Bistable spring construction for a stent and other medical apparatus

Abstract

The present invention is directed to bistable cells and their use in devices, particularly medical devices such as stents, clamps and valves. An expandable stent formed of a plurality of bistable cells is described. The stent has two or more stable configurations, including a first stable configuration with a first diameter and a second stable configuration with a second, larger diameter. A valve comprising a bistable cell for use in eliminating incontinence is also disclosed.

What is claimed is: 
     
         1 - 20 . (canceled) 
     
     
         21 . A bistable valve comprising:
 1) a conduit;   2) a stop surface extending across an interior of the conduit, the stop surface having an opening within;   3) bipositional unit cell, the unit cell including
 a substantially arcuate flexible member having a first end and a second end,
 the first end in communication with a trigger, 
 the trigger supported by a support emerging from an inner wall of the conduit, 
 the second end anchored to the stop surface; 
 
   4) a valve closure member.   
     
     
         22 . The bistable valve of  claim 21 , wherein the flexible member has a first position corresponding to a closed position and a second position corresponding to an open position. 
     
     
         23 . The bistable valve of  claim 21 , wherein the valve closure member actuates between open and closed position by the flexible member. 
     
     
         24 . The bistable valve of  claim 21 , wherein the valve closure member closes the opening in the stop surface when the flexible member is in the closed position. 
     
     
         25 . The bistable valve of  claim 21 , wherein the valve closure member opens the opening in the stop surface when the flexible member is in the opened position. 
     
     
         26 . The bistable valve of  claim 21 , wherein the conduit is opened by triggering the trigger to allow the flexible member to move between the closed position and the opened position. 
     
     
         27 . The bistable valve of  claim 21 , wherein the conduit is closed by triggering the trigger to allow the flexible member to move between the opened position and the closed position. 
     
     
         28 . The bistable valve of  claim 21 , wherein the trigger is a piezoelectric element. 
     
     
         29 . The bistable valve of  claim 28 , wherein the piezoelectric element restrains the flexible member. 
     
     
         30 . The bistable valve of  claim 28 , wherein the piezoelectric element decreases in length upon introduction of a small current to the piezoelectric element and releases the flexible member from its first position. 
     
     
         31 . The bistable valve of  claim 21 , wherein the support is a rigid member relative to the flexible member. 
     
     
         32 . The bistable valve of  claim 21 , wherein the stop surface has two oblique regions with a longitudinal region therebetween, the opening disposed in the longitudinal region. 
     
     
         33 . The bistable valve of  claim 32 , wherein the oblique regions are oblique relative to a longitudinal axis of the conduit. 
     
     
         34 . A bistable valve comprising a bistable cell for use in eliminating incontinence. 
     
     
         35 . A medical device comprising the bistable valve of  claim 21 . 
     
     
         36 . The medical device of  claim 35 , wherein the medical device is chosen from a shunt or an expansion ring. 
     
     
         37 . A method of controlling urinary incontinence comprising:
 1) inserting a medical device comprising the bistable valve of claim  1  into a portion of a urethra; and   2) optionally clamping the medical device in place by applying a clamp to the outside of the urethra;   wherein urine may be voided by triggering the bistable valve so as to switch it from the closed to the opened position, the valve being triggered so as to close following urination.   
     
     
         38 . Method of operating a bistable valve comprising:
 activating a trigger that releases a flexible member from its first position;   opening a valve closure member that forces the flexible member into a second position; and optionally activating the trigger that allows the flexible member to transition to its first position.