Erik Edqvist

Gentle dry etching of P(VDF-TrFE) multilayer micro actuator structures by use of an inductive coupled plasma

To fully utilize the actuator properties of poly(vinylidenefluoride) (P(VDF))-based polymers, the electric field has to be rather high and one way to accomplish this, in particular with low voltage drive signals, is to build multilayered structures. This paper focuses on how to structure poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) by presenting an etch method to create multilayered miniaturized actuators, with intermediate aluminium electrodes. To create inter-connect areas for the multilayer electrodes, a modified Bosch process in an inductive couple plasma (ICP) etcher is used to remove all P(VDF-TrFE) not covered by the electrodes. Since each electrode mask is slightly different from the others, the result is a staircase-like inter-electrode contact area that is connected from above using a conductive adhesive. The developed ICP etch results in high selective etching and a good agreement between theoretical and measured capacitance values. The manufactured cantilevers, consisting of a multilayer on top of a flexible printed circuit (FPC) board, were tested and the resonant stroke was confirmed to agree with expected values. The successful establishment of interlayer connections between the electrodes open up the possibility for batch fabrication of cheap low voltage micro actuators built on a standard substrate used in millions of commercial products.

Evaluation of building technology for mass producible millimetre-sized robots using flexible printed circuit boards

Initial tests of a building technology for a compact three-dimensional mass producible microrobot are presented. The 3.9 × 3.9 × 3.3 mm3 sized prototype robot represents a microsystem with actuators, sensors, energy management and integrated electronics. The weight of a folded robot is 65 mg and the total volume is less than 23 mm3. The design of the interfaces of the different modules in the robot, as well as the building technology, is described. The modules are assembled using conductive adhesive with industrial surface mounting technology on a thin double-sided flexible printed circuit board. The final shape of the microrobots is achieved by folding the flexible printed circuit board twice. Electrical and mechanical studies are performed to evaluate the assembly and it is concluded that the technology can be used for this type of microsystem. Several issues using the presented assembly technique are identified and addressed.

Design and manufacturing considerations of low-voltage multilayer P(VDF-TrFE) actuators

An actuator unit consisting of three multilayered cantilevers with poly(vinylidene fluoride-trifluoroethylene) on top of a flexible printed circuit board substrate is presented. The multilayer structure has five active polymer layers and six electrodes with an alternating ground and phase configuration. Different aspects regarding processing and deflection advantages, depending on which side of the substrate the multilayer structure is manufactured, are discussed. One of the cantilever configurations is dynamically modelled using finite element software and the results are compared to measured values. Because of the combination of a multilayer design and the resonant driving mode, the actuators could be powered by solar cells or used in portable electronics. A 2 V signal resulted in a tip deflection of 56 µm. To test the unit as a conveyer, speed measurements were conducted using the unit in an upright position. With a 2.5 V signal the speed was 29 µm s−1 whereas an 8 V signal resulted in 732 µm s−1. Motion in all four directions could be confirmed by tuning the frequency of a 10 V square wave signal from 640 Hz to 740 Hz.