Electrohydrodynamic coating fluid delivery apparatus and method

Abstract

An apparatus and method for improved control of low viscosity fluid flow during electrohydrodynamic spray deposition of the fluid to coat small targets, such as medical devices like stents. The apparatus includes a target holder which applies a first electrical potential to a target, a coating fluid transporter such as a wick, a siphon tube or a siphon tube with a wick therein along which the coating fluid flows from a reservoir to a dispensing end of the transporter, and an electrode which applied a second electrical potential to the coating fluid sufficient to cause the coating fluid to be attracted from the dispensing end of the transporter toward the target. This provides a target coating apparatus with highly self-regulating coating fluid flow characteristics despite the low viscosity of the coating fluid, while producing highly consistent and uniform target coatings.

1 - 18 . (canceled)  
   
   
       19 . An apparatus for electrohydrodynamic application of a coating fluid, comprising: 
 a target holder which holds a target at a first electrical potential;    a coating fluid reservoir containing a coating fluid; and    a coating fluid transporter comprising a first end and a second end, wherein the first end is in fluid communication with the coating fluid in the coating fluid reservoir, and the coating fluid transporter transports the coating fluid from the first end to the second end by capillary action,    wherein the coating fluid is at a second electrical potential that is greater than the first electrical potential thereby causing coating fluid at the second end of the coating fluid transporter to be attracted to the target and be discharged toward the target.    
   
   
       20 . The electrohydrodynamic coating apparatus of  claim 19 , further comprising 
 a controller, wherein the controller controls a voltage differential between the first electrical potential and second electrical potential thereby controlling the discharge of coating fluid from the second end of the coating fluid transporter toward the target.    
   
   
       21 . The electrohydrodynamic coating apparatus of  claim 19 , wherein 
 the coating fluid transporter is a wick.    
   
   
       22 . The electrohydrodynamic coating apparatus of  claim 21 , wherein 
 the coating fluid contains a therapeutic agent.    
   
   
       23 . The electrohydrodynamic coating apparatus of  claim 21 , wherein 
 the target is a medical device.    
   
   
       24 . The electrohydrodynamic coating apparatus of  claim 23 , wherein 
 the medical device is a stent.    
   
   
       25 . The electrohydrodynamic coating apparatus of  claim 19 , wherein 
 the coating fluid transporter is a siphon tube,    the first end comprises a first opening of the siphon tube in fluid communication with the coating fluid in the coating fluid reservoir,    the second end comprises a second opening of the siphon tube, and    the second opening is at a lower height than a coating fluid level height in the reservoir.    
   
   
       26 . The electrohydrodynamic coating apparatus of  claim 25 , wherein 
 the coating fluid contains a therapeutic agent.    
   
   
       27 . The electrohydrodynamic coating apparatus of  claim 25 , wherein 
 the target is a medical device.    
   
   
       28 . The electrohydrodynamic coating apparatus of  claim 25 , further comprising: 
 a float connected to the siphon tube.    
   
   
       29 . The electrohydrodynamic coating apparatus of  claim 28 , wherein 
 the float is slidably connected to the siphon tube.    
   
   
       30 . The electrohydrodynamic coating apparatus of  claim 28 , further comprising: 
 a counterweight connected to the float.    
   
   
       31 . The electrohydrodynamic coating apparatus of  claim 25 , further comprising: 
 a wick within the siphon tube.    
   
   
       32 . The electrohydrodynamic coating apparatus of  claim 19 , further comprising: 
 a coating fluid refiller, wherein the refiner is in fluid communication with the coating fluid reservoir and refills the reservoir.    
   
   
       33 . An apparatus for electrohydrodynamic application of a coating fluid, comprising: 
 a target holder which holds a target at a first electrical potential;    a coating fluid reservoir containing a coating fluid; and    a coating fluid transporter comprising a first end and a second end, wherein the first end is in fluid communication with the coating fluid in the coating fluid reservoir, and the coating fluid transporter transports the coating fluid from the first end to the second end by siphoning action,    wherein the coating fluid is at a second electrical potential that is greater than the first electrical potential thereby causing coating fluid at the second end of the coating fluid transporter to be attracted to the target and be discharged toward the target.    
   
   
       34 . The electrohydrodynamic coating apparatus of  claim 33 , further comprising 
 a controller, wherein the controller controls a voltage differential between the first electrical potential and second electrical potential thereby controlling the discharge of coating fluid from the second end of the coating fluid transporter toward the target.    
   
   
       35 . The electrohydrodynamic coating apparatus of  claim 33 , wherein 
 the coating fluid transporter is a siphon tube,    the first end comprises a first opening of the siphon tube in fluid communication with the coating fluid in the coating fluid reservoir,    the second end comprises a second opening of the siphon tube, and    the second opening is at a lower height than a coating fluid level height in the reservoir.    
   
   
       36 . The electrohydrodynamic coating apparatus of  claim 35 , wherein 
 the coating fluid contains a therapeutic agent.    
   
   
       37 . The electrohydrodynamic coating apparatus of  claim 35 , further comprising: 
 a wick within the siphon tube.    
   
   
       38 . The electrohydrodynamic coating apparatus of  claim 35 , further comprising: 
 a stopcock adjacent the second opening of the siphon tube.    
   
   
       39 . An apparatus for electrohydrodynamic application of a coating fluid, comprising: 
 a target holder which holds a target at a first electrical potential;    a coating fluid reservoir containing a coating fluid; and    means for transporting the coating fluid comprising a first end and a second end, wherein the first end is in fluid communication with the coating fluid in the coating fluid reservoir, and the means for transporting transports the coating fluid from the first end to the second end by capillary action,    wherein the coating fluid is at a second electrical potential that is greater than the first electrical potential thereby causing coating fluid at the second end of the means for transporting to be attracted to the target and be discharged toward the target.    
   
   
       40 . An apparatus for electrohydrodynamic application of a coating fluid, comprising: 
 a target holder which holds a target at a first electrical potential;    a coating fluid reservoir containing a coating fluid; and    means for transporting the coating fluid comprising a first end and a second end, wherein the first end is in fluid communication with the coating fluid in the coating fluid reservoir, and the means for transporting transports the coating fluid from the first end to the second end by siphoning action,    wherein the coating fluid is at a second electrical potential that is greater than the first electrical potential thereby causing coating fluid at the second end of the means for transporting to be attracted to the target and be discharged toward the target.