Active Bending Electric Endoscope Using Shape Memory Alloy Wires

Transcription

1 Active Bending Electric Endoscope Using Shape Memory Alloy Wires Takumi Kobayashi 1, Tadao Matsunaga 2 and Yoichi Haga 3 1) Graduate School of Engineering, Tohoku University 2) Micro System Integration Center, Tohoku University 3) Graduate School of Biomedical Engineering, Tohoku University International Workshop and Summer School on Medical and Service Robotics July 2014, EPFL Lausanne 1

2 1. Background Outline Endoscopy Previous study Method 2. Multidirectional bending mechanism Principle, Structure, Measurement 3. Active bending electric endoscope Structure Measurement of bending angle Measurement of surface temperature Active bending electric endoscope system Motion Discussion 4. Conclusion 5mm Multi bending device 5mm Active bending electric endoscope 2

3 Background 1:Endoscopy Endoscopy is widely used as minimally invasive therapy Field lens Stomach Light Stomach Work End Endoscope Invo ing osco Pylorus chan lved pe Endoscope Inserting endoscope from nose area nel Snare Bending part Involved part Shaft Reusable Infection due to lack of cleaning Wire Disinfection and sterilization time Angle knob Shaft Conventional endoscope structure For upper digestive Disposable High insert ability Ability to observe and bend 3

4 Background 2: Previous study Active bending device using SMA(Shape memory alloy ; Ti-Ni) coils External diameter : 3.9mm Bending part : 35mm 5 mm Complex circuit for CCD imager Need to dispose CCD imager Expensive SMA coils Difficult to be disposable *W. Makishi et al., The Institute of Electrical Engineers of Japan E,

5 Background 3 : Method Purpose Easily inserting to small bowel -Ability to observe and bend Disposable endoscope Miniaturized endoscope Mounted CMOS imager Using SMA(Shape memory alloy ; Ti-Ni) wires as actuators CMOS imager (mounted lens) 5

6 Background 3 : Method Mounted CMOS imager Using SMA wires as actuators CMOS imager (mounted lens) Medigus 1.2mm Camera Outer diameter : 1.2mm Rigid part : 5.0mm Pixel : pixels Field of view : 100,130 deg. Working distance: 4,8,10,20,30 Medigus Co. Characteristic compared to SMA coil Less heat generation Lower cost Avoiding overheat Better controllability Small contraction 6

7 Background 3 : Method Bending device L a L a Straight type l θ SMA wire Arc type l θ Relationship between bending angle and strain x = 1 2 L sin θ θ a 2 Straight; L Arc; x = aθ L x;contraction of SMA wires 7

8 Background 3 : Method When one SMA wire is driven, the others shift inward without strain. Initial state Actuation Stopper SMA wire Inner tube Link Minimum route of SMA wire l = 2( L θ + a)2 1 cos θ Maximum extended SMA wire =0.2% 8

9 Multidirectional bending device 5mm 5mm Actuation mechanism of Our device Bending motion (Current:280mA) Outer diameter; 1.7mm Bending length;35mm Bending angle;59, 53, 51 degree Radius of curvature ; 34, 37, 39 mm (280mA) T. Kobayashi et al., Sensors, Micromachines and Applied System, 5AM2-B-6,

10 Structure of Active bending electric endoscope (a) Links CMOS imager Lead wires for LEDs and SMA wires Inner tube Bending mechanism 5mm Observation part (b) (c) Bending part 1mm Outer tube 5mm O.D. of SMA wires:150 μm O.D.:4.1 mm LED Bending angle:35 mm LEDs Size : mm Luminous intesty : mcd 10

11 Measurement of bending angle Driven one SMA wire 5mm Driven two SMA wires Bending angle:50 deg Radius of curvature:40 mm 5mm Bending angle:37 deg Radius of curvature:54 mm 11

12 Measurement of surface temperature Observation method; Input static current in a thermostatic oven(38 ) observe bending angle to not increase temperature observe bending angle using a camera Driven one SMA wire Achievement Supply current of SMA wire: 300 ma Bending angle : 43 degree Maintaining the surface temperature of the device under 41 *Limitation temperature of protein denaturation * 12

13 Active bending electric endoscope system Monitor Controller for bending device Video unit Joy stick 10 mm Endoscope Controller for LEDs 13

14 Motion of active bending electric endoscope 5 mm 2 mm Motion of actuation device using controller Observation using CMOS imager in small intestine model Controlling bending angle Observation of circular folds (2 mm) in small intestine model 14

15 Discussion Observation of circular folds (2 mm) in small intestine model Application Pylorus Cardia inspection of stenosed lesion of the small intestine Stomach model navigation from cardia to pylorus High illumination intensity Luminous intensity : Size : mcd mm 85 LED paradise (Store) 61.7 cd mm Cree Inc. 15

16 Conclusion Active bending electric endoscope -Outer diameter:4.1 mm -Bending angle:50 deg (300 ma) Controlled Bending angle using controller Observed Small bowel model (a) Active bending mechanism (b) Small bowel model 5mm 1mm 16

17 Conclusion -In the future- Insertion test from cardia to duodenum using stomach model -Confirmation of observational function -Appropriate rigidity of shaft part Drug delivery using working channel Duodenum Cardia Working channel Stomach model Tip of active bending electric endoscope 17

18 Conclusion -In the future- Bending mechanism Feedback control using electrical resistance of SMA wires -Prevention of overheat -Precise position control Thermocouple (T type) (a) Without feedback (b) Feedback