Exfoliated Graphite Nanoplatelet-Carbon Nanotube Hybrid Composites for Compression Sensing

In this study, we investigated the gauge factor and compressive modulus of hybrid nanocomposites of exfoliated graphite nanoplatelets (xGnP) and multiwalled carbon nanotubes (MWCNTs) in a polydimethylsiloxane matrix under compressive strain. Mechanical and electrical tests were conducted to investigate the effects of nanofiller wt %, the xGnP size, and xGnP:MWCNT ratio on the compressive modulus and sensitivity of the sensors. It was found that nanofiller wt %, the xGnP size, and xGnP:MWCNT ratio significantly affect the electromechanical properties of the sensor. The compressive modulus increased with an increase in the nanofiller wt % and a decrease in the xGnP size and xGnP:MWCNT ratio. However, the gauge factor decreases with a decrease in the nanofiller wt % and xGnP size and an increase in the xGnP:MWCNT ratio. Therefore, by investigating the piezoresistive effects of various factors for sensing performance, such as wt %, xGnP size, and xGnP:MWCNT ratio, the concept of one- and two-dimensional hybrid fillers provides an effective way to tune both mechanical properties and sensitivity of nanocomposites by tailoring the network structure of fillers

Multilayered Composites with Modulus Gradient for Enhanced Pressure???Temperature Sensing Performance

Highly sensitive and flexible composite sensors with pressure and temperature sensing abilities are of great importance in human motion monitoring, robotic skins, and automobile seats when checking the boarding status. Several studies have been conducted to improve the temperature-pressure sensitivity; however, they require a complex fabrication process for micro-nanostructures, which are material-dependent. Therefore, there is a need to develop the structural designs to improve the sensing abilities. Herein, we demonstrate a flexible composite with an enhanced pressure and temperature sensing performance. Its structural design consists of a multilayered composite construction with an elastic modulus gradient. Controlled stress concentration and distribution induced by a micropatterned structure between the layers improves its pressure and temperature sensing performance. The proposed composite sensor can monitor a wide range of pressure and temperature stimuli and also has potential applications as an automotive seat sensor for simultaneous human temperature detection and occupant weight sensing

Hierarchical Micro-nano Structured Composites for Enhanced Mechanical Sensing and Power Generation

Department of Mechanical Engineeringclos

Multilayered Composites with Modulus Gradient for Enhanced Pressure—Temperature Sensing Performance

Highly sensitive and flexible composite sensors with pressure and temperature sensing abilities are of great importance in human motion monitoring, robotic skins, and automobile seats when checking the boarding status. Several studies have been conducted to improve the temperature-pressure sensitivity; however, they require a complex fabrication process for micro-nanostructures, which are material-dependent. Therefore, there is a need to develop the structural designs to improve the sensing abilities. Herein, we demonstrate a flexible composite with an enhanced pressure and temperature sensing performance. Its structural design consists of a multilayered composite construction with an elastic modulus gradient. Controlled stress concentration and distribution induced by a micropatterned structure between the layers improves its pressure and temperature sensing performance. The proposed composite sensor can monitor a wide range of pressure and temperature stimuli and also has potential applications as an automotive seat sensor for simultaneous human temperature detection and occupant weight sensing

Recent Development of Mechanical Stimuli Detectable Sensors, Their Future, and Challenges: A Review

By virtue of their wide applications in transportation, healthcare, smart home, and security, development of sensors detecting mechanical stimuli, which are many force types (pressure, shear, bending, tensile, and flexure) is an attractive research direction for promoting the advancement of science and technology. Sensing capabilities of various force types based on structural design, which combine unique structure and materials, have emerged as a highly promising field due to their various industrial applications in wearable devices, artificial skin, and Internet of Things (IoT). In this review, we focus on various sensors detecting one or two mechanical stimuli and their structure, materials, and applications. In addition, for multiforce sensing, sensing mechanism are discussed regarding responses in external stimuli such as piezoresistive, piezoelectric, and capacitance phenomena. Lastly, the prospects and challenges of sensors for multiforce sensing are discussed and summarized, along with research that has emerged

Shear-pressure multimodal sensor based on flexible cylindrical pillar array and flat structured carbon nanocomposites with simple fabrication process

Measuring shear displacement and pressure simultaneously is essential for various applications, such as tactile sensors for robotic finger tips, shoe soles for gait monitoring, etc. We present a simple means of transducing shear displacement and pressure change to flexible composite sensor. The presented sensor consists of an array of cylindrical pillars standing on a flat substrate, which is composed of carbon nanotubes (CNTs) and polydimethylsiloxane. The sensing mechanism is based on changing CNT network in pillar and flat structure under shear and pressure. When a shear displacement change occurs in the pillar array, which transfers shear and pressure to flat structure in the sample, the CNT network in the sample is changed due to bending of the pillars. Under pressure, the load is transferred from the pillar array to flat structure inducing changes in relative resistance. Load transfer through this hierarchical structure enabled measurement of shear displacement and pressure up to 5 mm and 1200 kPa, respectively. Therefore, it shows great potential applications in monitoring or even recognizing various human physiological activities

Colorimetric Sensor Based on Hydroxypropyl Cellulose for Wide Temperature Sensing Range

Recently, temperature monitoring with practical colorimetric sensors has been highlighted because they can directly visualize the temperature of surfaces without any power sources or electrical transducing systems. Accordingly, several colorimetric sensors that convert the temperature change into visible color alteration through various physical and chemical mechanisms have been proposed. However, the colorimetric temperature sensors that can be used at subzero temperatures and detect a wide range of temperatures have not been sufficiently explored. Here, we present a colorimetric sensory system that can detect and visualize a wide range of temperatures, even at a temperature below 0 degrees C. This system was developed with easily affordable materials via a simple fabrication method. The sensory system is mainly fabricated using hydroxypropyl cellulose (HPC) and ethylene glycol as the coolant. In this system, HPC can self-assemble into a temperature-responsive cholesteric liquid crystalline mesophase, and ethylene glycol can prevent the mesophase from freezing at low temperatures. The colorimetric sensory system can quantitatively visualize the temperature and show repeatability in the temperature change from -20 to 25 degrees C. This simple and reliable sensory system has great potential as a temperature-monitoring system for structures exposed to real environments

Real-time in situ monitoring of manufacturing process and CFRP quality by relative resistance change measurement

In situ monitoring of resin flow, impregnation of carbon fiber fabrics, and curing during composite manufacturing are very important for determining the quality of composite parts. In conventional methods, sensors, such as optical fibers and strain gages, are bonded to or embedded in the composites for measuring the changes in mechanical and chemical properties. Although they can detect resin curing behavior and impregnation of carbon fibers, they may adversely affect the manufacturing process or structural integrity of the composites. In this study, carbon fiber itself was used as a sensor that minimizes the degradation of mechanical properties and increases the efficiency of monitoring the manufacturing process. The change in the electrical resistance of carbon fiber fabrics was monitored during the various manufacturing processes when the resin flowed through the carbon fiber fabric and curing progressed. The effectiveness of this monitoring method was confirmed, and it is expected to be applicable in monitoring the quality of the finished composite parts

Carbon Nanocomposite Based Mechanical Sensing and Energy Harvesting

Progresses in sensor and energy technologies have been an important driving force for the rapid development of these industries and have drawn the attention of researchers on environmental concerns. In particular, carbon nanomaterial (carbon nanotubes, graphene, graphite, etc.)-based composites are widely used for sensor and energy harvesting applications owing to their excellent electrical, thermal, and mechanical properties. In this review, we have discussed various aspects of the use of carbon nanocomposites for the development of sensor and energy harvesting devices. These devices have shown outstanding sensing and energy harvesting performances. Various carbon nanomaterial-based composites with sophisticated structural and material designs have been developed to improve their sensing performance for various applications. We have also reviewed recent technological developments in carbon nanocomposite-based energy generators that adopt thermoelectric and triboelectric working mechanisms. Further research on the development of carbon nanocomposites with enhanced sensing and energy harvesting properties will expand the range of their applications to automotive, aerospace, artificial skin, healthcare, and environmental/infrastructure industries

Evaluation of the Impact of Activated Biochar-Manure Compost Pellet Fertilizer on Volatile Organic Compound Emissions and Heavy Metal Saturation

For this experiment, pelletized activated biochar made of rice hullsor palm bark with swine manure compost was prepared to demonstrate the significant benefits of applying activated biochar-manure compost pellet fertilizer (ABMCP) inmitigating volatile organic compounds (VOCs), odor emission, and heavy metal saturation. Morphology and surface area analysis indicated that the activated rice hull biochar-manure compost pellet (ARP) had a significantly lower surface area, porous volume, and Fe content the activated palm biochar-manure compost pellet (APP). However, the ARP presented great potential to mitigate VOCs and odorant emissions. Our results indicated that the ARP reduced total reduced sulfur (TRS) and volatile fatty acids (VFAs) emissions by 69% and 93%, respectively. Heavy metals such as Pb, As, and Cd were not detected in the leachates fromthe ARP, APP, and swine manure compost. These results suggest that ABMCP can be a potential adsorbent to control VOCs and odorant emissions andpromote sustainable swine manure management and agricultural application