Method and apparatus for propulsion of implements

Abstract

The present embodiments generally relate to a propulsion tube unit and a propulsion device for advancing an instrument along a passageway, and related methods of use. For example, the instrument may include a tool, sensor, probe, and / or monitoring equipment for medical use (e.g., endoscopy) or industrial use (e.g., mining). In some embodiments, the propulsion device may include an elongated tube defining a channel configured to contain a liquid and a pressure actuator in communication with the channel. The pressure actuator may be configured to selectively adjust the pressure of the liquid within the channel, alternately reducing the pressure to induce cavitation and form gas bubbles in the liquid, and increasing the pressure to collapse some or all of the gas bubbles back into the liquid, thereby accelerating at least a portion of the liquid toward a first end of the tube, transferring a propulsive force to the tube, and advancing the tube along the passageway. [Selected Figure] Figure 1

Description

[Technical Field]

[0001] The present embodiments generally relate to pusher tube units and pusher devices for advancing instruments along a passageway, and related methods of use. For example, the instruments may include tools, sensors, probes, and / or monitoring equipment for medical use (such as endoscopy) or industrial use (such as mining). The described embodiments may also be suitable for application in other fields for advancing instruments along a passageway. [Background technology]

[0002] There are several existing methods and devices for advancing instruments along passageways, including in mining and medical applications, such as endoscopy. There are several challenges in advancing conventional endoscopic instruments along passageways or lumens within a patient's body, and these challenges can pose associated risks of injury to the patient.

[0003] It would be desirable to address or ameliorate one or more shortcomings or disadvantages associated with existing propulsion devices for advancing instruments along a pathway, or at least to provide a useful alternative.

[0004] Any discussion of documents, statutes, materials, devices, articles or the like contained in this specification is not to be construed as an admission that any or all of such content forms part of the prior art or was common general knowledge in the art relevant to the present disclosure as it existed prior to the priority date of each claim of this application.

[0005] It will be understood that throughout this specification the word "comprise", or variations such as "comprises" or "comprising", imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Summary of the Invention

[0006] Some embodiments relate to a propulsion device for advancing an instrument along a passageway, the propulsion device comprising: an elongated tube having a first end and a second end opposite the first end, the tube defining a channel configured to contain a liquid, the first end of the channel being closed at or near the first end of the tube, and the second end of the channel being defined by the second end of the tube; a pressure actuator in communication with the second end of the channel and configured to selectively adjust the pressure of the liquid in the channel, the pressure actuator alternately comprising: reducing the pressure to induce cavitation and form bubbles in the liquid; and a pressure actuator that increases the pressure to collapse some or all of the bubbles back into liquid, thereby accelerating at least a portion of the liquid toward the first end of the tube, transferring momentum to the tube, and advancing the tube along the passageway.

[0007] Some embodiments include: an elongated tube having a first end and a second end opposite the first end, the tube defining a channel configured to contain a liquid, the first end of the channel being closed at or near the first end of the tube, and the second end of the channel being defined by the second end of the tube; a piston assembly connected to the second end of the tube, a body defining a hole in fluid communication with the channel of the tube; a piston assembly comprising a movable piston disposed within the bore and configured to seal against an interior surface of the bore; The piston assembly and the tube cooperate to define a sealed vessel containing a selected amount of liquid and a selected amount of gas, for a propulsion tube unit.

[0008] The piston assembly may be configured to cooperate with an actuator that effects movement of the piston to selectively adjust the pressure of the liquid in the channel, alternately reducing the pressure to induce cavitation and form gas bubbles in the liquid, and increasing the pressure to collapse some or all of the gas bubbles back into the liquid, thereby accelerating at least a portion of the liquid toward the first end of the tube, transferring momentum to the tube, and advancing the tube along the passage.

[0009] In some embodiments, the propulsion device or propulsion tube unit may include one or more features configured to promote cavitation in one or more regions of the channel when pressure is reduced, the one or more regions extending along at least a portion of the length of the channel. The one or more features may be configured to promote cavitation in multiple spaced apart regions along at least a portion of the length of the channel. The one or more features may include surface alterations to the interior surface of the channel.

[0010] The surface modification may include a coating. The coating may include a hydrophobic material. The coating may include a catalytic material. The coating may include one or more coatings selected from octadecyltrichlorosilane, a silane compound, parylene C, a fluoropolymer, PTFE (Teflon®), manganese oxide polystyrene (MnO2 / PS), nanocomposite zinc oxide polystyrene (ZnO / PS), nanocomposite precipitated calcium carbonate, fluorinated acrylate oligomers, urethanes, acrylics, polyvinylpyrrolidone (PVP), polyethylene oxide, a combination of hydroxyethyl methacrylate and acrylamide, or other hydrophobic compounds.

[0011] The surface variation can include a local topographic variation, which can have a surface roughness ranging from about 0.1 μm to 500 μm, from about 0.5 μm to 100 μm, or from about 1 μm to 10 μm, for example.

[0012] The local shape variations can include a scratched or dimpled surface. The local shape variations can define a plurality of V-shaped channels. The characteristic angle of the V-shaped channels can be, for example, in the range of about 10 to 90 degrees, about 30 to 60 degrees, or about 40 to 50 degrees. The average width of the V-shaped channels can be, for example, in the range of about 1 μm to 10 μm or about 2 μm to 4 μm.

[0013] The local shape variations can define a plurality of conical pits. The characteristic angle of the conical pits can be, for example, in the range of about 10 to 90 degrees, about 30 to 60 degrees, or about 40 to 50 degrees. The average width of the conical pits can be, for example, in the range of about 1 μm to 10 μm or about 2 μm to 4 μm.

[0014] The local shape change can define a plurality of protrusions. The average height of the protrusions can be, for example, in the range of about 0.1 μm to 1 mm, about 1 μm to 500 μm, or about 10 μm to 100 μm. The average width of the protrusions can be, for example, in the range of about 0.1 μm to 500 μm, about 0.5 μm to 100 μm, or about 1 μm to 10 μm. The average distance between adjacent protrusions can be, for example, in the range of about 0.1 μm to 500 μm, about 0.5 μm to 100 μm, or about 1 μm to 10 μm.

[0015] In some embodiments, the protrusions may comprise nanowires or hollow nanotubes, which may be formed from materials such as carbon or silicon.

[0016] For nanowires, the width of the protrusions can be in the range of about 10 nm to 500 nm, about 20 nm to 300 nm, or about 100 nm to 200 nm, the length or height of the protrusions 835 can be in the range of about 0.1 μm to 100 μm, about 1 μm to 50 μm, or about 10 μm to 20 μm, and the average spacing between the protrusions can be in the range of, for example, about 10 nm to 10 μm, about 10 nm to 100 nm, or about 100 nm to 1 μm.

[0017] With respect to nanotubes, the width of the protrusions may be in the range of about 10 nm to 100 nm, about 10 nm to 50 nm, or about 20 nm to 40 nm, the length or height of the protrusions may be in the range of about 1 μm to 50 μm, about 5 μm to 30 μm, or about 10 μm to 20 μm, the pore size (or inner diameter) of the protrusions may be in the range of about 1 μm to 40 μm, about 5 μm to 30 μm, or about 10 μm to 20 μm, and the average spacing between the protrusions may be in the range of, for example, about 10 nm to 10 μm, about 10 nm to 100 nm, or about 100 nm to 1 μm.

[0018] The localized shape change can define a porous surface. The porous surface can include, for example, a foam, a sintered material, or other porous material. The average pore size of the porous surface can be, for example, in the range of about 10 nm to 200 μm, about 20 nm to 250 nm, about 50 nm to 150 nm, about 10 μm to about 200 μm, or about 50 μm to about 100 μm. The porous surface can include a layer of porous material. The thickness of the porous layer can be, for example, in the range of about 10 μm to 1 mm or about 50 μm to 100 μm.

[0019] The one or more features may include a variation in the thermal conductivity of the tube wall along the length of the channel. The thermal conductivity of the wall is about 0.25 Wm -1 K -1 ~240Wm -1 K -1 The channel length may vary over a range of .mu.m to .mu.m.

[0020] The one or more mechanisms may include one or more acoustic transducers. The one or more acoustic transducers may be disposed inside the wall of the tube. The one or more acoustic transducers may be disposed outside the wall of the tube. The operating frequency of the acoustic transducers may be in the range of about 1 kHz to 100 kHz. The power associated with the ultrasonic radiation energy directed by the acoustic transducers toward the lumen of the channel may be in the range of about 10 mW to 100 mW.

[0021] In some embodiments, the propulsion device can be configured to advance the medical instrument along a lumen within a patient's body.

[0022] In some embodiments, the channel can be a continuously enclosed channel extending from a first end of the tube to a second end of the tube. The tube can be reinforced to resist expansion or contraction due to changes in internal pressure. The tube can be formed from a material suitable for sterilization.

[0023] In some embodiments, the propulsion device may include multiple tubes according to any one of the described embodiments extending side by side.

[0024] In some embodiments, the pressure actuator may include a flexible membrane defining a sealed chamber and an actuation mechanism configured to deform the flexible membrane to selectively adjust the pressure of the liquid in the channel.

[0025] In some embodiments, the pressure actuator may include a piston assembly including a movable piston disposed within a bore of the piston assembly, and a drive mechanism configured to drive the piston of the piston assembly to selectively adjust the pressure of the liquid in the channel. The piston assembly may be connected to a tube to form a sealed tube unit containing the liquid, and the piston assembly may be removably couplable to the drive mechanism.

[0026] Some embodiments include: one or more tubes according to any one of the described embodiments; a piston assembly connected to the second end of the tube, a body defining a hole in fluid communication with each channel of the one or more tubes; a piston assembly comprising: a movable piston disposed within the bore and configured to seal against an interior surface of the bore; The present invention relates to a propulsion pipe unit comprising:

[0027] Some embodiments include: a tube according to any one of the described embodiments; and a movable piston disposed within the channel at or near the second end of the tube and configured to seal against an interior surface of the channel; The present invention relates to a propulsion pipe unit comprising:

[0028] In some embodiments, the piston assembly and one or more tubes can cooperate to define a sealed vessel containing a selected amount of liquid and a selected amount of gas. The selected amounts of liquid and gas can be chosen for a particular length and diameter of the tube. The liquid and gas can be held at a predetermined pressure that is not significantly higher than the prevailing channel pressure during operation.

[0029] Some embodiments include: According to any one of the disclosed embodiments, a housing defining a socket configured to receive and engage a propulsion tube unit; an actuator configured to engage the piston; a controller configured to operate the actuator to move the piston and selectively adjust the pressure within the tube channel; The present invention relates to a drive console comprising:

[0030] Some embodiments relate to a method of advancing an instrument along a passageway, the method comprising selectively adjusting the pressure of a liquid within a tube connected to the instrument, sequentially inducing cavitation of gas bubbles in the liquid, subsequently collapsing the gas bubbles back into the liquid, accelerating the liquid within the tube, transferring motive force from the liquid to the tube, and advancing the tube along the passageway.

[0031] The exemplary embodiments will now be described in detail with reference to the drawings. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram of a propulsion device, according to some embodiments. [Figure 2]Figure 2A is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 2B is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 2C is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 2D is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 2E is a series of longitudinal cross sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and subsequent collapse of the gas bubbles back into the liquid, according to some embodiments. Figure 2F is a series of longitudinal cross sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and subsequent collapse of the gas bubbles back into the liquid, according to some embodiments. [Figure 3]Figure 3A is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 3B is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 3C is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 3D is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 3E is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 3F is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. Figure 3G is a series of longitudinal cross-sections of a portion of a tube of a propulsion device showing cycles of nucleation and cavitation of gas bubbles in a liquid contained within the tube and the collapse of the gas bubbles back into the subsequent liquid, according to some embodiments. [Figure 4] 1 is a longitudinal cross-section of a portion of a tube of a propulsion device showing a mechanism for promoting bubble nucleation and / or coalescence within a region inside the tube, according to some embodiments. [Figure 5] 1 is a longitudinal cross-section of a portion of a tube of a propulsion device showing a mechanism for promoting bubble nucleation and / or coalescence within a region inside the tube, according to some embodiments. [Figure 6] 1 is a longitudinal cross-section of a portion of a tube of a propulsion device showing a mechanism for promoting bubble nucleation and / or coalescence within a region inside the tube, according to some embodiments. [Figure 7]10 is an illustration of localized topographical surface variations to promote bubble nucleation, according to some embodiments. [Figure 8] Figure 8A shows an illustration of a series of different types of protrusions for promoting bubble nucleation, according to some embodiments. Figure 8B shows an illustration of a series of different types of protrusions for promoting bubble nucleation, according to some embodiments. Figure 8C shows an illustration of a series of different types of protrusions for promoting bubble nucleation, according to some embodiments. Figure 8D shows an illustration of a series of different types of protrusions for promoting bubble nucleation, according to some embodiments. Figure 8E shows an illustration of a series of different types of protrusions for promoting bubble nucleation, according to some embodiments. [Figure 9] 1 is an illustration of a porous surface for promoting bubble nucleation, according to some embodiments. [Figure 10] Figure 10A shows a series of examples of different types of localized topographical surface variations for enhancing momentum transfer between a liquid and a pipe, according to some embodiments. Figure 10B shows a series of examples of different types of localized topographical surface variations for enhancing momentum transfer between a liquid and a pipe, according to some embodiments. Figure 10C shows a series of examples of different types of localized topographical surface variations for enhancing momentum transfer between a liquid and a pipe, according to some embodiments. [Figure 11] 10 illustrates exemplary displacement and velocity profiles illustrating movement of a piston of a pressure actuator, according to some embodiments. [Figure 12] 1 illustrates an exemplary pressure cycle showing the pressure applied to a liquid in a tube, according to some embodiments. [Figure 13] Figure 13A shows cross sections of two devices with multiple tubes showing different arrangements of the tubes, according to some embodiments. Figure 13B shows cross sections of two devices with multiple tubes showing different arrangements of the tubes, according to some embodiments. [Figure 14] 1 shows a schematic diagram of a portion of a propulsion device with a removable tube and piston assembly, according to some embodiments. [Figure 15]15 shows the front panel of the drive console of the propulsion device of FIG. 14. [Figure 16] 15 illustrates an endoscopic system including the propulsion device of FIG. 14, according to some embodiments. [Figure 17] 10 illustrates a propulsion device with an alternative tube unit, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present embodiments generally relate to propulsion devices for advancing instruments along a passageway and related methods of use. For example, the instruments may include tools, sensors, probes, and / or monitoring equipment for medical use (such as endoscopy) or industrial use (such as mining). The described embodiments may also be suitable for application in other fields for advancing instruments along a passageway.

[0034] 1, a propulsion device 100 is shown, according to some embodiments. The propulsion device 100 comprises an elongate tube 110 defining a lumen or channel 120 configured to contain a liquid 130, and a pressure actuator 140 configured to selectively adjust the pressure of the liquid 130 in the channel 120, such as by varying the pressure, optionally continuously varying the pressure.

[0035] A first or distal end 122 of channel 120 is closed at or near a first or distal end 112 of tube 110. Distal end 112 of tube 110 is shown as being disposed within channel or lumen 101 of passageway 103 in FIG.

[0036] In some embodiments, the tube 110 may be configured to be inserted into and through a biological passageway, such as the lumen 101 of a passageway 103 of a patient. Examples of such biological passageways include the esophagus, stomach, intestine, colon, small intestine, large intestine, duodenum, or any one or more passageways of the gastrointestinal system. In some embodiments, the tube 110 may be configured to be inserted into and through another passageway 103 within a patient's body, such as, for example, a blood vessel, vein, or artery. In some embodiments, the tube 110 may be configured for human medical or veterinary applications. In some embodiments, the tube 110 may be configured for industrial applications, such as for use in plumbing pipes, wall cavities, cable tracks, machinery, mining, or wellbore applications.

[0037] In some embodiments, the tube 110 can be configured to be received within an insertion tube of an endoscope, which is configured to be inserted into a passageway 103, such as a passageway within a patient's body. An example of such an arrangement is shown in FIG. 16. The tube 110 of the propulsion device 100 can be received within a pusher tube channel (not shown) within the insertion tube. In some embodiments, the pusher tube channel can be concentric or coaxial with the outer diameter of the insertion tube and can extend along a central longitudinal axis of the insertion tube. In some embodiments, the pusher tube channel can be radially offset from the central axis of the insertion tube.

[0038] Pressure actuator 140 communicates with second or proximal end 124 of channel 120 at or near second or proximal end 114 of tube 110 opposite distal end 112. Channel 120 may comprise a continuously enclosed channel extending from first end 112 of tube 110 to second end 114 of tube 110.

[0039] Pressure actuator 140 may comprise any suitable device (e.g., a reciprocating piston, etc.) configured to selectively adjust the pressure of liquid 130 in channel 120. In some embodiments, pressure actuator 140 may comprise a piston driven by a motor, such as a linear motor, controlled by a controller (not shown).

[0040] The pressure actuator 140 gradually reduces the pressure in the channel 120, inducing cavitation and forming bubbles in the liquid 130, and then suddenly increases the pressure to compress and crush the bubbles back into the liquid 130, thereby accelerating at least a portion of the liquid 130 toward the first end 112 of the tube 110, whereby a motive force is transferred from the liquid to the tube 110 to propel the tube 110 along the passage.

[0041] In some embodiments, when channel 120 is at an initial or base pressure, there may be a volume of gas and liquid 130 within channel 120, and pressure actuator 140 may be controlled to increase the pressure to compress and decompose some or all of the gas within liquid 130. In some embodiments, channel 120 may be entirely filled with liquid 130, and pressure actuator 140 may decrease the pressure to induce cavitation of the gas out of liquid 130. In various embodiments, the base pressure may be set to a value at or near atmospheric pressure, a value significantly higher than atmospheric pressure, or a value significantly lower than atmospheric pressure.

[0042] Pressure actuator 140 may be configured to adjust the pressure in repeated cycles to induce cavitation of gas bubbles out of liquid 130, and subsequently compress some or all of the gas back into liquid 130. In various applications, the difference between the maximum pressure in channel 120 and the minimum pressure in channel 120 may be in a range of, for example, about 10 kPa to 100 MPa, about 10 kPa to 100 kPa, about 100 kPa to 1 MPa, about 1 MPa to about 10 MPa, or about 10 MPa to about 100 MPa. In some embodiments, the maximum pressure may be above, below, or near atmospheric pressure. In some embodiments, the minimum pressure may be above, below, or near atmospheric pressure, but may be other than zero difference from the maximum pressure.

[0043] For example, for gastrointestinal applications, the channel pressure may vary from 100 kPa below atmospheric pressure to 1000 kPa above atmospheric pressure, for cardiovascular applications, the channel pressure may vary from 20 kPa below atmospheric pressure to 300 kPa above atmospheric pressure, and for industrial applications, the channel pressure may vary from 1000 kPa below atmospheric pressure to 10,000 kPa above atmospheric pressure.

[0044] The liquid 130 in the channel 120 may include, for example, any one or more of a pure liquid, a solution, a gas / liquid solution (i.e., gas dissolved in a liquid), a mixture of gas and liquid, a mixture of liquid and solid particles such as a suspension, and a mixture of two or more miscible or immiscible liquids. In some embodiments, the volume ratio of gas to liquid at atmospheric pressure may be in the range of, for example, about 0.1% to 10%, about 0.5% to 5%, or about 1% to 2%.

[0045] The liquid 130 may include any suitable liquid, gas, solid particles, or solution, such as, for example, water, ethanol, carbon dioxide, nitrogen, air, nitric oxide, argon, salt, sodium chloride, potassium formate, acid, acetic acid, or lithium metatungstate.

[0046] Different liquids may be suitable for different applications. For example, in medical applications, preferred liquids may be biocompatible, non-toxic (or have fairly low toxicity), non-pyrogenic, non-inflammatory, non-hyperosmotic, relatively inert, and suitable for operation at relatively low pressures and temperatures similar to the patient's general body temperature. Examples include water, ethanol, carbon dioxide, nitrogen, air, nitric oxide, and argon.

[0047] In industrial applications where biocompatibility is not required, a high density liquid may be preferred, such as an aqueous solution of an inert inorganic compound. One suitable high density liquid may be an aqueous solution of lithium metatungstate, which has high density, low viscosity, and good thermal stability.

[0048] In various embodiments, the tube 110 may be formed from different materials depending on their suitability for a given application. For example, for medical applications, the tube 110 may be formed from a non-toxic material that is flexible enough to bend around corners or bends in a passageway within a patient's body.

[0049] Some examples of materials that may be used to form the tube 110 in different applications include polymers, plastics, polyethylene, high-density polyethylene, polytetrafluoroethylene, vinyl, nylon, rubber, elastomers, synthetic resins, or composite materials including textiles impregnated with polymers, elastomers, or synthetic resins. Polymers containing voids in their internal structure (foams) may also be used to increase flexibility, such as extruded polytetrafluoroethylene (ePTFE). Composite layers of these materials may also be used to increase strength, maintain flexibility, and resist internal pressure or twisting.

[0050] The wall 118 of the tube 110 should have sufficient strength and thickness to withstand the expected range of pressure differentials for a given application. In some embodiments, the tube 110 or tube wall 118 may be reinforced to mitigate against expansion and / or contraction of the tube due to pressure changes. Any suitable reinforcing material may be used, such as, for example, high tenacity fiber or ultra-high molecular weight polyethylene.

[0051] 2A-2F, a section of the tube 110 of the propulsion device 100 is shown in accordance with some embodiments to illustrate the cavitation process in a series of views.

[0052] 2A, at an initial or baseline pressure, the channel 120 may be substantially or entirely filled with liquid 130, with little or no gas inside the channel 120. (However, in some embodiments, there may be a significant volume of gas present in the channel at the baseline pressure.)

[0053] When the pressure in the channel 120 is gradually reduced by the pressure actuator 140, bubbles 133 may begin to form in the liquid 130 inside the channel 120, as shown in FIG. 2B. The bubbles 133 may comprise gas that has previously been dissolved in the liquid 130 and / or vapor (i.e., the gas phase of the liquid 130). The bubbles 133 may form by homogeneous nucleation of the liquid 130 at nucleation sites, such as particles suspended at nucleation sites within the liquid 130 and / or on the inner surface 126 of the tube 110, or by heterogeneous nucleation.

[0054] As the pressure is further reduced, the bubble 133 may increase in volume to form a larger bubble 133c, as shown in Figure 2C, and new bubbles 133 may continue to form by nucleation. Some of the bubbles 133, 133c may coalesce to form an even larger bubble 133d, as shown in Figure 2D.

[0055] 2E, the expanding bubble 133e may occupy the entire lumen of the channel 120, thereby separating different portions of the liquid 130 on one side of the bubble 133e. It may be desirable to encourage or facilitate the formation of such expanding bubbles 133e within the channel 120, as this may enhance or increase the propulsion effect by increasing the acceleration of the liquid 130 during a sudden pressure increase, and thus increasing the kinetic energy imparted to the liquid 130 and propulsion force being transported to the tube 110.

[0056] As the pressure increases (i.e., during compression), the liquid 130 accelerates in the distal direction (i.e., toward the first or distal end 122 of the channel 120), as shown by arrow 201 in Figure 2F. Due to the relatively high compressibility of the bubbles 133, which is several orders of magnitude greater than the relatively low compressibility of the liquid 130, the liquid 130 is able to rapidly accelerate and compress the bubbles 133, as shown in Figure 2F.

[0057] When the bubbles 133 are compressed, they experience a sudden increase in pressure and density, and collapse (i.e., break up and / or condense) back into liquid 130, as shown in Figure 2A. By increasing the total surface area of ​​the gas-liquid interface, one can increase the rate at which bubbles 133 break up / collapse within liquid 130. Therefore, it may be desirable to encourage or promote the formation of many bubbles 133, and preferably many expanding bubbles 133e.

[0058] There are several ways in which the likelihood of forming expanding bubbles 133e can be increased, some of which are described below. For example, in some embodiments, one or more additives can be included in the liquid 130 to enhance bubble coalescence. In some embodiments, the inner diameter of the channel 120 can be selected to be relatively small, thereby requiring only a relatively small volume of bubbles to expand into the lumen. However, the inner diameter of the lumen should still be large enough to allow the liquid 130 to flow along the channel 120 when pressure suddenly increases (i.e., when not significantly restricted by capillary resistance). In some embodiments, the propulsion device 100 can include multiple tubes 110 extending alongside one another, each defining a channel 120. This can allow the inner diameter of each channel 120 to be relatively small while maintaining a relatively large total mass of the liquid 130 inside the tube 110.

[0059] In some embodiments, cavitation, bubble nucleation, and / or bubble coalescence may be enhanced, encouraged, or promoted within certain regions of the channel 120 .

[0060] In some embodiments, the propulsion device 100 may include one or more mechanisms configured to promote cavitation, bubble nucleation, and / or bubble coalescence in one or more regions of the channel when pressure is reduced. The one or more regions may extend along at least a portion of the length of the channel 120. For example, the one or more mechanisms may be configured to promote cavitation, bubble nucleation, and / or bubble coalescence in multiple regions spaced along the length of the channel 120.

[0061] In some embodiments, each cavitation-promoting region may extend along a portion of the length of the channel a distance of about 10% to 400%, optionally about 30% to 300%, optionally about 50% to 200% of the inner diameter of channel 120. In some embodiments, the distance between adjacent cavitation-promoting regions may be greater than the inner diameter of channel 120 by, for example, a factor of about 2 to 50, about 5 to 30, or about 10 to 20.

[0062] 3A-3G, a section of the tube 110 of the propulsion device 100 is shown in accordance with some embodiments, illustrating the cavitation process in a series of views. The cavitation process is similar to that described with respect to FIGS. 2A-2F. However, the tube 110 shown in FIGS. 3A-3G also includes one or more features 330 configured to promote cavitation, bubble nucleation, and / or bubble coalescence within one or more regions of the channel 120 when pressure is reduced.

[0063] Referring to FIG. 3A, at base pressure, the channel 120 may be substantially or entirely filled with liquid 130 with little or no gas inside the channel 120.

[0064] When the pressure in the channel 120 is gradually reduced by the pressure actuator 140, bubbles 133 may begin to form within the liquid 130 inside the channel 120, as shown in Figure 3B. Some bubbles 133 may form randomly throughout the liquid 130. However, the likelihood of bubble 133 occurrence will be higher within the region of the cavitation-promoting feature 330.

[0065] As the pressure is further reduced, the bubble 133 may increase in volume to form a larger bubble 133c, as shown in Figure 3C, and new bubbles 133 may continue to form by nucleation. Some of the bubbles 133, 133c may coalesce to form an even larger bubble 133d, as shown in Figure 3D.

[0066] Bubbles 133 may coalesce to form luminal-spanning bubbles 133e that span the entire diameter of the lumen of channel 120, as shown in Figure 3E. The formation of luminal-spanning bubbles 133e may be more likely in the region of feature 330 due to the formation of a larger number or size of bubbles and / or improved bubble coalescence.

[0067] As the pressure increases, the liquid 130 accelerates in the distal direction (i.e., toward the first or distal end 122 of the channel 120), as shown by arrow 301 in FIG. 3F, and the bubble 133 compresses and reduces in volume, as shown in FIG. 3G.

[0068] When the bubbles 133 are compressed, they experience a sudden increase in pressure and density, and collapse (ie, break down and / or condense) back into liquid 130, as shown in FIG. 3A.

[0069] Mechanism 330 may include any suitable means for enhancing, facilitating, encouraging, or increasing the likelihood of cavitation, bubble nucleation, and / or bubble coalescence.

[0070] 4, in some embodiments, the one or more features 330 may include a variation in the thermal conductivity and / or thermal mass of the tube wall 118 along the length of the channel 120. This variation in thermal conductivity and / or thermal mass may be achieved by including wall portions 430 at different locations along the length of the channel 120 that include a material that has a higher thermal conductivity and / or thermal mass than the remainder of the wall 118. For example, in some embodiments, the wall 118 may be formed from an extruded polymer, and metal particles may be impregnated into certain portions of the wall 118 to create a wall portion 430 with a relatively high thermal mass and thermal conductivity.

[0071] Differences in thermal conductivity and / or thermal mass between wall portion 430 and the remainder of wall 118 may result in a higher likelihood of cavitation and bubble nucleation within the region of wall portion 430 compared to the remainder of channel 120.

[0072] In some embodiments, the thermal conductivity of the wall 118 is about 0.25 Wm -1 K -1 ~240Wm -1 K -1 In some embodiments, the thermal conductivity of wall 430 may be higher than the remainder of wall 118 by a factor of at least 10, at least 100, at least 500, or at least 1000. For example, in some embodiments, the thermal conductivity of wall 430 may be about 100 Wm -1 K -1 ~300Wm -1 K -1 , about 150Wm -1 K -1 ~250Wm -1 K -1 , or about 200Wm -1 K -1 while the thermal conductivity of the remainder of the wall 118 may be in the range of about 0.1 Wm -1 K -1 ~10Wm -1 K -1 , or about 0.5Wm -1 K -1 ~1Wm -1 K -1It can be in the range of

[0073] 5, in some embodiments, the one or more mechanisms 330 may include one or more acoustic transducers 530. The acoustic transducers 530 may be connected to a controller via one or more cables 535 and configured to emit acoustic energy with an amplitude and frequency that promotes cavitation, bubble nucleation, and / or bubble coalescence.

[0074] Acoustic transducer 530 may be coupled to an exterior or interior surface of tube 110, disposed outside wall 118 of tube 110, or, in some embodiments, disposed or embedded within wall 118 of tube 110. In some embodiments, acoustic transducer 530 may comprise a piezoelectric patch transducer.

[0075] The operating frequency of the acoustic transducer 530 may be in the range of about 1 kHz to 100 kHz or about 10 kHz to 25 kHz. The operating frequency of the acoustic transducer 530 may be selected to be higher than the break threshold for mechanical nucleation of at least 1 micrometer bubbles in a system with a gas saturation factor close to 1 (i.e., fully saturated). As the threshold increases, the frequency increases and the gas saturation decreases (for reference, see Acoustic cavitation prediction, REapfel, The Journal of the Acoustical Society of America 69, 1624 (1981)).

[0076] Acoustic ultrasound radiation energy may be directed into the lumen of the channel by the acoustic transducer 530 to promote, enhance, or assist in inducing cavitation within the liquid 130. In some embodiments, characteristics of the ultrasound radiation field may include, for example, a pressure change in the range of about 10 MPa to 100 MPa, a pulse duration in the range of about 0.2 ms to 10 ms, and a total power in the range of about 10 mW to 100 mW. In some embodiments, the acoustic transducer 530 may operate at a pressure of about 100 kPa, a displacement of about 25 μm, and a frequency of about 21 kHz.

[0077] In some embodiments, mechanism 330 may comprise one or more lasers configured to induce cavitation in liquid 130. For example, in some embodiments, mechanism 330 may comprise a micro-diode laser module embedded in wall 118 of tube 110. The laser module may be activated in pulses of 10 ms to 20 ms duration to coincide with the low-pressure phase of the pressure cycle and promote, enhance, or assist in inducing nucleation of bubbles 133.

[0078] In some embodiments, mechanism 330 may comprise one or more pairs of conductors disposed within the lumen of channel 120 and arranged to be closely spaced, approximately 0.1 mm to 0.5 mm apart, such that current can be discharged from one conductor to the other through liquid 130, causing ionization of liquid 130 and subsequent gas nucleation. The conductor pairs may be arranged in a ring-shaped configuration and embedded within the wall of a non-conductive polymer tube. The conductor pairs may be connected to a power source via conductors running along the length of tube 110. The power source may comprise a high-capacity, high-voltage, low-current discharge circuit that can be timed to discharge at the lowest point of the pressure cycle generated by pressure actuator 140. The supply voltage may be in the range of approximately 100 V to 200 V. The current may be in the range of approximately 1 mA to 10 mA.

[0079] 6, in some embodiments, the one or more features 330 may include a surface alteration 630 on the interior surface 126 of the tube 110. That is, the surface alteration 630 on the interior surface 126 is configured to differ from the remainder of the interior surface 126 and to promote or encourage bubble nucleation.

[0080] In some embodiments, the surface modification 630 may include a coating applied to a portion of the interior surface 126 of the tube 110. In some embodiments, the surface modification 630 may include a coating of a catalytic material, such as, for example, octadecyltrichlorosilane (to promote CO nucleation) or other similar compounds. In some embodiments, the surface modification 630 may include a hydrophobic coating, such as, for example, a silane (silicon hydride) compound, Parylene C, or a fluoropolymer such as PTFE (Teflon), manganese oxide polystyrene (MnO / PS), nanocomposite zinc oxide polystyrene (ZnO / PS), nanocomposite precipitated calcium carbonate, or a fluorinated acrylate oligomer.

[0081] In some embodiments, the remainder of interior surface 126 may be formed from or coated with a hydrophilic material, such as, for example, a combination of urethane, acrylic, polyvinylpyrrolidone (PVP), polyethylene oxide, hydroxyethyl methacrylate, or acrylamide, or another material suitable for inhibiting bubble nucleation on the remainder of interior surface 126 (i.e., the portion away from surface alteration 630).

[0082] In some embodiments, the surface variation 630 can include a localized shape variation. Relatively small localized shape variations (e.g., on a length scale of about 1 μm to 100 μm) can provide nucleation sites to encourage or facilitate bubble nucleation and growth. For example, the localized shape variation can include variations in surface roughness, microporous surfaces, scratched or dimpled surfaces, multiple protrusions, protruding fibers, nanotubes, pits, channels, ridges, fins, recesses, cavities, or other geometric variations. The localized shape variation can be formed, for example, by molding, scratching, cutting, scoring, etching, abrasion, or indentation. In some embodiments, porous particulates, such as ceramic, can be embedded in the wall 118 of the tube 110 at the inner surface 126 to provide nucleation sites.

[0083] In some embodiments, the localized shape change may extend across the entire interior surface 126 of the tube 110. In some embodiments, the tube 110 may be formed with a localized shape change that extends across the entire interior surface 126, and then a portion of the interior surface 126 may be smoothed (e.g., with a polymer coating), leaving an exposed / unsmooth portion of the localized shape change to form the surface change 630. For example, the wall 118 of the tube 110 may be formed of a porous material, and then a portion of the interior surface 126 may be sealed, leaving an exposed / unsealed portion of the interior surface 126 to form the surface change 630.

[0084] Surface variations 630 may include any suitable local shape variations for a given application. Some suitable local shape variations are described below.

[0085] In some embodiments, the local shape changes may define a plurality of V-shaped channels, which may be aligned parallel to one another or may be randomly oriented and cross one another.

[0086] The characteristic angle of the V-shaped channel (i.e., the angle of the apex of the V-shape) can be, for example, in the range of about 10 to 90 degrees, about 30 to 60 degrees, or about 40 to 50 degrees. The average width of the V-shaped channel can be, for example, in the range of about 1 μm to 10 μm or about 2 μm to 4 μm. The average depth of the V-shaped channel can be, for example, in the range of about 1 μm to 10 μm or about 2 μm to 4 μm.

[0087] Referring to Figure 7, in some embodiments, the surface alteration 730 may include a partially random pattern of intersecting V-shaped channels 737. This may be achieved by abrasion using diamond particles with a nominal size of 2 μm. The diamond particles may have sharp V-shaped apexes and may be sintered onto a metal rod for rotational application to the interior surface 126. The metal rod may be applied to the interior surface 126 with rotational vibration to create the surface alteration 730. An atomic force micrograph of a typical random V-shaped scratch pattern achieved using this method is shown in Figure 7.

[0088] In some embodiments, the local shape variations may define a plurality of conical pits, which may be arranged randomly or in a periodic array.

[0089] The characteristic angle of the conical pits (i.e., the angle of the apex of the conical pits) can be, for example, in the range of about 10 to 90 degrees, about 30 to 60 degrees, or about 40 to 50 degrees. The average width of the conical pits can be, for example, in the range of about 1 μm to 10 μm or about 2 μm to 4 μm. The average depth of the conical pits can be, for example, in the range of about 1 μm to 10 μm or about 2 μm to 4 μm.

[0090] In some embodiments, the local shape variations may define a plurality of protrusions. The protrusions may define any suitable shape, and in some embodiments, may define a plurality of different shapes. The protrusions may be arranged randomly or in a periodic array.

[0091] The average height of the protrusions may be, for example, in the range of about 0.1 μm to 1 mm, about 1 μm to 500 μm, or about 10 μm to 100 μm. The average width of the protrusions may be, for example, in the range of about 0.1 μm to 500 μm, about 0.5 μm to 100 μm, or about 1 μm to 10 μm. The average distance between adjacent protrusions may be, for example, in the range of about 0.1 μm to 500 μm, about 0.5 μm to 100 μm, or about 1 μm to 10 μm.

[0092] 8A-8E, several examples of surface variations 830 are shown according to some embodiments. Surface variations 830 each define a plurality of protrusions 835. In some embodiments, protrusions 835 may define fins or ridges 835 separated by channels 837.

[0093] In some embodiments, protrusions 835 may comprise nanowires or hollow nanotubes, which may be formed from materials such as, for example, carbon or silicon. For nanowires, the width of protrusions 835 may range from about 10 nm to 500 nm, about 20 nm to 300 nm, or about 100 nm to 200 nm, the length or height of protrusions 835 may range from about 0.1 μm to 100 μm, about 1 μm to 50 μm, or about 10 μm to 20 μm, and the average spacing between protrusions 835 may range from, for example, about 10 nm to 10 μm, about 10 nm to 100 nm, or about 100 nm to 1 μm. With respect to nanotubes, the width of protrusions 835 may be in the range of about 10 nm to 100 nm, about 10 nm to 50 nm, or about 20 nm to 40 nm, the length or height of protrusions 835 may be in the range of about 1 μm to 50 μm, about 5 μm to 30 μm, or about 10 μm to 20 μm, the pore size (or inner diameter) of protrusions 835 may be in the range of about 1 μm to 40 μm, about 5 μm to 30 μm, or about 10 μm to 20 μm, and the average spacing between protrusions 835 may be in the range of, for example, about 10 nm to 10 μm, about 10 nm to 100 nm, or about 100 nm to 1 μm.

[0094] In some embodiments, the localized shape change can define a porous surface, such as a foam, sintered material, or other porous material. The average pore size of the porous surface can be, for example, in the range of about 10 nm to 200 μm, about 20 nm to 250 nm, about 50 nm to 150 nm, about 10 μm to about 200 μm, or about 50 μm to about 100 μm. The porous surface can include a layer of porous material. The thickness of the porous layer can be, for example, in the range of about 10 μm to 1 mm or about 50 μm to 100 μm.

[0095] 9, a surface modification 930 including a porous layer 933 is shown according to some embodiments. The porous layer 933 may be formed from sintered particles 935 with diameters ranging from about 10 μm to about 100 μm, for example.

[0096] In some embodiments, the local shape variation can have a surface roughness in the range of, for example, about 0.1 μm to 500 μm, about 0.5 μm to 100 μm, or about 1 μm to 10 μm.

[0097] In some embodiments, one or more additives may be included in the liquid 130 to promote cavitation, bubble nucleation, and / or bubble coalescence. For example, additives may be included to modify the density, viscosity, pH level, gas solubility, coalescence characteristics, or surface tension of the liquid 130.

[0098] The solubility and coalescence characteristics of each fluid-gas combination may depend on controllable factors such as temperature and pH. In the case of CO2, it is believed that the pH of the solution should ideally be adjusted to 6-6.5 for optimal effectiveness. If the pH is above 6.5, it may be difficult to induce bubble nucleation due to the high solubility of the gas in water. In some embodiments, when CO2 is used as the gas, the pH of the solution may be reduced to a level of 6-6.5 using the addition of acetic acid to promote nucleation and coalescence of CO2 bubbles in the liquid.

[0099] In some applications, the mechanical action of the pressure actuator 140 causing a reaction in the liquid 130 may generate heat in the liquid 130, reducing the solubility of the gas 133 in the liquid 130. In some embodiments, the propulsion device 100 may include a heat sink (not shown) that draws excess heat away from the liquid 130. For example, the heat sink may include a metal heat sink positioned at or near the proximal end 114 of the tube 110, or may be positioned inside or adjacent to the pressure actuator 140. The heat sink may be cooled by air convection, refrigeration, or radiation.

[0100] In some embodiments, the thermal conductivity of the liquid 130 may be sufficient for heat to be transferred through the liquid 130 and along the tube 110 to a heat sink. In some embodiments, salts such as potassium formate may be added to water to increase the thermal conductivity and density of the liquid 130 without significantly increasing the viscosity or boiling point.

[0101] In some embodiments, the thermal mass and thermal conductivity of the tube 110 itself may be sufficient to transfer heat along the tube 110 to a heat sink. In some embodiments, the tube wall 118 may comprise one or more thermal conductors (such as metal films or wires) that transfer heat along the tube 110 to a heat sink.

[0102] In some embodiments, liquid 130 may specifically comprise a high density liquid, and / or one or more additives may be included in liquid 130 to increase the density or inertia of liquid 130 to increase the momentum generated as liquid 130 accelerates, thus increasing the momentum transferred to tube 110 and propelling tube 110 along the passage.

[0103] In some embodiments, such as for medical use, the liquid 130 may include water combined with one or more additives, such as ethanol to reduce surface tension and viscosity, citric acid or acetic acid to reduce pH levels, or salts such as sodium chloride to increase density.

[0104] In some embodiments, the interior surface 126 of the tube 110 may define a relatively large range of localized shape changes (e.g., changes on length scales ranging from about 5% to 10% of the inner diameter of the tube 110) configured to improve motive force transfer from the liquid 130 to the tube 110 during a sudden pressure increase.

[0105] 10A-10C, a section of tube 110 is shown, according to some embodiments, illustrating some examples of extensive local shape variations defined by interior surface 126. Interior surface 126 may define a plurality of periodic annular ridges 1010 with a swept-back angle in the proximal direction (toward second or proximal end 124 of channel 120). The ridges 1010 appear as a fir tree pattern extending backward in cross section or teeth extending backward proximally, as shown in FIGS.

[0106] The proximally extending annular ridge 1010 may create a fluidic diode effect, whereby there is more resistance to fluid flow in the distal direction and relatively less resistance to fluid flow in the proximal direction, which may improve motive force transfer from the liquid 130 to the tube 110 during sudden pressure increases.

[0107] In some embodiments, the annular ridge 1010 may not extend back proximally and the fluidic diode effect may be achieved by a different type of local shape change, or in some embodiments, may not be achieved at all.

[0108] As explained above, when the channel 120 contains a volume of liquid 130 in an initial or quiescent state and another volume of gas 133, the pressure actuator 140 may be configured to increase the channel pressure (which may be referred to as a pressure increase phase) to cause the gas 133 to break down within the liquid 130, and subsequently decrease the channel pressure (which may be referred to as a pressure decrease phase) to induce nucleation and cavitation of gas bubbles 133 within the liquid 130. Alternatively, when the channel 120 contains only the liquid 130 in an initial or quiescent state, the pressure actuator 140 may be configured to decrease the channel pressure (pressure decrease phase) to induce nucleation and cavitation of gas bubbles 133 within the liquid 130, and subsequently increase the channel pressure (pressure increase phase) to collapse the gas bubbles 133 (by condensing or breaking down) within the liquid 130.

[0109] In some embodiments, the pressure increase phase may be substantially similar in duration to the pressure decrease phase, hi some embodiments, the duration of the pressure increase phase may be significantly shorter than the duration of the pressure decrease phase.

[0110] In some embodiments, the pressure actuator 140 may be configured to increase the pressure over a time period that is about 1% to 50%, for example, optionally about 5% to 30%, optionally about 10% to 20%, of the time period that the pressure is decreased.

[0111] As described above, pressure actuator 140 may comprise any suitable device for varying channel pressure in the described manner. In some embodiments, pressure actuator 140 may comprise a flexible diaphragm with a mechanism configured to deflect or deform the diaphragm, changing the volume of the system and controlling the channel pressure. In some embodiments, pressure actuator 140 may comprise a reciprocating piston driven by a motor, such as, for example, an electric motor or a linear motor.

[0112] Referring to FIG. 11, an exemplary displacement profile x(t) and corresponding velocity profile v(t) are shown illustrating the movement of a pressure actuator 140 in the form of a piston over time, according to some embodiments.

[0113] The displacement and velocity profiles show a pressure increase phase 1110 followed by a pressure decrease phase 1120. During the pressure increase phase 1110 (corresponding to the compression stroke of the piston), the piston undergoes a rapid acceleration 1112 made possible by the highly compressible nature of the gas bubble 133.

[0114] Once the gas bubble 133 collapses back into the liquid 130, a sudden deceleration 1114 of the piston occurs due to the relatively incompressible nature of the liquid 130 (i.e., significantly less compressible than the gas 133). The sudden deceleration 1114 of the piston and liquid 130 results in a large impact and a transfer of momentum from the liquid 130 to the tube 110, and a resulting thrust effect that acts to advance the tube 110 along the passageway 103.

[0115] Once the channel pressure reaches a maximum value, after piston deceleration 1114, a pressure reduction phase 1120 begins as the piston is withdrawn. The withdrawal stroke (pressure reduction phase 1120) may be significantly slower than the compression stroke (pressure increase phase 1110) due to the time required for bubble 133 nucleation and cavitation to occur. The channel pressure then decreases to a minimum. The piston movement may then repeat in a similar manner to repeat the pressure fluctuation cycle.

[0116] The pressure actuator 140 may be configured to repeatedly increase and decrease the channel pressure, applying a driving force to the tube 110 in multiple impulses, with each impulse associated with a corresponding pressure increase step. In some embodiments, the channel pressure may be varied by the pressure actuator 140 in a periodic or cyclical manner with repeated pressure cycles (i.e., a pressure increase followed by a pressure decrease). In some embodiments, the pressure actuator 140 may be configured to vary the channel pressure according to repeated pressure cycles, with the repeated pressure cycles occurring at a frequency in the range of, for example, about 0.1 Hz to 10 Hz, about 0.5 Hz to 5 Hz, about 0.5 Hz to 1.5 Hz, about 2 Hz to 4 Hz, or about 3 Hz.

[0117] In some embodiments, the pressure actuator 140 can be configured to operate in a reverse cycle, modulating the channel pressure and applying a reverse impulse to the tube 110 to move the instrument proximally. This reverse pressure cycle can be used to withdraw the instrument from the passageway.

[0118] 12, an exemplary pressure / time profile is shown according to some embodiments, illustrating the change in channel pressure required to compress a gas bubble 133 within the liquid 130 as the pressure increases, followed by inducing cavitation of the gas bubble 133 within the liquid 130 as the pressure decreases. The pressure scale is shown in kilopascals (kPa) above atmospheric pressure, and the time scale is shown in seconds. The channel pressure gradually decreases over a period of about 0.3 s, then suddenly increases over a period of about 0.05 s. This pressurization cycle repeats at a frequency of about 3 Hz.

[0119] As previously mentioned, in some embodiments, it may be desirable for the channel 120 to be relatively small to increase the likelihood of an expanding bubble 133e forming prior to compression. The inner diameter of the channel 120 may range, for example, from 0.1 mm to 10 mm, 0.1 mm to 1 mm, 0.1 mm to 0.5 mm, 1 mm to 7 mm, or 2 mm to 5 mm. In some embodiments, the propulsion device 100 may include multiple tubes 110 extending side by side, as illustrated by the cross-sections of exemplary tube configurations shown in Figures 13A and 13B.

[0120] In some embodiments, the tubes 110 can be arranged around an instrument channel 1301 configured to receive a probe, such as an endoscope, as shown in Figure 13B. In some embodiments, the tubes 110 can be arranged in a bundle for insertion into a lumen of a probe, such as an endoscope, as shown in Figure 13A. In some embodiments, the tubes 110 can be integrally formed as part of a probe, such as an endoscope, and the tubes 110 run parallel to the instrument channel (e.g., video tube, lighting, irrigation, suction, steering, biopsy, and other instrument channels).

[0121] In some embodiments, the propulsion device 100 may comprise a first tube 110 within a second tube 110, with the liquid 130 and gas 133 contained within an annular channel 120 defined between the two tubes 110. The inner lumen of the first tube 110 may also contain the liquid 130 and gas 133. Or, alternatively, in some embodiments, the inner lumen of the first tube 110 may define an instrument channel.

[0122] The tube 110 or tubes 110 may be formed from a flexible material with sufficient strength and stiffness to withstand the forces expected for a given application. For medical applications, some suitable materials may include, for example, ultra-high molecular weight polyethylene or other biocompatible polymers. In some embodiments, the tube 110 or tubes 110 may be formed from a composite material, such as polyethylene spiraled with a coating of polyurethane and silicone elastomer.

[0123] The dimensions of the tubes 110 can vary for different applications. For example, for a medical endoscope, such as a gastrointestinal endoscope, a single tube pushing device can include a tube 110 with an outer diameter of 8 mm and an inner diameter of 6 mm, or an outer diameter of 6 mm and an inner diameter of 4.5 mm, while a multi-tube pushing device can include four tubes 110, each having an outer diameter of 3 mm and an inner diameter of 2 mm. In some embodiments, the tubes 110 of a single tube pushing device 100 or the multiple tubes 110 of a multi-tube pushing device 100 can have inner diameters ranging, for example, from 1 mm to 5 mm, and outer diameters ranging, for example, from 0.5 mm to 15 mm, 1 mm to 10 mm, 2 mm to 8 mm, or 4 mm to 6 mm. The length of a medical endoscope typically ranges, for example, from about 1 m to 5 m or from about 3 m to 4 m. In some embodiments, such as for gastrointestinal endoscopy, the tube(s) 110 may have lengths in the range of 3 m to 4 m, 1 m to 5 m, or even greater than 5 m, such as 5 m to 15 m or 7 m to 9 m, for example, for veterinary applications. In some embodiments, such as for arterioscopic endoscopy, the tube(s) may have lengths in the range of 0.5 m to 2 m, 0.7 m to 1.5 m, or 0.9 m to 1.2 m, for example. In some embodiments, such as for industrial endoscopy, the dimensions of the tubes may be significantly larger.

[0124] For medical applications, it will typically be important that the propulsion device 100 be sterile. Accordingly, it may be desirable for at least a portion of the device 100 to comprise disposable components that are provided in sterile packaging and can be discarded after use. Referring to FIG. 14 , a propulsion device 1400 is shown, according to some embodiments. The propulsion device 1400 includes features generally similar to those described with respect to the propulsion device 100 and are referred to by similar numerals. The proximal end 1414 of the tube 1410 defining the pressure actuator 1440 and the channel 1420 is shown. It will be understood that the tube 1410 extends to a distal end (not shown) as described with respect to the propulsion device 100 of FIG. 1. The tube 1410 may be referred to as a propulsion tube and may include features similar to the tube 110 described above. In some embodiments, the tube 1410 may comprise a tube 110 or a bundle of multiple tubes 110 as described with respect to FIG. 13A or 13B .

[0125] The pressure actuator 1440 comprises a housing 1442, a drive mechanism 1444 (in the form of a motor), an actuation rod 1446, and a socket 1448 defined in a side of the housing 1442. The pressure actuator 1440 further comprises a piston assembly 1450 comprising a body 1452 defining a cylinder 1454, a piston 1456 disposed within the cylinder, and a piston seal 1458 sealing the piston 1456 to an interior bore 1460 of the cylinder 1454. The piston 1456 and the cylinder 1454 act together to form a piston pump. However, in some embodiments, a different type of pump or compressor (e.g., a diaphragm pump) may be used to regulate the channel pressure within the tube 1410, as described below with respect to FIG. 17 .

[0126] Piston assembly 1450 is attached to tube 1410 to form tube unit 1401. Tube unit 1401 can be manufactured and filled with a predetermined mass of liquid 130 and a predetermined mass of gas 133 that are sealed inside channel 1420 of tube 1410 at a predetermined pressure. Tube unit 1401 can then be packaged and sterilized separately from housing 1442 (including socket 1448 and drive mechanism 1444), such that housing 1442 can be resterilized and reused, while tube unit 1401 can be manufactured and sterilized as a disposable unit that is discarded after use.

[0127] This arrangement allows the fluids 130, 133 and the tubing unit 1401 together to be more easily sterilized without the need to fill the tubing 1410 with sterile fluids 130, 133 in a sterile environment such as an operating room.

[0128] The piston assembly 1450 is removably coupled to the housing 1442 (i.e., removable from the socket 1448). The socket 1448 may include an interior cylindrical wall 1486 that defines the socket 1448 and helps to accommodate the piston assembly 1450 therein.

[0129] The body 1452 defines a first opening 1462 and a second opening 1464 in the cylinder 1454, which defines an open passage between the first opening 1462 and the second opening 1464. The proximal end 1414 of the tube 1410 is connected to the body 1452 of the piston assembly 1450 at the second opening 1464, thereby placing the channel 1420 in fluid communication with the cylinder 1454. The inner diameter or bore of the cylinder 1454 may be significantly larger than the inner diameter of the tube 1410, such that a relatively short stroke length is necessary to affect the desired pressure change in the tube 1410. For example, the ratio of the inner diameters of the tube 1410 and the cylinder 1454 may be in the range of 0.01 to 0.5, 0.05 to 0.4, 0.1 to 0.3, or 0.1 to 0.2.

[0130] The inner diameter of the cylinder 1454 may gradually taper to match the inner diameter of the tube 1410 at the second opening 1464. In some embodiments, the second opening 1464 may be offset from the central axis of the body 1452 and may be located at or near the top surface of the cylinder 1454 when the pressure actuator 1440 is positioned in a horizontal configuration. This may reduce the chance of air bubbles, which may form in the cylinder 1454 during cavitation, becoming trapped within the cylinder, instead allowing the bubbles to rise toward the second opening 1464 and into the tube 1410 due to gravity.

[0131] The pressure actuator 1440 is configured to adjust the channel pressure, such as by moving the piston 1456 back and forth along the length of the cylinder 1454, varying the channel pressure in the tube 1410. A compression stroke, or pressure increase stroke, moves the piston 1456 toward the tube 1410, pushing fluid from the cylinder 1454 and into the tube 1410, thereby increasing the channel pressure in the tube 1410. A return stroke, or withdrawal stroke or pressure decrease stroke, moves the piston 1456 away from the tube 1410, allowing fluid to flow from the tube 1410 back into the cylinder 1454, thereby decreasing the channel pressure in the tube 1410.

[0132] The motor 1444 and actuation rod 1446 are disposed within the housing 1442 such that when the piston assembly 1450 is disposed within the socket 1448, the actuation rod 1446 aligns with and passes through a first opening 1462 in the body 1452 and contacts and moves the piston 1456 within the cylinder 1454. In some embodiments, the channel pressure within the tube 1410 can be sufficient to move the piston 1456 through a return stroke when the actuation rod 1446 is withdrawn from the cylinder 1454. In some embodiments, the piston assembly 1450 may further include a biasing member 1470 (such as a spring) that biases the piston 1456 against the actuation rod 1446 and / or away from the tube 1410, such that the piston 1456 is pushed rearward through a return stroke by the biasing member 1470 when the actuation rod 1446 is withdrawn from the cylinder 1454. For example, the biasing member 1470 may include a stainless steel spring and / or a helical spring. In some embodiments, the actuation rod 1446 may be removably coupled to the piston 1456 itself, allowing the actuation rod 1446 to pull the piston 1456 rearward and, in turn, push the piston 1456 forward.

[0133] The piston assembly 1450 may further include a locking ring 1466 that limits removal of the piston 1456 from the cylinder 1454 through the first opening 1462. In some embodiments, the drive mechanism 1444 may include one or more electromagnets configured to drive the piston 1456 directly, rather than via a motor and actuation rod.

[0134] The body 1452 may further define one or more locking tabs 1468 configured to engage the socket 1448 and couple the piston assembly 1450 to the housing 1442. The socket 1448 may also include one or more external flanges 1488 configured to engage the tabs 1468 and secure the piston assembly 1450 within the socket 1448. In this manner, the piston assembly 1450 is configured to be removably coupleable to the housing 1442, such that the piston assembly 1450 and the tube 1410 can be manufactured together as a single disposable tube unit, while the housing 1442 and motor 1444 can be reused with a new tube unit for each new procedure. For example, the locking tabs 1468 may alternatively be referred to as tabs or radial protrusions.

[0135] The tube unit may be assembled with the liquid 130 and gas 133 disposed within the channel 1420 (either at atmospheric pressure or a higher pressure, depending on the application) and connected to the piston assembly 1450 to seal the liquid 130 and gas 133 within the tube unit. In some embodiments, the body 1452 may be secured to the proximal 1414 end of the tube 1410 and to the piston 1456, which may then be placed within the cylinder 1454 and locked with a locking ring 1466 to seal the liquid 130 and gas 133 within the channel 1420 and the cylinder 1454. The seal 1458 may include one or more gaskets, such as O-rings, that may be seated within the inner surface of the cylinder 1454, or with one or more corresponding gasket seats defined within the piston 1456.

[0136] In some embodiments, the body 1452 of the piston assembly 1450 may include an inlet valve 1490 for filling the cylinder 1454 and the channel 1420 of the tube 1410 with a predetermined mass of the selected liquid 130 and a predetermined mass of the selected gas 133. The body 1452 may also include an outlet valve 1492 for allowing air to escape from the channel 1420 and the cylinder 1454 while the channel 1420 and the cylinder 1454 are filled with the liquid 130 and the gas 133.

[0137] The valves 1490, 1492 may be located near one end of the body 1452 at the second opening and may be configured to maintain pressure within the cylinder 1454 and the channel 1420. In some embodiments, the valves 1490, 1492 may comprise spring plunger valves. As shown in FIG. 14 , the inlet valve 1490 may be located relatively closer to the second opening 1464 and the outlet valve 1492 may be located relatively farther from the second opening 1464.

[0138] To fill the tube unit 1401 with gas 133 and liquid 130, the body 1452 can be held upside down or arranged with the valves 1490, 1492 positioned above the second opening and most or substantially all of the volume of the channel 1420 and cylinder 1454 at a height lower than the outlet valve 1492. This is recommended so that when the channel 1420 and cylinder 1454 fill with liquid 130, excess air rises towards the outlet valve 1492. Air can be sucked out of the outlet valve 1492 via a vacuum line or other suction.

[0139] In some cases, the liquid 130 and gas 133 may be mixed together in a pressure vessel, whereby the gas 133 is completely dissolved in the liquid 130 in a saturated solution, in which case the gas / liquid solution can be introduced into the tube unit 1401 through the inlet valve 1490 as the air is removed through the outlet valve 1492. If the gas 133 and liquid 130 are introduced separately, it may be preferable to first remove as much air as possible from the channel 1420 and cylinder 1454 through the outlet valve 1492, remove any remaining air through the outlet valve 1492 before injecting the liquid 130 into the channel 1420 and cylinder 1454 through the inlet valve 1490, and then inject the gas 133 into the channel 1420 and cylinder 1454 through the inlet valve 1492.

[0140] Alternatively, tube 1410 can be formed with an open distal end, and liquid 130 and gas 133 can be drawn along channel 1420 and into cylinder 1454 as air is drawn from cylinder 1454, and the distal end of tube 1410 can then be closed with a plug and steel swage to retain the plug within channel 1420 and seal tube 1410. However, it may be preferable to form tube 1410 with a closed distal end to avoid having to close tube 1410 with a plug or other means.

[0141] Once the tube unit is fully assembled with the liquid 130 and gas 133 sealed inside the channel 1420 and cylinder 1454, the tube unit may be packaged and sterilized, for example, with gamma radiation. Together, the tube 1410 and piston assembly 1450 may define a sealed container containing a selected amount of liquid 130 and a selected amount of gas 133. In some embodiments, an airtight closure may fit onto the body 1452 of the piston assembly 1450 during packaging to close the first opening 1462 of the cylinder 1454 and to help maintain a selected tube channel pressure until use. The body 1452 may include an engagement portion (not shown) defining one or more recesses, notches, or protrusions to engage the closure and form an airtight seal.

[0142] In some embodiments, the pressure actuator 1440 may include a diaphragm pump instead of a piston pump to control the channel pressure in the tube 1410. Referring to Figure 17, the propulsion device 1400 is shown with an alternative tube unit 1701, including a diaphragm pump assembly 1750 instead of the piston assembly 1450 described above. In all other respects, the tube unit 1701 may be substantially similar to the tube unit 1401 described above, with like features indicated by like reference numerals.

[0143] The diaphragm pump assembly 1750 includes a body 1752 defining a chamber 1754 extending between a first opening 1762 and a second opening 1764, and a diaphragm 1770 closing or covering the first opening 1762 of the chamber 1754. The proximal end 1414 of the tube 1410 is connected to the body 1752 of the diaphragm pump assembly 1750 at the second opening 1764, thereby placing the channel 1420 in fluid communication with the chamber 1754. The body 1752 may further define one or more lugs 1468 configured to engage the flange 1488 of the socket 1448 and couple the diaphragm assembly 1750 to the housing 1442.

[0144] In some embodiments, the body 1752 of the diaphragm pump assembly 1750 may include an inlet valve 1790 and an outlet valve 1792, which may be configured in a manner similar to the valves 1490 and 1492 as described with respect to the tube unit 1401 and the body 1452.

[0145] The diaphragm 1770 may be separately formed and held in place across the first opening 1762 of the chamber 1754 by a clamp 1772. As shown in FIG. 17 , for example, the clamp 1772 may include a threaded locking ring configured to threadably engage the body 1752, thereby sandwiching the periphery of the diaphragm 1770 between the body 1752 and the clamp 1772. In other embodiments, the diaphragm 1770 may be integrally formed with the body 1752, for example, using an overmolding process.

[0146] The diaphragm 1770 comprises an elastically deformable membrane that can be deformed by an actuator to change the volume of a chamber 1754 that is in fluid communication with the channel 1420 of the tube 1410. A central portion 1774 of the diaphragm 1770 can be removably coupled to an actuation rod 1446 of the drive mechanism 1444. The diaphragm 1770 includes an elastically deformable portion 1776 around the periphery of the central portion 1774, allowing the diaphragm central portion 1774 to move back and forth relative to the body 1752 along an axis 1780 that is substantially perpendicular (perpendicular) to the surface of the central portion 1774, e.g., parallel to or aligned with the axial movement of the actuation rod 1446 of the drive mechanism or linear motor 1444.

[0147] As the center portion 1774 of the diaphragm 1770 moves back and forth between a compressed position 1778a (shown in dashed lines) and an extended position 1778b (shown in solid lines), the volume of the chamber 1754 changes. Thus, by controlling the position of the actuation rod 1446 and the center portion 1774 of the diaphragm 1770, the channel pressure in the tube 1410 can be adjusted and controlled.

[0148] The diaphragm 1770 may be circular or rotationally symmetric, but may define any suitable shape for an elastically deformable membrane. The chamber 1754 is shown in FIG. 17 as a cylinder, but may define any suitable shape for providing a desired range of channel pressures. In some embodiments, the chamber 1754 may be relatively short and tapered toward the second end 1764, allowing for a relatively wide diaphragm 1770 and a relatively narrow diameter of the second opening 1764, allowing for a larger range of channel pressures for relatively little axial movement of the diaphragm.

[0149] In some embodiments, different tube units for different medical applications may be fitted with similar piston assemblies, allowing each of the different tube units to be used with a common housing 1442 and motor 1444. In some embodiments, multiple tubes 1410 may be connected to a single piston assembly 1450, with each channel 1420 of the tubes 1410 in fluid communication with a cylinder 1454 of the piston assembly 1450.

[0150] In some embodiments, the housing 1442 may include a drive console or drive unit 1500 as shown in Figure 15. The drive console 1500 may include a power switch 1502 that controls the power supply from a power source 1560 to the drive console 1500.

[0151] The socket 1448 may include one or more circumferential flanges 1488 that extend a path partially around the circumference of the socket and extend radially inward to retain a tab 1468 of the body 1452 within the socket 1448. The tab 1468 is shown in dashed lines in FIG. 15 and projects radially away from the body 1452 housed within or beneath the flange 1488. The tab 1468 also extends circumferentially around a portion of the body 1452.

[0152] Both the tabs 1468 and the flanges 1488 are arranged such that when the piston assembly 1450 is coupled to or separated from the socket 1448, there is a spacing between the flanges 1488 that allows the tabs 1468 to pass and a gap between the tabs 1468 that allows the flanges 1488 to pass. To couple the piston assembly 1450 to the housing 1442, the body 1452 is inserted into the socket 1448 with the tabs 1468 aligning with the gap between the flanges 1488, and then the body 1452 is rotated to engage the tabs 1468 so that they fit within the space defined between the flanges 1488 and a surface (not shown) of the housing 1442 opposite and directly below the flanges 1488.

[0153] In some embodiments, the knob 1468 and / or flange 1488 may include a resilient click lock, clip, or latch that secures the body 1452 against rotation when aligned with the knob 1468 engaged with the flange 1488. The knob 1468 and / or flange 1488 may also include a stop that limits rotation of the piston assembly 1450 beyond the angle at which the knob 1468 is fully engaged with the flange 1488.

[0154] To separate the piston assembly 1450 from the housing 1442, the body 1450 is rotated to disengage the tabs 1468 from the flanges 1488, so that the tabs 1468 align with the gaps between the flanges 1488. The piston assembly 1450 can then be removed from the socket 1448.

[0155] In some embodiments, the body 1450 may include an indicator tab 1480 that indicates the correct orientation when coupling the piston assembly 1450 to the socket 1448. The flange 1488 may define a complementary notch or recess 1482 configured to allow passage of the indicator tab 1480 when the piston assembly 1450 is correctly oriented for insertion into the socket 1448. Once inserted into the socket 1448, the body 1450 may be rotated such that the indicator tab passes under one or more of the flanges 1488 until the tab 1468 is fully engaged with the flange 1488. In some embodiments, the housing 1442 may include indicia or markings that indicate the position of the indicator tab 1480 when the tab 1468 is fully engaged with the flange 1488.

[0156] Drive console 1500 may include a connection indicator light 1504 configured to illuminate when piston assembly 1450 is connected to drive console 1500. Drive console 1500 may include a sensor (not shown) that detects when piston assembly 1450 is connected to socket 1448 and / or when lug 1468 is fully engaged with flange 1488. When the sensor detects connection of piston assembly 1450 to drive console 1500, the sensor may activate a signal, or complete an electrical circuit, turning on connection indicator light 1504.

[0157] The drive console may include an operating or activation indicator light 1506 configured to illuminate when the pressure actuator 1440 is operating. The indicator light 1506 may be included in or coupled to an electrical circuit that controls the power supply to the motor 1444, such that the indicator light 1506 is on when the motor 1444 is operating.

[0158] In some embodiments, drive console 1500 may include a connection terminal 1508 configured to receive a connector of a signal cable from an external controller, such as a foot switch, for controlling operation of pressure actuator 1440. In some embodiments, drive console 1500 may include a display or user interface 1510 that provides a user with information regarding and / or allows a user to control operation of propulsion device 1400. In some embodiments, drive console 1500 may include a computer and / or controller 1550 configured to control operation of propulsion device 1400.

[0159] Computer 1550 may be connected to a user interface 1510 that provides information about the operation of propulsion device 1400, and in some embodiments may receive input from the user interface to select certain operating parameters. User interface 1510 may include an intelligent display graphic user interface, and computer 1550 may include a programmable microprocessor that controls the functions of drive console 1500 and drive mechanism 1444. Power supply 1560 may be connected to drive console 1500 and computer 1550, and computer 1550 may control the supply of power to various components of drive console 1500.

[0160] 16, an endoscopic system 1600 is shown, according to some embodiments. The endoscopic system 1600 includes an endoscope 1601 having an insertion tube 1610 for insertion into a patient's body, an endoscope console 1620 for controlling the operation of the endoscope, an endoscope handpiece 1630 for further and / or alternative control of the operation of the endoscope 1601, a propulsion device 1400 for advancing the endoscope 1601 and insertion tube 1610 along a passageway within the patient's body, and a power source (not shown) for providing power to the drive console 1500 and the endoscope console 1620.

[0161] The propulsion device 1400 comprises a propulsion tube 1410 for insertion into an insertion tube 1610 as described above, and a drive console 1500 for controlling the operation of the propulsion device 1400 .

[0162] The endoscope system 1600 may further include a monitor 1640 configured to display images received from the endoscope camera via the endoscope console 1620.

[0163] As explained above, the propulsion device 1400 may operate to provide propulsion to the endoscope 1601 and the insertion tube 1610 by means of a propulsion transport within the pusher tube 1410. The propulsion may be used to advance the endoscope 1601, the insertion tube 1610, and the pusher tube 1410 along a passageway within the patient's body.

[0164] When propulsion force is transferred to the pusher tube 1410 along its length, it may reduce the risk of clogging or reduce resistance as the insertion tube 1610 navigates around turns in the passageway (e.g., turns in the digestive tract), as can often occur with conventional pusher-type endoscopes. This method of propulsion may also reduce friction at each turn as the endoscope advances along the passageway, providing an alternative to simply pushing the endoscope against each turn to advance the endoscope further, as is done with conventional pusher-type endoscopes.

[0165] In some embodiments, the propulsion device 1400 may be capable of advancing the endoscope 1601 along the passageway at a forward speed of, for example, approximately 1.5 cm / s. Depending on various operating environments, conditions, and / or requirements, the forward speed may vary, for example, between 0.1 cm / s and 2 cm / s, or between 0.5 cm / s and 1 cm / s. In some applications, the time-pressure profile may be reversed to move the tube 1410 backward along the passageway, for example, to assist in withdrawing the tube 1410 from the passageway. The propulsion device 1400 may also enable improved completeness of intestinal endoscopy by enabling the endoscope 1601 to be advanced further or entirely along the length of the intestine, allowing the entire extent of the small intestine to be inspected. The propulsion device 1400 may also enable access to the entire gastrointestinal tract via endoscopy.

[0166] In various embodiments, the propulsion device 100, 1400, 1700 may be configured to advance any one or more of, for example, an instrument, a probe, a sensor, a camera, a surveillance device, a tool, a surgical tool, a mining tool, an excavation tool, an endoscope, an enteroscope, a duodenoscope, a borescope, a robotic tether, and an industrial endoscope along a passageway. The propulsion device 100, 1400, 1700 may be configured to assist in advancing an instrument, sensor, or tool along any one or more of a passageway, a shaft, a wellbore, a pipe, a sewer, a wall cavity, and a passageway within a patient's body (such as a lumen, artery, or tract of a biological passageway).

[0167] It will be appreciated by those skilled in the art that several variations and / or modifications may be made to the above-described embodiments without departing from the broad general scope of the present disclosure, and the present embodiments are therefore to be considered in all respects as illustrative and not restrictive.

Claims

1. a propulsion device for advancing the instrument along the passageway, comprising: an elongated tube having a first end and a second end opposite the first end, the tube defining a channel configured to contain a liquid, the first end of the channel being closed at or near the first end of the tube, and the second end of the channel being defined by the second end of the tube; a pressure actuator in communication with the second end of the channel and configured to selectively adjust the pressure of the liquid in the channel, the pressure actuator alternately comprising: reducing the pressure to induce cavitation and form gas bubbles in the liquid; increasing the pressure to collapse some or all of the bubbles back into the liquid, accelerating at least a portion of the liquid toward the first end of the tube, transferring a motive force to the tube, and advancing the tube along the passageway; the pressure actuator; one or more features configured to promote cavitation in one or more regions of the channel when the pressure is reduced, the one or more regions extending along at least a portion of the length of the channel; The propulsion device.

2. The propulsion device of claim 1 , wherein the tube is reinforced to resist expansion or contraction due to changes in internal pressure.

3. The propulsion device of claim 2 , wherein the one or more features include a surface variation on an interior surface of the channel.

4. The propulsion device of claim 3 , wherein the surface alteration comprises a coating.

5. 5. The propulsion device of claim 3 or 4, wherein the surface variations include local shape variations.

6. The propulsion device of claim 5 , wherein the localized shape change defines a porous surface.

7. A propulsion device according to any one of claims 2 to 6, wherein the one or more mechanisms comprise one or more acoustic transducers.

8. The pressure actuator a piston assembly including a movable piston disposed within a bore of the piston assembly; a drive mechanism configured to drive the piston of the piston assembly to selectively adjust the pressure of the liquid in the channel; and A propulsion device according to any one of claims 1 to 7, comprising:

9. the piston assembly is connected to the tube to form a sealed tube unit containing the liquid; The propulsion device of claim 8 , wherein the piston assembly is removably coupleable to the drive mechanism.

10. One or more tubes according to any one of claims 1 to 7; a piston assembly connected to the second end of the tube, a body defining a hole in fluid communication with the channel of each of the one or more tubes; a movable piston disposed within the bore and configured to seal against an interior surface of the bore; the piston assembly comprising: A propulsion pipe unit comprising:

11. A propulsion pipe unit, an elongated tube having a first end and a second end opposite the first end, the tube defining a channel configured to contain a liquid, the first end of the channel being closed at or near the first end of the tube, and the second end of the channel being defined by the second end of the tube; a piston assembly connected to the second end of the tube, a body defining a bore in fluid communication with the channel of the tube; a movable piston disposed within the bore and configured to seal against an interior surface of the bore; the piston assembly comprising: the piston assembly and the tube cooperate to define a sealed vessel containing a selected amount of liquid and a selected amount of gas; The propulsion pipe unit comprises: one or more features configured to promote cavitation in one or more regions of the channel when the pressure of the liquid and gas in the channel is reduced, the one or more regions extending along at least a portion of the length of the channel; The piston assembly is configured to cooperate with an actuator to effect movement of the piston to selectively adjust the pressure of the liquid in the channel, and alternately reducing the pressure to induce cavitation and form gas bubbles in the liquid; a propulsion tube unit that increases the pressure to collapse some or all of the bubbles back into the liquid, accelerating at least a portion of the liquid toward the first end of the tube, transferring a propulsive force to the tube, and propelling the tube along a passageway.

12. 12. The propulsion tube unit of claim 11, further comprising one or more mechanisms configured to promote cavitation in a plurality of spaced apart regions along at least a portion of the length of the channel when pressure is reduced.

13. A housing according to any one of claims 10 to 12, defining a socket configured to receive and engage a propulsion tube unit; an actuator configured to engage the piston; a controller configured to operate the actuator to move the piston and selectively adjust pressure within the channel of the tube; A driving console comprising:

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