fig1 shows valve 10 in the open position where voltage is applied to solenoid 104 forcing plunger 14 to the right ( proximal end ). fluid arriving at input port 102 fills chamber 106 and passes along plunger 14 via channels 12 . the fluid then passes around ( or through ) the ends of seal 13 ( for example , via openings 13 a ) and enters chamber 107 . the fluid then passes out of the valve via opening 108 and output port 103 . plunger 14 is longitudinally positioned within a hollow core of housing 101 through the center of solenoid 104 essentially forming a first chamber 106 at the proximal end of the plunger and a second chamber 107 at the distal end . spring 15 is positioned within chamber 106 and exerts longitudinal force on the proximal end of plunger 14 when the valve is open ( plunger 14 moved to the right toward the proximal end ). the force of spring 15 acting on plunger 14 is toward the distal end , when spring 15 is compressed . when it is desired to stop or reduce the fluid flow , electrical voltage is removed from solenoid 104 allowing spring 15 to push plunger 14 to the left ( toward the distal end ) forcing the body of seal 13 into contact with opening 108 of output port 103 so as to prevent ( or reduce ) fluid from passing out of valve 10 . in operation , the voltage can be pulsed on and off so that the amount of fluid delivered at the output of port 103 is precisely controllable . the power source for valve 10 can be either internal to the body or external , and can be a battery ( 33 , fig3 ) or other voltage source with power and control delivered via wires ( or wireless ) 304 . the pulsing of the solenoid can be hard wired controlled ( via wires not shown ) or can be wirelessly controlled . the valve can be designed to operate in the opposite manner such that when the voltage is applied the valve closes and when the voltage is removed the valve opens . however , for fail - safe purposes in most applications it would be desirable to have the valve close when power fails so that less and not more medication passes to the target site . note that in some embodiments the seal could be designed to allow some fluid to flow even when in the “ closed ” position . spring 15 can be , for example , 316 stainless steel or any other material acceptable for implantable use directly into the liquid stream being delivered to the target site . plunger 14 , is material responsive to the magnetic fields created by solenoid 104 . in the embodiment shown , plunger 14 is a chromium alloy , for example cr 18 . the portion of plunger 14 and interior chamber walls that contact the material to be delivered to the target site is coated in a biocompatible material , such as titanium nitride ( tin ). the coating material can be metallic or non - metallic as desired . housing 101 , which can be implantable in a human body , comprises material , such as 316 stainless steel which is known to be biocompatible for implant purposes where contact with the medication is not present . seal 15 on the end of plunger 14 can be , for example , silicone , which is also a biocompatible material . in one embodiment , the plunger is made of non - biocompatible or unknown biocompatible material , whose biocompatible properties are not well know . while analysis of each material &# 39 ; s biocompatible property could occur , this involves expensive and time consuming testing , which may not provide ascertainable results . such testing would delay introduction of materials into products and might not provide the surety needed to satisfy governmental approval for use . use of known biocompatible materials as a coating on parts having unknown biocompatiblility solves this problem . for one embodiment , titanium nitride ( tin ) is used for the above mentioned properties , thereby allowing the valve to be produced at a relatively low cost without costly testing . in operation , a user desiring to implant a device in a human ( or in an animal ) could select an off - the - shelf device having unknown biocompatible materials and then determine which portions of the selected device would cause problems if the material of the determined portions was not biocompatible with the human ( or animal ) body . once these “ potential ” trouble portions are identified , the user would select a material that is known to be biocompatible and also known to be compatible with the desired function within the device . the potential trouble spots are then coated by plating or otherwise with the selected material . in some situations , different portions of the device could have different requirements depending upon the function to be performed and the implanted location of the device . thus , as discussed herein , those portions of the device that are implanted under the skin may have a different biocompatibility requirement than does those portions of the device coming into contact with medication to be delivered or coming into contact with the blood supply of the patient . in some embodiments , the liquid could flow on the outside of plunger 14 provided plunger 14 was supported within the hollow core of housing 101 and provided any surface that the liquid contacted was of a biocompatible material . this support , for example , could be a series of o - rings , each having holes therethrough so that the liquid could pass around the plunger while the plunger is supported within the o - rings . the liquid would then flow into chamber 107 and out of outlet 103 when the plunger is in the open position . when the plunger moves to the closed position , seal 13 would be forced against opening 108 thereby stopping ( or reducing ) the flow of liquid . fig2 is a sectional view taken along section 2 - 2 of fig1 . housing 101 is shown around solenoid 104 which in turn surrounds plunger 14 and seal 13 . fluid channels 12 are shown around the outside of plunger 14 . note that the fluid channels can be spiraled , as shown in fig1 , or can be longitudinal along the plunger . these channels can be on the outside surface of plunger 14 or internal thereto , or a combination thereof . fig3 shows one illustrative system 30 in which catheter 302 delivers a measured amount of medication to human spine 303 within human body 32 . catheter 302 is connected to output port 103 of valve 10 . pump 31 is any pressure source which can deliver a measured amount of medication , under constant pressure if desired , to catheter 301 which , in turn , delivers the medication to input port 102 of valve 10 . valve 10 , then is operational to meter the medication to the target site , or sites , within spine 303 . in this embodiment , pump 31 , valve 10 and catheters 301 and 302 are all implanted within human body 32 . pump 31 could also be , for example , a spring driven infusion pump of the type described in u . s . pat . no . 4 , 772 , 263 . also , instead of a pump , or in addition thereto , a positive pressure reservoir can be used . since plunger 14 is constructed of a relatively hard material , such as chromium or a chromium alloy , the coating placed thereon should also be hard . accordingly , the use of titanium nitride ( tin ) which is a relatively brittle and hard material will work well . the thickness of the coated tin , in one embodiment is between 3 microns and 5 microns but may vary depending on the application . the metallic coating could be deposited using well - known vapor depositing techniques or any other process . one method for depositing the coating would be to put a pin ( or other holding device ) through hole 401 ( fig4 ) at the distal end of plunger 14 for the purpose of holding the plunger during the vapor depositing process . at the end of the coating process , the plunger is removed from the depositing bath and the pin ( or other holding device ) is removed . the plunger will then be coated , except possibly where the pin ( or other holding device ) had been positioned . as shown in fig4 , in one embodiment seal 13 then can be force fitted , or otherwise attached using adhesive or fasteners as desired , to circumferentially reduced portion 401 at the distal end of plunger 14 allowing the seal to effectively cover any portion of plunger 14 that was not fully coated . platinum would be another know biocompatible material , however platinum does not have the durability as does titanium nitride . by using titanium nitride , a known biocompatible material , and recognizing that it has the hardness required to coat a magnetic material , such as chromium , without interfering in the magnetic solenoid operation , a metering valve can be constructed from an essentially “ off - the - shelf ” valve that is human implantable , even though the “ off - the - shelf ” valve could not be so used without proper coating of the plunger . while an in - line valve ( liquid stopper ) has been shown in one embodiment , any type of valve could benefit form the concepts taught herein . for example , a rotary valve could be used which rotates open and closed with the areas touching the liquid being coated with a biocompatible material . also , while a human body has been shown , the concepts taught herein can be used for implantation in any body , including animals . although the present invention and its advantages have been described in detail , it should be understood that various changes , substitutions and alterations can be made herein without departing from the invention as defined by the appended claims . moreover , the scope of the present application is not intended to be limited to the particular embodiments of the process , machine , manufacture , composition of matter , means , methods and steps described in the specification . as one will readily appreciate from the disclosure , processes , machines , manufacture , compositions of matter , means , methods , or steps , presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized . accordingly , the appended claims are intended to include within their scope such processes , machines , manufacture , compositions of matter , means , methods , or steps .
there is disclosed a system and method for allowing use within a body of devices having material not known for its biocompatibility with the body . in one embodiment , a magnetically controlled solenoid / valve is used where portions of the valve are directly in contact with compositions that are to be delivered to a target site . advantage is taken of an existing solenoid / valve having chromium alloy parts by coating the portions of the valve that contact the deliverable composition with a known biocompatible material having good wear resistance . in one embodiment , titanium nitride is used as the coating material .