IMT Microtechnique

Hannes Bleuler EPFL

Microrobotics for MEMs and Nanotechnologies

Microrobotic Components:Microrobotic Components:

1.) Sensors1.) Sensors

2.) Actuators2.) Actuators

introduction, introduction, exampleexamples s (SPM)(SPM)

3.) Bearing & Guidance System3.) Bearing & Guidance System

““Guidages”, “Führungen”Guidages”, “Führungen”

4) Control! Integral part of 1-3)4) Control! Integral part of 1-3)

Hannes BleulerHannes Bleuler

EPFL, LSRO Laboratoire de Systèmes RobotiquesEPFL, LSRO Laboratoire de Systèmes Robotiques

IMT Microtechnique

Hannes Bleuler EPFL

In Microrobotics,these components arevery much integrated!

IMT Microtechnique

Hannes Bleuler EPFL

Sensors: Classification criteria

What is measured? (distance, force, pressure, What is measured? (distance, force, pressure, T, t, frequ., light, field, chemical composition T, t, frequ., light, field, chemical composition …) …)

IMT Microtechnique

Hannes Bleuler EPFL

Sensors: Classification criteria

whatwhat

Physical Principle Physical Principle (Optical, acoustical, electrostatic, (Optical, acoustical, electrostatic, magnetic, hall, inductive, eddy currents, magnetic, hall, inductive, eddy currents, dilatation, piezoelectric, piezoresistive, dilatation, piezoelectric, piezoresistive, magnetnetoresistive…)magnetnetoresistive…)

IMT Microtechnique

Hannes Bleuler EPFL

Sensors: Classification criteria

whatwhat

Physical principlePhysical principle

Metrological principles: Metrological principles: absolute, relative, incremental, absolute, relative, incremental, averaging, localaveraging, local, , intensity, time of flight, intensity, time of flight, phasephase, ,

Indirect meast.:Indirect meast.: nullingnulling..

IMT Microtechnique

Hannes Bleuler EPFL

Sensors: Classification criteria

whatwhat

Physical principlePhysical principle

MetrologyMetrology

Technology Technology (Analog, discrete, integrated (MEMS), thick-(Analog, discrete, integrated (MEMS), thick-film,film,Screen Printing, electronics Screen Printing, electronics (CMOS,CCD,SMD…)(CMOS,CCD,SMD…)

IMT Microtechnique

Hannes Bleuler EPFL

Example: Technology choice (PCB) leads to new sensor:

Transverse Flux Sensor

Philippe Bühler,

ISMB 9, Aug. 2004

•Analog

•RF Electromagnetic

•Distance, conductivity

•PCB technology

excitation coilpickup coil

standard Printed Circuit board

IMT Microtechnique

Hannes Bleuler EPFL

Transverse Flux Sensor

Excitation frequ.20 kHz to 3 MHz

depending on electr.& magnetic propertiesof target material

Potential for high precision since there is averaging over large target area.Unaffected by low frequ. & static fields.

IMT Microtechnique

Hannes Bleuler EPFL

Simple structure: Easy to adapt to harsh environements (hot, UHV, corrosive, liquid)

• Little effect of temperature:Has been made for T up to 500 °C

• UHV compatibility!In these cases not PCB, but screenprinting on Alumine substrate, Ag–Pd conductors

IMT Microtechnique

Hannes Bleuler EPFL

for Local Measurements

Other example

IMT Microtechnique

Hannes Bleuler EPFL

Just like an actuator, a sensor is basically a transducer from one form of energy to another

Input powere.g. mechanical

Output powere.g. electrical

Losses

Disturbances

IMT Microtechnique

Hannes Bleuler EPFL

Piezoelectric transducers:

Piezo as an actuator:charge –> strain –> stress

Piezo as a sensor:stress –> strain –> charge

IMT Microtechnique

Hannes Bleuler EPFL

Piezoelectric materials

• quartz (weak)

• salt (very weak)

polycrystaline ferroelectric ceramics:

• BaTiO3,

• Lead Zirconate Titanate (PZT)

IMT Microtechnique

Hannes Bleuler EPFL

Basic mechanism: Stress –> strain –> charge

• Also charge –> strain (actuator)

• complex geometry (polarisation direction, strain tensor, shear…)

• small displacements, high forces, high voltages(µm to tens of µm for cm size PZT, 100s of Volt)

• nonlinearity, hysteresis

• Ceramics –> brittle –> prestress