Electromechanical Sensitivity Research Articles

Enhancing electromechanical conversion and motion-monitoring application of pore-oriented cellulose nanocrystal/agarose aerogel modified with flexible heterojunction structures

Oriented-porous cellulose nanocrystal (CNC)-based aerogels excel in directional energy conversion but face reduced toughness, and triboelectric performance bottlenecks owing to the absence of electron acceptors. In this work, we crosslinked quaternary ammonium CNC with another flexible carboxymethyl agarose (AG-), via borate dynamic bonds, exploiting the electron-accepting traits of boron and electrophilic modifications to boost the mechanical and triboelectric performance of aerogels. These results demonstrate that the compressive resilience and modulus of CNC/AG aerogel are improved up to 70.79 % (after 10-cycle 20 % strain) and 18.77 kPa attributing to the borate cross-linking network and oriented structure. Furthermore, the electromechanical response sensitivity and output energy density of the CNC/AG aerogel increased by 6.06 times (to 7.51 V/Hz) and 28.3 times (to 1.87 W/m2), respectively. The structure characteristics of the CNC/AG aerogel reveal that the oriented structure and heterojunction of the CNC/AG aerogel with electron transfer pathways reduce dielectric losses. The COMSOL simulation also show that oriented pores increase the polarization and charge density of the CNC/AG aerogel, thereby improving the electromechanical conversion efficiency. This work offers a synergistic approach for toughening aerogels and generating heterojunctions via flexible modification, presenting significant potential for smart devices with energy-collection ability.

High Sensitivity Performance of Piezoelectric Micromachined Ultrasonic Transducer Employing Sc-Doped AlN Thin Film

Abstract Aluminum Nitride (AlN) based piezoelectric micromachined ultrasonic transducers (PMUTs) have been the prime choice in acoustic imaging, because it has advantages of high frequency and thus high resolution. However, low piezoelectric constants of AlN gives rises to limitation in transmitting sensitivity. Scandium (Sc) doping method for AlN can be used to improve its piezoelectricity. In this paper, single element PMUT based on ScAlN thin film was proposed and modeled by performing finite element method (FEM). Influence of different electrode configurations on PMUT performance were studied. The results show that, compared with other electrode configurations, PMUT has the best overall performance when the upper electrode is platinum (Pt) and the lower electrode is molybdenum (Mo). In addition, the acoustic field characteristics and its dynamic analysis of PMUT based on ScAlN in water were studied. The investigation results demonstrated that the relative pulse-echo sensitivity level M of PMUT is significantly improved with the increase of Sc doping concentration in AlN thin film. When the Sc concentration is 40%, the M reaches -44 dB, which is 20 dB higher than that without Sc (-64 dB). The PMUT based on the high Sc-doped AlN thin film has a larger effective electromechanical coupling coefficient and sensitivity, which is beneficial to the application in high sensitivity ultrasound imaging.

Tetrodotoxin-resistant mechanosensitivity and L-type calcium channel-mediated spontaneous calcium activity in enteric neurons.

Gut motility undergoes a switch from myogenic to neurogenic control in late embryonic development. Here, we report on the electrical events that underlie this transition in the enteric nervous system, using the GCaMP6f reporter in neural crest cell derivatives. We found that spontaneous calcium activity is tetrodotoxin (TTX) resistant at stage E11.5, but not at E18.5. Motility at E18.5 was characterized by periodic, alternating high- and low-frequency contractions of the circular smooth muscle; this frequency modulation was inhibited by TTX. Calcium imaging at the neurogenic-motility stages E18.5-P3 showed that CaV1.2-positive neurons exhibited spontaneous calcium activity, which was inhibited by nicardipine and 2-aminoethoxydiphenyl borate (2-APB). Our protocol locally prevented muscle tone relaxation, arguing for a direct effect of nicardipine on enteric neurons, rather than indirectly by its relaxing effect on muscle. We demonstrated that the ENS was mechanosensitive from early stages on (E14.5) and that this behaviour was TTX and 2-APB resistant. We extended our results on L-type channel-dependent spontaneous activity and TTX-resistant mechanosensitivity to the adult colon. Our results shed light on the critical transition from myogenic to neurogenic motility in the developing gut, as well as on the intriguing pathways mediating electro-mechanical sensitivity in the enteric nervous system. HIGHLIGHTS: What is the central question of this study? What are the first neural electric events underlying the transition from myogenic to neurogenic motility in the developing gut, what channels do they depend on, and does the enteric nervous system already exhibit mechanosensitivity? What is the main finding and its importance? ENS calcium activity is sensitive to tetrodotoxin at stage E18.5 but not E11.5. Spontaneous electric activity at fetal and adult stages is crucially dependent on L-type calcium channels and IP3R receptors, and the enteric nervous system exhibits a tetrodotoxin-resistant mechanosensitive response. Abstract figure legend Tetrodotoxin-resistant Ca2+ rise induced by mechanical stimulation in the E18.5 mouse duodenum.

Electromechanical sensitivity of ZnO thin films at high-pressure regime for SAW strain sensor applications

This paper employs Density Functional Theory (DFT) to investigate the influence of high hydrostatic pressure on the piezo-elastic properties of ZnO with a specific focus on its repercussions for Surface Acoustic Wave (SAW) devices. Our findings reveal a significant enhancement in the piezoelectric coefficient d33 under high-pressure conditions, particularly reaching 13.09 pC/N at 8 GPa compared to the unpressurized state. This noteworthy improvement directly contributes to an overall enhancement in the electromechanical coupling coefficients (K2), emphasizing for the first time the potential of high-pressure conditions to positively influence the performance of ZnO/Al2O3 SAW devices. To confirm that, we utilized the Finite Element Method (FEM) to analyze the performance of a Surface Acoustic Wave (SAW) device based on ZnO for both propagating modes, namely Rayleigh and Sezawa, under elevated pressure conditions. We observed an improvement in the electromechanical coupling factor (K2) for the Rayleigh and the Sezawa modes, with enhancements of approximately 23% and 52%, respectively, under an applied pressure of 8 GPa compared to 0 GPa. Furthermore, we found that the Sezawa mode exhibits eight times greater sensitivity to pressure variations compared to the Rayleigh mode. These findings provide designers with a better understanding of the electromechanical responsivity and sensitivity of the ZnO-SAW devices to high level of applied pressure.

Fabrication of High-Performance Natural Rubber Composites with Enhanced Filler-Rubber Interactions by Stearic Acid-Modified Diatomaceous Earth and Carbon Nanotubes for Mechanical and Energy Harvesting Applications.

Mechanical robustness and high energy efficiency of composite materials are immensely important in modern stretchable, self-powered electronic devices. However, the availability of these materials and their toxicities are challenging factors. This paper presents the mechanical and energy-harvesting performances of low-cost natural rubber composites made of stearic acid-modified diatomaceous earth (mDE) and carbon nanotubes (CNTs). The obtained mechanical properties were significantly better than those of unfilled rubber. Compared to pristine diatomaceous earth, mDE has higher reinforcing efficiencies in terms of mechanical properties because of the effective chemical surface modification by stearic acid and enhanced filler-rubber interactions. The addition of a small amount of CNT as a component in the hybrid filler systems not only improves the mechanical properties but also improves the electrical properties of the rubber composites and has electromechanical sensitivity. For example, the fracture toughness of unfilled rubber (9.74 MJ/m3) can be enhanced by approximately 484% in a composite (56.86 MJ/m3) with 40 phr (per hundred grams of rubber) hybrid filler, whereas the composite showed electrical conductivity. At a similar mechanical load, the energy-harvesting efficiency of the composite containing 57 phr mDE and 3 phr CNT hybrid filler was nearly double that of the only 3 phr CNT-containing composite. The higher energy-harvesting efficiency of the mDE-filled conductive composites may be due to their increased dielectric behaviour. Because of their bio-based materials, rubber composites made by mDE can be considered eco-friendly composites for mechanical and energy harvesting applications and suitable electronic health monitoring devices.

Investigating the Electromechanical Sensitivity of Carbon-Nanotube-Coated Microfibers.

The piezoresistance of carbon nanotube (CNT)-coated microfibers is examined using diametric compression. Diverse CNT forest morphologies were studied by changing the CNT length, diameter, and areal density via synthesis time and fiber surface treatment prior to CNT synthesis. Large-diameter (30-60 nm) and relatively low-density CNTs were synthesized on as-received glass fibers. Small-diameter (5-30 nm) and-high density CNTs were synthesized on glass fibers coated with 10 nm of alumina. The CNT length was controlled by adjusting synthesis time. Electromechanical compression was performed by measuring the electrical resistance in the axial direction during diametric compression. Gauge factors exceeding three were measured for small-diameter (<25 μm) coated fibers, corresponding to as much as 35% resistance change per micrometer of compression. The gauge factor for high-density, small-diameter CNT forests was generally greater than those for low-density, large-diameter forests. A finite element simulation shows that the piezoresistive response originates from both the contact resistance and intrinsic resistance of the forest itself. The change in contact and intrinsic resistance are balanced for relatively short CNT forests, while the response is dominated by CNT electrode contact resistance for taller CNT forests. These results are expected to guide the design of piezoresistive flow and tactile sensors.

Research Trends of Piezoelectric Nanomaterials in Biomedical Engineering

Piezoelectric nanomaterials are functional materials that hold a great promise for the nanoscale conversion of mechanical energy and electrical signals. Owing to their excellent electromechanical dependence, catalytic activity, and response sensitivity, piezoelectric nanomaterials are widely used in energy harvesting, sensors, actuators, resonators, and medical detectors. Nano‐piezoelectric materials exhibit unique electrical and chemical activities in the field of biomedical engineering, such as disease diagnosis and treatment. The working principles, device‐design mechanics, and classification of piezoelectric nanomaterials are systematically reviewed. Then, the recent advances in piezoelectric nanomaterials and their applications in tissue regeneration, antitumor/antibacterial therapy, cell force detection, controlled drug release, and pathological/physiological parameter monitoring are highlighted. Finally, the perspectives on the development of future smart piezoelectric nanomaterials, and how they can serve as a building block to inspire and impact the development of novel diagnosis and treatment applications, are presented.

(Invited) Organic Thin Films Transistors: From Mechanical to Biochemical Sensors

Interest in organic electronic materials, and in particular their potential for low-cost fabrication over large areas, led to the development of organic field-effect transistors (OFETs). The potential of OFETs has been demonstrated in a variety of applications, including pixel drivers for displays, bionic skin, wearable electronics and sensitive chemical sensors that can operate in aqueous environments. OFETs use conjugated, semiconducting small molecules and polymers and offer an alternative to inorganic devices for applications in which facile processing on different substrates and tunable electronic properties are required. The flexibility requirement implies either performance stability towards deformation, or conversely, detectable response to the deformation itself. The knowledge of the electromechanical response of organic semiconductors to external stresses is therefore not only interesting from a fundamental point of view, but also necessary for the development of real world applications. To this end, this presentation highlights the importance of the choice of functional materials (organic semiconductors and dielectrics) as well as the relationship structure/properties in transistors based sensors. Organic semiconductors (OSCs) are promising transducer materials when applied in OFETs taking advantage of their electrical properties that highly depend on the morphology of the semiconducting film. The effects of a high-performance p-type organic semiconductor, namely dinaphtho [2,3-b:2,3-f] thieno [3,2–b] thiophene (DNTT) thickness on its piezoresistive sensitivity are presented. A critical thickness corresponding to the appearance of charge carriers percolation paths in the material can tune the gauge factors (GFs) by a factor 10. In addition, single crystal OSC are regarded as promising electroactive materials for strain sensing application. Herein this talk, we will present how strain induces simultaneous mobility changes along all three axes, and that in some cases the response is higher along directions orthogonal to the mechanical deformation. These variations cannot be explained by the modulation of intermolecular distances, but only by a more complex molecular reorganisation, which is particularly enhanced, in terms of response, by p-stacking and herringbone stacking. This microscopic knowledge of the relation between structural and mobility variations is essential for the interpretation of electromechanical measurements for crystalline organic semiconductors, and for the rational design of electronic devices. Alternatively, this talk will highlight how the use of an active gate dielectric layer such as poly(vinylidenefluoride/trifluoroethylene) (P(VDF-TrFE)) piezoelectric polymer can lead to highly efficient electro-mechanical sensitivity. In such case, the sensing mechanism of the electro-mechanical transducer originates from the piezoelectric material itself, which affects the electrical behavior of the transistor as signature of a mechanical event. The second part of this talk will focus on another kind of TFT based sensor, namely the organic electrochemical transistors (OECTs) which have found recently applications in chemical and biological sensing and interfacing and neuromorphic computing. OECT rely on ions that are injected from the electrolyte into polymer-based mixed conductors, thereby changing its doping state and hence its conductivity. While great progress has been achieved, organic mixed conductors frequently experience significant volumetric changes during ion uptake/rejection, i.e., during doping/ de-doping and charging/discharging. Although ion dynamics may be enhanced in expanded networks, these volumetric changes can have undesirable consequences, e.g., negatively affecting hole/electron conduction and severely shortening device lifetime. New materials able to transport ions and electrons/holes and that exhibits low swelling will be presented, expanding the materials-design toolbox for the creation of low-swelling soft mixed conductors with tailored properties and applications in bioelectronics and beyond.

Carbon‐based conductive rubber composite for 3D printed flexible strain sensors

AbstractPolymeric‐based flexible electronic devices are in high demand due to its wide range of applications. Natural rubber (NR) shows a great potential as matrix phase for flexible conductive polymer composites with its high elasticity and fatigue resistance. In this study, a new 3D printable conductive NR (CNR) composite was developed for strain sensor applications. Different contents of conductive carbon black (CCB) were mixed with NR latex to investigate the effect of the filler content on electrical and mechanical properties of the composites. The best‐known CNR composite with the CCB content of 12 phr was selected in order to produce the feedstock for the stereolithography process (SLA). The morphological, electrical, and mechanical properties of cast and 3D‐printed samples were investigated and compared. Although the 3D‐printed CNR sample had slightly lower conductivity than the cast one, it possessed comparable tensile strength and elongation at break, with values of 12.4 MPa and 703%, respectively. In addition, electrical responses of the CNR samples were investigated to demonstrate the electromechanical property of the material as a strain sensor. The 3D‐printed CNR sample exhibited the highest electromechanical sensitivity with a gauge factor (GF) of 361.4 (ε = 210%–300%) and showed good repeatability for 500 cycles. In conclusion, the development of this 3D printable functional material with great sensing capability will pave the way for innovative designs of personalized sensing textiles and other smart wearable devices.

Effect of the Particle Size and Layer Thickness of GNP Fillers on the Dielectric Properties and Actuated Strain of GNP-PDMS Composites.

Dielectric elastomer actuators (DEAs), a type of electroactive polymers (EAPs), are smart materials that are used in various fields such as artificial muscles and biomimetic robots. In this study, graphene nanoplatelets (GNPs), which are conductive carbon fillers, were added to a widely used DEA, namely, polydimethylsiloxane (PDMS), to improve its low actuated strain. Four grades of GNPs were used: H5, H25, M5, and M25 (here, the number following the letter indicates the average particle size of the GNPs in μm). The average layer thickness of the H grade is 13–14 nm and that of the M grade is 5–7 nm. PDMS composites were prepared by adding 0.5, 1, 2, and 3 wt% of each GNP, following which the mechanical properties, dielectric properties, and actuated strain of the composites were measured. The mechanical properties were found to increase as the particle size increased. Regarding the dielectric characteristics, it was found that the higher the aspect ratio of the filler, the easier the formation of a micro-capacitor network in the composite—this led to an increase in the dielectric constant. In addition, the higher amounts of GNPs in the composites also led to an increase in the dielectric constant. For the actuated strain analysis, the electromechanical sensitivity was calculated using the ratio of the dielectric constant to the Young’s modulus, which is proportional to the strain. However, it was found that when the loss tangent was high, the performance of the actuated strain decreased owing to the conversion of electric energy into thermal energy and leakage current loss. As a result, the highest actuated strain was exhibited by the M25 composite, with an actuated strain value of 3.01% measured at a low electric field (<4 kV/mm). In conclusion, we proved that the GNP–PDMS composites with a thin layer and large particle size exhibited high deformation.

3D interpenetrating piezoceramic-polymer composites with high damping and piezoelectricity for impact energy-absorbing and perception

Materials and structures with enhanced energy-absorbing and impact perception capabilities are widely deployed for crash mitigation, protective packaging of sensitive elements, and personal impact protection. However, conventional lightweight structures with a monolithic constitutive material cannot simultaneously achieve exceptional energy-absorbing capacity and electromechanical sensitivity. Here we proposed a new class of architected ceramic-polymer composites with improved energy-absorbing capacity and piezoelectric performance. An interconnected porous lead zirconate titanate ([Pb(Zr 0.52 Ti 0.48 )O 3 ], PZT) skeleton with uniformly distributed cellular-like pores in the transverse section and directionally aligned porous structure in the longitudinal section was fabricated using a facial camphene-templated freeze-casting method. Subsequently, the polymeric polydimethylsiloxane (PDMS) was impregnated into the skeleton to form the three-dimensional (3-D) interpenetrating-phase piezoelectric composite (IP 3 C). The as-fabricated interpenetrating architecture with each phase interconnected has endowed the proposed IP 3 C with an unprecedented combination of mechanical-damping (energy-absorption efficiency ∼ 7.71 MJ m −3 ) and electromechanical-conversion (piezoelectric constant d 33 ∼ 146 pC N −1 ) properties, which are 9 times and 7 times higher than the conventional counterpart 0–3 piezoelectric composite, respectively. As evidenced by numerical simulations, this remarkable enhancement is attributed to the high stress transfer efficiency within the IP 3 C, which is intrinsically controlled by the rationally designed interpenetrating architecture. The findings reported here demonstrate that multifunction, e.g., exceptional energy absorption and high sensitivity, can be achieved in one composite with architecture design, thereby driving forward and expanding the fundamental understanding in the area of multifunctional materials in hostile loading environments. • An interconnected porous lead zirconate titanate ([Pb(Zr 0.52 Ti 0.48 )O 3 ], PZT) skeleton with uniformly distributed cellular-like pores in the transverse section and directionally aligned porous structure in the longitudinal section was fabricated using a facial camphene-templated freeze-casting method. • The as-fabricated interpenetrating architecture with each phase is interconnected has endowed the proposed IP 3 C with an unprecedented combination of mechanical-damping and electromechanical-conversion properties, which are 9 times and 7 times higher than the conventional counterpart 0–3 piezoelectric composite, respectively. • The findings reported here demonstrate that multifunction, e.g., exceptional energy absorption and high sensitivity, can be achieved in one composite with architecture design, thereby driving forward and expanding the fundamental understanding in the area of multifunctional materials in hostile loading environments.

Nanosheet-Stabilized Emulsions: Near-Minimum Loading and Surface Energy Design of Conductive Networks.

Here, we develop a framework for assembly, understanding, and application of functional emulsions stabilized by few-layer pristine two-dimensional (2D) nanosheets. Liquid-exfoliated graphene and MoS2 are demonstrated to stabilize emulsions at ultralow nanosheet volume fractions, approaching the minimum loading achievable with 2D materials. These nanosheet-stabilized emulsions allow controlled droplet deposition free from the coffee ring effect to facilitate single-droplet devices from minute quantities of material or assembly into large-area films with high network conductivity. To broaden the range of compositions and subsequent applications, an understanding of emulsion stability and orientation in terms of surface energy of the three phases is developed. Importantly, this model facilitates determination of the surface energies of the nanosheets themselves and identifies strategies based on surface tension and pH to allow design of emulsion structures. Finally, this approach is used to prepare conductive silicone emulsion composites with a record-low loading level and excellent electromechanical sensitivity. The versatility of these nanosheet-stabilized emulsions illustrates their potential for low-loading composites, thin-film formation and surface energy determination, and the design of functional structures for a range of segregated network applications.

Characterization of slide ring materials for dielectric elastomer actuators

This paper investigates the characteristics of sliding ring materials (SRMs), which are promising elastomeric materials for dielectric elastomer actuators (DEAs). Two different types of SRMs with Young’s modulus of 0.8 MPa and 3.3 MPa, respectively, are prepared, and their material and mechanical properties and electro-mechanical performances at electric fields of up to 30 V µm−1 are characterized. For comparison, the same tests are also performed on several commercially available elastomers: Elastosil 2030, Ecoflex 00-30, CF19-2186, and VHB 4905. The results reveal that SRMs demonstrate negligible Mullins effect and hysteresis, while their dielectric strength (62.4–112.4 V µm−1) and viscoelasticity ( 0.07–0.24 at 10 Hz) are comparable or even superior to those of other elastomers. In addition, elongation at break is found to be 163.8%–172.1%. SRMs exhibit excellent electro-mechanical performance; for instance, one of the two types has an actuation force 293.2 mN at 24.9 V µm−1 and a strain of 5.2% at 22.3 V µm−1. These values are the largest or larger than most of the tested elastomers. The high performance of SRMs results from their dielectric constant, which ranges from 10.3 to 13.4, leading to an electro-mechanical sensitivity of up to 15.3 MPa−1. These results illustrate SRMs as attractive material options for DEAs.

Poly(thioether)-b-polysiloxane-b-poly(thioether) triblock copolymer towards homogeneous dielectric elastomer with high dielectric performance

Dielectric elastomers (DEs) have drawn much attention owing to their application prospects in artificial muscles and soft robotics, it is still a big challenge to prepare DEs with high electromechanical performances. This work reports a highly stretchable poly(thioether)-b-polysiloxane-b-poly(thioether) triblock copolymer based homogenous DEs with high electromechanical properties. The triblock copolymer (PSiPGE) was synthesized through the ring-opening polymerization (ROP) of phenyl glycidyl ether (PGE) and carbonyl sulfide (COS) catalyzed by silicon alkoxides. The dipoles (benzene rings) on the side groups of PSiPGE improved the dipole polarizations and the phase separation structure of this triblock copolymer enhanced the interfacial polarizations between poly(thioether) and polysiloxane, and thus improving the dielectric constant (ε’, up to 5.8). In addition, the PSiPGE exhibited low elastic modulus (Y, 0.04 MPa), and thus possessed high electromechanical sensitivity (β, ∼145 MPa−1) which is much higher than that of most homogenous DEs. This work provides a new strategy to construct homogenous DEs with excellent electromechanical performances, leading to a greater application aspect in the actuated devices.

Structural health monitoring of CFRPs using electrical resistance by reduced peripheral electrodes

In this study, structural health monitoring (SHM) methods of carbon fiber reinforced plastics (CFRPs) were investigated using electrical resistance. The developed sensing technique monitored electrical resistance in accordance with the impact damage of a CFRP. The changes in electrical resistances with multiple electrode sets enabled SHM without extra sensors so that this technique can be called self-sensing. Moreover, this study proposed electrodes only at peripheral side of a structure to minimize the number of electrodes compared to those in an array which has square number of sensors as the sensing area increases. For the intensive investigation, electromechanical sensitivity in terms of electrode distance was analyzed and optimized under drop weight impact testing. Then, SHM methods with electrodes in an array and electrodes in peripheral edges were comparatively investigated. The developed methods successfully localized impact damages into 2D coordinates. Furthermore, damage severity can be shown with a damage map by calculating electrical resistance change ratio. Therefore, structural health self-sensing system using electrical resistance was successfully developed with the minimum number of electrodes.

Machine learning aided design of smart, self-sensing fiber-reinforced plastics

Numerous techniques have been developed for the non-destructive evaluation (NDE) of impact damage in fiber reinforced plastics (FRPs), following the increasing demands for their safety and maintenance. Considering the large-scale detection and the vast amount of data involved, machine learning (ML) can be utilized in NDE for damage type analysis and impact damage localization. Furthermore, self-sensing using carbon fiber in FRPs is an emerging technique for NDE that can be combined with ML. In this study, ML was used to design smart FRPs by selecting the fiber type and electrode distance considering the cost and electromechanical sensitivity. Furthermore, a novel algorithm for structural health self-sensing was suggested using an artificial neural network. The developed ML algorithms are advantageous since they do not require a theoretical model when all the factors and the variables of FRPs, such as the maximum absorbed impact energy, maximum impact force, initial electrical resistance, number of electrodes, fiber types, and electrode distance, are to be considered. The algorithm was trained using given input data and the target, and the output could be successfully obtained when new input data were provided. Therefore, the proposed ML algorithms hold great potential and applicability to FRP design and for NDE methods.

Development of a multifunctional nanoindenter integrated in-situ Scanning Electron Microscope - application to the monitoring of piezoresponse and electro-mechanical failures

The rising complexity of multi-material structures integrated into multi-functional devices requires the development of dedicated characterization tools capable of simultaneously monitoring different physical magnitudes with a relevant spatial resolution. This paper reports the development and the application of an original instrument based on a nanoindenter coupled with fine electrical measurements and integrated in-situ a Scanning Electron Microscope (SEM). The performances and capabilities of this home-developed instrument are illustrated through two different case studies.First, a micrometer-scale piezoelectric structure made up of wurtzite-single crystalline AlN islands grown on top of conductive Si pillars is tested. In-situ SEM imaging is used to precisely position the indenting probe on these individual islands, while the instrument sensitivity and repeatability are used to monitor their low-signal piezoresponse. Effective piezoelectric coefficients are also extracted for different loading/unloading conditions.Secondly a Si3N4/AlSiCu/SiO2 stack, which is standardly integrated as a passivation structure on top of microelectronic chips, is electrically and mechanically stressed and monitored up to its failure. The mechanical failure mechanisms (buried or emerging cracks) are discriminated thanks to the real-time SEM imaging of the indentation test. The instrument high sensitivity is used to monitor early current leakages that are attributed to conduction paths induced by mechanical failures.Combining high electro-mechanical sensitivity and precise probe positioning appears as an efficient way to monitor and analyze low-level electrical responses of small-scale structures. This approach paves the way to the fine characterization of micro/nano-systems displaying mechanically-driven electrical properties (conduction mechanism, leakage, breakdown,) like 2D-materials, dielectrics in microelectronic devices, strain-sensors, enamelled Litz wires,…

Multi-scale hybrid In situ tow scale carbon fiber reinforced thermoplastic strain sensor

In this study, strain self-sensing of carbon fiber reinforced thermoplastic (CFRTP) composite was investigated using the electrical resistance. The self-sensing researches limited to the thermoset composites motivated the study for the investigations with CFRTP. Additional treatment was performed during the manufacturing to enhance its electromechanical sensitivity and mechanical properties by subtracting carbon fiber tows, in situ interfacial polymerization, and adding graphene oxide (GO) to the polymer. Isolating the sensing tow increased the electromechanical sensitivity because the reduced electrical network was more sensitive to the mechanical deformation. In-plane electrical network to the nearby tows was restricted by eliminating the adjacent carbon fiber tows from the sensing tow. Through-thickness network was controlled by the in situ interfacial polymerization of the sensing tow with polyamide 6,6 (PA 6,6). GO was added to the polymer to enhance the mechanical properties. These additional treatments were converted into equivalent electrical circuit modeling to comprehend the electromechanical behavior of the CFRTPs. The electromechanical sensitivities of the developed CFRTPs increased by 270% compared with control sample. The novel advantages of the proposed method are low cost, easy implementation, in situ integrated smart sensors, and tunable customized electromechanical sensitivity.

Fuzzy Logic-Based and Nondestructive Concrete Strength Evaluation Using Modified Carbon Nanotubes as a Hybrid PZT–CNT Sensor

Concrete strength and factors affecting its development during early concrete curing are important research topics. Avoiding uncertain incidents during construction and in service life of structures requires an appropriate monitoring system. Therefore, numerous techniques are used to monitor the health of a structure. This paper presents a nondestructive testing technique for monitoring the strength development of concrete at early curing ages. Dispersed carbon nanotubes (CNTs) were used with cementitious materials and piezoelectric (PZT) material, a PZT ceramic, owing to their properties of intra electromechanical effects and sensitivity to measure the electromechanical impedance (EMI) signatures and relevant properties related to concrete strength, such as the elastic modulus, displacement, acceleration, strength, and loading effects. Concrete compressive strength, hydration temperature, mixture ratio, and variation in data obtained from the impedance signatures using fuzzy logic were utilized in the comparative result prediction method for concrete strength. These results were calculated using a fuzzy logic-based model considering the maturity method, universal testing machine (UTM) data, and analyzed EMI data. In the study, for data acquisition, a hybrid PZT–CNT sensor and a temperature sensor (Smart Rock) were embedded in the concrete to obtain the hydration temperature history to utilize the concrete maturity method and provide data on the EMI signatures. The dynamic changes in the medium caused during the phase in the concrete strengthening process were analyzed to predict the strength development process of concrete at early curing ages. Because different parameters are considered while calculating the concrete strength, which is related to its mechanical properties, the proposed novel method considers that changes in the boundary condition occurring in the concrete paste modify the resonant frequency response of the structure. Thus, relating and analyzing this feature can help predict the concrete strength. A comprehensive comparison of the results calculated using the proposed module, maturity method, and cylindrical specimens tested using the UTM proved that it is a cost-effective and fast technique to estimate concrete strength to ensure a safe construction of reinforced cement concrete infrastructures.

Modelling the electromechanical sensitivity of silicone composites using response surface methodology

Dielectric elastomers are used for sensor and actuator applications. These materials convert voltage applied directly into strain through Maxwell stress. An important parameter in the determination of voltage induced strains is electromechanical sensitivity. This paper presents an approach to establish the model for predicting the electromechanical sensitivity of silicone dielectric elastomer composites using the response surface methodology. Two-factor and two-level, face-cantered composite design is used for experimentation. The parameters which affect the electromechanical sensitivity are selected as superconducting carbon black (SCCB) and barium titanate (BT). Response surface methodology is used to derive second-order quadratic model with interactions. Investigation showed that SCCB has more significant effect than parameter BT, on controlling the electromechanical sensitivity of these composites. Maximum electromechanical sensitivity for these composites was found at around ≤ 4 parts per hundred weight fractions for both the parameters.