Piezo Pumps, Microdosing, Biohandling, Computer Aided Surgery, Microscopy

Medical Design and Drug Research

Piezo for Motion Control in

Medical Motor, Medical Actuator, Medical Pump, Sterile Pump, Piezo Pump

Bio-Medical EngineeringW W W. P I . W SW W W. P I . W S

Flexure Lever Actuators

PiezoWalk® Linear Motors

Ultrasonic Linear Motors

Types of Piezo Actuators

Flexure Guiding System Response <1 msec Travel to 2 mm, Compact

Long TravelFast: 350 mm/secLow Profile, Self Locking

All: Sterile, Low Power, No Lubricants, Non- Magnetic, Vacuum Compatible; High Resolution: Sub-Nanometer to Sub-Micron

Not all Piezo Motors are Created Equal

Direct Actuators: Z-Stacks, Shear (X, XY)

Direct Motion = High Force & Very Fast Response (to Microseconds)

Travel Range typically 10µm to 300µm Z, X, XYZ Motion No Wear & Tear

Long TravelHigh Force Self Locking

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S S u E 4 3

Microdispensers for nanoliter dosing are used in the manufacture of microar-

rays and lab-on-a-chip systems as well as in researching active agents. They

must be able to generate perfect droplets, taking into account the viscosity

and surface tension of the media and the dosing speed. Misting, satellite

formation on impact or dripping must be reliably prevented.

Piezo Actuators Are the Driving Force:

Nanoliter Dosing for Biotechnology, Diagnostics and Industry

Piezo-Driven Direct Displacement: PipeJet Technology

The best conditions for this are provided by the PipeJet™ technology developed by Biofluidix, which uses piezo-driven direct displacement for the dosing. The nanodispensers allow non-contact and flexible dosing of liquids in the volume range from a few nanoliters to several microliters per second.

TOPICS P I E Z O N A N O P O S I T I O N I N G

The PipeJet dosing principle: The valveless method is based on the piezo-driven direct displacement of the liquid by an elastic polymer tube with a well-defined internal diameter (Photo: Biofluidix)

Bio-Medical EngineeringW W W. P I . W SW W W. P I . W S

TOPICS P I E Z O N A N O P O S I T I O N I N G

The piezo-driven direct displacement method of the PipeJet™ dispenser uses a fluid line made from an elastic polymer tube with a well-defined internal diame-ter which is not firmly attached to a piezo actuator. In order to provide suf-ficient force for force for the precise dosing of difficult media, Biofluidix employs a PI Ceramic multilayer PICMA® piezo stack compressing the polymer tube via a piston with 100 times the force of the conventional ring actuators. The particular volume is controlled via the amplitude of the piezo actuator. The dispenser is used in clinical diagnostics in Lateral Flow Assays, which are test strips requiring a specific dosage of fluids.

Fast, Precise and Durable: PICMA®

One of the key components in the dis-penser is the P-885 PICMA® piezo stack, because of its high force, precise dis-placement controllability (to nanome-ters) and fast response. Its effect on the fluid-filled dosing tube causes the dro-plet to break away determining the pro-perties of the drop. The actuators can also be used in multi-channel applicati-

ons, where every channel can be con-trolled individually and the separation between the dispensing points is at least 9 mm. The modules are suitable for droplet volumes between 5 nL (nanoli-ters) and 60 nL with a dosing frequency of up to 100 hertz.

The high repetition rate puts extra high demands on the reliability of the actua-tors. PICMA® stack actuators were desi-gned for consistent performance over billions of cycles. Long term results are shown in. They meet and exceed all the requirements of microdosing or pum-ping applications and operate with short response times down to the microsecond range and sub-nanometer resolution. Both the response and stroke can be controlled with extreme precision allo-wing for highly random motion profiles. The fast response makes it possible to implement short dosing cycles. The dosing processes can be precisely con-trolled by the variable stroke.

PI piezo actuators have gone through seve-ral billion cycles in endurance tests without measurable changes in their behavior (Photo PI)

dispensing element

“clip-on” tube guide

PI Piezos

PICMA®: Patented, fully ceramic encapsulated multilayer piezo stack design provides maxi-mum operating life: (Photo: PI)

electrical interface

piston

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Miniaturized Technology

Displacement pumps are used world-wide in many diverse branches of in-dustry. Increasing miniaturizationmeans the market for their smaller“relatives“ is also growing: Micro-dispensers take on distribution anddosing tasks where small volumes inthe milliliter or microliter range haveto be controlled

Wide Range of Applicationsfor Promising Technology

In laboratory and medical engineer-ing, biotechnology or chemical analy-sis, tiny dispensers accurately doseactive substances or medicines.Micropumps take care of the removalof reaction gases in closed processes.Industrial machines benefit from thepossibility of using micro-valves toapply lubricants such as oils or greasein a decentralized way at the pointwhere they are required – in an eco-nomical, precise and automated way.

Piezo is the Driving Force

The design is based on the familiarprinciples of diaphragm pumps andvalves and also makes use of theperistaltic principle. The miniaturizeddrives are based on piezoelectricactuators in various shapes anddegrees of integration.

Adapted for Precision & Force

The properties of the pump media –viscosity and drop size, for example –determine the different forces whichhave to be applied and hence the sizeof the piezo actuator used. The piezodisplacement is a variable parameterwhich controls the dosing volume.With micropumps, the frequency alsodetermines the flow rate that can beachieved.

Piezo for Micro Pumps & ValvesPrecision Dosing of Small Volumes

The principle of peristaltic pumping makesdirectional valves obsolete; the pumpingdirection in this case is specified by the orderin which the individual actuator elementsare driven.

Micro-diaphragm pumps operate in a similarway to piston pumps, but the medium to betransported is separated from the drive by adiaphragm. Passive inlet and outlet valvescontrol the pumping direction. Piezo elementsin disk form which are mounted directly ontoa metal disk make ideal drive systems formicro-diaphragm pumps: This drive solutionoccupies extremely little space, and the piezodisplacement can be very finely adjusted,allowing the pumped volumes to be veryprecisely defined.

Working principle of a diaphragm valve.Usually, valve applications require higherforces than pumps.

Variety of piezoactuators and lever-amplified systems

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Reliable and Fast

The special properties of the piezoceramics permit flexible flow rates of afew tenths of a microliter to severalhundred milliliters per minute at pump-ing frequencies up to the kilohertzrange accompanied by high dosingaccuracy. The switching times of a fewmicroseconds are significantly fasterthan those of magnetic designs. Thepiezo drives have the power and stiff-ness values required to also workagainst pressures of up to tens of barsand are thus also suitable for use withmore viscous media.

Piezo ceramics are fundamentally verysimple to use and integrate; their com-pact size even makes them suitablefor integration into so-called labs-on-a-chip.

Variable Shapes, Different Forces

Simple piezo ceramic disks or rings aremounted onto a metal or silicon diskand, as the most compact benderelement, thus control the opening orclosing of diaphragm pumps or valves.

An alternative is to use piezo benderelements, which PI Ceramic canmanufacture in almost all shapes andforms.

Small piezoelectric tubes have alsobeen used for a long time for the drop-

on-demand method as used in ink-jet-printing, for example. Piezo patchesor, for greater forces, piezo stack actu-ators operate peristaltic pumps.

The corresponding drive electronicsare compact and can even be used inportable instruments – for dosingmedication, for example.

In micro-valves, particularly where viscousliquids are processed with higher pressures,translational actuators with and without prestresscan be used. Where larger strokes of the valvetappet are required, the actuator stroke can beamplified by levers.

Piezo Actuators: Fast, Reliableand Easy to Integrate

Piezo actuators convert electricalenergy directly into mechanical energyand vice versa. Travel ranges of up toone millimeter can typically beachieved with resolutions down to thenanometer range. High dynamics withfrequencies of up to several kilohertzare also achievable. The movement isbased on crystalline effects and sothere are no rotating parts and no fric-tion; piezo actuators are thereforemaintenance-free and non-wearingand, because no lubrication is required,they are vacuum compatible. They canmove large loads and have a very com-pact design.

Piezo: Compact─Fast─ High-DynamicsPiezoceramic Elements Drive Micropumps

PI offers a large selection of different piezoelectric components: disks, tubes, benders, patches…

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pi_091227_news40_uk.qxp 19.11.2009 9:13 Uhr Seite 6

The continuing miniat urization in medical engineer ing places ev er in-

creasing demands on the components. Piezo drives are the solution for many

motion control applications; the piezo ef fect ef ficiently generates fast

and precise motion while requiring very little space.

Custom piezo disks precisely dose liquidsand gases in the ThinXXS micropump.(source: thinXXS Microtechnology AG)

Efficient Aerosol Generation with

Piezo Elements

The treatment of respiratory diseasesoften involves medications beingadministered directly with atomizers.One method of atomization is togenerate very fine droplets with theaid of ultrasonic piezo ceramics.

Specially shaped piezo disks excite a stainless steel diaphragm withseveral thousand holes to executeultrasonic oscillations at more than100 kilohertz: this produces par-ticularly homogenous aerosols,allowing the medications to be dosedaccurately and administered in amore targeted way.

An annular piezo disk serves as an ultra-sonic transducer to produce the aerosolin the atomizer head of the eFlow® rapidElectronic Nebulizer series.(source: Pari Pharma GmbH)

Piezo elements from PI Ceramic. The broad spectrum of standard products issupplemented by custom engineered products, with the shortest-possible time-to-market

Moreover, the piezo technologyreduces the time required to atomizemedications by up to 50 % comparedto conventional systems increasingthe quality of life for patients withchronic diseases.

Piezo ceramics meet the specialhygiene requirements in medicalengineering; the aerosol generatorscan be sterilized at high tem-peratures, even in autoclaves. Theultrasonic operation is soundless for humans, and the low powerconsumption of the piezo com-ponents allows battery operation.

Piezoelectric Drives in Microfluidics

Piezo-driven microdispensers, i.e.micropumps and microvalves, candose minute volumes down to themicroliter range with very high ac-curacy. Disk-shaped piezo elementsmounted directly onto a metal micro-diaphragm provide the highly dy-namic drive for precision miniatureliquid or gas pumps. Due to theseparation of drive and mediumthrough the diaphragm, interferencewith the pumped media is completelyavoided.

Lab-on-a-chip applications are madepossible by the minute dimensions.

Medical Engineering News:Driven by Piezo

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5

Movement in Micropositioning Technology

Low Cost PI Drives for M-228 StepperMikes offer a low-

Automation and Handling cost alternative.

Setting valves, adjusting components, pick and place ...

The specifications for these types of These requests have led to the de-motion control applications dif fer velopment of the M-228 and M-229 M-228 and M-229 are character-

ized by the following data:from those PI is used to dealing with linear actuators. These have travelin only two respects: Not one nano- ranges of 10 or 25 mm and use classic ■ bi-directional repeatability:meter but 10 micrometers and more stepper motors – with either a com- 5 µmare suf ficient for the positioning pact (motor + gearbox) or cubic (direct ■ unidirectional repeatability: accuracy. The price plays a muc h drive) configuration. Despite the low 2 µmmore important role, however. prices, the user need not forego

■ resolution 80 nm (with C-663useful features such as mechanicalGood quality and good service are Mercury™ Step controller) position display, a non-rotating spindletwo things which customers do not ■ backlash: 5 µmor safety limit switches.want to forego, which is why PI has

■ speed: 2 mm/secrecently received many requests from

■ positioning accuracy: 10 µmthe market segments mentioned.

Dispenser for Bio-Handling

Small and fast is not only a require-ment in classical micropositioningtechnology, however. Piezo ultrasonicmotors are also extremely well suitedto applications where the accuracyrequirements are not quite so demand-ing – in the range between 5 and 100 micrometers for example, whichis usually suf ficient for industrialautomation and handling tasks.

PI has developed the low cost M-664KCEP dispenser dri ve withPILine® piezo ultrasonic motors forthis kind of application. Eight or moreof these dri ves stac ked together can mo ve pipet tes ver tically and

independently of each other in orderto dispense liquids into well plates. A single actuator is only 9 millimeterswide to matc h the standardiz ed sample holder.

The M-664KCEP co vers the travelrange of 50 millimeters in less than250 milliseconds and generates forcesof up to 4 N. The resolution of thepositioning sensor is matched to theapplication and amounts to 5 micro-meters.

PI is increasingly employing PILine® piezo ultrasonic drives in its positioning

stages as an alternative to motor/leadscrew designs – particularly when the

stages must be small and fast.They achieve positioning accuracies of up to

0.1 µm and speeds of up to several 100 mm/s.

Stack of 8 M-664KCEP linear actuators,shown with well plate. The integrated

ceramic piezomotor provides highspeeds of more than 200 mm/sec.

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N-310 NEXACT® PiezoWalk® lin-ear drives feature travel rangesof 20 mm and push/pull forcecapacities to 10 N in a compactpackage of only 25 x 25 x 12 mm.With their high resolution,NEXACT® drives, are ideal forhigh-precision positioning overlong travel ranges.

The N-310 can be operated inopen-loop and closed-loop mo-de (with the addition of an ex-ternal position sensor). A varie-ty of NEXACT® controllers facil-itates the integration into micro-or nanopositioning applications.

Advantages of PiezoWalk®

Piezo Stepping Drives

NEXLINE® and NEXACT® drivesoffer several advantages overtraditional drive technologies:� Resolution in the picometer

range� Compact dimensions� High drive forces from ten

newtons (NEXACT®) up toseveral hundred newtons(NEXLINE®)

� High-dynamics performancewith sub-microsecond res-ponse

� Self-locking when powereddown; no holding current

� Zero backlash, no wear ormaintenance, no mechani-cal components like gearsor leadscrews.

� Non-Magnetic and VacuumCompatible Operating Prin-ciple

Working Principle forApplication Flexibility

NEXACT® PiezoWalk® technolo-gy overcomes the limitationsof conventional nanoposition-ing drives and combines virtu-ally unlimited travel rangeswith high stiffness in a verysmall package. Furthermore,NEXACT® actuators providepiezo-class resolution (farbelow one nanometer) andmillisecond responsiveness.The special drive designreduces the operating voltageto 45 V and below.

In operation, piezoceramicbending elements act on therunner, which is connected tothe moving part of the appli-cation. The length of the run-ner determines the travelrange. Force capacity, resolu-tion and velocity are deter-mined by the piezo geometryand drive electronics and arescalable. To move the runnerover longer distances the step-ping mode is used, whereas fordistances smaller than onestep, the linear (analog) modeenables high-dynamics posi-tioning with resolutions farbelow one nanometer.

Wear- and Maintenance-Free

In contrast to ordinary DC orstepper motor drives, thePiezoWalk® drives effect linearmotion directly, without theneed to transform rotation withmechanical elements such asgears, leadscrews andnuts. Therefore, mechanical

limitations such as backlashand wear are eliminated andthe drive is maintenance-free.

Self-Locking PiezoWalk® PiezoStepping Drive

NEXLINE® and NEXACT® exhib-it high stiffness and are self-locking even when powereddown due to the clampingaction of the piezo actuators inthe mechanics. This entailsnanometer position stability atrest, with no heat dissipationor servo-dither.

Controller and DriveElectronics Optimizedfor the Application

NEXACT® actuators requirespecial drive electronics tocontrol the complex steppingsequences. The E-860 seriesNEXACT® controllers are a-vailable in different open-andclosed-loop versions. Forexample, the E-861 includes acomplete NEXACT® servo-con-troller with low-noise, 24-bitdrivers and a powerful DSP. Italso comes with ample soft-ware for easy integration andhighly effective computer con-trol. For applications which donot require the highest reso-lution lower-priced drive elec-tronics, ranging all the way toOEM boards, can be ordered.

The products described in thisdocument are in part protectedby the following patents:German Patent No. P4408618.0

Non Magnetic Piezo MotorsCompact, High-Speed PiezoWalk® Drive

� 20 mm Standard Travel Range, Flexible Choice of theRunner Length

� Compact and Cost-Effective Design� 0.03 nm Resolution**� To 10 N Push/Pull Force� Low Operating Voltage� Self Locking at Rest, No Head Dissipation,

Nanometer Stability� Non-Magnetic and Vacuum-Compatible Working Principle

Application Examples

� Semiconductor technology

� Wafer inspection

� Nano lithography

� Surface MeasurementTechnique

� Profilometry

� Microscopy

� Motion in strong magneticfields

N-310 Actuator with E-861 Servo-Controller (integrated drive electronics)

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Technical Data

Tolerance

Active axes XMotion and positioning

Travel range 20 mmStep size (in step mode) 5 nm to 5 µm

Travel range in analog operation 7 µm max.Open-loop resolution 0.03 nm** typ.

Step frequency 1.5 kHz* max.Max. speed 10 mm/s* max.

Mechanical propertiesPush/Pull force (active) 10 N max.

Drive propertiesDrive type NEXACT® linear drive

Operating voltage -10 V to +45 VMiscellaneous

Operating temperature range 0 to 50 °CBody material Stainless steel, non-magnetic

Mass 50 g ±5 %Cable length 1.5 m ±10 mm

Connector HD Sub-D connector15 pin, single channel

Recommended controller/driver E-860-series (see p. 1-20)

*Depending on the control electronics.**Depending on the drive electronics. 1 nm with E-861.

Translation stage with N-310 NEXACT® drive.The positioner offers 20 mm travel range with

an encoder resolution of 25 nm

N-381 piezo stepper linear actuator for samplepositioning and manipulation provides long travel,high speed and very high resolution;

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The innovative N-111 NEX-LINE® OEM linear actuators arecompact actuators for nanopo-sitioning with travel ranges to10 mm, high resolution, andgenerated forces to 50 N. Theoperating principle is based oncoordinated motion of a num-ber of highly preloaded linearand shear piezo elements act-ing on a runner. NEXLINE®

drives thus combine long trav-el ranges with piezo-class pre-

cision. For closed-loop opera-tion without an additional posi-tion sensor the N-111.2A isequipped with a linear encoderthat provides 5 nm resolutionover the full travel range. Inopen-loop operation positionresolution down to 25 pico-meters can be achieved by useof a high-dynamics analogmode.

One Working Principle –Different Operating Modes

NEXLINE® PiezoWalk® drivesovercome the limitations ofconventional nanopositioningsystems in their combinationof long travel ranges and highresolution and stiffness. Thepiezoceramic clamping andshear elements act directly ona moving runner that is cou-pled to the moved object.While in full step mode the run-ner can be moved over largerdistances with maximumvelocity, nanostepping modeallows uniform motion withhighly constant speed. In open-loop operation any positionresolution may be achievedwhich only depends on thestability of the control signal.Analog operation over a dis-tance of less than one stepenables high-dynamics posi-tioning with resolutions farbelow one nanometer.

Choice of Controllersfor Optimization

NEXLINE®operation is support-ed by two motion controllermodels providing different fea-tures. The E-755 controlleroffers full functionality fornanometer precise positioning.The E-712 supplies moresophisticated linearization

algorithms resulting in verysmooth motion with highlyconstant velocity. It can alsoprovide higher speed withmaximum force.

Patented Technology

The products described in thisdocument are in part protectedby the following patents:German Patent No. 10148267US Patent No. 6,800,984

NEXLINE® Working Principlefor Application Flexibility

NEXLINE® PiezoWalk® drivescan be used wherever highloads must be positioned veryprecisely over long distancesand then perhaps subjected tosmall-amplitude dynamic ad-justment, as for active vibra-tion control. By varying thecombination of longitudinaland shear piezo elements, thestep size, dynamic operatingrange (analog travel), clampingforce, speed and stiffness canall be optimized for a particularapplication.

NEXLINE® OEM Linear ActuatorNon-Magnetic and Vacuum-Compatible Working Principle

� Travel Range 10 mm� Resolutionto 0.025 nm Open-Loop, 5 nm Closed-Loop� Up To 50 N Force Generation and 70 N Holding Force� Self Locking at Rest, No Heat Generation� Non-Magnetic and Vacuum-Compatible Working Principle� Cleanroom Compatible

N-111 compactOEM nanopositioning actuator.In principle the movement bypiezo steps allows an infinitetravel range

N-216 NEXLINE® High-Load Actuator. Feed motion is realized by piezo steppingmotion which allows basically unlimited travel ranges with nanometer accuracy

� Travel Range 20 mm� Resolutionto 0.03 nm Open-Loop, 5 nm Closed-Loop� Up to 800 N Holding Force� Self Locking at Rest� Non-Magnetic and Vacuum-Compatible Working Principle� Cleanroom Compatible

NEXLINE® High-Force Non-Magnetic Linear Actuator

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M-850 Hexapod Advances Research in Dental BiomechanicsFrom Christoph Bourauel and Ludger

Keilig–Department for Orthodontics at

the Rheinischen Friedrich-Wilhelms-

Universität, Bonn.

Dental biomechanics deals with theinteractions between dental materi-als, treatment instruments or den-tures and the reaction of teeth, bio-logical tissues, etc. to mechanicalstresses. A wide spectrum of forcesystems occur here with masticatoryforces exerting loads to 380 N andtorques to several Nm.

At the same time, movements of several orders of magnitude areinvolved: orthodontic equipment canchange the position of teeth by up toseveral mm, whereas—during masti-cation—teeth are deflected by lessthan 100 µm and implants by as littleas a few microns or less. These com-binations of small forces with largedeflections, on the one hand, andlarge forces and extremely smalldeflections on the other , represent achallenge with respect to the biome-chanical metrology.

To deal with this challenge, theDental Clinic of the University ofBonn designed the HexMeS (Hexa-pod Measuring System) based on theM-850.50 Hexapod. The ability tomove in 6 degrees of freedom andthe combination of small dimensions,very high stiffness and resolution ofless than 1 µm (1 arcsec) were the keyreasons for choosing the M-850 sys-tem.

HexMeS also features two 6-compo-nent force/torque sensors for theHexapod with measuring ranges of12 N (120 Nmm) and 130 N (10 Nm)respectively and an optical detectionsystem equipped with 3 CCD cam-eras.

Because of its high stiffness (100N/µm), sample deflections can usual-ly be calculated directly from theHexapod motion.

For high-load testing—simulations of mastication in the 100 N range—the optical portion of the HexMeS is used. It resolves sample deflectionsto 0.7 µm / 0.2 arcsec.

The M-850-based HexMeS currentlyrepresents one of the most flexiblemeasuring systems in the field ofdental biomechanics. Its efficiencyand the broad spectrum of its appli-cation have been demonstrated in awhole series of experimental investi-gations into dental implants, tele-scope crowns and orthodontic pros-theses.

Load testing of a double crown.

3D position sensing PC(CCD cameras)

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-850

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Sample

Sample holder

Sensor electronics

Hexapod controller

HexMeS block diagram.

www.pi.ws

Click here for Article on Hexapods in Spine Surgery

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In medical engineering, modern PILine® ultrasonic piezo motor drives are

opening up applications which were impossible using classic electric motor

leadscrew systems. Due to the piezoelectric effect and the direct creation of

linear motion, PILine® drives are not only faster, lighter and more compact

than conventional motorized drives, but they can also be made non-magnetic.

They achieve resolutions of 20 nm (0.02 µm) and v elocities of up to 1 m/s.

Their travel range is basically unlimited, and they are available in a number of

different integration levels to match the desired (OEM) application. Medical

engineering provides an up-to-date example.

Issue 37

OCT: Piezo Motors in Medical DesignUltrasonic piezo linear drives—new application in non-invasive medical technology

Piezo t echnologyenables fast, com-

pact, high-resolutionOCT scanner

In addition to the clas-sic, in vasive, punc hbiopsy technique, there

are a number of only par-tially satisfactory non-invasive

procedures in clinical and cos-metic researc h for properly cate-gorizing skin changes. Those basedon ultrasound do not provide goodresolution, and confocal microscopycannot penetrate sufficiently belowthe epidermis. Now, however, thereis a practical alternati ve: the newSkinDex scanner – developed by ISISOptronics in Mannheim, Germany –combines the advantages of ultra-sound and confocal microscopy.

Piezo · Nano · Positioningnews

Bio-Medical EngineeringW W W. P I . W SW W W. P I . W S

The SkinDex scanner is based on the technology of optical coherencetomography (OCT) and examines thetissue on and under the skin surfacenon-invasively. The results obtainedare extraordinary. The informationcontained in the 2-D and 3-D sectionalimages is comparable to that of a histological examination.

OCT uses the basic transparency ofskin together with the interferencefringes obtainable with white light.The optical paths are made up ofoptical fibers.

Exact positioning for precise results

To enable creation of 2- and 3-dimen-sional images from interferencepatterns, the optical fibers must bemoved both axially and laterallyduring the scan. This task requirespositioners capable of the highestprecision. Ultimately, it is the perfor-mance of the drives which determinethe system resolution and hence thequality of the images.

A PILine® P-661 OEM motor is usedto position the reference-arm mirror(depth parameter). This motor waschosen primarily because of its com-pact design and, considering its size,its high force capacity of 2 newtons(0.5 lbf). Total travel is 2 mm, the po-sition resolution in this application30 nm (0.03 µm, 1.18 micro-inch).

As the images are recorded sequen-tially, the high speed and excellentdynamic response of the drive is agreat advantage. As a result, theSkinDex needs only a few seconds to generate its highly informati veimages. The lateral motions of theoptical fiber s in the sensing arm executing the surface scan are alsoperformed by a PI drive.

In this case it is a PIHera® P-622.2CD,

a flexure-guided, 2-axis, piezo nano-

positioning system, which provides

a resolution of 1 nm (0.001 µm, 0.04

µ-inch) and covers an area of 250 x

250 µm. Piezo-motor drives have thus

again contributed to an innovation

from which many people will benefit

in the future.

Continued from page 1

Integration levels in PILine® ultrasonicpiezo motor technology: from 8-mmdrives, through the successful Rod-Drive linear drive, to integrated multi-axis systems.

The SkinDex scanner based on OCTtechnology for non-invasive but reliableexamination of the tissue on and underthe skin surface (photo ISIS Optronics).

A look under the skin of the ball of thethumb. Even the untrained eye canrecognize the spiral-shaped sweat-gland ducts.

3-D OCT image: Individual laminar and cylindrical structures such as largerblood vessels are visible under therough skin surface.

White-light interferometry is the basis of OCT. Using optical fibers, light isdivided into a sensing and a referencebeam. After being reflected by the target(i.e., a cutaneous structure) and thereference mirror respectively, the beamsare recombined and enter the detector. An interference signal pattern results(photo: ISIS Optronics).

Working principle of an ultrasonicpiezo motor drive.

Mountingplattform

Bearing

Gluedfrictionbar

Friction tip Piezo Actuator(stationary)

exitationelectrodes

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Bio-Medical EngineeringW W W. P I . W SW W W. P I . W S

nano™ Precision PositioningSystems for Microscopy

PI nano™ series comprising E-545 controller, P-545 piezo system and M-545 manual stage

The P-545 piezo stage provides 200 µmtravel per axis with sub-nanometerresolution. PI nano™ features a largeraperture for 1x3 ‘‘ slides.

Due to their low profile, PI nano™ piezo stages can easily be integratedinto existing microscope setups

Scanning microscopy methodssuch as single molecule fluo-rescence microscopy provide highlateral positioning resolution evenbelow the limitations of the nu-merical aper ture. They require correspondingly precise samplepositioning with resolutions in the range of a few nanometers. ThePI nano™ system is designed sothat its performance data andrange of functions cor respondexactly to these requirements.

■ Piezo-based XY/XYZ nanposition-ing system with 200 µm travel for planar scanning and verticalfocusing/z-stack acquisition

■ Optional 25 x 25 mm coarse-positioning stage with manual orstepper motor drives, preloadedfor high stability

■ Nanopositioning system withlarge aperture and 20 mm lowprofile for easy integration intothe microscope

■ Mechanical compatibility withinverted microscopes from Zeiss,Nikon, Leica, Olympus

■ Accessories and sample holders

■ Powerful controller with USB andEthernet Interface, and extensivesoftware support

The new PI nano™ positioning sys-

tem from PI was specifically designed

for applications in optical microscopy.

The core component of the PI nano™is an XY or XYZ piez o nano-positioning stage with a low profileof only 20 mm and a large centralaperture for transmitted-light micro-scopy. The stage is equipped withlong-life PILine® piezo actuators andprovides travel ranges of 200 µm withnanometer positioning resolution.It comes with a matched piezo con-troller featuring a 24-bit interface(USB, Ethernet and RS-232) and ahigh-bandwidth analog interface.The contoller is suppor ted by allmajor image acquisition sof twarepackages.

An optional, manual XY stage forcoarse sample positioning can beequipped with stepper motor drivesif required. The preloaded XY stagecan be mounted directly onto themicroscope and it pro vides the stiffness required to carry a highlydynamic piez o nanopositioningsystem.

pi_091227_news40_uk.qxp 19.11.2009 9:13 Uhr Seite 4

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Single molecule analysis provides de-

tailed information on chemical char-

acteristics or biological functions, but

the detection of individual molecules

is by no means easy. The extremely

sensitive method of laser-based fluo-

rescence analysis is thus used t o

increase the signal-to-noise ratio.

Confocal microscope with singlemolecule sensitivity

PicoQuant of Berlin, Germany sup-plies the MicroT ime 20 0 confocal,time-resolved fluorescence micro-scope for this task. “This system usesthe time-cor related single photoncount for its data acquisition and canproduce both 2D and 3D images”explains Dr. Felix Koberling, Head ofSystem Development at PicoQuant.This makes it possible to realiz e avariety of the methods currently usedin fluorescence microscopy such asFCS (Fluorescence Correlation Spec-troscopy) and FRET (FluorescenceResonance Energy Transfer) as wellas so-called fluorescence lifetimeimaging. Here not only the measuredintensity but also the respective fluo-rescence lifetime is used for thevisualization and quantification inorder to analyz e intracellular pro-cesses even in living cells. Its modu-

lar design means the fluorescencemicroscope is also very flexible inadjusting to different applications.(www.picoquant.de)

Maximum r epeatability thanks t odynamic digital linearization

The P-733.2CD piezo stage was thescanner system of c hoice for themicroscope. With a travel range of 100 x 100 µm and sub-nanometerresolution, this high-accuracy nano-positioning system matches the re-quirements of fluorescence micro-scopy perfectly.

Issue 39 · April 2009

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Moving samples into the spotlight:

Nanopositioning systems in fluorescence microscopy

Piezo · Nano · Positioningnews

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If the sample cannot be mo ved because it is enclosed in an environ-mental chamber, for example, thesame positioning system can be usedto the microscope objective instead.In all cases, however, the integrateddirect-measuring capacitive sensorsallow the scanner to produce an ac-curate determination of the actualposition value. The first step is typi-cally to record the image of a sampleby scanning an area quickly before in a second step indi vidual points of interest are analyzed in detail. Inorder to return to the exact locationof these points within a few nano-meters, an advanced digital controlalgorithm (DDL) w as devised. TheDynamic Digital Linearization algo-rithm improves scanning linearity, i.e. repeatability by up to three ordersof magnitude compared to conven-tional PID (proportional, integral, deri-vative control).

The third dimension: Additionalfocus adjustment

The P-721.CLQ PIFOC® Z-drives areused for three-dimensional images.They provide millisecond responsetimes and their flexure guiding and

capacitive sensors enable very accu-rate positioning, even when the travelranges are relatively large. “PI’s piezo-based nanopositioning systems make

a decisi ve contribution to the fact that we can achieve very high-qualityresults with our MicroTime 200”, saysKoberling in conclusion.

Single molecule image of a mixture of immobilized Atto665- and Cy5-molecules.The single molecules can be distinguished by the fluorescence lifetime.(Photo: PicoQuant)

Fluorescence intensity image (left) and fluorescence lifetime image of a liver cancercell, stained with the NBD dye to analyze the organization of lipids. In the image onthe right, the lifetime can be used to clearly identify different lipid structures. (Photo: PicoQuant)

The P-733 piezo-based nanoposition-ing system provides a travel range of 100 x 100 µm. The optional Dynamic Digital Linearisation (DDL) features fordigital motion controllers improves the scanning linearity by a factor of to 1000. Tracking error and phase lag arereduced to almost non noticeable values. (Photo: Physik Instrumente (PI))

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PIFOC® Revisited: P-737 Piezo-Z Microscopy Specimen Scanning Stage

PIFOC® P-737 high-speed ver ticalpositioning systems are designed forintegration into motorized XY micros-copy stages of leading manufacturerssuch as Märzhäuser . While the XYstage positions the sample, the piezoflexure-based P -737 mo ves thesample along the optical axis to adjustthe focus quic kly and precisely .Vertical stepping with nanometer pre-cision takes only a few milliseconds.The large aper ture is designed toaccommodate a variety of specimenholders including slides or multiwellplates.

High-speed Z-steps for fast focuscontrol and imaging

The immediate response of the solid-state piez o dri ves enables rapid Z-steps with typically 10-to-20-times-faster step-and-settle than classicalstepper motor drives. This leads tosignificantly higher image acquisitionspeed and throughput. The P-737 isavailable with travel ranges of 100 or250 µm and offers a choice of feed-back sensors between strain gauge ornon-contact, capaciti ve positionsensors, depending on the accuracyrequirements.

The P-737 together with the E-625 piezo-controller, offers a cost-effectivesystem for high-speed, high-resolution positioning of microscopyspecimens. The controller features a choice of a 20-bit digital interface ora broadband analog interface for the target position.

The capacitive-sensor-equipped version can also be operated with thesophisticated E-753 digital servo-controller. The main advantage of thiscontroller is its adaptability to changing load conditions on the piezostage. No matter what load is applied, the system can always provide anoptimum combination of speed, settling time and resolution.

Analog or Digital Systems

PIFOC® objective positioners and scannersare available with travel ranges of up to400 µm. QuickLock thread adapters enablefast mounting of the PIFOC® on the micros-cope and flexible replacement of objective

Settling time is in the 10 ms range –here, 1 µm steps

PI is the inventor of high-speedPiezo-Z objective steppers. Todaythe term PIFOC ® is practicallysynonymous with all high-reso-lution vertical drives for micro-scope objectives. Depending onthe application, it can be advan-tageous to adjust the sampleinstead of the objective. While nosample stage can beat the speedof the fastest PIFOC ® objectivepositioners (due to the stiffer andmore compact design), the P-737stage allows for con venient Z-stack imaging with multipleobjectives and very high through-put. Im both cases the ef fectremains the same: the focal planemoves through the sample. Thisis why the P-737 is also marketedunder the PIFOC® trademark.

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Piezo = nano = expensive?

Piezo actuators can do a lot more than“just“ precision. Their excellent dyna-mics and high force play a crucial role inmany areas, while the (nanometer) pre-cision is of lesser importance: e.g. forfast switching, vibration cancellation, orto adjust tools in machines.

In these applications the piezo actuatoris one – if not the only – solution and inthe case of the new PiezoMove OEMactuators, at a very attractive price.

PiezoMove OEM actuators: Applymotion, how and where it is required

PiezoMove actuators combine guidedmotion and long travel ranges up to1 mm and provide precision in the 10 nmrange if ordered with the position sensoroption. They are very compact, easy tointegrate, require no maintenance andprovide service life of Billions (109) ofcyles.

PI supplies a variety of standard integra-tion levels and also customized versions:From simple piezo stack componentsand preloaded linear actuators throughto 6-axis positioning systems with sub-nanometer precision.

PiezoMove: Moving, Positioning, ScanningMicrofluidics, Biotechnology, Medical Engineering, Adaptronics

Application fields

Microfluidics:

Valves, pumps, microliter and nanoliter dosing

Biotechnology:

Cell manipulation, patch-clamp, microarrays, nanoliter dosing, dispensers,microstructuring with imprint processes

Medical engineering:

Diaphragm pumps, valves, dosing, injection, sample handling

Mechatronics, adaptronics:

Active structures, vibration isolation, active tools, structure deformation

Laser technology, metrology:

Cavity tuning, adjustment of optics or slit widths, sample positioning, beamcontrol

3 Actuator Families

P-601: Travel ranges to 400 µm, slight tilt

Linear actuators can be used in micro-valves, particularly where viscous liquidswith a tendency towards higher back pressures are processed; where larger strokesof the valve tappet are required, with lever amplification as well

P-602: Travel ranges to 1000 µm, slight tip and tilt, high stiffness

P-603: Travel ranges to 500 µm, slight tilt, cost-optimizedfor high quantities

For more information visit http://www.pi.ws

P-882 · P-888 PICMA®

Multilayer Piezo Stack ActuatorsP-601 PiezoMove Linear Actuator

P-712 Low-Profile Piezo Scanner

E-621.SR Motion Controller Module

Piezo Actuator / Description Travel Range Guiding System Mechanical Levels Positioning StiffnessStage up to of Integrations Sensor

P-882 - P-888 PICMA® 30 µm - - optional SGS up to 200 N/µmMultilayerPiezo StackActuators

P-871 PICMA® Piezo 1600 µm - - optional SGS 0.02 N/µmBender Actuator

P-842 - P-845 Preloaded Piezo 90 µm - case, mechanically optional SGS up to 200 N/µmActuators preloaded

P-601 PiezoMove 400 µm flexure guiding motion amplifier, optional SGS up to 0.8 N/µmLinear Actuator system prevents mechanically

tip and tilt preloaded

P-602 PiezoMove 1000 µm flexure guiding motion amplifier, optional SGS up to 2.3 N/µmFlexure system provides mechanicallyActuator with straight motion preloadedHigh Stiffness with no tip and

minimum tilt

P-603 PiezoMove 500 µm flexure guiding motion amplifier, optional SGS up to 0.36 N/µmLinear Actuator system prevents mechanically

tip and tilt preloaded

P-712, P-713 Low-Profile 30 µm in X, XY flexure guiding motion amplifier, optional SGS up to 0.8 N/µmPiezo Scanner system provides mechanically

straight motion preloaded,with no tip and P-713 parallel-minimum tilt kinematics

P-611 NanoCube® 100 µm in flexure guiding motion amplifier, optional SGS up to 0.8 N/µmXYZ Piezo Stage up to 3 axes system provides mechanically

straight motion preloaded,with no tip and serial kinematicsminimum tilt

Low-cost Piezo Systems with Various Levels of Integration

Controller Function Positioning Sensor Number of Peak Output Current Peak Output PowerChannels

E-831 Piezo Amplifier - 1 100 mA (< 8 ms) 2 W without heat sink,5 W with additionalheat sink

E-610.00 Piezo Amplifier - 1 180 mA (< 15 ms) 18 W (< 15 ms)

E-610.S0 Motion Controller SGS 1 180 mA (< 15 ms) 18 W (< 15 ms)

E-621.SR Networkable Motion SGS 1, networkable 120 mA (< 5 ms) 12 W (< 5 ms)Controller Module up to 16

P-871 PICMA® Piezo Bender Actuator P-842 · P-845 PreloadedPiezo Actuators

P-611 NanoCube® XYZ Piezo Stage E-831 Piezo Amplifier E-610 Piezo Amplifier/Motion Controller

P-603 PiezoMove Linear ActuatorP-602 PiezoMove Flexure Actuatorwith High Stiffness

P-713 Low-Profile Piezo Scanner

For more information visit http://www.pi.ws

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Systems Thinking

PI provides a range of different controlelectronics for PiezoMove actuators.These range from solderable OEM piezodriver modules to advanced digital motioncontrollers.PI’s wide range of actuators and controlelectronics allows for an optimum matchof performance and cost for any applica-tion.In addition to standard products, modifiedor completely custom engineered solu-tions are available at competitive prices.The following parameters can be modifiedto suit an application:� Travel range� Dynamics� Force� Precision

PiezoMove: Travel Ranges to 1 mmEasy Integration and Adaptation

Different Piezo Solutions: Simple PiezoComponents to Complex (Nano)Positioning SystemsActuator: Piezo ceramic stack actuatorsare the driving force in many of PI'smotion systems. Piezo actuators canmove very rapidly due to their high stiff-ness; response times are as short asmicroseconds and scan frequencies upto several tens of kilohertz are feasible.The resolution is virtually unlimited,depending only on the electrical noise ofthe driver, making piezo actuators pre-destined for precision motion applica-tions. The displacement of basic actua-tors is limited to a few tens of microme-ters, however, and they need to be hand-led with care.Preloading and Decoupling AgainstLateral Forces: Encased piezo stacks canhandle higher forces. The housing candecouple the piezo ceramics from lateralforces. Integrated mechanical preloadingallows dynamic operation with higherloads.Guiding System: Piezo ceramic stacks donot move in perfectly straight lines. Forprecise linear motion, a guiding systemis required. Flexures guarantee the bestperformance because they provide fri-ctionless, backlash-free motion and unli-mited lifetime. If designed well, preloa-ding and decoupling of unwanted forcescan also be integrated without negativeeffects on the system stiffness.

Lever Amplification for Longer TravelRanges: The guiding system can bedesigned in such a way that it acts like amechanical lever and increases the dis-placement of the piezo ceramic stack.Lever amplifiers reduce the system stiff-ness and this is where experience paysoff. PI uses CAD modeling, FEA analysisand laser vibrometry for design optimi-zation and testing. Based on 3 decadesof experience with piezo flexure designPI actuators provide the best combi-nation of lifetime, stiffness, precisionand size.Sensor: Position feedback sensorsare available when absolute positioninformation is required. Strain gaugesensors (lower cost, accuracy to 0.5%)and capacitive sensors (higher precisionto 0.01 %) are available.Controller: The higher the demands pla-ced on the system precision, the largerthe role played by the motion controller.Open-loop actuators can be controlleddirectly via a voltage amplifier. To a-chieve maximum positional accuracyand scanning linearity, however, closed-loop control and digital control algo-rithms are indispensable.Multi-Axis Positioners are constructedas parallel-kinematic systems for thehighest possible precision, and control-led by advanced digital nanopositioningcontrollers.

PI Actuators Offer LongerService Life

The ceramic insulating layer prevents the penetrationof water molecules and reliably protects the sensitiveinternal electrodes from mechanical damage and dirt

Stack actuators Lever-amplified actuators Positioning systemsTravel ranges up to approx. 150 µm up to 1 mm up to 2 mmAxes moved one one up to three linear axes and three tip/ tilt axesSensors SGS optional SGS optional SGS or direct measuring capacitive sensorsLinearity up to 99.8 % up to 99.8 % over 99.9 %Guidance none flexures for rotations <10" flexures for rotations <2"Space required low low depends on featuresPrice low low depends on featuresIntegration effort high low low

Levels of Integration: From Stack Actuator to 6-Axis Stage

For more information visit http://www.pi.ws

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Nevertheless, control is 100 % com-patible to previous standard PIHexapods.

As with other parallel-kinematicspositioners from PI, the six high-resolution actuators are connecteddirectly to a single moving platform.The user is able to define the centerof rotation (pivot point) independentof platform motion with a simple soft-ware command.

In contrast to conventional, stacked,multi-axis systems, there is no accu-mulation of guiding and lever -armerrors.

The compact M-810 is smaller in diameter than a CD, but offers long travel ranges in six axes with excellent position resolution

Six Degrees of Freedom in a Small PackageNew Ultra-Compact Miniature Hexapod

The new M-810 miniature Hexapodcombines all advantages of PI’s otherproven parallel-kinematic systems inthe smallest of packages. With a dia-meter of only 10 cm and a height of

11.8 cm, the M-810 offers travelranges of up to 40 mm in the XY plane and 13 mm in the Z-

direction. Despite of its small size, the hexapod canreliably position loads of up to 5 kg at velocities of

10 mm/s.

The limited space necessitated the usage of new tec hnologies for encoders, motors and limit switches.

Physik Instrumente (PI) GmbH & Co. KG

Auf der Römerstraße 1D-76228 Karlsruhe

Tel. +49 721 4846-0Fax +49 721 4846-100info@pi.wswww.pi.ws

PI Ceramic GmbH

LindenstraßeD-07589 Lederhose

Tel. +49 36604 882-0Fax +49 36604 882-25info@piceramic.dewww.piceramic.de

PI USA

PI (Physik Instrumente) L.P.16 Albert St.Auburn, MA 01501Tel: +1 (508) 832 3456Fax: +1 (508) 832 0506info@pi-usa.uswww.pi-usa.us

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