Ultrasonic Material Removal System For Cardiopulmonary Bypass and Other Applications

Abstract

Devices, systems, and methods manipulate target materials within fluids, and may be useful for removing microbubbles and other materials from blood. Ultrasound or acoustic filtering waves may be directed across a flow of blood, and differences in density between the target microbubbles and the blood may enhance separation by driving the lighter matter upward for removal from the blood stream. A disposable acoustically transmissive conduit can replaceably engage an ultrasound transmitter to facilitate sterilization. Exemplary conduits have elongate lumen cross-sections and an axial path resembling a portion of a Mobius strip.

1 . A filter for separating a target matter from a fluid flow, the filter comprising:
 a fluid conduit having an input for receiving the fluid flow, an output, and a lumen defining a fluid flow path from the input to the output;   an ultrasound or acoustic transmitter for transmitting ultrasound or acoustic waves; and   a target matter port in fluid communication with the conduit lumen, the transmitter oriented so that the waves drive the target matter across the fluid flow path toward the port.   
   
   
       2 . The filter of  claim 1 , the fluid flow at the input comprising the target matter and a biological fluid, the target matter being less dense than the fluid, wherein transmitter is disposed below the fluid flow path and the port is disposed above the fluid flow path. 
   
   
       3 . The filter of  claim 2 , wherein the fluid conduit has an upper surface, the upper surface sloping, along the fluid flow path, upward toward the port and then downward away from the port. 
   
   
       4 . The filter of  claim 3 , wherein fluid path resistance across the lumen is balanced. 
   
   
       5 . The filter of  claim 4 , wherein the lumen defines an axis and at least 180 degrees of axial twist along the flow path. 
   
   
       6 . The filter of  claim 4 , wherein the conduit comprises a first body, a second body, and a third body, each body having a channel and sandwiched between a first end plate and a second end plate, the channels together defining the lumen;
 the channel of the second body defining the upper surface and at least a portion of a target matter lumen;   the first body disposed between the second body and the first end plate, the channel of the first body coupling the input to the channel of the second body with a 90 degree twist therebetween;   the third body disposed between the second body and the second end plate, the channel of the third body coupling the channel of the second body to the output with a 90 degree twist therebetween.   
   
   
       7 . The filter of  claim 4 , wherein axial twist extends along a significant length of the lumen. 
   
   
       8 . The filter of  claim 1 , wherein the fluid path comprises a laminar fluid path. 
   
   
       9 . The filter of  claim 8 , wherein a bifurcation couples a target matter lumen to the lumen at the port, the bifurcation having an acute bifurcation angle. 
   
   
       10 . The filter of  claim 1 , wherein the conduit comprises a material having an acoustic impedance sufficiently matching an impedance of the fluid flow to inhibit reflection of the waves. 
   
   
       11 . The filter of  claim 1 , wherein the transmitter is oriented so that the ultrasound waves impinge on a lumen wall of the conduit at an angle so as to inhibit reflection of the waves. 
   
   
       12 . The filter of  claim 1 , wherein the transmitter is attached to a structure having a receptacle, the receptacle removably receiving the conduit so that the transmitter is acoustically coupled to the lumen. 
   
   
       13 . The filter of  claim 1 , further comprising a power source coupled to the transducer, the power source applying an alternating waveform to the transducer, the waveform having a curvature with a plurality of changes in sign between a maximum amplitude of the waveform and an adjacent minimum amplitude of the waveform. 
   
   
       14 . The filter of  claim 1 , further comprising a power source coupled to the transducer, the power source applying a waveform to the transducer, the waveform having a frequency that varies during driving of the target matter with the waves. 
   
   
       15 . The filter of  claim 1 , wherein the target matter comprises gas bubbles and the fluid flow comprises blood flow. 
   
   
       16 . The filter of  claim 1 , wherein the lumen has an elongate cross section with a first cross sectional dimension between adjacent the transmitter and adjacent the target matter lumen, and a second smaller cross sectional dimension transverse to the first cross sectional dimension.