US20110031268A1 - Electrokinetic pump designs and drug delivery systems - Google Patents

Abstract

One embodiment of the present invention provides a piston assembly having a piston housing filled with an electrolyte; a housing within the piston housing that divides the piston housing into a first portion and a second portion, the housing having apertures, a shaft connecting the housing to a piston head outside of the piston housing; and a porous material inside of the housing in contact with the electrolyte. Additionally, there are provided a method for filling the delivery chamber with a delivery fluid by withdrawing the piston head from within the delivery chamber. Yet another embodiment provides a method for filling a fluid delivery assembly by withdrawing a shaft from within the fluid delivery assembly to simultaneously displace a moving pump element within the delivery chamber and bypass fluid around a housing in the pump chamber.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 11/603,926, filed Nov. 22, 2006, titled “Electrokinetic Pump Designs and Drug Delivery Systems,” which claims the benefit of U.S. Patent Provisional Application No. 60/739,390, filed Nov. 23, 2005, titled “Electrokinetic Pump Designs and Drug Delivery Systems,” each of which are incorporated herein by reference in its entirety.
• This application is related to the following co-pending patent applications: U.S. patent application Ser. No. 11/603,926, filed Nov. 22, 2006, titled “Electrokinetic Pump Designs and Drug Delivery Systems;” U.S. patent application Ser. No. 10/198,223, filed Jul. 17, 2002, titled “Laminated Flow Devices;” U.S. patent application Ser. No. 10/273,723, filed Oct. 18, 2002, titled “Electrokinetic Device Having Capacitive Electrodes;” U.S. patent application Ser. No. 10/322,083, filed Dec. 17, 2002, titled “Electrokinetic Device Having Capacitive Electrodes;” and U.S. patent application Ser. No. 11/112,867, filed Apr. 21, 2005, titled “Electrokinetic Delivery Systems, Devices and Methods,” each of which are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
• Pumps and pumping systems exist for the delivery of various fluids. A variety of pumps are used in a number of various different configurations and uses. Pumps are used for infusion of drugs or delivery of drugs into mammals, the sterility of the drugs is very important. In addition, contamination of the drug or delivery fluid from the pump system should be reduced or eliminated. Additionally, it remains an important aspect to minimize contact between the drug to be delivered and the internal components of the pump being used to deliver the drug. Filling or preparing the drug or fluid for delivery should not be time consuming. These and other difficulties are encountered using conventional filling and pumping systems.
• Related U.S. patent application Ser. No. 11/112,867, filed Apr. 21, 2005, titled “Electrokinetic Delivery Systems, Devices and Methods,” discloses a technique for filling a pump with fluid for delivery. This technique involves operating the pump system in reverse to draw the delivery fluid into the pump. Then, after filling the pump with the delivery fluid, the pump direction is reversed and the delivery fluid is delivered from the pump. Reversing pump direction may be a good solution for small amounts of fluid or for pump configurations that have a very high linear flow rate. However, the time requirements for loading large volumes of delivery fluid using this technique may be prohibitive for time conscious applications and problematic for later pump operation.
• What are needed are improved techniques for providing the delivery fluid into the pumping system. The pump filling procedures should be simple and require small amounts of time.
SUMMARY OF THE INVENTION
• One embodiment of the present invention provides a piston assembly having a piston housing; a housing within the piston housing that divides the piston housing into a first portion and a second portion, the housing having apertures that provide fluid communication between the first portion and the second portion; a shaft connecting the housing to a piston head outside of the piston housing; and a porous material inside of the housing. In one aspect, the piston housing is filled with an electrolyte. In another aspect, the porous material inside of the housing is in contact with the electrolyte.
• In one aspect, the porous material is a porous dielectric material adapted for operation as part of an electrokinetic pump. In another aspect, there is a sealing element around the piston head or the housing. In yet another aspect, there is a second shaft connecting the housing to a handle outside of the piston housing. In another aspect there is a valve within the second shaft wherein actuation of the valve provides a flow path between the first portion and the second portion. In yet another aspect, the flow path from one side of the housing to the other side of the housing includes a bypass through the porous material contained in the housing. In another aspect, the valve is actuatable from a handle attached to the second shaft. In another aspect, the shaft extends through a wall in the piston housing. In another aspect, the sealing element around the material housing seals the housing to a wall of the piston housing. In another aspect, there is an electrode in the first portion and an electrode in the second portion. In one embodiment, the electrodes have a double layer capacitance of greater than 10⁻⁴microfarad/cm².
• In another embodiment of the invention, there is provided a pump having a delivery chamber, a pump chamber and a wall separating the pump chamber from the delivery chamber; a piston assembly having a piston head in the delivery chamber, a housing in the pump chamber and a shaft connecting the piston head to the housing and passing through the wall separating the pump chamber from the delivery chamber; and a dielectric material in the housing.
• In one aspect, there is a pair of electrodes in the pump housing. In one aspect, there is one electrode is on each side of the housing. In one embodiment, the pair of electrodes are made from a material selected to electrokineticly move a fluid in the pump chamber. In one aspect, the delivery chamber and the pump chamber are in a single housing. In another aspect, the housing divides the pump chamber into a first portion and a second portion. In yet another aspect, there is provided apertures in the housing that provide fluid communication between the first portion and the second portion. In another aspect, there is an electrolyte in the pump chamber. In a further aspect, each electrode in the pair of electrodes has a double layer capacitance of more than 10⁻⁴microfarad/cm². In yet another aspect, there is a bypass valve in the shaft that provides a fluid pathway from one side of the housing to the other side of the housing. In one aspect, the bypass valve in the shaft that provides a fluid pathway from the first portion to the second portion. In another aspect, the delivery chamber is filled with a delivery fluid by relative movement between the pump chamber and the delivery chamber. In another aspect, application of an electric field across the electrodes moves the fluid in the pump chamber from one side of the housing to the other side of the housing. In one aspect, application of an electric field across the electrodes moves the piston head in the delivery chamber. In another aspect, application of an electric field across the electrodes moves the housing relative to the pump chamber.
• In another embodiment, there is provided a method for operating a fluid delivery system by inserting a piston assembly into a delivery chamber, the piston assembly having a pump housing, a piston head outside of the pump housing and attached to a shaft extending through a wall in the pump housing, a housing attached to the shaft and between electrodes in the pump housing; and filling the delivery chamber with a delivery fluid by withdrawing the piston head from within the delivery chamber. In one further aspect, the method fixes the position of the pump housing relative to the delivery chamber. In another aspect, there is provided the step of advancing the piston head in the delivery chamber by moving fluid in the pump chamber. In one aspect, moving fluid within the pump chamber comprises electrokineticly moving fluid through the housing. In another aspect, moving fluid within the pump chamber comprises providing an electric field between the electrodes. In yet another aspect, the filling step comprises withdrawing the pump assembly.
• In another embodiment, there is a method for operating a fluid delivery assembly having a pump chamber and a delivery chamber by withdrawing a shaft from within the fluid delivery assembly to simultaneously displace a moving pump element within the delivery chamber and bypass fluid around a housing in the pump chamber.
• In one aspect, withdrawing a shaft from the pump assembly introduces a delivery fluid into the delivery chamber and into contact with the moving pump element. In another aspect, advancing the moving pump element in the delivery chamber by applying an electrical field across electrodes in the pump chamber and on either side of the housing. Still another aspect provides electrokineticly moving fluid in the pump chamber to dispense fluid from the delivery chamber. In still another aspect includes actuating a bypass in the shaft during the withdrawing step.
INCORPORATION BY REFERENCE
• All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
• The novel features of the invention are set forth with particularity in the claims that follow. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
• FIG. 1A is section view of an exemplary pump system;
• FIG. 1B is an exploded view of a flow-through pump element ofFIG. 1A;
• FIGS. 2A-2E illustrate details for the loading and delivery of fluid using the pumping system900;
• FIGS. 3A-3E illustrate details for the loading and delivery of fluid using thepumping system1000; and
• FIG. 4 illustrates a method of fluid delivery.
DETAILED DESCRIPTION OF THE INVENTION
• FIGS. 1A and 1B will be described to provide an understanding of the basic components and operation of a typical fluid delivery system.FIG. 1A illustrates a cross section view of a fluid delivery system1. The fluid delivery system has afirst chamber30, a second chamber32 and athird chamber35. A flow through pump element20 (such as electrokinetic pump, as shown inFIG. 1B) separates thefirst chamber30 from the second chamber32. A moveable pump element40 (such as a floating piston, as shown) separates the second chamber32 from thethird chamber35. While in this illustrative embodiment themoveable element40 is a floating piston, any device that provides a moveable barrier may be used as will be illustrated in the examples that follow. In this embodiment, the first, the second and the third chambers are within asingle housing15.Seals42 are used to seal themoveable pump element40 as it moves within thehousing15. An outlet45 provides communication between thethird chamber35 and the exterior ofhousing15. Anoutlet55 provides communication between the second chamber32 and the exterior ofhousing15. In this embodiment, avalve60 separates thesecond outlet55 from the exterior ofhousing15.
• As illustrated, aconduit71 connects theoutlet55 to theopening70. Avalve60 in theconduit71 controls fluid flow from theoutlet55 to theopening70. Thevalve60 has adisc62,stem64, aspring66 and a disc orseal68.Seats72,74 in the housing are shaped to seal with, respectively, discs or seals62,68.Valve60 is shown in the closed position wherespring66 holdsdiscs68,62 in place againstseats72,74. In this embodiment,conduit71 andvalve60 are disposed in a wall ofhousing15. Other configurations are possible such as a separate valve assembly that attaches directly toport55 or a valve/conduit configuration that ports through thepump element20 rather than around thepump element20 as shown.
• In the illustrated embodiment, thefirst chamber30 contains a moveable pump element82 (i.e., a diaphragm adjacent the pump element20). Thefirst chamber30 also contains avent75, if needed to ensure free movement of themoveable element82. The space between thediaphragm82 and thepump element20 contains a buffer or pump fluid80 that is selected to operate with the type of pump element used. If thepump element20 is an electrokinetic pump, then thebuffer80 would be an electrolyte selected to operate with the electrode and porous material materials and desired operation of the pump. Examples of specific electrolytes and other details of electrokinetic pumps are described in co-pending and commonly assigned patent application serial numbers U.S. patent application Ser. No. 10/198,223, filed Jul. 17, 2002, titled “Laminated Flow Devices;” U.S. patent application Ser. No. 10/273,723, filed Oct. 18, 2002, titled “Electrokinetic Device Having Capacitive Electrodes;” U.S. patent application Ser. No. 10/322,083, filed Dec. 17, 2002, titled “Electrokinetic Device Having Capacitive Electrodes” and U.S. patent application Ser. No. 11/112,867, filed Apr. 21, 2005, titled “Electrokinetic Delivery Systems, Devices and Methods,” each of which are incorporated herein by reference in its entirety.
• Thepump element20 is connected to supporting electronics5 byelectrical connectors26. The supporting electronics5 may be altered depending upon the type of pump element(s) used but will generally include a user control interface6, electronic control circuitry8 and apower supply10. The user control interface6 may be a touch screen or other input means to allow a user to operate the delivery system, select a program or otherwise provide programming instructions to the system. The electronic control circuitry contains the programming instructions needed to translate the user inputs into commands to operate the pump element. The electronic control circuitry also regulates the power supply to achieve user desired pumping characteristics such as flow rate and delivery timing. Thepower supply10 may contain a battery or the delivery system may be plugged into an electrical supply. The supporting electronics are conventional and will be understood by those of ordinary skill in the art.
• An exploded view of one type ofpump element20 is shown inFIG. 1B. Thepump element20 shown inFIG. 1B is an electrokinetic pump element. Electrokinetic pump element contains aporous material22 between twocapacitive electrodes24. Illustrative electrode materials include carbon aero gel or carbon nanofoam. One example of a suitable porous membrane is a microporous filter having a pore size ranging from tens of nanometers to micron size. In one embodiment, the preferred pore size is 100-200 nanometers. The capacitive electrodes are connected to the supporting electronics5 byelectrical connectors26. The pump element contains a pump fluid or buffer80 that is moved through theporous material22 from one electrode towards the other electrode depending on how voltage is applied between theelectrodes24. The electrokinetic flow produced by thepump element20 may be in one direction (from one electrode to the other electrode) or may alternate directions of flow (towards one electrode and then away from that electrode and towards the other electrode). Examples of electrokinetic pumps configurations, electrolytes, electrodes, porous materials (also referred to as porous dielectric materials) and other details of are described in co-pending and commonly assigned patent applications: U.S. patent application Ser. No. 10/198,223, filed Jul. 17, 2002, titled “Laminated Flow Devices;” U.S. patent application Ser. No. 10/273,723, filed Oct. 18, 2002, titled “Electrokinetic Device Having Capacitive Electrodes;” U.S. patent application Ser. No. 10/322,083, filed Dec. 17, 2002, titled “Electrokinetic Device Having Capacitive Electrodes” and U.S. patent application Ser. No. 11/112,867, filed Apr. 21, 2005, titled “Electrokinetic Delivery Systems, Devices and Methods,” each of which are incorporated herein by reference in its entirety.
• Optionally, astorage fluid50 fills the second chamber. Thestorage fluid50 may be a fluid used to maintain the integrity of thepump element20 during storage or prior to operation. Thestorage fluid50 may be the same or different than the fluid80 stored in the first chamber. Thestorage fluid50 may also be a pump fluid (i.e., such as electrolyte suited to operation in an electrokinetic pump) moved by operation of thepump element20. Adelivery fluid36 is stored in thethird chamber35. In some embodiments, the delivery fluid is a drug, a pharmacological or therapeutic agent, or other substance to be delivered by operation of thepump element20.FIG. 1A also illustrates aconventional syringe90 is also illustrated having abody91 with atip92. Aplunger93 is attached to handle95 byshaft94 is disposed within thebody91.
• Pump system1 provides one solution to loading the pump system without the use of thepump element20 by bypassing the pump element. Additionally, thepump element20 remains in a fixed position within the pump housing during both filling and pumping operations. Thepump systems900 and1000 provide an alternative apparatus and method for filling and delivering fluid. In contrast to the fixed pump element fluid system1, the pump element inpump systems900,1000 moves within the pump housing during fluid delivery operations. The pump element influid system1000 also moves during pump filling operations. These and other details of thepump systems900,1000 are described below.
• FIGS. 2A-D andFIGS. 3A-E illustrate pumpingsystems900,1000. Novel piston assemblies are at the heart of the systems. The piston assemblies are designed to move within another pump component to deliver fluid. Piston assembly970 (illustrated inFIG. 2B) and piston assembly990 (illustrated inFIG. 3B) have several common components. Apiston head972 is connected to ahousing980 by ashaft976. Thehousing980 contains aporous material984 and a plurality ofapertures982 allow fluid flow through thehousing980 and theporous material984. In one embodiment, theporous material984 is a dielectric material adapted for operation as part of an electrokinetic pump. Examples of porous dielectric materials described in the co-pending patent applications described above. A sealing element orelements974 are provided around the perimeter of thepiston head972. Thepiston head972 is sealed within a delivery chamber that is separate from the pump chamber (i.e.,delivery chamber910 inFIG. 2A) or integrally formed with the pump chamber (i.e.,delivery chamber1010 inFIG. 3A). One ormore sealing elements978 is provided around the perimeter of thehousing980. Thehousing980 is sealed within the pump chamber using sealingelements978 as shown inFIGS. 2A and 3A. Suitable materials for construction of components include polypropylene, polycarbonate and medical grade plastics.
• FIG. 2A illustrates a pump900 that includes adelivery chamber910, a pump chamber orpiston housing950 and a wall931 separating thepump chamber950 from thedelivery chamber910. Thepiston housing950 is filled with asuitable electrolyte80. Apiston assembly970 has apiston head972 in the delivery chamber910 (i.e., outside of the pump housing950), ahousing980 in the piston housing or pumpchamber950 and ashaft976 connecting thepiston head972 to thehousing980. Theshaft976 passes through the wall931 separating thepump chamber950 from thedelivery chamber910. As shown inFIG. 2B, thehousing980 divides thepiston housing950 into afirst portion950A and a second portion950B. A pair ofelectrodes924 are in thepump housing950 where there is oneelectrode924 is on each side of thehousing980. There is anelectrode924 in thefirst portion950A and anelectrode924 in the second portion950B. In one embodiment, each electrode in the pair of electrodes has a double layer capacitance of more than 10⁻⁴microfarad/cm². Aporous material984 is contained inside of thehousing980 and in contact with theelectrolyte80. Thehousing980 hasapertures982 that provide fluid communication between thefirst portion950A and a second portion950B. Thehousing980 is sealed within thepiston housing950 using sealingelement978.
• Thehousing910 includes anoutlet945 and aninterior space915. Theinterior space915 is sized and shaped to sealingly receive thepiston head972. Thepiston housing950 is adapted for pumping operations using thepiston assembly970. Thehousing950 includeselectrodes924 positioned on either end of housing interior. Thepiston assembly970 is disposed within thehousing950 withshaft976 extending through a sealedopening943. Thehousing950 is inserted into theinterior space915 and thepiston972 is advanced against the interior915 adjacent theoutlet945. The pump system900 is now ready for filling.
• The pump system900 is filled by attaching avial105 or other suitable container to theoutlet945 and then withdrawing thepiston housing950 from thedelivery interior915 as indicated by the arrow inFIG. 2C. The relative movement of thepump chamber950 to thedelivery chamber910 draws thedelivery fluid36 fromvial105 through theoutlet945 and into the interior915 as shown inFIG. 2C. Next, thevial105 is removed and a delivery device, such as an infusion set96, is attached tooutlet945. An optional purge or prime procedure is illustrated inFIG. 2D. Before attachment of the delivery device, after attachment of the delivery device or both before and after attachment of the delivery device the system may be primed or purged of air by advancing thepiston housing950 relative to thedelivery chamber910 as indicated by the arrows inFIG. 2D.
• Prior to commencement of pumping, the position of thepiston housing950 is fixed relative to thedelivery chamber910. In one embodiment, thehousings910,950 are fixed whenfeature912 ondelivery chamber910 and feature934 onchamber950 are locked inplace using bars492 andspaces494 within the frame490 as illustrated inFIG. 2E.
• Pumping begins when an electric field is applied acrosselectrodes924. Application of an electric field across theelectrodes924 moves electrolyte80 in thepump chamber950 from one side of the housing980 (i.e., the portion950B) to the other side of the housing (i.e. theportion950A). In one embodiment, theelectrolyte80 is moved electrokineticly through theapertures982 and theporous material984 from oneelectrode924 towards the other as indicated by the arrows inFIG. 2E. This movement of the electrolyte decreases the volume of the portion950B and increases the volume of theportion950A. Increasing volume ofportion950A moves thehousing980 and thepiston head972 towards theoutlet945 which in turn expelsdelivery fluid36 out throughoutlet945.
• Turning now toFIGS. 3A and 3B that illustrate thepumping system1000. Thepumping system1000 includes adelivery chamber1010 and apump chamber1020 within a single housing (i.e., the pump housing1005). Thedelivery chamber1010 has anoutlet1045 and avent1012. Avial105 filled with adelivery fluid36 is attached tooutlet1045 and thepump system1000 is ready for filling. Thepiston assembly990, illustrated inFIG. 3B, is disposed within thepump housing1005. Thepiston assembly990 is arranged within a piston housing or pumpchamber1020 filled with anelectrolyte80. Ahousing980 within the piston housing divides the piston housing into afirst portion980A and asecond portion980B and maintained byseals978. Thehousing980 hasapertures982 that provide fluid communication between thefirst portion980A and thesecond portion980B. Thehousing980 contains aporous material984 in communication with theelectrolyte80. Theporous material984 may be a porous dielectric material adapted for operation as part of an electrokinetic pump. A pair ofelectrodes1024 are provided in thepump chamber1020. Oneelectrode1024 is provided on each side of the housing980 (i.e., one electrode in thefirst portion980A and one electrode in thesecond portion980B). In the illustrated embodiment, the electrodes, dielectric material and electrolyte are selected to provide electrokinetic movement of the electrolyte within the pump chamber and through thehousing980. In one embodiment, the electrodes are made of a material having a double layer capacitance greater than 10⁻⁴microfarads/cm².
• Ashaft976 connects thehousing980 to a moveable pump element (here, a piston head972) and ahandle994 outside of thepiston housing1020. Theshaft976 may be a single piece as illustrated or be formed of multiple pieces. An example of a multiple piece shaft would be a first shaft connecting thehousing980 to thepiston head972 and a second shaft connecting thehousing980 to thehandle994.Sealing elements1018,1028 maintain the fluid integrity where the shaft passes through the pump chamber walls viaopenings1014,1026. Thepiston assembly990 also includes a bypass feature not found inpiston assembly970. Thepiston assembly990 includes avalve988 within theshaft976 that provides a fluid pathway from one side of the housing980 (i.e., thefirst portion980A) to the other side of the housing980 (i.e., thesecond portion980B) without passing the fluid through theporous material984. Thevalve988 or fluid path through theshaft976 provides a bypass through the porous material contained in the housing without requiring operation of the electrodes or inducing flow though thematerial984. Thevalve988 is actuatable from ahandle994 attached to thehousing980. In the illustrated embodiment, abutton996 located on thehandle994 is used to depress the spring in986,open valve988 and to allow fluid flow through theshaft976 around thehousing980.
• FIG. 3C illustrates a method of operating afluid delivery system1000 having apump chamber1020 and adelivery chamber1010. Filling is performed by withdrawing theshaft976 within the fluid delivery assembly to simultaneously displace a moving pump element within the pump chamber (i.e., the piston head972) and bypass fluid around thehousing980 in the pump chamber1020 (as shown by the arrows in pump chamber1020).FIG. 3C also illustrates that thebutton996 inhandle994 is depressed (thereby opening the bypass with valve988) while thehandle994 is withdrawn. Once avial105 or other suitable container is attached to theoutlet1045, withdrawing theshaft976 from the pump assembly also introduces thedelivery fluid36 into thedelivery chamber1010 and into contact with the moveable pump element (i.e., the piston head972). When thebutton996 is depressed thebypass valve988 allows fluid allowsbuffer80 to pass from one side of thehousing980 to the other side as illustrated by the arrows. Now thatbuffer80 may move freely within thepumping chamber1020, thehandle994 is withdrawn thereby withdrawingpiston head972 within thedelivery chamber1010. This action drawsdelivery fluid36 into the delivery chamber theoutlet1045.
• As shown inFIG. 3D, when the filling operation is complete, thebutton996 is released. Whenbutton996 is released, action byspring986 forces thevalve988 closed thereby preventing further passage ofbuffer80 through the bypass valve as illustrated inFIG. 3D. A delivery device is attached to theoutlet1045. In the illustrated embodiment, the delivery device is an infusion set96 having an outlet orconduit1080.
• Pumping begins with the application of an electric field across theelectrodes1024 that moves theelectrolyte80 in the pump chamber from one side of thehousing980 to the other as indicated by the arrows insidechamber1020 inFIG. 3E. The movement of electrolyte fromportion980B into980A moves thehousing980 and thepiston head972 towards theoutlet1045 by increasing the volume ofportion980A while decreasing the volume of theportion980B. In the illustrated configuration, when an electric field is applied acrosselectrodes1024,electrolyte80 is moved electrokineticly through theapertures982 and theporous material984 from oneelectrode1024 towards theother electrode1024 as indicated by the arrows insidechamber1020. As such, movement of thebuffer80 through theapertures982 moves thehousing980. Movement of thehousing980 in turn advances thepiston head972 to expeldelivery fluid36 out throughoutlet1045 anddelivery device96.
• FIG. 4 illustrates aflow chart400 depicting an exemplary fluid delivery method. First, atstep410, the step of inserting a piston assembly into a delivery chamber. By way of non-limiting examples, this step is illustrated and described with regard toFIGS. 2A and 3A. Next, atstep420, the step of attaching a vial to a delivery chamber. By way of non-limiting examples, this step is illustrated and described with regard toFIGS. 2C and 3C. Next, atstep430, is the step of filling the delivery chamber by withdrawing the piston assembly from the delivery chamber. By way of non-limiting examples, this step is illustrated and described with regard toFIGS. 2C, and3C. The next step,step440, is the step of attaching a delivery device to the delivery chamber. By way of non-limiting examples, this step is illustrated and described with regard toFIGS. 2D and 3D. Optionally, before or after attaching the delivery device, the system may be primed or purged (step450) as shown and described, for example, with regard toFIG. 2D. Finally,step460, the step of operating a pump in the pump chamber to deliver fluid through the delivery device. By way of non-limiting examples, this step is illustrated and described with regard toFIGS. 2E, and3E.
• The foregoing illustrative embodiments have used certain terms to provide an explanation of the principal involved or operation of the illustrated systems. It is to be appreciated that numerous alternatives for components and elements are possible. For example, the pump element and components in the pump chamber may form an electrokinetic pump as described but may be reconfigured to accommodate the use of diaphragm pumps, piston pumps, and piezoelectric pumps. The supporting electronics5 andelectrical connectors26 would be modified as needed according to the type of pump element and other components used. Additionally, many of the illustrative configurations described the use of a movable pump element such aspiston head972. It is to be appreciated that the movable pump element may be a piston or a diaphragm and that both may be used in a single system (i.e., as illustrated inFIG. 1A). The diaphragm may be a ‘rolling’ type diaphragm. Rolling diaphragms have a convolute that allows predictable travel of the diaphragm. While a rolling diaphragm does have advantages, the invention is not so limited and other types of diaphragms and moveable pump elements may be used.
• The process of drug aspirating and air purging has been shortened in many of the illustrative descriptions. For configurations describing filling the pump with delivery fluid, the description simply indicates to pull back on a handle or pump housing to drawn drug or delivery fluid in. Those of ordinary skill will appreciate that this is an abbreviated instruction. Like any drug aspiration process, trapped air is vented before the drug is delivered. As such, the full process includes drawing drug in by pulling back on the handle or housing, then while holding the unit with the drug exit port at the top, flick the unit to release bubbles, and then press the syringe handle in to purge air out of the unit. The process is repeated if necessary until all visible air is removed and the unit is filled with the desired amount of drug. This process is identical to the typical method used by medical practitioners to aspirate drug into syringes and purge air.
• A generic infusion set96 is described and many of the pump system embodiments are represented as connected to an infusion set. While not illustrated in every embodiment, a similar configuration of an infusion set connection or other suitable delivery device can be inferred for all pump system embodiments. Alternatively, thedelivery fluid36 or drug may be dispensed without an infusion set such as, for example, when it is delivered directly into a canula or elsewhere.
• The use of liquid and/or air seals have been illustrated in some embodiments. In some embodiments, those components requiring seals (piston head972,housing980, etc.) have two o-ring seals while in other embodiments only one o-ring seal shown. Two seals are typically used in medical syringes and have thus been shown in pairs on most of the pistons described herein. It is to be appreciated that one or more o-rings may be used, however, or alternate types of seals may be employed. O-rings may be made from conventional sealing materials suited to medical application such as silicone and urathane, for example
• Any of the configurations may be partially filled with drug or delivery fluid to any desired amount. Additionally, in some embodiments, the portion of pump housing (i.e.delivery chambers910,1010) that stores the delivery fluid would be transparent and graduated to allow visibility and amount of thedelivery fluid36 present. In addition, a transparent housing generally would also allow visibility of any air that needs to be purged during the filling process. Volumetric increment markings may also be appropriately provided on the pump housing by printing, stamping, embossing, painting or otherwise indicating the contents of thedelivery fluid36 within a drug or delivery chamber. Suitable materials for construction of components include polypropylene, polycarbonate and medical grade plastics.
• One benefit of the pumping systems described herein is that these systems provide indirect pumping of delivered liquids regardless of the type of pump used forpump element20 or pumping configuration. The pump components are contained withinpiston housing950 orpump chamber1020 and as the descriptions above make clear, thedelivery fluid36 does not pass through any pump mechanism and is actually separated from the pump components. Another advantage is the decreased likelihood of damage to fluids that are susceptible to mechanical and/or chemical degradation such as long chain protein molecules and peptides. Mechanical actions including compression, shearing, and extrusion, as well as exposure to electrical currents can cause molecular level damage to some fluids. By obviating the need for the fluids to pass through the pump mechanism, concern over pumping damage to these compounds is diminished.
• The term buffer has been used throughout the description. Buffer refers to any suitable working fluid that may be used by a particular pumping system. In many pumping system embodiments, the buffer or working fluid is any fluid having a viscosity low enough to be pumped through the pump element. In those embodiments where the pump element is an electrokinetic pump, working fluid is an electrolyte suited to the specific electrodes and dielectric material used by the electrokinetic pump. In one specific embodiment, the electrolyte is a buffered electrolyte. One buffered electrolyte is a buffer made from TRIS [tris (hydroxmethyl) aminomethane] and sorbic acid at a concentration of 10 Mm and a pH of 8.3. Other common buffer ions work as well. For example, TRIS-HCL, borate or sodium acetate buffers can be used. The buffer may also include other additives such as preservatives.
• The term delivery fluid has been used throughout the description. In many pumping system embodiments, the delivery fluid is any fluid having a viscosity low enough to be pumped through action of the pump element. In some embodiments, the delivery fluid is a pharmacological agent. In other embodiments, the delivery fluid is a therapeutic agent. In still other embodiments, the delivery fluid is a saline solution or Ringers solution.
• While numerous embodiments of the present invention have been shown and described herein, one of ordinary skill in the art will appreciate that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. In addition, the intended uses of the present invention include a variety of medical applications as well as other applications where highly precise, compact devices for fluid transport are needed. It should be understood that various alternatives to these embodiments of the invention described herein may be employed in practicing the invention. It is intended at the following claims defined the scope of the invention and it methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims (23)

1.-28. (canceled)

29. A method for operating a fluid delivery system comprising:

providing a delivery chamber having a piston assembly therein, wherein the piston assembly includes a pump housing having a pair of electrodes therein, a piston head outside of the pump housing and attached to a shaft extending through a wall in the pump housing, and a material housing attached to the shaft and between the electrodes; and

filling the delivery chamber with a delivery fluid by drawing the piston assembly at least partially out of the delivery chamber.

30. (canceled)

31. A method for operating a fluid delivery system according toclaim 29 further comprising:

advancing the piston head in the delivery chamber to expel the delivery fluid from the delivery chamber.

32. A method according toclaim 31 wherein advancing the piston head comprises electrokinetically moving pump fluid in the pump housing through the material housing.

33. A method according toclaim 32 wherein electrokinetically moving pump fluid within the pump chamber comprises providing an electric field between the pair of electrodes.

34. (canceled)

35. A method for operating a fluid delivery assembly having a pump housing including a pump chamber and a delivery chamber, the method comprising:

withdrawing a shaft from the pump housing to simultaneously displace a moving pump element within the delivery chamber and bypass fluid around a material housing in the pump chamber.

36. A method for operating a fluid delivery assembly according toclaim 35 wherein withdrawing the shaft introduces a delivery fluid into the delivery chamber and into contact with the moving pump element.

37. A method of operating fluid delivery assembly according toclaim 35 further comprising:

advancing the moving pump element in the delivery chamber to expel the delivery fluid from the delivery chamber.

38. A method of operating a fluid delivery assembly according toclaim 37, wherein advancing the moving pump element comprises electrokinetically moving fluid in the pump chamber.

39. The method ofclaim 35 further comprising:

actuating a bypass in the shaft during the withdrawing step.

40. A method for operating a fluid delivery system according toclaim 31, further comprising:

fixing the position of the pump housing relative to the delivery chamber after filling the delivery chamber and before advancing the piston head.

41. A method for operating a fluid delivery system according toclaim 29, further comprising:

removably attaching a container including the delivery fluid to an outlet in the delivery chamber prior to filling the delivery chamber, wherein filling the delivery chamber comprises drawing delivery fluid from the container into the delivery chamber.

42. A method for operating a fluid delivery system according to31, further comprising:

attaching a delivery device to an outlet in the delivery chamber prior to advancing the piston head, wherein the delivery fluid is expelled into the delivery device during the advancing step.

43. A method for operating a fluid delivery system according toclaim 35, further comprising:

removably attaching a container including the delivery fluid to an outlet in the delivery chamber prior to withdrawing the shaft, wherein withdrawing the shaft comprises drawing delivery fluid from the container into the delivery chamber.

44. A method for operating a fluid delivery system according toclaim 37, further comprising:

attaching a delivery device to an outlet in the delivery chamber prior to advancing the moving pump element, wherein the delivery fluid is expelled into the delivery device during the advancing step.

45. A method for operating a fluid delivery system comprising:

filling a delivery chamber with a delivery fluid by drawing a piston assembly at least partially out of the delivery chamber, the piston assembly including a piston head and a pump housing having a pair of electrodes therein;

providing an electric field between the pair of electrodes; and

advancing the piston head within the delivery chamber using electrokinetic energy created by the pair of electrodes such that the delivery fluid is expelled from the delivery chamber.

46. The method ofclaim 45, wherein providing an electric field causes a pump fluid to move in the pump housing to create electrokinetic energy.

47. The method ofclaim 46, wherein the fluid moves through a porous material in the material housing.

48. The method ofclaim 45, wherein the piston system further includes a shaft extending through a wall in the pump housing, and wherein drawing the piston assembly at least partially out of the delivery chamber comprises moving the shaft.

49. A method for operating a fluid delivery system according toclaim 45, further comprising:

removably attaching a container including the delivery fluid to an outlet in the delivery chamber prior to filling the delivery chamber, wherein filling the delivery chamber comprises drawing delivery fluid from the container into the delivery chamber.

50. A method for operating a fluid delivery system according toclaim 45, further comprising:

attaching a delivery device to an outlet in the delivery chamber prior to advancing the piston head, wherein the delivery fluid is expelled into the delivery device during the advancing step.

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