A strain sensor has been fabricated from a polymer nanocomposite with multiwalled carbon nanotube (MWNT) fillers. The piezoresistivity
of this nanocomposite strain sensor has been investigated based on an improved three-dimensional (3D) statistical resistor network
model incorporating the tunneling effect between the neighboring carbon nanotubes (CNTs), and a fiber reorientation model. The
numerical results agree very well with the experimental measurements. As compared with traditional strain gauges, much higher sensitivity
can be obtained in the nanocomposite sensors when the volume fraction of CNT is close to the percolation threshold. For a small
CNT volume fraction, weak nonlinear piezoresistivity is observed both experimentally and from numerical simulation. The tunneling
effect is considered to be the principal mechanism of the sensor under small strains.

Tunneling effect in a polymer/carbon nanotube nanocompositestrain sensor

Piezocatalysis and Piezo-Photocatalysis: Catalysts Classification and Modification Strategy, Reaction Mechanism, and Practical Application

We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically 3 graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC, and characterized by surface-science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kOhm to 225 kOhm at 4 K, with positive magnetoconductance). Low resistance samples show characteristics of weak-localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 10^{12} cm^{-2} per graphene sheet. The most highly-ordered sample exhibits Shubnikov - de Haas oscillations which correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic techniques, and we demonstrate modulation of the film conductance using a top-gate electrode. These key elements suggest electronic device applications based on nano-patterned epitaxial graphene (NPEG), with the potential for large-scale integration.

Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics

CRISPR-Cas12a-driven MXene-PEDOT:PSS piezoresistive wireless biosensor

The subject of thermal transport at the mesoscopic scale and in low-dimensional systems is interesting for both fundamental research and practical applications. As the first example of truly two-dimensional materials, graphene has exceptionally high thermal conductivity, and thus provides an ideal platform for the research. Here we review recent studies on thermal and thermoelectric properties of graphene, with an emphasis on experimental progresses. A general physical picture based on the Landauer transport formalism is introduced to understand underlying mechanisms. We show that the superior thermal conductivity of graphene is contributed not only by large ballistic thermal conductance but also by very long phonon mean free path (MFP). The long phonon MFP, explained by the low-dimensional nature and high sample purity of graphene, results in important isotope effects and size effects on thermal conduction. In terms of various scattering mechanisms in graphene, several approaches are suggested to control thermal conductivity. Among them, introducing rough boundaries and weakly-coupled interfaces are promising ways to suppress thermal conduction effectively. We also discuss the Seebeck effect of graphene. Graphene itself might not be a good thermoelectric material. However, the concepts developed by graphene research might be applied to improve thermoelectric performance of other materials.

Thermal and Thermoelectric Properties of Graphene

Fabricating flexible pressure sensors with high sensitivity in a broad pressure range is still a challenge. Herein, a flexible pressure sensor with engineered microstructures on polydimethylsiloxane (PDMS) film is designed. The high performance of the sensor derives from its unique pyramid-wall-grid microstructure (PWGM). A square array of dome-topped pyramids and crossed strengthening walls on the film forms a multiheight hierarchical microstructure. Two pieces of PWGM flexible PDMS film, stacked face-to-face, form a piezoresistive sensor endowed with ultrahigh sensitivity across a very broad pressure range. The sensitivity of the device is as high as 383 665.9 and 269 662.9 kPa-1 in the pressure ranges 0-1.6 and 1.6-6 kPa, respectively. In the higher pressure range of 6.1-11 kPa, the sensitivity is 48 689.1 kPa-1, and even in the very high pressure range of 11-56 kPa, it stays at 1266.8 kPa-1. The pressure sensor possesses excellent bending and torsional strain detection properties, is mechanically durable, and has potential applications in wearable biosensing for healthcare. In addition, 2 × 2 and 4 × 4 sensor arrays are prepared and characterized, suggesting the possibility of manufacturing a flexible tactile sensor.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202000154

Engineered Microstructure Derived Hierarchical Deformation of Flexible Pressure Sensor Induces a Supersensitive Piezoresistive Property in Broad Pressure Range.

Synthesis of Wafer-Scale Graphene with Chemical Vapor Deposition for Electronic Device Applications

https://onlinelibrary.wiley.com/doi/pdf/10.1002/eom2.12018

Designing a bioinspired synthetic tree by unidirectional freezing for simultaneous solar steam generation and salt collection

Assembling Sn3O4 nanostructures on a hydrophobic PVDF film through metal-F coordination to construct a piezotronic effect-enhanced Sn3O4/PVDF hybrid photocatalyst

Manufacture of uniform, sensitive, and durable microtextured sensing materials is one of the greatest challenges for pressure sensors and electronic skins. Reported in this article is a gold nanoparticle-assembled, 3D-interconnected, graphene microchannel-embedded PDMS (3D GMC-PDMS) film for strain and pressure sensors. The film consists of porous nickel foam with its inner walls coated by multilayer graphene. Embedding in PDMS with etching removal of the Ni yields a 3D GMC-PDMS. Coating the inner walls with Au nanoparticles yields an Au nanoparticle-assembled 3D GMC-PDMS (AuNPs-GMC-PDMS) film, which is useful as an ultrasensitive pressure and strain sensor. This sensor exhibits a wide detection range (∼50 kPa) and ultrahigh sensitivity of 5.37, 1.56, and 0.5 kPa-1 in the ranges of <1, 1-10, and 10-50 kPa, respectively. Its lower detection limit is 4.4 Pa, its response time is 20 ms, and its strain factor is up to 15. Comparison of a AuNPs-GMC-PDMS film with a 3D GMC-PDMS film reveals a sensitivity improvement of 40 times in the 0-1 kPa pressure range and a gauge factor of more than 4 times in the 0-30% tensile strain range. The device has broad applications as a traditional or wearable medical sensor.

Duo Chen

Papers

Engineered Microstructure Derived Hierarchical Deformation of Flexible Pressure Sensor Induces a Supersensitive Piezoresistive Property in Broad Pressure Range.

Synthesis of Wafer-Scale Graphene with Chemical Vapor Deposition for Electronic Device Applications

Designing a bioinspired synthetic tree by unidirectional freezing for simultaneous solar steam generation and salt collection

Assembling Sn3O4 nanostructures on a hydrophobic PVDF film through metal-F coordination to construct a piezotronic effect-enhanced Sn3O4/PVDF hybrid photocatalyst

Fabrication of a Sensitive Strain and Pressure Sensor from Gold Nanoparticle-Assembled 3D-Interconnected Graphene Microchannel-Embedded PDMS.