Electromechanical Material Research Articles

Emergent local negative electrostriction induced by oxygen vacancy in BaHfO3: Defect engineering

Realization of ultrasmall scale electromechanical materials has been promising for advanced functional devices. Recently, single-atom devices have been proposed as the ultimate miniaturization of functional devices beyond the nanoscale; however, achieving an atomic-scale local electromechanical response is still challenging due to physical size limitation of electromechanical properties as well as technical difficulties in fabricating the functional materials in a single atom precision. Here, we demonstrate a non-trivial negative electromechanical response at an oxygen vacancy in paraelectric BaHfO3 using first-principles finite electric field calculations. We find an electrostrictive response at the vacancy site in the same order of magnitude in well-known oxide materials. Surprisingly, we also discover an unusual “negative” sign of electrostriction in the oxygen vacancy. The detailed electronic structure analysis demonstrates that a unique electric field response of a localized defect electronic structure is the origin of this negative electrostriction of vacancy. The present results provide an important implication for the design of ultra-small electromechanical functions at an atomic scale.

Analysis and Guideline for Determining Piezoelectric Coefficient for Films With Substrate Constraint.

Piezoelectric films including coatings are widely employed in various electromechanical devices. Precise measurement for piezoelectric film properties is crucial for both piezoelectric material development and design of the piezoelectric devices. However, substrate constraint on the deformation of piezoelectric films could cause significant impacts on the reliability and accuracy of the piezoelectric coefficient measurement. Through both theoretical finite element analysis (FEA) and experimental validation, here we have identified three important factors that strongly affect the measurement results: ratio of Young's modulus of substrate to piezoelectric film, ratio of electrode size to substrate thickness, and test frequency. Our investigations show that a relatively smaller substrate's Young's modulus to film, and a larger ratio of electrode size to substrate thickness would cause a larger substrate bending effect and thus potentially more significant measurement errors. Moreover, intense transversal displacement fluctuation can be excited at excessively high frequencies, leading to unreliable measurements. Various well-established piezoelectric measurement methods are compared with outstanding measurement issues identified for those commonly used piezoelectric films and substrates. We further establish the guidelines for piezoelectric coefficient measurements to achieve high reliability and accuracy, thus important to the wide technical community with interests in electromechanical active materials and devices.

Noncontact excitation of multi-GHz lithium niobate electromechanical resonators

The demand for high-performance electromechanical resonators is ever-growing across diverse applications, ranging from sensing and time-keeping to advanced communication devices. Among the electromechanical materials being explored, thin-film lithium niobate stands out due to its strong piezoelectric properties and low acoustic loss. However, in nearly all existing lithium niobate electromechanical devices, the configuration is such that the electrodes are in direct contact with the mechanical resonator. This configuration introduces an undesirable mass-loading effect, producing spurious modes and additional damping. Here, we present an electromechanical platform that mitigates this challenge by leveraging a flip-chip bonding technique to separate the electrodes from the mechanical resonator. By offloading the electrodes from the resonator, our approach yields a substantial increase in the quality factor of these resonators, paving the way for enhanced performance and reliability for their device applications.

Solid-State Electromechanical Smart Material Actuators for Pumps—A Review

Solid-state electromechanical smart material actuators are versatile as they permit diverse shapes and designs and can exhibit different actuation modes. An important advantage of these actuators compared to conventional ones is that they can be easily miniaturized to a sub-millimeter scale. In recent years, there has been a great surge in novel liquid pumps operated by these smart material actuators. These devices create opportunities for applications in fields ranging from aerospace and robotics to the biomedical and drug delivery industries. Although these have mainly been prototypes, a few products have already entered the market. To assist in the further development of this research track, we provide a taxonomy of the electromechanical smart material actuators available, and subsequently focus on the ones that have been utilized for operating pumps. The latter includes unidirectional shape memory alloy-, piezoelectric ceramic-, ferroelectric polymer-, dielectric elastomer-, ionic polymer metal composite- and conducting polymer-based actuators. Their properties are reviewed in the context of engineering pumps and summarized in comprehensive tables. Given the diverse requirements of pumps, these varied smart materials and their actuators offer exciting possibilities for designing and constructing devices for a wide array of applications.

Clamping enables enhanced electromechanical responses in antiferroelectric thin films.

Thin-film materials with large electromechanical responses are fundamental enablers of next-generation micro-/nano-electromechanical applications. Conventional electromechanical materials (for example, ferroelectrics and relaxors), however, exhibit severely degraded responses when scaled down to submicrometre-thick films due to substrate constraints (clamping). This limitation is overcome, and substantial electromechanical responses in antiferroelectric thin films are achieved through an unconventional coupling of the field-induced antiferroelectric-to-ferroelectric phase transition and the substrate constraints. A detilting of the oxygen octahedra and lattice-volume expansion in all dimensions are observed commensurate with the phase transition using operando electron microscopy, such that the in-plane clamping further enhances the out-of-plane expansion, as rationalized using first-principles calculations. In turn, a non-traditional thickness scaling is realized wherein an electromechanical strain (1.7%) is produced from a model antiferroelectric PbZrO3 film that is just 100 nm thick. The high performance and understanding of the mechanism provide a promising pathway to develop high-performance micro-/nano-electromechanical systems.

Accurate vertical nanoelectromechanical measurements

Piezoresponse Force Microscopy (PFM) is capable of detecting strains in piezoelectric materials down to the picometer range. Driven by diverse application areas, numerous weaker electromechanical materials have emerged. The smaller signals associated with them have uncovered ubiquitous crosstalk challenges that limit the accuracy of measurements and that can even mask them entirely. Previously, using an interferometric displacement sensor (IDS), we demonstrated the existence of a special spot position immediately above the tip of the cantilever, where the signal due to body-electrostatic (BES) forces is nullified. Placing the IDS detection spot at this location allows sensitive and BES artifact-free electromechanical measurements. We denote this position as xIDS/L=1, where xIDS is the spot position along the cantilever and L is the distance between the base and tip. Recently, a similar approach has been proposed for BES nullification for the more commonly used optical beam deflection (OBD) technique, with a different null position at xOBD/L≈0.6. In the present study, a large number of automated, sub-resonance spot position dependent measurements were conducted on periodically poled lithium niobate. In this work, both IDS and OBD responses were measured simultaneously, allowing direct comparisons of the two approaches. In these extensive measurements, for the IDS, we routinely observed xIDS/L≈1. In contrast, the OBD null position ranged over a significant fraction of the cantilever length. Worryingly, the magnitudes of the amplitudes measured at the respective null positions were typically different, often by as much as 100%. Theoretically, we explain these results by invoking the presence of both BES and in-plane forces electromechanical forces acting on the tip using an Euler–Bernoulli cantilever beam model. Notably, the IDS measurements support the electromechanical response of lithium niobate predicted with a rigorous electro-elastic model of a sharp PFM tip in the strong indentation contact limit [deff≈12pm/V, Kalinin et al., Phys. Rev. B 70, 184101 (2004)].

Strip-saturation model for arbitrary polarized electro-elastic material weakened by an eccentrically situated anti-plane semi-permeable crack

A strip-saturation model is studied to observe the effect of changing polarization axis on an electro-elastic strip, weakened by an eccentrically situated anti-plane semipermeable crack. The model is modified by considering that the saturated limit of electric displacement over rims of the saturation zone is quadratic interpolating polynomial times. The proposed model is formulated and then solved by using the Fourier integral transform technique and integral equations method. Closed-form analytic expressions are derived for developed saturation zone and fracture parameters viz. electric crack condition parameter, crack-sliding displacement, crack-opening potential drop, field intensity factors, energy release rate, etc. The influence of poling angle, prescribed electro-mechanical loadings, crack length, and material constants on fracture parameters are presented and analyzed graphically.

Biodegradable Piezoelectric Polymers: Recent Advancements in Materials and Applications.

Recent materials, microfabrication, and biotechnology improvements have introduced numerous exciting bioelectronic devices based on piezoelectric materials. There is an intriguing evolution from conventional unrecyclable materials to biodegradable, green, and biocompatible functional materials. As a fundamental electromechanical coupling material in numerous applications, novel piezoelectric materials with a feature of degradability and desired electrical and mechanical properties are being developed for future wearable and implantable bioelectronics. These bioelectronics can be easily integrated with biological systems for applications, including sensing physiological signals, diagnosing medical problems, opening the blood-brain barrier, and stimulating healing or tissue growth. Therefore, the generation of piezoelectricity from natural and synthetic bioresorbable polymers has drawn great attention in the research field. Herein, the significant and recent advancements in biodegradable piezoelectric materials, including natural and synthetic polymers, their principles, advanced applications, and challenges for medical uses, are reviewed thoroughly. The degradation methods of these piezoelectric materials through in vitro and in vivo studies are also investigated. These improvements in biodegradable piezoelectric materials and microsystems could enable new applications in the biomedical field. In the end, potential research opportunities regarding the practical applications are pointed out that might be significant for new materials research.

Electromechanical phase-field fracture modelling of piezoresistive CNT-based composites

We present a novel computational framework to simulate the electromechanical response of self-sensing carbon nanotube (CNT)-based composites experiencing fracture. The computational framework combines electrical-deformation-fracture finite element modelling with a mixed micromechanics formulation. The latter is used to estimate the constitutive properties of CNT-based composites, including the elastic tensor, fracture energy, electrical conductivity, and linear piezoresistive coefficients. These properties are inputted into a coupled electro-structural finite element model, which simulates the evolution of cracks based upon phase-field fracture. The coupled physical problem is solved in a monolithic manner, exploiting the robustness and efficiency of a quasi-Newton algorithm. 2D and 3D boundary value problems are simulated to illustrate the potential of the modelling framework in assessing the influence of defects on the electromechanical response of meso- and macro-scale smart structures. Case studies aim at shedding light into the interplay between fracture and the electromechanical material response and include parametric analyses, validation against experiments and the simulation of complex cracking conditions (multiple defects, crack merging). The presented numerical results showcase the efficiency and robustness of the computational framework, as well as its ability to model a large variety of structural configurations and damage patterns. The deformation-electrical-fracture finite element code developed is made freely available to download.

Exploring the dynamic fracture performance of epoxy/cement based piezoelectric composites with complex interfaces

Dynamic intensity factors (IFs) are the key parameters in comprehending and forecasting dynamic fracture behavior of piezoelectric composites. A domain-independent interaction integral (DII-integral) is developed to extract the dynamic stress intensity factors (SIFs) and electric displacement intensity factor (EDIF). The DII-integral is theoretically proved that there is no need to consider the electromechanical material derivatives and complicated material interfaces have no effect on the application of the method. Evaluating the results with the published data yields a good agreement and good domain-independence of the proposed I-integral is checked for multi-interface piezoelectric composites. The numerical simulations show that the amplitudes of the dynamic IFs decrease as the size of piezoelectric particle increases and crack damage is prevented as the number of piezoelectric particles increases. The peak values of the dynamic IFs are not monotonically related to the distance between the particles due to the superposition of elastic waves. The dynamic IFs increase when the volume percentage of piezoelectric fiber rises, while the opposite change is observed in laminated composites. Generally, the dynamic IFs of fiber-reinforced composites are smaller (larger) than that of laminated composites when the volume fraction of piezoelectric ceramics is higher (lower) than 40 percent.

A Tutorial on the Stability and Bifurcation Analysis of the Electromechanical Behaviour of Soft Materials

AbstractSoft materials, such as liquids, polymers, foams, gels, colloids, granular materials, and most soft biological materials, play an important role in our daily lives. From a mechanical viewpoint, soft materials can easily achieve large deformations due to their low elastic moduli; meanwhile, surface instabilities, including wrinkles, creases, folds, and ridges, among others, are often observed. In particular, soft dielectrics subject to electrical stimuli can achieve significantly large deformations that are often accompanied by instabilities. While instabilities are often thought to cause failures in the engineering context and carry a negative connotation, they can also be harnessed for various applications such as surface patterning, giant actuation strain, and energy harvesting. In the biological world, instability and bifurcation phenomena often precede important events such as endocytosis, and cell fusion, among others. Stability and bifurcation analysis (especially for soft materials) is challenging and often present a formidable barrier to entry in this important field. A multidisciplinary audience may lack the background in one or more areas that are needed to carry out the requisite modeling or even understand papers in the literature. Furthermore, combining electrostatics together with large deformations brings its own challenges. In this article, we provide a tutorial on the basics of stability and bifurcation analysis in the context of soft electromechanical materials. The aim of the article is to use simple examples and “gently” lead a reader, unfamiliar with either stability analysis or electrostatics of deformable media, to develop the ability to understand the pertinent literature that already exists and position them to embark on state-of-the-art research on this topic.

Controllable Piezo-flexoelectric Effect in Ferroelectric Ba0.7Sr0.3TiO3 Materials for Harvesting Vibration Energy.

The rapid development of the automotive and aerospace industries has led to an increasingly urgent need for electromechanical coupling materials and devices. Here, we have demonstrated the tunable piezo-flexoelectric effect in ferroelectric Ba0.7Sr0.3TiO3 materials for scavenging vibration energy. The positive peak output current of an ITO/Ba0.7Sr0.3TiO3/Ag cantilever device based on the flexoelectric effect is only 45 nA at room temperature, which is promoted to 90 nA by the piezo-flexoelectric effect. In addition, the piezo-flexoelectric current of the device can be further boosted to 270 nA by increasing the working temperature to 41.0 °C with a corresponding enhancement ratio of 348.28%. The significantly improved piezo-flexoelectric current is ascribed to the ultrahigh dielectric constant, which is related to the tetragonal-cubic phase transition of the Ba0.7Sr0.3TiO3 materials. This work reveals the temperature-modulated piezo-flexoelectric effect in ferroelectric Ba0.7Sr0.3TiO3 materials, providing a convenient route for scavenging and sensing of vibration energy.

(Invited, Digital Presentation) Yet Another Symmetry Breaking in Electromechanical Materials

The wide range of fascinating properties observed in complex oxide continue to attract great interest such as ferro-, piezo- and pyroelectricity. Several strategies have been employed to break the lattice symmetry and expand the range of functionalities. Electrostriction is a general property of all dielectrics and occurred when the deformation of a dielectric material is proportional to the square of the applied electric field. Recently, Gd2O3-doped CeO2 (CGO) has emerged as a new family of electrostriction materials with the maximum stress exceeding 500 MPa. To date, various efforts have been made to improve the strain output, such as stimulate by electric field, varying the temperature and aging the defects. However, materials that simultaneously satisfy the requirements of fast response, large strain and high energy density are still very rare. The development of materials with large dielectric breakdown strength, high dielectric constant and low elastic modulus is still challenging.Heterostructure interfaces plays an important role by contributing to its unique structural and physical properties which result in symmetry breaking, electronic and/or atomic reconstruction(s) as well as strain gradients from which a wealth of new intriguing properties can emerge. Such richness arises from a strong interaction between the charge, orbital, spin, and lattice degrees of freedom.Here, I will show how symmetry breaking offers extraordinary opportunities such as stabilizing phases which are otherwise not stable using highly coherent interfaces and enhancing the electromechanics with interfaces or inducing piezoelectricity in otherwise centrosymmetric system. In one example I will show the results obtained with a stack of ultrathin defective oxide single-crystal layers with stable phases and electrostriction properties exceeding any known system. Alternating layers of Gd2O3-doped CeO2 (CGO) and Er2O3-stabilized δ-Bi2O3 (ESB) were deposited on NdGaO3 substrates. The measured electrostriction coefficients found to follow a linear increase with the decrease of the number of interfaces. We have observed the highest electrostriction coefficient which surpasses any known electrostrictive materials, including the commercial relaxor ferroelectrics, such as PMN-PT. In another examples I will show our recent discovery illustrating the possibility to induce a large piezoelectric response in centrosymmetric oxides, i.e., in cubic fluorite oxides, Gd-doped CeO2-x. Surprisingly, the results show the generation of large low-frequency piezoelectric responses (d33 ~ 100,000 pm/V). Such a high piezoelectric response from intrinsically nonpiezoelectric materials has not been observed before in centrosymmetric materials.This collection of possibilities offers unique opportunities for a wide range of rich world and new functionality of complex oxide and their interfaces.

Surface wave dispersion in imperfectly bonded flexoelectric-piezoelectric/FGPM bi-composite in contact of Newtonian liquid

The present research article manifests the dissipation and dispersion characteristics of Love-type waves in a flexoelectric-piezoelectric/functionally graded piezomagnetic material structure, loaded with Newtonian liquid. The interface between the piezoelectric plate and the piezomagnetic substrate is considered mechanically and electromagnetically imperfect. Transcendental complex dispersion relations for electrically and magnetically open and short cases are obtained by rigorous analytical methods. A particular numerical example is considered and dispersion, as well as attenuation curves are obtained for it. Influences of mechanical and electromechanical imperfections, flexoelectricity, layer-thickness, and material gradient parameters on phase velocity and attenuation of Love-type waves are meticulously examined.

Polarization response characteristics of PDMS rectangular laminas with different inner layers under impact load

Polydimethylsiloxane (PDMS) dielectric materials, which have a wide application prospect in the field of electromechanical conversion materials, can withstand large deformation. Therefore, it is of great significance to explore the polarization response characteristics of PDMS under impact load. Rectangular PDMS specimens with monolayer structure, inner bonded/unbonded frustum of a pyramid and cone structure were prepared to investigate the structural correlation and internal charge motion of PDMS. The mechanical and polarization characteristics of materials were obtained by using Split Hopkinson Pressure Bar (SHPB) system and digital oscilloscope. The electromechanical coupling numerical simulation of different structural PDMS and the polarization law of PDMS with different structures under impact load were carried out with COMSOL Multiphysics finite element software. The results show that: (i) When impact rod acts on convex surface, the maximum stress induced by PDMS is 2–3 times of that on concave surface; the maximum stress of inner bonded PDMS with frustum of a cone structure is 75% of that with unbonded structure; (ii) The calculated flexoelectric coefficients are as follows: μzzzz = −8.46 × 10−10C/m，μxxzz = 3.32 × 10−10C/m，μxzxz = −3.5 × 10−10C/m; (iii) The polarization voltage of inner bonded PDMS is larger when impact rod acts on concave surface, and the magnitude of voltage induced by inner unbonded PDMS is about 1/10 of that with bonded structure; (iv) The interfacial charge order of inner bonded PDMS is 10 times that of monolayer PDMS, and the polarization voltage induced by coupled electric field is significantly increased.

Solid solution enhanced electrostriction in the YSZ-GDC system

Giant electrostrictors based on oxygen deficient fluorites are of great technological and scientific interest due to their unusual electromechanical properties. It is, however, still not clear whether solid solutions between different fluorites can affect the electrostrictive properties.In this work, we investigated the electromechanical response of four different solutions of 10 mol% gadolinium-doped ceria (GDC10) and 8mol% yttria-stabilized zirconia (8YSZ), corresponding to 1, 5, 10 and 20 wt% of 8YSZ into GDC10. An increase in the electrostriction coefficient with the 8YSZ content (maximum between 10 and 20 wt%) was registered. This effect suggests that the development of complex solid solutions could represent a new tool to develop electromechanical materials with superior properties.

A Study on Thermal and Electrical Conductivities of Ethylene-Butene Copolymer Composites with Carbon Fibers

Abstract Ethylene-butene copolymer (EBC)/carbon-fiber (CF) composites can be utilized as an electromechanical material due to their ability to change electric resistance with mechanical strain. The electro-mechanical properties and thermal conductivity of ethylene butene copolymer (EBC) composites with carbon fibers were studied. Carbon fibers were introduced to EBC with various concentrations (5 to 25 wt%). The results showed that carbon fibers’ addition to EBC improves the electric conductivity up to 10 times. Increasing the load up to 2.9 MPa will raise the electric resistance change by 4 500% for a 25% fiber sample. It is also noted that the EBC/CF composites’ electric resistance underwent a dramatic increase in raising the strain. For example, the resistance change was around 13 times higher at 15% strain compared to 5% strain. The thermal conductivity tests showed that the addition of carbon fibers increases the thermal conductivity by 40%, from 0.19 to 0.27 Wm–1K–1.

Materials Perspectives for Self-Powered Cardiac Implantable Electronic Devices toward Clinical Translation.

Represented by pacemakers, implantable electronic devices (CIEDs) are playing a vital life-saving role in modern society. Although the current CIEDs are evolving quickly in terms of performance, safety, and miniaturization, the bulky and rigid battery creates the largest hurdle toward further development of a soft system that can be attached and conform to tissues without causing undesirable physiologic changes. Over 50% of patients with pacemakers require additional surgery procedures to replace a drained battery. Abrupt battery malfunction and failure contributes up to 2.4% of implanted leadless pacemakers. The battery also has risks of lethal interference with diagnostic magnetic resonance imaging (MRI). Applying the implantable nanogenerators (i-NGs) technology to CIEDs is regarded as a promising solution to the battery challenge and enables self-powering capability. I-NGs based on the principle of either triboelectricity (TENG) or piezoelectricity (PENG) can convert biomechanical energy into electricity effectively. Meanwhile, a complete heartbeat cycle provides a biomechanical energy of ~0.7 J or an average power of 0.93 W, which is sufficient for the operation of CIEDs considering the power consumption of 5-10 μW for a pacemaker and 10-100 μW for a cardiac defibrillator. It is therefore practical to leverage the effective, soft, flexible, lightweight, and biocompatible i-NGs to eliminate the bulky battery component in CIEDs and achieve self-sustainable operation. In this rapidly evolving interdisciplinary field, materials innovation acts as a cornerstone that frames the technology development. Here we bring a few critical perspectives regarding materials design and engineering, which are essential in leading the NG-powered CIEDs toward clinical translations. This Account starts with a brief introduction of the cardiac electrophysiology, as well as its short history to interface the state-of-the-art cardiac NG technologies. Three key components of NG-powered CIEDs are discussed in detail, including the NG device itself, the packaging material, and the stimulation electrodes. Cardiac NG is the essential component that converts heartbeat energy into electricity. It demands high-performance electromechanical coupling materials with long-term dynamic stability. The packaging material is critical to ensure a long-term stable operation of the device on a beating heart. Given the unique operation environment, a few criteria need to be considered in its development, including flexibility, biocompatibility, antifouling, hemocompatibility, and bioadhesion. The stimulation electrodes are the only material interfacing the heart tissue electrically. They should provide capacitive charge injection and mimic the soft and wet intrinsic tissues for the sake of stable biointerfaces. Driven by the rapid materials and device advancement, we envision that the evolution of NG-based CIEDs will quickly move from epicardiac to intracardiac, from single-function to multifunction, and with a minimal-invasive implantation procedure. This trend of development will open many research opportunities in emerging materials science and engineering, which will eventually lead the NG technology to a prevailing strategy for powering future CIEDs.

Tendon grafts with preserved muscle demonstrate similar biomechanical properties to tendon grafts stripped of muscular attachments: a biomechanical evaluation in a porcine model

Purpose(1) To evaluate the biomechanical properties of a porcine flexor digitorum superficialis tendon graft with preserved muscle fibers and (2) to compare these results with the biomechanical properties of a porcine tendon graft after removal of associated muscle.MethodsEighty-two porcine forelegs were dissected and the flexor digitorum superficialis muscle tendons were harvested. The study comprised of two groups: Group 1 (G1), harvested tendon with preserved muscle tissue; and Group 2 (G2), harvested contralateral tendon with removal of all muscle tissue. Tests in both groups were conducted using an electro-mechanical material testing machine (Instron, model 23-5S, Instron Corp., Canton, MA, USA) with a 500 N force transducer. Yield load, stiffness, and maximum load were evaluated and compared between groups.ResultsThe behavior of the autografts during the tests followed the same stretching, deformation, and failure patterns as those observed in human autografts subjected to axial strain. There were no significant differences in the comparison between groups for ultimate load to failure (p = 0.105), stiffness (p = 0.097), and energy (p = 0.761).ConclusionIn this porcine model biomechanical study, using autograft tendon with preserved muscle showed no statistically significant differences for yield load, stiffness, or maximum load compared to autograft tendon without preserved muscle. The preservation of muscle on the autograft tendon did not compromise the mechanical properties of the autograft.Level of evidenceLevel III Controlled laboratory study

Experimental investigation on the physical parameters of ionic polymer metal composites sensors for humidity perception

Ionic polymer metal composite (IPMC) is one of typical electromechanical transducing materials integrating actuation and sensing functions. In this work, we systematically investigate the evolutions of the capacitance, surface resistance and ionic electrical response of strip shaped IPMC under different humidity conditions. For each parameter, we have performed a set of static and dynamic humidity sensing tests, considering the change of the thickness, cations type and impregnation-reduction plating (IRP) times. Through conducting a series of experiments, it is concluded that the humidity-capacitance sensing has achieved a much wider sensing range (22 % RH - 100 %RH in this work, comparing with 40 % RH - 90 %RH in previous work) and an increased sensitivity (256μF in this work, comparing with140nF in previous work). In the meantime, humidity-surface resistance sensing has the perception of the full humidity range. While the humidity-ionic electrical response sensing can only respond to dynamic humidity changes but showing a very fast response time less than 0.5 s, which will be of great significance in some special humidity detection scenarios, such as the rapid detection and alarm for leakage of equipment with constant humidity. For each case, it implies a fact that the water absorption capacity of surface electrode and inter layer determines the humidity sensing abilities, such as response speed, amplitude and so on.