Endoscope apparatus, actuators, and methods therefor

• US 20070239138A1
• Filed: 04/07/2006
• Published: 10/11/2007
• Est. Priority Date: 04/07/2006
• Status: Active Grant

• Current Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Original Assignee: University of Colorado System
• Inventors: Lawrence, Dale A., Aphanuphong, Sutha
• Granted Patent: US 8,123,678 B2
• Time in Patent Office: Days
• US Class Current: 604/531
• CPC Class Codes: A61B 1/012 characterised by internal passages or accessories therefor
• CPC Class Codes: A61B 1/2676 Bronchoscopes
• CPC Class Codes: A61B 2017/003 Steerable
• CPC Class Codes: A61B 2017/00398 using powered actuators, e.g. stepper motors, solenoids
• CPC Class Codes: A61B 2017/00867 shape memory effect

Abstract

The present invention provides, in part, a dexterous endoscope apparatus, referred to herein as a MicroFlex Scope (MFS). The MFS is an novel, small diameter, e.g., less about 1 mm to about 4 mm, about 1 mm to about 3 mm, etc., dexterous endoscope that allows for access, direct visualization, tissue sampling, treatment, etc. of body lumens. In one embodiment, the distal end of the MFS of the invention is an ultra-flexible tip that comprises a plurality of thin, curved shape memory alloy (SMA) actuator elements attached to at least one structural skeleton, e.g., a coil spring skeleton or hinge structure. The SMA actuator elements in each structural skeleton segment are indirectly heated by a heater element and produce force in response to their temperature relative to specific thresholds. In certain embodiments, the heater element may include an integrated heater/sensor element adapted to heat the actuator element and to sense the temperature and bend state of the actuator element. In configurations comprising a plurality of actuator elements, multiplexing/demultiplexing of heating currents and sensor voltages may be accomplished via a parallel bus and demulitplexing circuit. In this regard, a demultiplexing circuit using standard microelectronic fabrication techniques may be designed to achieve individual sensing and control over each actuator element.

Claims

1. An actuator element comprising:

a shape memory alloy (SMA) layer adapted to exhibit a variation in bend state corresponding to a variation in temperature of the SMA layer;

an integrated heater/sensor layer interfaced with said SMA layer, wherein said heat/senor layer is adapted to indirectly heat the SMA layer upon application of current to the heater/sensor layer, to sense the temperature and bend state of the SMA layer, and to produce a voltage in proportion to the sensed temperature and bend state of the SMA layer; and

a demultiplexing circuit and parallel bus interfaced with said heater/sensor layer, wherein said demultiplexing circuit and parallel bus are adapted to allow for connection of multiple actuator elements thereby enabling communication and control of individual actuator elements when multiplexed with a plurality of actuator elements.

2. The actuator element of claim 1, wherein the parallel bus comprises a multi-wire flex cable bus system configured to interconnect multiple actuator elements.

3. The actuator element of claim 1, further comprising an exterior insulation sheath adapted to minimize exposure of tissue to electrical current or elevated temperatures when used in vivo.

4. The actuator element of claim 1, wherein the exterior surface of said SMA layer is at least partially interfaced with a closed circuit cooling system configured to provide a chilled bias temperature state to the SMA layer.

5. The actuator element of claim 1, wherein said SMA layer comprises a NiTi alloy with a bend state activation temperature between 17 deg C. and 67 deg C.

6. The actuator element of claim 1, wherein the heater/sensor layer interfaces with the SMA layer via a strain-isolating adhesive layer.

7. The actuator element of claim 1, wherein the heater/sensor layer comprises two metal layers separated by a dielectric layer, capable of heating and sensing temperature and bending strain.

8. A method of making an actuator element of claim 1, said method comprising:

providing a patterned SMA layer fixed to a handling frame via anchor links;

providing an integrated heater/sensor layer fixed to a substrate;

providing a demultiplexing circuit and parallel bus fixed to the substrate and electrically connected to the heater/sensor layer;

positioning the SMA layer and the heater/sensor layer via a mask aligner such that the handling frame and substrate are aligned face-to-face over each other;

bonding the SMA layer to the heater/sensor layer via a strain-isolating adhesive layer once aligned;

removing the substrate from the heater/sensor layer via an etch process.

9. The method of claim 8, wherein the demultiplexing circuit and parallel bus comprises a multi-wire flex cable bus and demultiplexing circuit chips;

and wherein the method for making the demultiplexing circuits and parallel bus and heater/sensor layers comprises;

constructing the demultiplexing circuits on a silicon substrate using metal oxide semiconductor processes selected from the group consisting of;

photolighographic patterning, oxidation, dopant diffusion or implantation, and metal sputtering or evaporation;

depositing and patterning alternate layers of polyimide and metal over said demultiplexing circuits to thereby provide said multi-wire bus and heater/sensor layers;

removing the silicon substrate via back side etching to thereby provide the separate demultiplexing circuits and heater/sensor layers, connected by the parallel bus.

10. An actuated coil segment comprising:

a plurality of shape memory alloy (SMA) actuator elements interconnected via a lattice structure adapted to provide skeleton attachment points, wherein said SMA actuator elements comprise a SMA layer interfaced with an integrated heater/sensor layer configured so as to indirectly heat the SMA layer; and

a coil spring skeleton secured to said plurality of SMA actuator elements via the attachment points of said lattice structure.

11. The actuated coil segment of claim 10, wherein the SMA actuator elements are interconnected in a lattice structure, and the lattice structure is secured to the coil spring skeleton such that the coil skeleton contacts the lattice structure at the attachment points, and abuts the lattice structure at load-bearing points.

12. The actuated coil segment of claim 11, wherein the lattice structure comprises at least one series segment of at least one parallel SMA actuator, each interconnected via the SMA lattice structure and parallel bus.

13. The actuated coil segment of claim 10, wherein the SMA actuator elements are secured to a coil skeleton via a welding band with spot welds at the attachment points of the lattice structure, and via mating of load-bearing features on the coil spring skeleton with corresponding patterned features in the SMA lattice structure.

14. A method of making a coil segment of claim 10, said method comprising:

providing the plurality of SMA actuator elements as an interconnected lattice structure to provide skeleton attachment features;

providing the SMA coil skeleton located about its exterior perimeter to a welding probe and interior copper mandrel adapted to act as resistance welding electrodes;

wherein the ends of the SMA coil skeleton are secured to tension fixtures at their distal ends to thereby provide axial tension to the SMA coil skeleton and compression forces between copper electrodes while located on the welding fixture;

aligning the SMA coil skeleton located on the electrode mandrel over the SMA actuator lattice structure such that coil skeleton attachment and load-bearing features interface with the corresponding features on the SMA lattice;

rolling the copper mandrel relative to the SMA actuator lattice structure while selectively energizing the copper mandrel and copper welding probe at locations corresponding to the skeleton attachments points so as to form spot welds at said attachment points; and

releasing the proximal ends of the SMA coil skeleton from tension fixtures following formation of said spot welds, thereby allowing the axial tension in the SMA coil skeleton to compress the plurality of SMA actuator elements inward, resulting in a compressed state coil segment.

15. A microdexterous endoscope apparatus comprising:

a catheter with fixed tool tip, or having a lumen comprising at least one port in the interior of said lumen;

at least one actuated coil segment at the distal end of the catheter, wherein the actuated coil segment comprises a plurality of indirectly heated shape memory alloy (SMA) actuators secured to a SMA coil skeleton, wherein each SMA actuator is adapted to exhibit a variation in bend state corresponding to a variation in temperature of the SMA actuator;

a control system configured to monitor and control actuation of said at least one coil segment based at least in part on temperature and strain feedback from said actuated coil segment; and

an electrical bus traversing the length of the catheter and interfacing with said at least one actuated coil segment and said control system;

wherein the control system is adapted to modulate application of a current to thereby independently control the temperature of the plurality of SMA actuators to achieve a desired bend state based at least in part on control system capable of compensating for the non-linear hysteresis in the SMA using feedback voltages obtained from the SMA actuator via the electrical bus.

16. A microdexterous endoscope apparatus of claim 15, wherein said catheter comprises a plurality of actuated coil segments located along the length of said catheter, and said control system is adapted so as to control actuation of said actuated coil segments such that the proximal end of the catheter follows the same path as the distal end of the catheter when used in vivo.

17. A method of direct visualization of a body lumen, said method comprising:

providing a microdexterous endoscope of claim 15, wherein the at least one port of the catheter lumen comprises an image guide to thereby enable visualization of a body lumen;

inserting the catheter of said endoscope into a subject comprising a body lumen to be visualized;

manipulating placement of the distal end of said catheter in the body lumen to be visualized via said at least one actuated coil segment; and

directly visualizing said body lumen via the image guide.

18. The method of claim 17, wherein the body lumen is selected from the group consisting of lung airways, bronchial airways, and sinus cavities.

19. The method of claim 17, wherein said catheter comprises at least two ports, and the second port guides a tool configured to interact with tissue, and wherein said method further comprises:

manipulating placement of the distal end of said catheter via said at least one actuated coil segment to thereby locate said tissue interaction tool at a desired location; and

interacting with tissue via said tool, wherein said interaction is selected from the group consisting of;

excision, ablation, treatment, manipulation, and sampling.

20. The method of claim 17, wherein said catheter further comprises an inflatable cuff located prior to the actuated distal end;

and wherein said method further comprises;

inflating said inflatable cuff to stabilize the position of the catheter once inserted in said subject, distend tissue for better access of the actuated distal end and/or block leakage.