executed in a variety of ways. For instance, it can be implemented as a computer-aided design (CAD) program for design, analysis, and implementation of the elastomeric circuits or networks. The CAD program can be provided separately to individual users or distributed over networks such as the Internet so that it can be centrally maintained and controlled.
Although the above functionality has generally been described in terms of specific hardware and software, it Would be recognized that the invention has a much broader range of applicability. For example, the software functionality can be further combined or even separated. Similarly, the hardware functionality can be further combined, or even separated. The software functionality can be implemented in terms of hardware or a combination of hardware and software. Similarly, the hardware functionality can be implemented in software or a combination of hardware and software. Any number of different combinations can occur depending upon the application.
Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
This application claims priority from and incorporates by reference in its entirety U.S. Provisional Patent Application No. 60/214,595, titled “Biological Design Automation System,” by Michael Lee, et. al., filed Jun. 27, 2000. The following concurrently filed, commonly owned, patent applications are incorporated herein by reference in their entirety: U.S. patent application Ser. No. ______, entitled “A Computer Aided design Method and System For Developing A Microfluidic System,” by Michael Lee, et. al., (Attorney Docket No. 020174-005400US). U.S. patent application Ser. No. ______, entitled “An Object Oriented Microfluidic Design Method And System,” by Gregory Harris, et. al., (Attorney Docket No. 020174-006800US). The following references are incorporated herein by reference each in its entirety: PCT Patent Application No. PCT/US00/17740, entitled “Microfabricated Elastomeric Valve and Pump Systems,” filed Jun. 27, 2000 (U.S. patent application Ser. No. 09/605,520); PCT Patent Application No. PCT/US99/13050, entitled “Microfabricated Sorter for Biological and Chemical Materials” filed May 21, 1999; and U.S. Provisional Patent Application Ser. No. 60/282,253, entitled “Microfabricated Fluidic Circuit Elements and Applications,” filed Apr. 6, 2001.
| Number | Date | Country | |
|---|---|---|---|
| 60214595 | Jun 2000 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09894857 | Jun 2001 | US |
| Child | 10976643 | Oct 2004 | US |
