Showing papers by "Tran Quang Trung published in 2015"
TL;DR: The concept of a self-powered patchable sensor system integrated with a supercapacitor and a triboelectric nanogenerator that can be used universally as an autonomous invisible sensor system was used to detect the wide range of strain on human skin.
Abstract: Monitoring of human activities can provide clinically relevant information pertaining to disease diagnostics, preventive medicine, care for patients with chronic diseases, rehabilitation, and prosthetics. The recognition of strains on human skin, induced by subtle movements of muscles in the internal organs, such as the esophagus and trachea, and the motion of joints, was demonstrated using a self-powered patchable strain sensor platform, composed on multifunctional nanocomposites of low-density silver nanowires with a conductive elastomer of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/polyurethane, with high sensitivity, stretchability, and optical transparency. The ultra-low-power consumption of the sensor, integrated with both a supercapacitor and a triboelectric nanogenerator into a single transparent stretchable platform based on the same nanocomposites, results in a self-powered monitoring system for skin strain. The capability of the sensor to recognize a wide range of strain on skin has the potential for use in new areas of invisible stretchable electronics for human monitoring. A new type of transparent, stretchable, and ultrasensitive strain sensor based on a AgNW/PEDOT:PSS/PU nanocomposite was developed. The concept of a self-powered patchable sensor system integrated with a supercapacitor and a triboelectric nanogenerator that can be used universally as an autonomous invisible sensor system was used to detect the wide range of strain on human skin.
406 citations
TL;DR: The hybrid-channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices.
Abstract: Ultraviolet (UV) photodetectors based on ZnO nanostructure/graphene (Gr) hybrid-channel field-effect transistors (FETs) are investigated under illumination at various incident photon intensities and wavelengths. The time-dependent behaviors of hybrid-channel FETs reveal a high sensitivity and selectivity toward the near-UV region at the wavelength of 365 nm. The devices can operate at low voltage and show excellent selectivity, high responsivity (RI ), and high photoconductive gain (G). The change in the transfer characteristics of hybrid-channel FETs under UV light illumination allows to detect both photovoltage and photocurrent. The shift of the Dirac point (V Dirac ) observed during UV exposure leads to a clearer explanation of the response mechanism and carrier transport properties of Gr, and this phenomenon permits the calculation of electron concentration per UV power density transferred from ZnO nanorods and ZnO nanoparticles to Gr, which is 9 × 10(10) and 4 × 10(10) per mW, respectively. The maximum values of RI and G infer from the fitted curves of RI and G versus UV intensity are 3 × 10(5) A W(-1) and 10(6) , respectively. Therefore, the hybrid-channel FETs studied herein can be used as UV sensing devices with high performance and low power consumption, opening up new opportunities for future optoelectronic devices.
161 citations
TL;DR: In this article, a 3D reduced graphene oxide (R-GO) nanosheets on 3D SU8 micro-pillar arrays were used for a simple 3D chemiresistor-based gas sensor platform with an increased surface area.
Abstract: The sensing performance of chemical sensors can be achieved not only by modification or hybridization of sensing materials but also through new design in device geometry. The performance of a chemical sensing device can be enhenced from a simple three-dimensional (3D) chemiresistor-based gas sensor platform with an increased surface area by forming networked, self-assembled reduced graphene oxide (R-GO) nanosheets on 3D SU8 micro-pillar arrays. The 3D R-GO sensor is highly responsive to low concentration of ammonia (NH3) and nitrogen dioxide (NO2) diluted in dry air at room temperature. Compared to the two-dimensional planar R-GO sensor structure, as the result of the increase in sensing area and interaction cross-section of R-GO on the same device area, the 3D R-GO gas sensors show improved sensing performance with faster response (about 2%/s exposure), higher sensitivity, and even a possibly lower limit of detection towards NH3 at room temperature.
157 citations
TL;DR: The fabrication of a highly sensitive, pressure-responsive organic field-effect transistor (OFET) array enabling both RA- and SA- mode detection by adopting easily deformable, mechano-electrically coupled, microstructured ferroelectric gate dielectrics and an organic semiconductor channel is demonstrated.
Abstract: Mechanically adaptive electronic skins (e-skins) emulate tactition and thermoception by cutaneous mechanoreceptors and thermoreceptors in human skin, respectively. When exposed to multiple stimuli including mechanical and thermal stimuli, discerning and quantifying precise sensing signals from sensors embedded in e-skins are critical. In addition, different detection modes for mechanical stimuli, rapidly adapting (RA) and slowly adapting (SA) mechanoreceptors in human skin are simultaneously required. Herein, we demonstrate the fabrication of a highly sensitive, pressure-responsive organic field-effect transistor (OFET) array enabling both RA- and SA- mode detection by adopting easily deformable, mechano-electrically coupled, microstructured ferroelectric gate dielectrics and an organic semiconductor channel. We also demonstrate that the OFET array can separate out thermal stimuli for thermoreception during quantification of SA-type static pressure, by decoupling the input signals of pressure and temperature. Specifically, we adopt piezoelectric-pyroelectric coupling of highly crystalline, microstructured poly(vinylidene fluoride-trifluoroethylene) gate dielectric in OFETs with stimuli to allow monitoring of RA- and SA-mode responses to dynamic and static forcing conditions, respectively. This approach enables us to apply the sensor array to e-skins for bio-monitoring of humans and robotics.
88 citations
TL;DR: The attributes of high stability, selectivity, and sensitivity of this flexible UV photodetector based on a ZnO NRs/Gr hybrid FET indicate promising potential for future flexible optoelectronic devices.
Abstract: A flexible ultraviolet (UV) photodetector based on ZnO nanorods (NRs) as nanostructure sensing materials integrated into a graphene (Gr) field-effect transistor (FET) platform is investigated with high performance. Based on the negative shift of the Dirac point (VDirac) in the transfer characteristics of a phototransistor, high-photovoltage responsivity (RV) is calculated with a maximum value of 3 × 108 V W–1. The peak response at a wavelength of ∼365 nm indicated excellent selectivity to UV light. The phototransistor also allowed investigation of the photocurrent responsivity (RI) and photoconductive gain (G) at various gate voltages, with maximum values of 2.5 × 106 A W–1 and 8.3 × 106, respectively, at a gate bias of 5 V. The UV response under bending conditions was virtually unaffected and was unchanged after 10 000 bending cycles at a bending radius of 12 mm, subject to a strain of 0.5%. The attributes of high stability, selectivity, and sensitivity of this flexible UV photodetector based on a ZnO NR...
74 citations
TL;DR: In this paper, a new kind of transparent and flexible IR photodetector is presented using a field effect transistor (FET) structure in which an IR-responsive nanocomposite layer of R-GO and poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) is employed as the channel.
Abstract: Photodetectors using optically responsive graphene (Gr) or reduced graphene oxide (R-GO) on rigid substrates have showed promising results for detection of broad band light including infrared (IR). However, there have been only a few reports on Gr or R-GO photodetectors with new functionalities such as optical transparency and/or flexibility. Herein, a new kind of transparent and flexible IR photodetector is presented using a field-effect transistor (FET) structure in which an IR-responsive nanocomposite layer of R-GO and poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) is employed as the channel. The IR photodetector exhibits high IR responsivity, stability, and reproducibility under mechanical strain and ambient conditions. In addition, the capability of measuring the distribution of responses from each device in the transparent and flexible nanocomposite FET array under IR radiation from the human body is also demonstrated. Therefore, the development of a flexible IR photodetector with high responsivity, transparency, ease of integration, and stability in an ambient environment is a suitable alternative approach for achieving the stable monitoring of IR in many flexible and transparent electronic systems.
34 citations
TL;DR: In this article, a new approach for utilizing flexible magnetoelectric (ME) materials as gate dielectric layers in ME organic field effect transistors (ME-OFET) was demonstrated.
Abstract: Flexible magnetoelectric (ME) materials have been studied for new applications such as memory, energy harvesters, and magnetic field sensors. Herein, with the widely studied and progressive advantages of ME phenomena in the multiferroic field, we demonstrate a new approach for utilizing flexible ME materials as gate dielectric layers in ME organic field-effect transistors (ME-OFET) that can be used for sensing a magnetic field and extracting the ME properties of the gate dielectric itself. The magnetoelectric nanohybrid gate dielectric layer comprises sandwiched stacks of magnetostrictive CoFe2O4 nanoparticles and a highly piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) layer. While varying the magnetic field applied to the ME gate dielectric, the ME effect in the functional gate dielectric modulates the channel conductance of the ME-OFET owing to a change in the effective gate field. The clear separation of the ME responses in the gate dielectric layer of ME-OFET from those of the other parameters was demonstrated using the AC gate biasing method and enabled the extraction of the ME coefficient of ME materials. Additionally, the device shows high stability after cyclic bending of 10,000 cycles at a banding radius of 1.2 cm. The device has significant potential for not only the extraction of the intrinsic characterization of ME materials but also the sensing of a magnetic field in integrated flexible electronic systems.
15 citations
01 Jan 2015
3 citations