BIOLOCH 6 th month Meeting BIOmimetic structures for

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

Agenda of the Meeting (2/2) Saturday, November 9, 2002 09. 00 – 09. 15 Coordinator) Presentation of the second day objective (Project 09. 15 – 11. 00 Enabling 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, Uo. P, FORTH. 11. 00 – 11. 15 Coffee Break 11. 15 – 12. 30 Enabling technologies for the design and fabrication of the systems identified on the first day - continuing. Final Discussion 12. 30 – 12. 45 Decision for the next meetings and end of the meeting

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

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

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

Concepts of locomotion in the gastrointestinal tract: CRIM background experience

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

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

Global level: kynematics and mechanism

Global level - mechanisms 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 Hydraulic Inch-worm Locomotion Micropump Elastic tubes Micromotor 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.

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

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

Global level - mechanisms 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 Icy/Sticky Clamping Mechanism Icy/sticky joints are built to clamp the microcapsule to the tissues

Local level: active surfaces

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

Local level - active surfaces implemented solutions

Exploring the Environment

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

Exploring the environment Lessons learned Bio-tribological Structural Safety F 0. 1 N 10 mm D To exert significant pushing forces on the tissue, very high displacements are required ( 10 mm), because the tissue is very compliant. Sucking is an adequate solution. 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. 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.

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

New Concepts for locomotion taking inspiration from nature

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

Biomimetic devices: Taenia Solium Biological system: TAENIA SOLIUM Adhesion principles: Artificial sucker 1. Suction 2. Mechanical clamping Microhooks embedded in an elastic membrane 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

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)

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

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

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

Biomimetic devices: Taenia Solium 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. T = 20°C Cylinder of polimeric material (Nylon) T = 237°C Nylon melts Comparison between an artificial hook and a tapeworm hook Liquid bridge can be stretched

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)

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

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

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

Enabling technologies 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

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

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

Biomimetic devices: Taenia Solium A prototype of biomimetic Taenia – like device has been fabricated The elastic membrane is GI 1110 (sylicone inc. ) The used actuator is an electroactive polymer (IPMC)

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

Enabling technologies Sensor flexible packaging F a silicon microfabricated sensor based on the piezoresistive transduction can be integrated in a flexible structure Section of sensor 3 D model a “sensing” flexible structure 50 micron polyurethane film on top of the sensors Kapton foil Soft polyurethane matrix Silicon microstructures Final thickness: 1. 5 mm

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…

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 ?

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

Design and Fabrication How to proceed?