Abstract:
Low power integrated pumping and valving arrays which provide a revolutionary approach for performing pumping and valving approach for performing pumping and valving operations in microfabricated fluidic systems for applications such as medical diagnostic microchips. Traditional methods rely on external, large pressure sources that defeat the advantages of miniaturization. Previously demonstrated microfabrication devices are power and voltage intensive, only function at sufficient pressure to be broadly applicable. This approach integrates a lower power, high-pressure source with a polymer, ceramic, or metal plug enclosed within a microchannel, analogous to a microsyringe. When the pressure source is activated, the polymer plug slides within the microchannel, pumping the fluid on the opposite side of the plug without allowing fluid to leak around the plug. The plugs also can serve as microvalves.

Description:
The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory. 

   BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The present invention relates to microfluidic systems, particularly to the control delivery and manipulation of fluids in a microfluidic system, and more particularly to low power integrated pumping and valving arrays for microfluidic systems. 
   In the last decade, considerable research efforts have been devoted to the development of microfluidic systems, such as the Micro Total Analysis Systems (micro TAS). Instruments of such systems integrate microfabricated sensors, flow channels (microchannels), reaction chambers, pumps, and valves with control and data processing. Applications include miniature, portable and deployable instruments for detecting chemical and biological warfare agents, medical diagnostics, drug discovery, transdermal drug delivery via microneedles, and DNA analysis/sequencing. These prior are exemplified by U.S. Pat. No. 5,161,774 issued Nov. 10, 1992; U.S. Pat. No. 5,681,024 issued Oct. 28, 1997; and U.S. Pat. No. 5,992,820 issued in Nov. 30, 1999, along with International Applications No. WO 98/13605 published Apr. 2, 1998; No. WO 98/32616 published Jul. 20, 1998; No. 98/53236 published Nov. 26, 1998; and No. WO 99/24744 published May 20, 1999. Despite this effort, there is still a need for integrated, low power pumps and valves for manipulating fluids in the micro devices. This need has been emphasized in a recent $30 M call for proposals by the Department of Defense for microfluidic bio chips (“Bio Flips”) to develop technologies that lead to total integration of peripheral functions onto single microchips, including innovative low power/pressure sources for on-chip fluidic manifolds. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to satisfy the need for integrated, low power pumps and valves for manipulating fluids in micro-devices. 
   A further object of the invention is to provide low power integrated approach for performing pumping and valving operations in microfabricated fluid systems. 
   Another object of the invention is to provide low power integrated pumping and valving arrays (microsyringes) for microfluidic systems. 
   Another object of the invention is to integrate a low power, high-pressure source with a plug or piston enclosed within a microchannel for carrying out pumping and valving operations. 
   Another object of the invention is to provide a microfluidic pumping and/or valving arrangement, wherein a polymer, ceramic, or metal plug is pushed through a microchannel to either pump fluid therein or control fluid passing there-through. 
   Another object of the invention is to provide a low power, high-pressure source using micropumps and microvalves which include a slidable plug movable in a microchannel. 
   Another object of the invention is to create arrays of the microdevices, such as microsyringes, that can be operated independently to control microfluidic systems and to vary dose, and/or vary the fluid being injected. 
   Another object of the invention is to provide integrated pumping and valving arrays using slidable plugs for controlling complex fluidic processes on-chip. 
   Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The invention involves low power integrated pumping and valving (microsyringes) for microfluidic systems. The invention produces a revolutionary approach for performing pumping and valving operations in microfabricated fluid systems for applications such as medical diagnostic microchips. The invention integrates a low power, high-pressure source with a polymer, ceramic, or metal plug enclosed within a microchannel, analogous to a microscale syringe. When the pressure source is activated, such as by heating a fluid, the plug slides within the microchannel, pumping the fluid on the opposite side of the plug without allowing fluid to leak around the plug. In other words, the plug forms a seal with the microchannel, which can be accomplished by using a compressible plug in a rigid channel or a rigid plug in a flexible channel. The fluid activated plug can function as a microvalve for controlling fluid passing through a microchannel. The integrated pumps/valves can be easily fabricated in array format for controlling complex fluidic processes on-chip. The invention can be used for example, for fluid control for portable and/or deployable chemical/biological warfare detection instruments, microfluid control systems for instruments that monitor military or civilian health, or to administer medication in response to biological threats, as well as in microfabricated microfluidic instrumentation for medical diagnostics, programmable drug delivery devices, drug discovery, or DNA analysis/sequencing. Thus, the present invention provides a solution to the above mentioned need for integrated, low pressure pumps and valves for manipulating fluids in microdevices. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated into and form a part of the disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principals of the invention. 
       FIG. 1  illustrates a manifold chip with a plurality of thermopneumatic microsyringe (plug) pumps made in accordance with the present invention. 
       FIGS. 2A and 2B  illustrate an embodiment of a thermopneumatic plug type valve assembly in a normally open position in  FIG. 2A  and closed position in 
       FIG. 2B  in accordance with the invention. 
       FIGS. 3A and 3B  illustrate another embodiment of a microsyringe type thermopneumatic plug type valve with the valve being normally closed in  FIG. 3A  and open in  FIG. 3B . 
       FIG. 4  illustrates an exemplative sequence or functions integrated by a single chip when utilizing several integrated thermally activated plugs as pumps and as valves. 
       FIG. 5  illustrates a stepper microsyringe pump similar to  FIG. 1 , but interfaced to external piston actuators. 
       FIGS. 6A and 6B  illustrate an embodiment of a piezo electric controlled valve for microfluidics. 
       FIGS. 7A and 7B  illustrates top and side views of a microsyringe array application, such as transdermal drug delivery via microneedle. 
       FIGS. 8A and 8B  and  FIGS. 9A and 9B  illustrate first and second molds for producing a frame fixture assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is directed to low power integrated pumping and valving arrays for microfluidic system. The invention integrates a low power, high pressure source with a movable polymer, ceramic, or metal plug enclosed within a microchannel, analogous to a microscale syringe, with the plug being actuated by pressure generation mechanisms involving a chamber containing a fluid, which when heated, as a resistive heating element, either expands or creates bubbles in the fluid, which drives the plug. The pressure generation mechanisms include; liquid-vapor transformation or thermal expansion of the liquid (thermopneumatic), electro osmotic, electro kinetic, solid-liquid phase transformation, piezo-electric or magnetic microactuator pushing on a filled reservoir, shape memory alloy membrane actuator, and electrochemical. The driver plug either functions as a piston to drive a fluid through a microchannel, or functions as a valve to cut off or divert fluid flow in the microchannel. The thermopheumatically driven plugs, for example, may function as an array of pumps, valves, or combinations thereof and be incorporated in a microfluidic chip. 
     FIG. 1  illustrates an example of an integrated micropump or microsyringe manifold formed in a biofluidic chip with three pumps made in accordance with the invention for injecting different solutions into a common mixing/reaction chamber. Each of the three micropumps or microsyringes includes an etched or molded microchannel, a reservoir or supply containing the fluid sample, analyte, reagent or other solution required for the assay to be performed, connected to the microchannel via an inlet, a pressure generating thermopneumatic chamber, for example, comprising a fluid, a heating means, such as a resistive heater, and a plug or piston in alignment with the microchannel. 
   Applying a voltage across the resistive heater (which can also act as a temperature sensor by monitoring the variation in resistivity with power) causes a vapor bubble to form within the contained fluid, increasing the pressure within the sealed microchannel, and forcing the plug or piston to slide along the microchannel pushing (pumping) any solution ahead of the plug or piston when acting as a pump. When acting as a valve the plug or piston moves to open or close a transversely located fluid passageway, such as a microchannel. The plug or piston can slide within the microchannel. It&#39;s outer dimension is such that it forms a fluid seal with the channel surface, preventing fluids from leaking around the plug edges, this seal being provided by the use of a compressible plug and a rigid channel or rigid plug and flexible channel. 
   Referring now to  FIG. 1 , a microfluidic chip  10  is provided with three (3) microchannels  11 ,  12  and  13  which are adapted to be filled in inlets  14 ,  15  and  16  with a fluid or solution, such as a sample fluid, an analyte, a reagent, or other solution required for the assay to be performed. The microchannels  11 – 13  having one end connected to a common channel  17  via connector channels  18 ,  19  and  20 . In alignment with microchannels  11 – 13  are three (3) thermopneumatic or pressure generating chambers  21 ,  22  and  23  containing a fluid. The chambers  21 – 23  constitute in this embodiment, end portions of the microchannels  11 – 13 , and located therein are three (3) plugs or pistons  24 ,  25  and  26 , constructed of a polymer, for example, for rigid channels. The plugs or pistons  24 – 26  have external surfaces which correspond to the internal surfaces of microchannels  1 – 13  whereby the plugs  24 – 26  can slide along the microchannels  11 – 13 , but cooperate with the microchannel surface to form a seal to prevent fluid leakage. Each of the thermopneumatic chambers  21 – 23  is provided with a heater  27 ,  28  and  29 , such as a resistive heater, each being individually controlled. 
   Upon activation of one or more of the heaters  27 – 29 , a vapor bubble is formed in the fluid within corresponding chambers  21 – 23  increasing the pressure and causing the plugs or pistons  24 – 26  to move thereby ejecting/pumping the fluid (solution) in the microchannels forcing same along the microchannels to the common channel  17  and onto a point of use. Also, one piston at a time can be actuated. 
   The same type of thermopneumatic chamber and sliding piston can be utilized in a T-configured microchannel arrangement for valving as shown in  FIGS. 2A and 2B  or  3 A and  3 B. As seen in  FIGS. 2A–2B , a microchannel  30 , such as the microchannels in  FIG. 1 , having a fluid flow there through as indicated by arrow  31  is provided with a transverse connecting channel  32  forming a T-configuration. Located in channel  32  is a thermopneumatic or pressure generating chamber  33 , a plunger, plug, or piston  34 , a fluid  35  contained in chamber  33 , and a resistive heater  36 . The device of  FIG. 2A  is shown in a valve open position. As shown in  FIG. 2B , when fluid  35  is heated by heater  36 , a vapor bubble  37  is created in fluid  35  which causes plunger  34  to move and close microchannel  30 , a closed position, as seen in  FIG. 2B . By control of the heater  36 , the size of the bubble  37  can be controlled and thus the amount of movement of plunger  34  can be controlled, whereby the plunger  34  functions as a variable displacement valving member such that flow of fluid  31  through microchannel  30  can be controlled or stopped. The embodiment of  FIGS. 2A–2B  provides a normally open valve arrangement. These are one-time use valves. Also the valves can be configured as multiple use open-close valves, which is an important feature. 
   The embodiment of  FIGS. 3A–3B  provides a normally closed valve arrangement, and corresponding components have been given corresponding reference numerals. In this embodiment channel  32   1  extends across channel  30   1  and heating of the fluid  35   1  in chamber  33   1  by resistive heater  36   1  creates bubble  37   1  and forces movement of plunger or piston  34   1  to move, as shown in  FIG. 3B . Plunger  34   1  has reduced diameter section  38  which extends into channel  30   1  and allows fluid to flow through channel  30   1  as indicated by arrow  39 . The device of  FIGS. 3A–3B  could have two thermopneumatic sources to open and close the valve. 
   Advantages of the thermopneumatic/plug pump or valve arrangement include: 
   1. Compact design, suitable for chip-scale integration. 
   2. Low power, with the devices consuming zero power when idle, and minimal power (milliwatts) over a short time period when activated. The valve, or fluidic switch, requires no power when the channel is in an open state, and no power when the channel is closed after actuation, unlike most valves which require power in one state or the other. 
   3. Ability to fabricate arrays of devices, taking advantage of batch/fabrication processes (low cost, reduced manual assembly), without compromising small size. 
   4. Sensitive biological working fluids are thermally isolated form the actuation portion of the device. 
   5. Fluids can be stored and sealed within the device for long shelf life. 
   The following table summarizes the features of the present invention compared to existing technology. 
   
     
       
             
             
             
             
           
         
             
               TABLE 
             
             
                 
             
             
               Pump/Valve 
               Power 
               Size 
               Other 
             
             
                 
             
           
           
             
               Microsyringe 
               mW 
               Same scale as 
               Arrays possible, 
             
             
                 
               Power only required 
               microchannels 
               controlled fluid 
             
             
                 
               when switching 
                 
               pumping, does not heat 
             
             
                 
                 
                 
               working fluid. 
             
             
               External Pressure- 
               mW-Watts 
               Large external pressure 
               External pressure 
             
             
               Driven Pumps &amp; Valves 
               Power determined by 
               source and valve 
               effectively control 
             
             
                 
               macrovalves 
               manifolds 
               microfluidic devices 
             
             
               Redwood Thermopneumatic 
               mW-Watts 
               4 mm diameter 
               Can seal against high 
             
             
               Valve 
               Power required to 
               footprint (large in 
               pressures. Too large for 
             
             
                 
               maintain one state 
               comparison to chip) 
               arrays on single chip, 
             
             
                 
                 
                 
               heats working fluid. 
             
             
               Electoosmotic Pumping 
               High voltage required 
               Large external power 
               Arrays possible, no 
             
             
                 
                 
               source required 
               moving parts, 
             
             
                 
                 
                 
               electrolysis an issue, 
             
             
                 
                 
                 
               must work with 
             
             
                 
                 
                 
               conductive solution, 
             
             
                 
                 
                 
               sensitive to surface 
             
             
                 
                 
                 
               properties of 
             
             
                 
                 
                 
               microchannel. 
             
             
               Piezoelectric Disc Pump 
               High voltage required 
               5–10 mm discs required. 
               Disc are too large for 
             
             
                 
               (100&#39;s of volts) 
               Large power supply. 
               arrays on single chip, 
             
             
                 
                 
                 
               cavitation can be a 
             
             
                 
                 
                 
               problem. 
             
             
               Magnetohydrodynamic 
               Watts 
               Requires relatively large 
               Must work with 
             
             
               Pump 
                 
               external magnet and 
               conductive solution, 
             
             
                 
                 
               power supplies 
               fluid not contained 
             
             
                 
                 
                 
               when pump is inactive. 
             
             
                 
             
           
        
       
     
   
   As an example, the integrated system comprises a chip-scale microfluidic system that incorporates, for example, a thermopneumamtic/plug (microsyringe) approach of the invention can be fabricated by existing technology for controlling injection and valving of various fluids in order to prepare blood samples for RNA analysis. The single chip integrates the following functions: 
   1. Microbiopsy to collect blood or tissue samples. 
   2. Introduce osmotic solution to burst the red cells. 
   3. Filter out the cellular debris. 
   4. Lyse the white blood cells with a gunadinuim solution. 
   5. Introduce ethanol to precipitate out the RNA. 
   6. Wash the RNA with ethanol. 
   7. Dry off the ethanol. 
   8. Elute the RNA into the polymerase chain reaction (RCR) chamber. 
   9. Perform the reverse transcriptase and PCR in conjunction with real-time detection. 
   The above described sequence is illustrated in  FIG. 4 . When injecting solution into a chamber, a plug, or cork-like seal may be used to initially isolate the fluid from the other solutions. Upon actuation of the syringe, the pressure generated uncorks this plug, allowing the fluid to be injected to the chamber. The plug will either be trapped in a downstream section of microchannel such that fluid can flow around it, or it will be allowed to enter the reaction chamber where it will not adversely affect the reaction. Likewise, for step  5  in  FIG. 4 , to open the valve, a plug will be uncorked from a narrow section of channel with a microsyringe device that uses water as a working fluid. 
   As shown in  FIG. 5 , a microfluidic chip, generally similar to  FIG. 1  and indicated at  40 , includes three (3) microchannels  41 ,  42 , and  43  which are interfaced to external piston actuators  44 ,  45 , and  46 , or other internal pressure sources/micropumps can also be used to drive micro-syringes or pistons  47 ,  48  and  49  located in microchannels  41 – 43 , respectively. The microchannels  41 – 43  have one end connected to a common channel  50  via connector channels  51 ,  52  and  53 . External piston actuators  44 – 46  direct fluid indicated at  54 ,  55  and  56  against pistons  47 – 49  causing pistons  47 – 49  to move against the fluid  57 ,  58  and  59  forcing the fluid into common channel  50 . However, each of pistons  47 – 49  can be actuated independently. 
   The plug is most readily moved through a microchannel having a configuration corresponding to the external configuration of the plug. Generally, a circular shaped microchannel and corresponding configured plug is preferable, although other shapes having rounded corners are acceptable. Recently, a process has been developed for producing circular microchannels in glass, and is described and claimed in copending U.S. application Ser. No. 09/(IL-10581), filed May 7, 2001, entitled “Method for Producing Microchannels Having Circular Cross-Sections in Glass”, assigned to the same assignee. In that method a substrate having etched microchannels is bonded to a top plate and then annealed to allow surface tension forces and diffusional effects to lower the overall energy of the microchannel by transforming the cross-section to a circular shape. 
   An important aspect of the polymer microchannel with hard plug implementation is the method for forming a perfectly round channel, which is essential for achieving a seal. This was done by casting the polymer around a smooth, fine-diameter wire or pin, then removing the wire or pin after the polymer has cured. 
   The polymer channel should be hydrophobic to improve the seal. Since surface effects dominate fluid flow on the microscale, optimal fluid loading and channel sealing is dependant on selective poly (dimethylsiloxane) (PDMS) surface modifications. The polymer channel should be hydrophobic and pneumatic fluid should be hydrophilic when using hydrophilic reagents or vice versa (Polymer channel should be hydrophilic and pneumatic fluid should be hydrophobic when using hydrophobic reagent) for leak proof seal. 
   Another approach to the formation of circular cross-section microchannels, as mentioned above involves molding or embedding of wires or round members of a desired diameter in a desired configuration creating a mold to pour polydimethylsiloxane (PDMS) in, and then pulling out the wire or member following the curing process which creates perfectly circular channels. In addition to PDMS, other silicones, or other polymers may be used. This results in a flexible microfluidic device with perfectly circular and smooth channels that can be applied in various biomedical microdevices and other microsystems. This process is both time and cost effective due to the simplicity of the approach. An example of a channel made using this technique has been shown in an SEM cross-sectional image, and small hard balls have been loaded into these soft PDMS channels and have been driven with an external pheumatic actuator (syringe). Fluid was successfully pumped using the microsyringe, with the balls forming effective seals against the PDMS microchannels. 
   One of the target applications of these integrated microsyringes is a Transdermal drug delivery patch via microneedles as illustrated in  FIGS. 7A and 7B , and described hereinafter. This device is a programmable multidosage/multidrug delivery patch that will employ microneedles to facilitate the transdermal diffusion process, which is the critical hindrance of conventional systems. Each microsyringe will contain one preset dosage that would be delivered at a rate to achieve the drug concentration that maximizes therapeutic effect and minimize side effects. The Microsyringes in the array could contain the same drug or different drugs. 
   Another application is for Biological/Chemical manipulation and analysis. This will be used for Environmental and Medical diagnostics. 
   Another application is cell manipulation and testing. For example the microchannels would be ideal for making flow chambers for biofluidics and cellular mechanics experiments. The Circular cross section of the channels mimics the physiological nature of blood vessels and the optical properties of PDMS would allow for easy visualization. 
     FIGS. 6A and 6B  illustrate a piezo controlled valve for microfluidics. The valve assembly comprises a glass substrate  60  having a pair of microchannels  61  and  62  etched therein to a depth of 40 microns, for example, with the glass intermediate the pair of microchannels forming a seat or closure  63  for the valve. A thin (0.1 micron) gold layer  64  was sputtered onto the top surface of seat  63  and then patterned into a 700 micron diameter circle, for example using a mask and photolithography. A 300 micron thick PDMS film  65  was produced using two flat surfaces as a press and then curing. The film  65  was then bonded on the glass substrate  60  to cover the channels  61  and  62  and the gold circle layer  64  using standard soft lithography bonding techniques. Then two radically expanding ceramic piezos were epoxied together forming a bimorph  66 , which bends when provided with a voltage because one piezo expands while the other contracts. Wires, not shown, were expoxied onto the top and bottom of the bimorph  66  for providing desired current to the piezos. The bimorph was dipped in pre-cured PDMS to provide an initial bond to the PDMS film, and the piezo bimorph  66  was bonded to film  65  so as to be over the gold circle  64  of seat  63  connecting the two channels  61  and  62 . Precured PDMS was then poured all around the piezo bimorph  66  and the film  65  to provide a backing and support  67  with the composite films being shown generally at  68  with the piezo bimorph  66  embedded there. The entire structure was cured for 1 hour at 120° C. Two holes were bored through the PDMS film composite  68  at both ends of the channel  61  and  62  and peek tubing  69  and  70  were inserted therein to provide a fluid inlet and a fluid outlet. As shown in  FIG. 6A , the valve is closed, and upon a voltage being applied the piezo bimorph  66  bends, and this bending lifts the PDMS membrane or film  65  from the gold layer  64  of seat  63 , and opens a path  71  between channel  61  and  62  as seen in  FIG. 6B . When the voltage is reversed, the piezo bimorph  66  presses the film  65  downward against the gold layer  64  creating a sealed valve between the two channels  61  and  62 , as seen in  FIG. 6A . Application of 100 volts at low frequencies such as 10 Hz has been successful in bending the film  65  and actuating the valve. This device also can be used to generate pressure for the microsyringe. 
     FIGS. 7A and 7B  illustrate top and side views of a microsyringe array for an application involving transdermal drug delivery via microneedles. A PDMS substrate  80  is provided with a plurality of thermopneumatic chambers which may include resistive heaters  81 ′– 85 ′ and indicates at  81 ,  82 ,  83 ,  84  and  85  each chamber connected to a respective channel  86 ,  87 ,  88 ,  89  and  90  formed in the substrate  80 . Each chamber  81 – 85  is connected to a programmable chip or microchip controller  91  via leads  92 ,  93 ,  94 ,  95  and  96 . Channels  86 – 90  are each provided at an outer end with a plurality of microneedles  97  (see  FIGS. 7B ) and each channel  86 – 90  contains a piston  98 ,  99 ,  100 ,  101  and  102  and is provided with a desired reagent  103  intermediate pistons  98 – 102  and microneedles  97 . The reagent  103  in each of the channels  86 – 90  may be the same or different, depending on the desired application. Each channel  86 – 90  contains a driving or actuation fluid  104  located intermediate pistons  98 – 102  and thermopneumatic chamber  81 – 85 . 
   In operation, one or more resistive heaters  81 ′– 85 ′ heat fluid in thermopneumatic chambers  81 – 85  which cause the expansion of the driving fluid  104  and movement of one or more pistons  98 – 102  along channels  86 – 90  forcing the desired reagent  103  toward microneedles  97  for delivery of the reagent to a patient or other point of use. 
   The Channels in  FIGS. 7A and 7B  may be formed by embedding wires of the desired diameter into the PDMS and then pulling out the wire following the curling process creates perfectly circular channels. This results in a flexible microfluidics device with perfectly circular and smooth channels that can be applied in various systems such as drug delivery devices. The shape is not limited to only circular channels, but other desired structures and shapes like cork screw shape channels or spring like springs could be obtained. This process is both time and cost effective due to its simplicity and quick turnover. The channels can be fabricated in an hour and the cost is tremendously reduced since no microfabrication techniques are employed. Previous methods to fabricate circular channels encountered numerous difficulties including alignment problems, etching defects, the inability to produce perfectly circular channels, time consuming and costly labor. 
   The following description in accompaniment with  FIGS. 8A–8B  and  9 A– 9 B illustrate an application of the PDMS or polydimethyl (siloxane) process.  FIG. 8A  is a 3-D overall of a first mold, with  FIG. 8B  being a top view of the frame for the first mold.  FIG. 9A  is a 3-D overall of a second mold, and  FIG. 9B  is a top view of the frame for the second mold. The process is as follows: 
   1. Mix PDMS (Sylard® 184 from Dow Corning) with curing agent in 10:1 ratio respectively. 
   2. Stir well and degas to releases all the air bubbles. 
   3. Frame fixture assembly of  FIGS. 8A–8B  and  9 A– 9 B
         a. Frame fixture consists of metal base with four walls. For reference we will call the End-walls  1 A for first mold ( FIGS. 8A–8B ) and  2 A for second mold ( FIGS. 9A–9B ). The side-walls will be  1 B for first mold and  2 B for second mold.   b. The  1 A end-walls have slits in them to accommodate for wires strung to mold channels. (There is no limit on the number of channels to make.)   c. Reservoir mold pieces are screwed on to the acrylic top cover.   d. Desired diameter wires are threaded through reservoir mold pieces.   e. The Acrylic cover, containing the reservoirs and wires, is screwed to the top of the frame.   f. The wires are tightened using end screws on the frame bed.   g. Inject PDMS through one of the fill port on top of the frame. The other fill port is to allow air out so bubbles are trapped.       

   4. Cure for 1 hr. @ 66° C. 
   5. Cut wires and pull past reservoir and remove reservoir piece. Do not pull wires all the way out. Keep wires in while in the plasma etcher to prevent channels from becoming oxidized. If channels become oxidized there will not be a tight seal between the piston and the channels, which will result in leakage. Oxidizing the reservoir on the other hand helps minimize the air bubble formation when filling later. Also protects channel from getting refilled during second mold process. 
   6. Replace the  1 A end-walls with heater frame  2 A end-walls to accommodate heaters and replace  1 B side-walls with  2 B. Notice  2 A and  2 B are a little higher than previous walls to accommodate the 2 nd  molding process. 
   7. Place piston in channel through the reservoir port as seen in  FIG. 2A . 
   8. Clean heaters with ethanol and dry. 
   9. Place tape on heater pads to protect pads when spinning on PDMS. 
   10. Spin PDMS onto glass heaters (Resistive heaters on glass) to assure bonding where the platinum resistive heaters are. 
   11. Apply heaters on
         a. Clean PDMS with ethanol and dry   b. Place both heaters and PDMS part in plasma etcher for 1 min to oxidize surface to form bond
           i. RF @ 100 watts   ii. Oxygen flow   
               

   12. After applying heaters remold PDMS on top to cap in the heaters 
   13. Cure for 1 hour @ 66° C. 
   14. Remove PDMS from the fixture 
   15. Remove the wires 
   16. Fill actuation reservoir with desired actuation fluid and seal with bullet like cork made from glass or silicon. Or seal with wire rod dipped in silicon. The size of the rod should be double the size of wire used to mold the channel. 
   17. Fill channel with regent or drug to be delivered. 
   It has thus been shown that the present invention has provided a new approach for performing pumping and valving operations in microfabricated fluid systems for applications such as medical diagnostic microchips. The invention provides for low power integrated pumping and valving arrays. By the use of the thermopneumatic chamber/plug the device can be effectively utilized as either an injection pump or as a control valve, with the valve having a variable operational capability. A chip scale integrated sample preparation system can be produced utilizing the invention. 
   While particular embodiments of the invention have been described and illustrated, such are not intended to be limiting. Modifications and changes may become apparent to those skilled in the art and it is intended that the invention be limited only the scope of the appended claims.