Abstract:
An implantable pressure-activated microvalve is disclosed. The valve includes a chamber that can be coupled to an external reservoir. A deflectable diaphragm is fluidically coupled to the chamber and arranged such that pressure of an in vitro fluid will bear against the deflectable diaphragm. When the pressure exceeds a selected threshold, the diaphragm deflects and allows material within the chamber to mix with the in vitro fluid.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    This application claims the priority of an earlier filed co-pending provisional Patent Application Serial No. 60/370,819, filed Apr. 8, 2002 entitled IMPLANTABLE PRESSURE-ACTIVATED MICROVALVE. 
     
    
     
         [0002]    Current medical treatments are aided by a vast array of methods and devices for delivering substances, such as medicines, to a patient. One example of such systems is the implantable drug delivery system. However, generally, most implantable drug delivery systems are relatively complex and costly. Usually the cost of such systems is tolerated because implantable drug delivery is of such importance and/or convenience. However, a device and method that could provide at least some of the benefits of implantable drug delivery with significantly reduced costs would benefit patients.  
         SUMMARY OF THE INVENTION  
         [0003]    An implantable pressure-activated microvalve is disclosed. The valve includes a chamber that can be coupled to an external reservoir. A deflectable diaphragm is fluidically coupled to the chamber and arranged such that pressure of an in vitro fluid will bear against the deflectable diaphragm. When the pressure exceeds a selected threshold, the diaphragm deflects and allows material within the chamber to mix with the in vitro fluid. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is a diagrammatic view of pressure-activated micro-valve  10  implanted within a patient in accordance with an embodiment of the present invention.  
         [0005]    [0005]FIG. 2 is an enlarged perspective view of a pressure activated micro-valve in accordance with an embodiment of the invention.  
         [0006]    [0006]FIG. 3A is a top plan view of valve  10  in accordance with an embodiment of the present invention.  
         [0007]    [0007]FIG. 3B is a side elevation cross-section view of valve  10  in a “closed” state in accordance with an embodiment of the present invention.  
         [0008]    [0008]FIG. 3C is side elevation cross-section view of valve  10  in the open or dispensing state in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0009]    Embodiments of the present invention include a simple implantable pressure-activated micro-valve that is adapted for in vitro use and can selectively provide a substance, such as a medicine, in response to a pressure of a body fluid, such as blood, reaching a selected threshold. It is anticipated that embodiments of the present invention will be useful for control of elevated blood pressure. For example, drugs that treat such conditions can be dispensed in direct response to a pressure signal of the blood itself. It is believed that such drug delivery can help ameliorate short term “pressure spikes” in blood pressure.  
         [0010]    Although aspects of the present invention will be described with respect to dispensing blood pressure lowering drugs, any suitable medicines or substances can be used in response to any in vitro fluid pressure. In accordance with some aspects, additional medicines, or other suitable substances are stored in a reservoir that can be disposed outside the body. Preferably, the valve itself is constructed from microelectromechanical systems (MEMS) based materials which are generally compatible with in vitro operation. Examples of such materials include, but are not limited to silicon, Sapphire, ceramic, and other known bio-compatible materials. Metals such as titanium can also be used. Further, the pressure valve itself is preferably sized such that it can be implanted through a hypodermic needle. In accordance with aspects of the invention, the pressure valve is all mechanical and highly reliable. Further, a diaphragm of the pressure valve can be designed to allow a very accurate range of opening pressures. Examples of such pressures can include 180, 200, 220 Torr. As will be appreciated, the pressure-activated micro-valve will respond as needed, thus closing or generally ceasing dispensation when the pressure passes below the selected threshold. The valve itself is anticipated to be extremely inexpensive such that it can be used for disposable applications.  
         [0011]    [0011]FIG. 1 is a diagrammatic view of pressure-activated micro-valve  10  implanted within a patient. In accordance with one aspect of the present invention, micro-valve  10  is fluidically coupled, via line  12 , to external reservoir  14 .  
         [0012]    [0012]FIG. 2 is an enlarged perspective view of valve  10 . Preferably, valve  10  is disposed within stainless steel sheath  16  which facilitates introduction of valve  10  into the body. Valve  10  is generally constructed from a sandwich of MEMs materials. Valve  10  includes bottom layer  18 , deflectable diaphragm  20  and top layer  22  bonded together in accordance with known techniques. Bottom layer  18  includes a recess allowing deflectable diaphragm  20  to deflect therein, while top layer  22  includes a chamber  28  that provides the desired material when diaphragm  20  deflects. Those skilled in the art will recognize that this geometry may be reversed without departing from the spirit and scope of the invention. Thus, more generally, a first layer includes a recess for diaphragm deflection, while the second layer includes the chamber for the selected pharmaceutical material.  
         [0013]    The materials selected for bottom layer  18 , deflectable diaphragm  20 , and top layer  22  are preferably materials such as silicon, Sapphire and ceramic. While it is preferable that all such layers are the same material, they need not be.  
         [0014]    [0014]FIG. 3A is a top plan view of valve  10 . Deflectable diaphragm  20  can be seen extending beyond edge  24  of top layer  22 . Top layer  22  is bonded to deflectable diaphragm  22  at area  25 , but not at area  26 . The portion of diaphragm  20  proximate edge  24  is deflectable such that when pressurized with sufficient pressure, diaphragm  20  deflects in the area of crosshatching  26  to allow the contents of chamber  28  to pass therethrough.  
         [0015]    [0015]FIG. 3B is a side elevation cross-section view of valve  10  in a “closed” state. In this state, valve  10  is subjected to an external pressure of P 0 . A region  30  below diaphragm  20  is pressurized to pressure P. When the difference between pressure P 0  and pressure P exceeds the preloaded sealing force of deflectable diaphragm  20 , diaphragm  20  itself will deflect away from surface  32  of top layer  22  thereby allowing contents  34  within chamber  28  to be dispensed.  
         [0016]    [0016]FIG. 3C is side elevation cross-section view of valve  10  in the dispensing state. FIG. 3C shows deflectable diaphragm  20  deflected from surface  32  to generate gap  36  allowing contents of chamber  28  to pass therethrough.  
         [0017]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.