Papers by Keyword: Electromechanical Properties

Abstract: Additive manufacturing (AM) technologies have enabled the fabrication of customizable, low-cost capacitive sensors for a wide range of applications, including robotics, automation, and bioelectronics. Although various AM techniques have been explored, structural inconsistencies often remain a challenge, limiting the performance and reproducibility of printed dielectric layers. Stereolithography (SLA), offers higher resolution and denser prints, yet the use of commercial photopolymer resins as dielectric materials remains underexplored. This study investigates two commercial SLA-compatible resins, a flexible medical-grade elastic resin and a dental-grade resin, as potential dielectric layers for capacitive force sensors. Both resins are biocompatible for short-term use or skin contact, making them suitable also for medical applications. The elastic 50A-V1 resin exhibited a Young’s modulus of E = 5.0 ± 0.2 MPa up to approximately 60% strain, whereas the Dental Clear V2 resin showed a significantly higher modulus of E = 1020 ± 80 MPa under the same conditions. Therefore, the elastic resin was subsequently chosen as the dielectric material to fabricate a proof-of-concept capacitive force sensor, which exhibited a final capacitance of 1.13 ± 0.03 pF within a force range of 10 to 400 N. The findings serve as a preliminary step towards the development of fully 3D-printed capacitive force sensors for integration into soft robotic and smart biomedical systems.

Abstract: Lead-free ferroelectric materials of sodium-potassium bismuth titanate, (1-x)NBT-xKBT systems were synthesized by a hydrothermal process. In this way, the appropriate conditions for the hydrothermal synthesis of NBT and KBT (i.e., concentrations of synthetic precursors, solution pH and temperature) are given graphically. Ceramics of (1-x)NBT-xKBT with (x(mol.%) = 0; 12; 16; 20; 30 and 100) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The rhombohedral-tetragonal morphotropic phase boundary (MPB) was confirmed to be in the region of 0.12 ≤ x ≤ 0.20 for (1-x)NBT-xKBT at ambient temperature. Scherrer's formula and the Williamson-Hall (W-H) analysis were used to examine the average crystallite size and lattice strain. Raman spectroscopy was effectively applied to study the structural evolution of the (1-x)NBT-xKBT phase. The ceramics exhibited a high temperature of maximum dielectric permittivity at (Tmax = 343 °C at 100 kHz) along with electromechanical coupling factors (kp = 0.34, d33 = 147 pC/N). Based on the composition of all specimens, the results indicate a diffuse phase transition, probably of second order, between ferroelectric and paraelectric phases.

Abstract: The microstructure, energy dispersive X-ray spectra, and field dependent polarization and electrostrictive strain characteristics of x(Ba_0.7Ca_0.3)TiO₃–(1-x)Ba (Zr_0.2Ti_0.8)O₃; x = 0, 0.5, and 1.0 synthesised using solid-state reaction process are discussed in this work. The X-ray diffraction process and scanning electron microscope were, respectively taken into use to examine the forming of single-phase compound and the surface morphology as well as elemental analyses of all of the samples. The grains sizes were found to lie between 3–12 μm and was largest for x = 0.5. The value of piezoelectric coefficient, converse piezoelectric effect (strain maximum to peak electric field), and electrostrictive coefficient were found to be the highest for x = 0.5 sample. Ba_0.85Ca_0.15Zr_0.10Ti_0.90O₃ was shown to be a potential lead-free electrostriction material for industrial applications, particularly in positioning actuators, based on field-dependent polarisation and strain experiments at ambient temperature.

Abstract: Polyvinylidene fluoride (PVDF) – Lead Zirconate Titanate (PZT) is a polymer composite that is becoming increasingly popular in micro-scale sensors and actuators because of its unique properties such as high flexibility, low density and high piezoelectric constants. However, lead-based piezoceramics, despite their superior properties, are toxic and are known to damage the environment, and as such a conscientious effort is being made by the scientific community towards replacing lead-containing piezoceramics with environmentally-friendlier and lead-free piezoceramics. Barium Titanate (BaTiO₃) is one such piezoceramics that is widely studied today to be a potential replacement of PZT in many applications. As such, in this work, effort has been made to predict the effective mechanical, dielectric and piezoelectric properties of PVDF-BaTiO₃ composite system using Finite Element Method (FEM). Kinematic Uniform Boundary Conditions (Displacement and Voltage) are used for this analysis. For evaluation of the effective material constants of the composite, several types of representative volume elements are considered. The effects of volume fraction, effect of the size of the micro-particles i.e. mono-modal versus multi-modal size distribution, effect of periodic versus quasi-random distribution of microparticles in the matrix, the effect of clustering of the particles, effect of orientation of the microparticles i.e. unidirectional or randomly oriented are discussed. Finally, a comparison of properties between PVDF-PZT and PVDF-BaTiO₃ is made, so as to see whether PVDF-BaTiO₃ can be a potential replacement for PVDF-PZT composite.

Abstract: Recently, ionic actuator as a kind of artificial muscle has attracted great attentions according to their remarkable strain under low-voltage stimulation. Here, we investigated a biocompatible ionic polymer actuator, which consists of multi-walled carbon nanotubes (MCNTs) film as the double electrode layer and an electrolyte layer equipped with a chitosan polymer skeleton. As a result, we found it presented various electromechanical properties under the preparation factors of the different additive glycerol (0mL, 2mL, 4mL). The actuators with 2mL glycerol behaved a longer life bending (65 times), which was obviously surpassed by the others. Also, based on strain and stress testing, Young's modulus of the electrolyte presented a decreasing trend. In fact, the improvement was mainly due to the weakened inter-molecular hydrogen and the rotation molecular of the electrolyte film. Results show the additive inside the electrolyte is very effective to improve the performance of artificial muscle.

Abstract: K_0.5Na_0.5NbO₃ (KNN) was manufactured by spark plasma sintering (SPS), which is a fast sintering method allowing to control the grain growth. Different samples of KNN are sintered with SPS at 920°C under 50 MPa for 5 minutes. High densities over than 97% are achieved. In order to make domain engineering, KNN crystals are grown by floating zone method. Stable molten zone is reached when oxygen or nitrogen gas flux is used, leading up to 50 mm length of crystals. High electromechanical coupling factor kt about 46 %, kp around 45 % and ε33S/ε0 of 253 are achieved for KNN ceramics poled at optimum electric field about 3 kV / mm. KNN crystal boule exhibits kt about 40 % against 34 % for KNN ceramic, both poled at 1 kV / mm. These results are promising to replace PZT for transducers applications.

Abstract: In this paper a simple method is used for fabrication of vertically aligned carbon nanotube (VACNT) within the cylindrical pores anodic aluminum oxide (AAO) substrate. Electronic and mechanical properties of VACNT have been obtained after removing AAO substrate. Vertically aligned carbon nanotube shows very interesting electromechanical properties which can be used in CNT-based sensors to detect chemical analytical or physical properties such as temperature orpressure.

Abstract: In this study, %7 Li modified and 0.67 % copper oxide added potassium sodium niobate (KNN) ceramics were investigated. Copper oxide was used as a sintering aid. The ceramics were prepared with conventional solid state calcination technique. All samples were crystallized in pure perovskite phase with no additional peak. The density of the samples increased with copper addition and lithium modification. The Curie temperature of KNN ceramics was found to shift to lower temperatures by CuO addition. The Curie temperature was measured as 414°C and 504°C for copper oxide added and lithium modified KNN samples, respectively. The maximum strain of copper oxide added sample was 0.12%, whereas Li modified KL ceramics yielded up to 0.10 %.

Abstract: Periodic and non-periodic 1-3 type cement based piezoelectric composites were fabricated by cut and filling technique, using P(MN)ZT ceramic as functional material and cement as matrix. The influences of periodicity of piezoelectric ceramic rods in the composites on electrical properties of all the composites were discussed. The results show that the non-periodic composites have larger dielectric factor and piezoelectric strain constant than those of the periodic composite. The impedance-frequency spectra analysis indicates that the non-periodic arrangement of ceramic rods can effectively restrict the lateral structural mode of the composite, accordingly reduces the coupling resonant between the thickness resonant mode and lateral resonant mode. The thickness electromechanical coupling coefficient of non-periodic composites is larger than that of the periodic composite. With increasing the non-periodic level of P(MN)ZT ceramic in the composites, the mechanical quality factor of the composites increases gradually. Therefore, 1-3 type cement based piezoelectric composites with different special abilities can be obtained by varying the periodic arrangement of P(MN)ZT ceramic rods in the composites.

Abstract: Sulphoaluminate cement and Lead Niobium-Magnesium Zirconate Titanate ceramic [P(MN)]ZT were used as matrix and functional phase respectively to fabricate 1-3-2 cement-based piezoelectric composites by dice and filling technique. The influences of base thickness on piezoelectric properties, electromechanical properties and acoustic impedance properties of the composites were discussed. The results show that as the base thickness increases, the piezoelectric stain factor d33 increases gradually, while the piezoelectric voltage factor g33 decreases. The planar electromechanical coupling coefficient Kp exhibits the trend of decrease, while the thickness electromechanical coupling coefficient Kt and acoustic impedance show the increasing trend. The mechanical quality factor Qm reaches the minimum (1.49) when base thickness is 2.00 mm. The results reveal that the 1-3-2 piezoelectric composite will be suitable for application by changing the base thickness.