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Monolithic fabrication of multilayer P(VDF-TrFE) cantilevers
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
2008 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 144, no 2, 314-320 p.Article in journal (Refereed) Published
Abstract [en]

When operating a piezoelectric actuator the use of multilayers has for a long time proven to be a good solution to maintain a high electric field at a reduced applied voltage. The piezoelectric copolymer polyvinylidene-trifluoroethylene P(VDF-TrFE) has rather low piezoelectric constant compared to piezoceramics but it can withstand much higher electric fields. As the copolymer can be spin coated the individual layer thickness of the multilayer can easily be reduced to a few m and rather large strains can be achieved at a moderate voltage. Here a monolithic fabrication technique for producing P(VDF-TrFE) actuators, without any lamination or adhesive layers, is presented. To fabricate the multilayer successive spin coating of the piezoelectric polymer polyvinylidene-trifluoroethylene P(VDF-TrFE) and electrode evaporation on a substrate was performed. Four different substrate materials were coated with a multilayer stack of 6 active P(VDF-TrFE) layers and 7 aluminum electrodes. The monolithic multilayer structures with patterned electrodes were diced by a cutting saw to produce unimorph cantilevers. No delamination or dissolution could be observed between adjacent copolymer layers. The cantilevers were evaluated in terms of static and resonant deflection and the Q-factor was estimated from the frequency spectra. A discussion regarding the influence of the Q-factor on the fabrication process tolerance is given. The different substrate materials used was stainless steel, flexible printed circuit board (FPC), polycarbonate and aluminum. The Q-factor varied from 30 for the polycarbonate to 83 for the stainless steel. These results provide guidelines for the material choices of a forthcoming locomotion module to be used in the 3 mm 3 mm 3 mm I-SWARM robots. The FPC substrate showed to have the best compatibility to the fabrication processes and the most suitable Q-value of 42. This together with the high deflections makes the FPC the preferred substrate materials the future actuators for the I-SWARM locomotion module. 2008 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
2008. Vol. 144, no 2, 314-320 p.
Keyword [en]
Piezoelectric actuators, Copolymers, Electric fields, Multilayers, Printed circuit boards, Spin coating
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-108492DOI: 10.1016/j.sna.2008.01.004ISI: 000256896700010ISBN: 09244247 (print)OAI: oai:DiVA.org:uu-108492DiVA: diva2:236047
Available from: 2009-09-20 Created: 2009-09-20 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Actuators for autonomous microrobots
Open this publication in new window or tab >>Actuators for autonomous microrobots
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents actuators used in autonomous microsystems. Characteristic for all actuators presented is the low drive voltage and the low power consumption. Different motion mechanisms have been studied and applied in various locomotion modules for microrobots.

High resolution movement of a monolithic piezoceramic PZT rotational arm module, using a quasi-static motion mechanism, was demonstrated in a 10x10x20 mm3 autonomous robot. The rotational arm comprises multilayer PZT bimorphs and is fabricated by a wet-building technology. The multilayer approach enables operation of the modules at the low drive voltages provided by the robot electronics. In addition a locomotion module has been designed and fabricated based on the above principles.

A three-legged locomotion module with piezoceramic unimorphs, moving by tapping the legs against the floor, has been investigated. Characteristics such as low power consumption, high velocities, low drive voltages and a high weight carrying capability were demonstrated using a resonant motion mechanism.

Highly miniaturized three-legged locomotion modules were developed for a 3x3x3 mm3 autonomous microrobot. The modules comprise a multilayer structure of the electroactive copolymer P(VDF-TrFE) on a flexible printed circuit board (FPC) substrate. A novel multilayer fabrication process suitable for mass production was used. It is based on sequential deposition of spun cast copolymer with evaporated aluminum electrodes. Reactive ion etching is used to microstructure the copolymer and the FPC. The mechanical deformability of the FPC is exploited when folding the 2D FPC-multilayer assembly into 3D locomotion modules. Locomotion was demonstrated by moving a glass slider corresponding to the robot weight.

A modular building technology for microsystems is presented. It uses surface mounting technology and conductive adhesives to assemble modules on a double-sided FPC. Complex geometries were achieved by subsequent folding the FPC. The feasibility of the technology was demonstrated by assembly of the 3x3x3 mm3 autonomous microrobots.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 431
Keyword
Engineering physics, Locomotion, Microrobot, PZT, P(VDF-TrFE), Autonomous, Multilayer, Actuator, Teknisk fysik
Identifiers
urn:nbn:se:uu:diva-8720 (URN)978-91-554-7196-5 (ISBN)
Public defence
2008-05-23, Siegbahnsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2008-04-29 Created: 2008-04-29 Last updated: 2009-09-21Bibliographically approved
2. Applications of active materials
Open this publication in new window or tab >>Applications of active materials
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy efficiency is a vital key component when designing and miniaturizing self sustained microsystems. The smaller the system, the smaller is the possibility to store enough stored energy for a long and continuous operational time. To move such a system in an energy efficient way, a piezoelectrical locomotion module consisting of four resonating cantilevers has been designed, manufactured and evaluated in this work. The combination of a suitable substrate, a multilayered piezoelectric material to reduce the voltage, and a resonating drive mechanism resulted in a low power demand.

A manufacturing process for multilayer cantilever actuators made of P(VDF-TrFE) with aluminum electrodes on a substrate of flexible printed circuit board (FPC), has been developed. An important step in this process was the development of an etch recipe for dry etching the multilayer actuators in an inductive plasma equipment.

Formulas for the quasi static tip deflection and resonance frequency of a multilayered cantilever, have been derived. Through theses, it was found that the multilayered structures should be deposited on the polymer side of the FPC in order to maximize the tip deflection.

Both a large and a miniaturized locomotion module were manufactured and connected by wires to verify that the three legged motion principal worked to move the structures forward and backward, and turn it right and left. By touching and adding load, to a fourth miniaturized cantilever, its ability to act as a contact sensor and carry object was verified.

The presented locomotion module is part of a multifunctional microsystem, intended to be energy efficient and powered by a solar panel with a total volume of less than 25 mm3 and weight 65 mg. The whole system, consisting of a solar cell, an infra red communication module, an integrated circuit for control, three capacitors for power regulating, the locomotion module and an FPC connecting the different modules, was surface mounted using a state of the art industrial facility. Two fully assembled systems could be programmed both through a test connector and through optical sensors in the multifunctional solar cell. One of these was folded together to the final configuration of a robot. However, the entire system could not be tested under full autonomous operating conditions. On the other hand, using wires, the locomotion module could be operated and used to move the entire system from a peak-to-peak voltage of 3.0 V.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 672
Keyword
Energy efficient, microsystem, resonating cantilevers, microactuators, P(VDF-TrFE), surface mounting assembly, multi layers, flexible printed circuit board, conveyer, three legged
National Category
Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-108696 (URN)978-91-554-7609-0 (ISBN)
Public defence
2009-10-30, 2001, Ångström Laboratory, Uppsala, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2009-10-09 Created: 2009-09-28 Last updated: 2009-10-09Bibliographically approved

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Snis, NiklasEdqvist, ErikJohansson, Stefan

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