Piezoresistive Characteristics Research Articles

Mechanical and piezoresistive performance of additively manufactured carbon fiber/PA12 hybrid honeycombs

This study investigates a novel self-sensing honeycomb composite structure composed of two distinct cellular layers with differing unit cell architectures, specifically hexagonal and re-entrant designs. Short carbon fiber (CF)/polyamide 12 (PA12) composite filaments with 0, 5 or 15 wt.% CF content were utilized to additively manufacture the honeycomb structures via Fused Filament Fabrication (FFF), and their mechanical and piezoresistive self-sensing characteristics were experimentally investigated under quasi-static in-plane and out-of-plane compression at both room temperature and elevated temperatures. The results reveal that the hybrid hexagonal/re-entrant (HR) honeycombs mechanically outperform their non-hybrid double-layer and single-layer counterparts under in-plane loading, reporting an increase in collapse strength and energy absorption by factors of 1.64 and 2.25, respectively. These improvements are attributed to the mechanical interactions occurring at the interface between the auxetic and non-auxetic layers within the hybrid structure, effectively enhancing its structural attributes. Furthermore, the double-layer honeycombs display excellent strain-sensing capabilities within the elastic regime, with gauge factors reaching values as high as 146. Mechanical tests conducted at elevated temperatures reveal that the CF/PA12 honeycombs retain a significant portion of their elastic modulus, strength and energy absorption even at 125 °C, while maintaining high gauge factors of up to 72.4. These honeycombs also exhibit pronounced thermoresistive behavior, evidenced by a decrease in electrical resistance of up to 41.3 % with increasing temperatures from 25 to 125 °C. Considering their exceptional combination of thermo-mechanical, thermoresistive and piezoresistive characteristics, these hybrid double-layered CF/PA12 honeycombs hold promise for potential applications in multifunctional lightweight structures, offering integrated temperature and strain-sensing capabilities.

Evaluating the effect of unidirectional loading on the piezoresistive characteristics of carbon nanoparticles

The piezoresistive effect of materials can be adopted for a plethora of sensing applications, including force sensors, structural health monitoring, motion detection in fabrics and wearable, etc. Although metals are the most widely adopted material for sensors due to their reliability and affordability, they are significantly affected by temperature. This work examines the piezoresistive performance of carbon nanoparticle (CNP) bulk powders and discusses their potential applications based on strain-induced changes in their resistance and displacement. The experimental results are correlated with the characteristics of the nanoparticles, namely, dimensionality and structure. This report comprehensively characterizes the piezoresistive behavior of carbon black (CB), onion-like carbon (OLC), carbon nanohorns (CNH), carbon nanotubes (CNT), dispersed carbon nanotubes (CNT-D), graphite flakes (GF), and graphene nanoplatelets (GNP). The characterization includes assessment of the ohmic range, load-dependent electrical resistance and displacement tracking, a modified gauge factor for bulk powders, and morphological evaluation of the CNP. Two-dimensional nanostructures exhibit promising results for low loads due to their constant compression-to-displacement relationship. Additionally, GF could also be used for high load applications. OLC’s compression-to-displacement relationship fluctuates, however, for high load it tends to stabilize. CNH could be applicable for both low and high loading conditions since its compression-to-displacement relationship fluctuates in the mid-load range. CB and CNT show the most promising results, as demonstrated by their linear load-resistance curves (logarithmic scale) and constant compression-to-displacement relationship. The dispersion process for CNT is unnecessary, as smaller agglomerates cause fluctuations in their compression-to-displacement relationship with negligible influence on its electrical performance.

Protective and Collision‐Sensitive Gel‐Skin: Visco‐Elastomeric Polyvinyl Chloride Gel Rapidly Detects Robot Collision by Breaking Electrical Charge Accumulation Stability

Human–robot collaboration (HRC) is effective to improve productivity in industrial fields, based on the robot's fast and precise work and the human's flexible skill. To facilitate the HRC system, the first priority is to ensure safety in the event of accidents, such as collisions between robots and humans. Therefore, a protective and collision‐sensitive robot skin, named Gel‐Skin is proposed to guarantee the safety in HRC. The Gel‐Skin is composed of polyvinyl chloride (PVC) gel, which is a functional material with piezoresistive characteristics and impact absorption capability. In particular, the PVC gel has a distinctive piezoresistive property that the relation between mechanical pressure and electrical resistance is tunable depending on an applied voltage. When a voltage is applied to the PVC gel, the electrical charges are accumulated around the anode and it shows increased piezoresistive sensitivity. In this study, it is verified for the PVC gel to exhibit the 4.78 times higher sensitivity by simply applying a voltage. This novel physical phenomenon enables the Gel‐Skin to detect the collision rapidly. Finally, the Gel‐Skin is applicated to a real robot system and it is verified that the Gel‐Skin can detect a collision and absorb impact to ensure safety.

Exploring potential of MXenes in smart sensing and energy harvesting

In present work, MXene based piezo-resistive stress sensor device is fabricated using a freeze-dry method. The device was tested to measure the mechanical stress, sensitivity, and triboelectric response by converting them into electrical signals as readout. With high electrical conductivity, mechanical flexibility, and piezo-resistive characteristics, MXene-based device offers novel sensing and triboelectric-related applications. This study showed an extensive characterization after fabricating the sensor using a simple and scalable process to ensure their performance in terms of sensitivity, stability, and repeatability. Using pure MXene layer as the core material, this paper pioneers an interesting investigation focusing on stress monitoring by piezoresistive stress sensor and triboelectric nanogenerator.

Thin and high conductive multi‐walled carbon nanotubes/polydimethylsiloxane composite film prepared via solvent method as strain sensors

AbstractFlexible strain sensors based on conductive fillers and flexible polymers possessed significant advantages in human motion detection. Preparing a strain sensing layer with high electrical conductivity and excellent mechanical property under high content of conductive filler contributed to the stability of flexible strain sensors. In this study, MWCNTs/PDMS composite film was prepared by the organic solvent method. The microstructure, electrical conductivity, mechanical property, and piezoresistive characteristics of the composite film at different MWCNTs contents were characterized and discussed. When the mass fraction of MWCNTs in the composite film was 5%, the composite film exhibited a high electrical conductivity of 9.56 S/m while maintaining ideal mechanical properties, and the film thickness was just about 180 μm. The relationship between electrical signals and film strain was performed. The piezoresistive characteristic results demonstrated that the prepared composite film could be used as flexible strain sensor for human motion detection. The prepared thin MWCNTs/PDMS composite film in this paper illustrated high conductive and desired flexibility, and was an alternative material for human motion detection.

Piezoresistive Characteristics of Carbon Nanotube Polymer Composites with Different Filler Content and Aspect Ratio for Pressure Sensors

Polymer composites enriched with conductive fillers hold immense potential for flexible pressure sensors, because of the remarkable piezoresistive effect they possess. Research on polymer composite pressure sensors has been actively ongoing because of their flexibility and high electrical resistance performance. This paper presents a comprehensive comparison of the piezoresistive characteristics of conductive composites for pressure sensors, focusing on the influence of carbon nanotube (CNT) content and aspect ratio. Polymer composites with conductive fillers, specifically CNTs, have demonstrated significant potential for pressure sensing applications based on the piezoresistive effect. By systematically varying the CNT concentration and aspect ratio, we investigated the impact of these parameters on the piezoresistive behavior of the composites. A pressure in the range of 0-200 kPa was applied to the conductive composite, and resistance change due to pressing was measured. The best performing samples were evaluated in 150 cycle tests to verify repeatability and durability. Experimental analysis and characterization revealed the intricate relationship between CNT content, aspect ratio, and the resulting piezoresistive properties. Through this study, we aim to enhance understanding of how CNT concentration and aspect ratio influence the performance of CNT/PDMS composites as pressure sensors, thereby facilitating the development of optimized sensing materials for various pressure sensing applications.

Investigation of MEMS Single Turn Meander-Shaped Silicon Carbide Piezoresistive Pressure Sensor on a Clamped Circular Diaphragm for High Pressure Harsh Environment Applications

Silicon-based Microelectromechanical System (MEMS) pressure sensors are extensively used and have the advantages of high accuracy and miniaturization. Despite this, due to inherent material limitations, they are not easily able to withstand high temperatures greater than 150°C. To overcome this disadvantage, Silicon Carbide (SiC) is the preferred material because it has excellent thermomechanical properties and operates above 600°C. Piezoresistive pressure sensors made of Silicon Carbide are ideally able to detect pressures beyond 600°C. Our work presents MEMS Single turn meander-shaped piezoresistive pressure sensor on a circular SiC diaphragm for high pressure applications of pressure range 0–40[Formula: see text]MPa in harsh environment. This work models and analyses the piezoresistive pressure sensor characteristics using an analytical modeling and simulation method to choose the best design. To ascertain its sensitivity, expressions are computationally simulated with MATLAB software using the thin plate and small deflection theory. To evaluate the viability of the model, COMSOL Multiphysics simulation is used. When compared to recent studies, our proposed sensor provides a sensitivity of near about 5.4[Formula: see text]mV/V/MPa across a pressure range of 0–40[Formula: see text]MPa.

Piezoresistive behavior of MWCNT/PA12 honeycomb composites processed via selective laser sintering

This study examines the piezoresistive and mechanical behaviors of multiwalled carbon nanotube (MWCNT)/polyamide (PA12) lattice composites processed via selective laser sintering (SLS). Firstly, neat PA12 powder was ballmilled with either 0.3, 0.5, or 1.0 wt% MWCNT loading to obtain nanoengineered powder feedstocks. The feedstocks were used to realize electrically conductive MWCNT/PA12 bulk and honeycomb lattice structures via SLS. The piezoresistive and mechanical characteristics of bulk samples were assessed under tensile, compressive, and flexure loadings while those of honeycombs were investigated under in-plane and out-of-plane compression. The morphological and thermal characterizations were carried out to gain insight into the processing-structure-property relations. The microstructural observations, including in situ μ-CT imaging, revealed that the porosity of the sintered parts significantly increased (≈150%) with increasing MWCNT loading, resulting in reduced elastic stiffness and strength of the sintered composites, despite their slightly higher crystallinity (+6% for 0.5 wt% MWCNT loading). The bulk nanocomposites exhibited excellent piezoresistive characteristics, showing a maximum gauge factor of 31 (in compression), which is significantly higher than the sensitivity factors of extant piezoresistive self-sensing composites. The honeycomb structures showed a maximum specific energy absorption of 3 and 24 J g−1 at 40% relative density under in-plane and out-of-plane compression loading, respectively. It was also demonstrated, that the MWCNT/PA12 honeycombs possess excellent strain sensing characteristics due to their pronounced piezoresistivity, reporting gauge factors up to 25 and 17 for in-plane and out-of-plane loading, respectively.

Multifunctional characteristics of 3D printed polymer nanocomposites under monotonic and cyclic compression

This study presents the multifunctional characteristics of multi-walled carbon nanotube (MWCNT)/polypropylene random copolymer (PPR) composites enabled via fused filament fabrication (FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity (⁓10−1S/cm), improved mechanical performance (modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response (gauge factor of 27.9–8.5 for bulk samples) under compression. The influence of strain rate on the piezoresistive response of bulk samples (4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression (2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed. The gauge factor of BCC and FCC cellular composites (4 wt% of MWCNT) with a relative density of 30% was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.

Dual-Sensing Piezoresponsive Foam for Dynamic and Static Loading.

Polymeric foams, embedded with nano-scale conductive particles, have previously been shown to display quasi-piezoelectric (QPE) properties; i.e., they produce a voltage in response to rapid deformation. This behavior has been utilized to sense impact and vibration in foam components, such as in sports padding and vibration-isolating pads. However, a detailed characterization of the sensing behavior has not been undertaken. Furthermore, the potential for sensing quasi-static deformation in the same material has not been explored. This paper provides new insights into these self-sensing foams by characterizing voltage response vs frequency of deformation. The correlation between temperature and voltage response is also quantified. Furthermore, a new sensing functionality is observed, in the form of a piezoresistive response to quasi-static deformation. The piezoresistive characteristics are quantified for both in-plane and through-thickness resistance configurations. The new functionality greatly enhances the potential applications for the foam, for example, as insoles that can characterize ground reaction force and pressure during dynamic and/or quasi-static circumstances, or as seat cushioning that can sense pressure and impact.

Effect of rGO/GNP on the electrical conductivity and piezoresistance of cement-based composite subjected to dynamic loading

Graphene has good compatibility with cement-based materials. It can be introduced into cement to produce cement-based composite with electrical conductivity and loading sensitivity, and can effectively monitor the internal state of concrete components under stresses such as compression, bending, and tension. The electrical properties of such cement-based composites vary with the type and doping level of graphene. In this study, two types of reduced graphene oxide (rGO) with varying oxygen contents and two types of graphene nanoplates (GNPs) with varying sheet sizes were selected, and the conductivity and piezoresistive properties of the rGO/GNP cement-based composites subjected to cyclic compressive and tensile stress were investigated. Both tunnelling effect and percolation phenomena simultaneously played important roles in conductivity and electromechanical properties of graphene cement-based composite. The rGO/GNP cement-based composites exhibited excellent piezoresistive characteristics under compressive or tensile stress and stable repeatability. The cement-based composites filled with high oxygen content graphene (rGO-HO) or large sheet size graphene (GNP-L) has a larger stress sensitivity coefficient. This study reveals the great potential of graphene for real-time and in situ health monitoring of concrete structures. The excellent loading response ability of graphene has laid the foundation for the development of new smart materials based on graphene cement, which is of great significance for expanding the use of graphene and for the intelligent of traditional building materials.

Design of a smart lime mortar with conductive micro and nano fillers for structural health monitoring

Structural health monitoring is an essential tool for assessing the performance of buildings and infrastructure, especially after critical events or the application of structural interventions. When dealing with architectural heritage structures, both structural health monitoring instrumentation and intervention materials need to be as inconspicuous and unintrusive as possible, both in terms of mechanical compatibility and aesthetics. Therefore, the design of smart sensors based on construction materials used in conservation engineering promises to provide an acceptable integrated structural health monitoring and upgrading solution for historic structures. In this paper an experimental investigation of smart intervention materials for historic masonry structures is presented. The materials consisted of natural hydraulic lime mortars modified through the inclusion of electrically conductive micro- and nanofillers: graphite, carbon nanotubes and carbon microfibres. The fillers provide multifunctionality to the matrix material based on an enhancement of its piezoresistive characteristics. Further, they result in an improvement of the mechanical properties of the intervention material without compromising its mechanical and chemical compatibility with the original structure. The resulting materials were evaluated based on mechanical property improvement, piezoresistivity enhancement and ease of production.

Lime-based nanocomposites for masonry restoration: Towards the implementation of small-scale restoration

The structural integrity of historic and traditional buildings can be affected by natural weathering and incompatible restoration interventions. Traditionally, lime binders have been used extensively for restoration applications, while the incorporation of multi walled carbon nanotubes (MWCNTs) in such a binder, enhances the restoration material with increased mechanical as well as with self-sensing properties due to its piezoresistive characteristics. The focal point of the present investigation was the examination of the electrical, mechanical, and piezoresistive properties of a composite nano-reinforced lime-based mortar paste under different geometrical sizes (scale-up tests). Firstly, prismatic specimens of two different sizes, composed of the proposed nano-reinforced lime-based mortar were subjected to testing and compared against reference prismatic prisms of traditional non-reinforced lime-based mortar with a similar composition. The results showed a 24 % increase in the compressive strength and a 37.5 % decrease in the electrical resistance. Secondly, electrical resistance measurements were carried out on a small-scaled masonry specimen built with the MWCNTs reinforced lime-based mortar, to determine potential structure inhomogeneity effects. The tests revealed approximately 50 % electrical resistance decrease in comparison to the non-reinforced reference prismatic specimens. Lastly, the composite restoration material was applied at an actual masonry restoration project at the public library “Korais” of Chios Island, Greece, with the aim to monitor the composite material’s electrical resistance under real conditions.

Innovative nano reinforced restoration materials: Design at the nanoscale, piezoresistive evaluation at the microscale and their sustainability

In the present article, the holistic concept of designing reinforcement at the nanoscale for lime-based restoration materials up to the sustainability aspects of the restoration with innovative materials is assessed. Within the framework of research project “Advanced Cultural Heritage”, the University of the Aegean was the responsible partner to perform the design at the nanoscale, i.e., to perform an investigation on the appropriate process parameters to uniformly disperse the carbon-based nanostructures (CBNs) on aqueous solution. The type, concentration, and dispersion capability of the CBNs are critical to the restoration material, since they are responsible to enhance the material with another functionality (piezo-resistivity) that enables for remote structural health monitoring of the restored area. As a working example, it was shown that the addition of 0.15 wt% multi-wall carbon nanotubes (MWCNTs), increases by 25 % the compression strength of the ternary binder as well as the binder was enabled with piezo-resistive characteristics. An approximate 22 % normalized electrical resistance change under compression loading – unloading loops at loading level of 50 % compressive strength was noticed. The economic viability and sustainability of the new technology was demonstrated for a 25 years’ service life, where the innovative restoration approach with the exploitation of nano reinforced material, proved to cost less for maintenance and monitoring activities over the designated time span.

3D printed flexible wearable sensors based on triply periodic minimal surface structures for biomonitoring applications

Soft piezoresistive wearable conductors have led to a paradigm shift in the monitoring of human bodily motions. Cellular additively manufactured conductors are promising piezoresistive components as they offer mechanical tunability and provide controllable percolation pathways. In the present study, we engineer high surface-area cellular structures with the triply periodic minimal surface (TPMS)-based architectures to tailor their piezoresistive response for use in wearable devices. A simple and economical fabrication process is proposed, wherein a fused deposition modeling 3D printing technique is utilized to fabricate flexible thermoplastic polyurethane (TPU) cellular structures. Interconnectivity of TPMS designs enables the coating of a continuous graphene layer over the TPU internal surfaces via a facile dip-coating process. The effects of pore shape on piezoresistivity are studied in four different TPMS structures (i.e. Primitive, Diamond, Gyroid, and I-WP). Mechanical properties of sensors are evaluated through experimental procedures and computation methods using finite element analysis of the Mooney–Rivlin hyperelastic model. The piezoresistive performance of sensors exhibits durability under cyclic compression loading. Finally, we conclude that the Primitive structure offers suitable piezoresistive characteristics for sensing of walking, whereas the Diamond structure presents favorable results for respiration monitoring.

Structural performance of reinforced concrete beams with 3D printed cement-based sensor embedded and self-sensing cementitious composites

Cementitious composites containing conductive functional fillers can achieve self-sensing and continuous monitoring of the damages and cracks through piezoresistive characteristics defined as the electrical resistivity change under external deformation. Previous studies developed two types of self-sensing cementitious composites expressing superior piezoresistive characteristics, as well as good linearity, repeatability, and sensitivity. This research further investigates the flexural damage sensing capability of the developed self-sensing cementitious composites by applying them to reinforced concrete beams. The 3D printed self-sensing cementitious composites containing carbon fibre (CF) at 0.7 wt% and activated carbon powder (ACP) at 0.25 wt% were tested as the embedded sensors in this study. Mould cast self-sensing cementitious composites developed by 100 wt% of magnetite aggregate (MA), 0.3 wt% of CF, and 0.05 wt% of carbon nanotube (CNT) were examined in bulk form. The corresponding fractional change in resistivity (FCR) was attained on the tension face of the reinforced concrete beams when subjected to flexural loading. Experimental findings suggest that the embedded 3D printed cement-based sensors in beam elements can contribute to the load-carrying capacity of the reinforced concrete beam, achieving an average load of yielding at 88.65 kN and a maximum loading capacity of 111.09 kN, which is 10% and 12% higher compared with the controlled reinforced concrete beam, respectively. In terms of sensing performance, both 3D printed self-sensing cementitious composites in sensor form and mould cast self-sensing cementitious composites in bulk form could reflect stress and strain changes and detect crack formation in reinforced concrete beams, which demonstrate gage factors at 318 and 527, respectively. However, 3D printed cementitious sensors are more effective when reinforced concrete beams are severely damaged. In terms of self-sensing cementitious composites in bulk form, the randomly distributed CF and CNT could provide a more pronounced crack and damage sensing capability, with fluctuations that can be observed at both low and high levels of damage.

Effects of graphene nanoplatelets type on self-sensing properties of cement mortar composites

Graphene nanoplatelets (GNPs) that possess high electrical conductivity and relatively low cost have been considered to obtain self-sensing capability in cementitious composites. However, there is limited understanding on the effects of physical properties of GNPs such as particle size and surface area on the self-sensing characteristics of the cement composites. In this study, nine types of GNPs that have different surface areas, particle sizes, and thicknesses are considered in the development of self-sensing mortar composites. For each type of GNPs, specimens with GNP concentrations of 2.5%, 5%, and 7.5% by weight of cement were prepared. The bulk electrical resistivity of the developed mortar composites was measured at different curing ages. The compressive strength of the specimens was also evaluated. The piezoresistive behaviors of the GNP-reinforced mortar composites were studied through cyclic compressive loading tests at different load levels. During piezoresistivity tests, the measurements were conducted through both direct current (DC) and alternating current (AC) and the results obtained from each method were evaluated. Results reveal that GNPs with very small particle sizes and large surface areas cannot disperse effectively in the cement matrix and do not provide piezoresistive characteristics. For GNPs with relatively smaller surface areas, the GNPs with higher particle sizes form effective conductive paths and exhibit better piezoresistive characteristics.

Rate dependent piezoresistive characterization of smart aerospace sandwich structures embedded with reduced graphene oxide (rGO) coated fabric sensors

In this study, the piezoresistive performance of smart aerospace sandwich structures was investigated by conducting three-point bending tests at variable loading rates (0.2, 2.0, and 20 mm/min). A reduced graphene oxide (rGO) coated glass fabric piezoresistive sensor was embedded in the facesheet of a sandwich structure. An integrated framework was designed to measure piezoresistive performance of the sandwich structure i.e. from fabrication of facesheets to electromechanical testing. The three-point bending tests performed on beams consisting of the coated fabric sensors with several different geometries (variable beam widths and core thicknesses) showed that the piezoresistivity of the fabric sensors was inversely proportional to the loading rate. Moreover, the study showed that the rate dependency was prominent in beams with larger widths having maximum percent decrease of 43% in the piezoresistivity (core thickness of 3 mm) with increasing the loading rate. However, the normalized piezoresistivity with width of the beam was found to be consistent for different widths, showing good application of the fabric sensor with any arbitrary width of interest. Furthermore, the piezoresistivity rate dependency was more prevalent in the non-linear region with a maximum of 68% decrease in piezoresistivity as compared to 42% found for the elastic region (width 75 mm, thickness 5 mm).

Ultrasensitive piezoresistive behavior of silicon carbonitride thin films by optimizing nanomorphologies

Silicon carbonitride (SiCN)-containing amorphous carbon network is a promising piezoresistive material for pressure sensor due to superior high temperature stability and strong piezoresistive properties. However, current works mainly concerned on bulk SiCN that is unable to satisfy rapid development of large area electronics, and the mechanism of the superior piezoresistive characteristics is still not clear. In this work, SiCN thin films with various carbon concentrations are prepared by magnetron sputtering, and first principles approach is applied to reveal the piezoresistive mechanism of SiCN. The SiCN sample with moderate carbon content features ultrahigh gauge factors range of 1713–7290 under varied stress, which are significantly larger than those of existing piezoresistive thin films. By combining with first principles calculations, it is concluded that the distance between carbon clusters is crucial for piezoresistive effect of SiCN, and a distance of 1.8 Å is optimal for generating tunneling effect and obtaining outstanding piezoresistive performance. Moreover, the influence of carbon concentration on resistance change in experiments is nicely predicted by the bandgap change calculated by first principles, which can be applied to evaluate the nanostructure–property relationship for piezoresistive materials.

Porous polyvinyl alcohol/graphene oxide composite film for strain sensing and energy-storage applications

In this study, a flexible porous polyvinyl alcohol (PVA)/graphene oxide (GO) composite film was developed and tested for flexible strain sensing and energy-storage applications. Morphology and mechanical properties were studied; tensile strength and Young’s modulus increased by 225% and 86.88%, respectively, at 0.5 wt% GO. The PVA/GO film possesses exceptional sensing ability to various mechanical strains, such as tension, compression, bending, and torsion. For example, the gauge factor of the PVA/GO film as a tensile-strain sensor was measured as 2.46 (246%). Under compression loads, the PVA/GO composite film showed piezoresistive and capacitive strain-sensing characteristics. Under 5 kPa of compression load, the relative resistance increased by 81% with a 100 msec response time; the relative capacitance increased by 160% with a 120 msec response time. The PVA/GO strain sensor exhibited high durability and reliability over 20 × 103 cycles of tensile strain and bending at 3.33 Hz. Moreover, the PVA/GO composite film showed good electrochemical properties due to its porous structure; the maximum capacitance was 124.7 F g−1 at 0.5 wt% GO. After 20 × 103 charging–discharging cycles, the capacitance retention rate was 94.45%, representing high stable capacitance performance. The results show that electrically conductive porous PVA nanocomposite films are promising candidates for strain sensing and energy-storage devices.