1. BIOLOCH 6 th month Meeting BIO-mimetic structures for LOComotion in the Human body 8-9 November 2002 Scuola Superiore Sant’Anna, Polo Sant’Anna Valdera, Pontedera (PI), Italy

2. Saturday, November 9, 2002 09.00 – 09.15 Presentation of the second day objective (Project Coordinator) 09.15 – 11.00Enabling technologies for the design and fabrication of the systems identified on the first day The aim of the second day is to identify which technologies, which control strategies, which design method can be exploited to implement the “preferred” biomimetic units in a concrete way. Main contributions are expected by SSSA, UoP, FORTH. 11.00 – 11.15Coffee Break 11.15 – 12.30Enabling technologies for the design and fabrication of the systems identified on the first day - continuing. Final Discussion 12.30 – 12.45Decision for the next meetings and end of the meeting Agenda of the Meeting (2/2)

3. From models to applications / from applications to models? Locomotion models Applications Enabling Technologies Endoscopy Underground locomotion Paddleworm ………… Adhesion models Octopus ………

4. Enabling technologies for the design and fabrication of the systems identified on the first day

5. Enabling Technologies Enabling technologies: - for concept design of locomotion and adhesion systems - for fabricating locomotion and adhesion systems - for actuating locomotion and adhesion systems - for sensorising locomotion and adhesion systems

6. Enabling Technologies Enabling technologies: - for concept design of locomotion and adhesion systems - for fabricating locomotion and adhesion systems - for actuating locomotion and adhesion systems - for sensorising locomotion and adhesion systems

7. Concepts of locomotion in the gastrointestinal tract: CRIM background experience

8. the gastrointestinal tract is slippery, delicate, movable and compliant. Moreover it has high damping coefficients the problem of bio-compatibility is not trivial the propulsion mechanism has to adapt to different diameters and surface textures Concepts Relevant Issues

9. Local level contact between “ active surfaces ” (surfaces that transmit forces) and soft tissues. Final goal: enhancing the ability of exerting forces without damaging the living tissues Global level How to impose a propelling motion to the active surfaces. Concepts: multi-level analysis

10. Global level: kynematics and mechanism

11. SMA-wires based extension system allows the adaptability of locomotion system to different diameters of gastrointestinal tracts Full-extended configuration. The number and dimensions of wheels will be object of a dedicated study Global level - mechanisms

12. Hydraulic Inch-worm Locomotion A complete view of the locomotion system; on the right, a particular of the micromotor dedicated to the axial turning. The extensible elastic tubes connect the micropump with the two active surfaces. Elastic tubesMicromotorMicropump Global level - mechanisms

13. Tracked wheels device Vibrating Propulsion Mechanism IDM (Impact Drive Mechanism) Global level - mechanisms

14. Mechanical “inchworm” device Flexural wave mechanism Global level - mechanisms

15. Icy/Sticky Clamping Mechanism Icy/sticky joints are built to clamp the microcapsule to the tissues Helical Screw Device Two helical screws are mated together in parallel. Driven by a motor, the device is capable of propelling itself by using its surrounding environment as support Global level - mechanisms

16. Local level: active surfaces

17. Micro Scale friction enhancing active surface Meso Scale Compliant micro tips Macro Scale Wheels Details of a wheel up to the microscale. Compliant microtips support the microfabricated active surfaces, and gently soften the contact with organic tissues Local level - active surfaces

18. an isometric view of the active surface (a) normal configuration; (b) flow in; (c) flow out Hydraulically activated active surface The friction is enhanced when the compliant tips are pushed outward Local level - active surfaces

19. implemented solutions

20. Exploring the Environment

21. HMI interface Test Bench Thermocouple Exploring the environment Traction test Friction test Mechanical drivers

22. Structural Bio-tribological Safety F D 10 mm 0.1 N Lessons learned To exert significant pushing forces on the tissue, very high displacements are required (  10mm), because the tissue is very compliant. Sucking is an adequate solution. The limit forces exertable on the tissues are those which do not endanger the integrity of vascular system. The exertable limit of vacuum pressure is -0.4 bar, about 10 times the limit pressure which causes ischemia. The friction coefficient of gut walls is very low (f  10 -3 ). Significant values are reacheable via hysteretical deformation (f  0.5), best obtainable by sucking the tissue against patterned surfaces. Exploring the environment

23. Implemented solutions: Large deformation hystertical friction + Mechanical clamping P Exploring the environment

24. New Concepts for locomotion taking inspiration from nature

25. Expandible volumetric actuators (thermic phase change or electrochemical) embedded in elastic frame ~30° rotation <10% volumetric expansion Miniaturized leg: a concept 3 axis force microsensor (CRIM) 1 mm

26. Biomimetic devices: Taenia Solium Biological system: Artificial sucker The sucker needs vacuum to operate. Vacuum can be generated by a simple cylinder – piston mechanism The membrane can be stretched by a sliding mechanism TAENIA SOLIUM Microhooks embedded in an elastic membrane Adhesion principles: 2. Mechanical clamping 1. Suction

27. Biomimetic devices: Taenia Solium When sliding part moves upward: a vacuum is generated (sucker can work); the membrane is stretched (hooks can grasp the tissue)

28. Locomotion peristaltic module A locomotion peristaltic module can be fabricated by using 3 SMA wires (120°) embedded in a sylicone matrix A spring allows the mechanism to return to the initial position

29. Locomotion peristaltic module Assembling different modules a snake – like locomotion can be obtained. The device presents many degrees of freedom to be controlled.

30. Enabling Technologies Enabling technologies: - for concept design of locomotion and adhesion systems - for fabricating locomotion and adhesion systems - for actuating locomotion and adhesion systems - for sensorising locomotion and adhesion systems

31. Biomimetic devices: Taenia Solium Liquid bridge can be stretched Cylinder of polimeric material (Nylon) T = 20°C Nylon melts T = 237°C An exploitable process suitable for the fabrication of micro-hooks consists in melting a polymer (e.g.: Nylon) and shaping it thanks to the surface tension and to the viscosity of the material in the liquid phase. Comparison between an artificial hook and a tapeworm hook

32. Biomimetic devices: Taenia Solium A parallel approach to create microhooks consists of fabricating many hooks in a batch process. Some T–shaped tracks are fabricated by using KERN with a micro–milling tool T–shaped tracks are cutted by a fine wire of an Electrical Discarge Machine (EDM)

33. Biomimetic devices: Taenia Solium Aluminium hooks are used to create a special wax mould to fill with Epotex (epoxy bicomponent resin).

34. Enabling technologies FIB (Focused Ion Beam) FIB can be used in microsystem technology for: inspection metrology failure analysis FIB can be used as a tool for maskless micromachining: milling (max aspect ratio 10-20) deposition (max aspect ratio 5-10) combination of implantation of silicon with subsequent wet etching Best resolution of FIB images equals the minimum ion beam spot size : 10nm FIB is useful for building micro- and nano-structure prototypes

35. Shape Deposition Manufacturing (Stanford University) Promising technique to fabricate flexible bio-mimetic structures embedding sensors and actuators Enabling technologies

36. Lithographically induced self-assembly of periodic polymer micropillar arrays (a) a thin layer of polymer is spin coated on a flat silicon wafer (b) another silicon wafer is placed a distance above the polymer film, but separated by a spacer (c) a voltage is applied between the two surfaces and the resulted capacitor device is heated up and than cooled

37. Enabling technologies Lithographically induced self-assembly of periodic polymer micropillar arrays a characteristic exagonal pattern formation takes place in the polymer film dielectric media experience a force in an electric field gradient strong field gradients can produce forces that overcome the surface tension in thin liquid films, inducing an instability that features a characteristic hexagonal order it can be used to generate gecko-like surface that adhere by van der Waals forces

38. Enabling Technologies Enabling technologies: - for concept design of locomotion and adhesion systems - for fabricating locomotion and adhesion systems - for actuating locomotion and adhesion systems - for sensorising locomotion and adhesion systems

39. Biomimetic devices: Taenia Solium A prototype of biomimetic Taenia – like device has been fabricated The elastic membrane is GI1110 (sylicone inc.) The used actuator is an electroactive polymer (IPMC)

40. Enabling Technologies Enabling technologies: - for concept design of locomotion and adhesion systems - for fabricating locomotion and adhesion systems - for actuating locomotion and adhesion systems - for sensorising locomotion and adhesion systems

41. Sensor flexible packaging Enabling technologies Section of sensor 3D model F Silicon microstructures Kapton foil Soft polyurethane matrix 50 micron polyurethane film on top of the sensors Final thickness: 1.5 mm a silicon microfabricated sensor based on the piezoresistive transduction can be integrated in a flexible structure a “sensing” flexible structure

42. QUESTIONS TO BE ANSWERED Are polychaete the most suitable animal models for devices capable of moving in the GI tract (or other human cavities?) Accurate (biomechanical) model of the working principles Which “legs” and “leg motion” (Piston or Sweeping) ? Which propulsion ? Which are the typical dimensions? Total length, segments lenght, diameters…

43. QUESTIONS TO BE ANSWERED Which mechanism for the body ? Which mechanisms for locomotion (moving wave? Random to purposive?) Which actuators ? Which sensors ? Which control: autonomous, teleoperated… Which tools on board ?

44. The meeting output The Consortium has to analyse in deep the Nereis locomotion: -Biomechanical model of the Nereis Locomotion -Control model of Nereis Locomotion vs. lamprey or leech -Performance (force, stroke, speed) of Nereis Locomotion -Compatibility with adhesion systems: what adhesion principles can be exploited depending on the environment (grasping? friction? gluing?). Which subsystems can be integrated into the paddles to improve locomotion in unstructured enviroments -Fabrication/actuation/sensorization technologies

45. Design and Fabrication How to proceed?