High strains of the relaxor ferroelectric polymers allows to build efficient actuators. While the mechanical impedance of such actuators can be optimized via their morphology, their practical realization requires flexible and versatile fabrication processes. This work devises an efficient procedure for manufacturing unimorph bending actuators basing on the P(VDF-TrFE-CTFE) electroactive polymer (EAP). The fabrication process consists of inkjet printing the Ag electrodes and stencil printing the active P(VDF-TrFE-CTFE) layer. The effect of constituent layer dimensions and properties are analytically modelled to estimate the optimal morphology for highest strains. Actuators are manufactured on polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) substrates and their performance is characterized. On PET substrate, the EAP layer thicknesses of 5 μm up to 24 μm are studied. The PEN-based actuators achieved up to 759 μm deflections in quasi-static (1 Hz, 560 Vpp) and up to 5.95 mm in resonant operation (52 Hz, 550 Vpp). The PET-based actuators achieved up to 486 μm deflections in quasi-static (1 Hz, 980 Vpp) and up to 4.44 mm in resonant operation (116 Hz, 700 Vpp). These results indicate an up to 123% improvement in quasi-static and 60% resonant actuation strains compared to the previously reported similar actuators. Modelling predicts that significantly larger deflections are feasible when fabricating the transducers with optimized morphology.
Dielectric elastomers (DEs) have received significant attention for their good performance among different smart material transducers. This study demonstrates the feasibility of fabricating dielectric elastomer actuators (DEAs) using exclusively inkjet printing technique. The manufactured unimorph bending cantilevers are composed of a polydimethylsiloxane (PDMS) active layer, sandwiched between two compliant electrodes, and printed onto a thin polyimide (PI) substrate. This study addresses the key fabrication challenges associated with inkjet printing such a layered actuator structure. This entails the consistent printing of the Ag electrodes on the smooth PI substrate, a PDMS layer on the Ag electrodes, the Ag electrodes on the smooth PDMS surface, and the respective steps of processing and curing. The fully inkjet-printed DEAs exhibited a maximum tip displacement of 36 μm in quasi-static operation (1 kVpp) and 12.8 μm in resonant operation (50 Hz, 800 Vpp). This is the first time that inkjet-printing has been employed to print an entire dielectric elastomer actuator, broadening the outlooks to develop innovative devices that base on smart material transducers.
This work addresses inkjet printing and material selection in the fabrication of P(VDF-TrFE-CTFE) actuators. It investigates different substrate (PEN, polyimide and a PET-based) and conductive ink (metal- and carbon-based) combinations to minimize process complexity and need for specialized equipment. Fabrication study indicated that PEN and carbon black combination best meets these objectives, attaining an actuator's electrical bandwidth of 9.36 kHz. The manufactured actuators achieved 206 μm tip deflections upon quasi-static excitation, and up to 3 mm in resonant operation at 115 Hz. Therefore, manufacturing flexible designs of well-performing smart material actuators is viable using widely available and low-budget equipment.
Limitations of conventional actuators and sensors in small-scaled and complex devices have diverted the researches’ attentions towards smart material transducers such as ionic polymer-metal composites (IPMCs). In addition to actuation capabilities, IPMCs generate voltage when subjected to mechanical deformation. Utilization of IPMCs as sensors has been studied much less than IPMC actuation, and direct comparison of sensing methods is required for efficient implementation. This paper characterizes IPMC active sensing methods i.e. voltage, current, and charge in terms of frequency responses, coherence, noise, and repeatability. IPMC is excited mechanically between 0.08 Hz and 60 Hz under identical experimental conditions, while signal and displacement are measured. The results provide an absolute comparison for IPMC active sensing dynamic methods, for a typical IPMC (Nafion, Pt, Na+).
IPMC (Ionic Polymer Metal Composite) is a class of electroactive polymers (EAP) that bend when electric field is
applied to the material. From our theoretical studies of the material it appears that IPMC can be modelled as a lossy
transmission line. From simulations it appears that IPMC reaction time depends on length of the strip used. Also the
shorter the transmission line the less complex it is to model. We have also mechanically modeled an IPMC. It appears
that the output force does not depend on length on IPMC but on width. Also the shape unpredictability is the larger the
longer the strip is. Based on these results the concept of a short IPMC with rigid extension was created. From
simulations and experiments it was seen that there exists a certain length of IPMC at which output force and deflection
angle remain close to those of a long IPMC while precision increases. Also, the material becomes easier to model and its
short-term stability appears to be sufficient to be controlled. A manipulator was built to verify IPMC compatibility as
links, tested for accuracy and compared with a long sheet of IPMC. The manipulator appeared to be 314% more accurate
and twice as fast compared to the long strip of an IPMC and thus confirming the usability of the described design.
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