Bimodal Sensor Research Articles

Enhanced luminescence and paramagnetic properties of Gd2O3:Tb3+ multifunctional nanoparticles by K+/Co2+ doping

Multifunctional Gd2O3:Tb3+ nanoparticles doped with different concentrations of K+/Co2+ were synthesized by polyol method. The samples were characterized by X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscope (SEM), X-ray energy spectrometer (EDS), Malvern laser particle size analyzer, transmission electron microscope (TEM), photoluminescence spectrometer (PL), vibrating sample magnetometer (VSM) and magnetic resonance imager (MRI). The results showed that the synthesized spherical particles were cubic crystals with a diameter of 12–15 nm. Significant increase in fluorescence intensity was observed for Gd2O3:Tb3+ doped with K+/Co2+ ions. The optimal doped ion concentrations were found to be 3 mol% K+ ions and 4 mol% Co2+ ions, and the corresponding absolute quantum yields (QYs) were 7.21% and 5.90%. The maximum magnetization was obtained for the sample doped with 3 mol% K+/Co2+ ions. The ion-doped samples showed enhanced r1 relaxivity of water protons. Therefore, the multifunctional nanoparticles Gd2O3:Tb3+ doped with K+/Co2+ ions can potentially be used in displays, luminescence and MR bimodal imaging, sensors, magnetic separat, and other applications.

Lead Zirconate Titanate (a piezoelectric ceramic)-Based thermal and tactile bimodal organic transistor sensors

Abstract Multifunctional transistor sensors hold great potential in the next generation of smart portable electronics and artificial intelligence products owing to their very large-scale integration capability. Wearable thermal and tactile bimodal sensors are among the most emerging and attractive multifunctional devices having the ability of mimicking skin-like perception. Piezoelectric ceramics have been widely used in pressure sensing devices, however, their potential in thermal and tactile bimodal transistor sensors is rarely explored. Herein, organic thermal and tactile bimodal transistor sensors with a simple structure and fabrication technology are developed based on a piezoelectric ceramic substrate, Lead Zirconate Titanate (PZT). The as-fabricated devices demonstrate high sensitivity and linear response to the temperature change from 20 °C to 60 °C, and also exhibit sensitive response to the tapping on the device surface. These devices render a step forward towards the practical applications of human-interactive devices such as e-skin and smart tactile sensing systems.

Transparent and Flexible Mayan-Pyramid-based Pressure Sensor using Facile-Transferred Indium tin Oxide for Bimodal Sensor Applications

Transparent and conducting flexible electrodes have been successfully developed over the last few decades due to their potential applications in optoelectronics. However, recent developments in smart electronics, such as a direct human-machine interface, health-monitoring devices, motion-tracking sensors, and artificially electronic skin also require materials with multifunctional properties such as transparency, flexibility and good portability. In such devices, there remains room to develop transparent and flexible devices such as pressure sensors or temperature sensors. Herein, we demonstrate a fully transparent and flexible bimodal sensor using indium tin oxide (ITO), which is embedded in a plastic substrate. For the proposed pressure sensor, the embedded ITO is detached from its Mayan-pyramid-structured silicon mold by an environmentally friendly method which utilizes water-soluble sacrificial layers. The Mayan-pyramid-based pressure sensor is capable of six different pressure sensations with excellent sensitivity in the range of 100 Pa-10 kPa, high endurance of 105 cycles, and good pulse detection and tactile sensing data processing capabilities through machine learning (ML) algorithms for different surface textures. A 5 × 5-pixel pressure-temperature-based bimodal sensor array with a zigzag-shaped ITO temperature sensor on top of it is also demonstrated without a noticeable interface effect. This work demonstrates the potential to develop transparent bimodal sensors that can be employed for electronic skin (E-skin) applications.

Enokitake Mushroom-like Standing Gold Nanowires toward Wearable Noninvasive Bimodal Glucose and Strain Sensing.

We have recently demonstrated that Enokitake mushroom-like gold with nanoparticles as the "head" and nanowires as the "tail" could grow directly on elastomeric substrates, which are extremely stretchable electrodes that can be used as wearable sensors for detecting strain and pressure. In this work, we show that such electrodes can also be used as intrinsically stretchable glucose biosensors. By modifying the vertical gold nanowire electrodes with glucose oxidase and Prussian blue nanoparticles, a limit of detection of 10 μM, sensitivity of 23.72 μA·mM-1·cm-2, and high selectivity can be achieved. The as-obtained glucose biosensors were able to maintain a high sensing performance under various mechanical deformations. Even for 30% strain, a sensitivity of 4.55 μA·mM-1·cm-2 toward glucose detection in the artificial sweat was possible. Furthermore, it was found that strains could be simultaneously detected with a gauge factor of 2.30 (strain 0-10%) and 22.64 (strain 10-20%), demonstrating the potential of such bimodal sensors to allow simultaneous monitoring of physical and biological signals.

E-Skin Bimodal Sensors for Robotics and Prosthesis Using PDMS Molds Engraved by Laser.

Electronic skin (e-skin) is pursued as a key component in robotics and prosthesis to confer them sensing properties that mimic human skin. For pressure monitoring, a great emphasis on piezoresistive sensors was registered due to the simplicity of sensor design and readout mechanism. For higher sensitivity, films composing these sensors may be micro-structured, usually by expensive photolithography techniques or low-cost and low-customizable molds. Sensors commonly present different sensitivities in different pressure ranges, which should be avoided in robotics and prosthesis applications. The combination of pressure sensing and temperature is also relevant for the field and has room for improvement. This work proposes an alternative approach for film micro-structuration based on the production of highly customizable and low-cost molds through laser engraving. These bimodal e-skin piezoresistive and temperature sensors could achieve a stable sensitivity of −6.4 × 10−3 kPa−1 from 1.6 kPa to 100 kPa, with a very robust and reproducible performance over 27,500 cycles of objects grasping and releasing and an exceptionally high temperature coefficient of resistance (TCR) of 8.3%/°C. These results point toward the versatility and high benefit/cost ratio of the laser engraving technique to produce sensors with a suitable performance for robotics and functional prosthesis.

Fabrication of Large‐Area Bimodal Sensors by All‐Inkjet‐Printing

AbstractElectronic skin (e‐skin) is a wearable smart terminal that senses changes of external environment like human skin. It will develop into an indispensable way of interaction between humanity and technology. Here, this bimodal e‐skin that senses bending strain and pressure using an all‐inkjet‐printing method is synthesized. It is based on a microcracked metal film and a sandwich capacitor structure. It is characterized by the metal film of the strain sensor as a bottom electrode of pressure sensor; the electrode plate of the device plays a dual role. When tested, the strain sensor and pressure sensor do not interfere with each other. The device has excellent performance with low pressure‐detection of 2 Pa and high stability over more than 5700 cycles for pressure sensor and high gauge factor (4000) and good stability (over 4500 cycles) for strain sensor, which can recognize the radius of curvature of human activities and objects, and can detect the pressure distribution and the curvature of irregular surfaces, showing its potential applications in wearable devices.

A flexible bimodal sensor based on an electrospun nanofibrous structure for simultaneous pressure-temperature detection.

We developed a flexible and multifunctional resistive sensor integrating uniform conductive coating layers with an interlaced nanofibrous structure through a large-scale and cost-efficient strategy. The elastomer nanofiber framework not only endows the multi-mode sensor with superior flexibility, but also provides abundant contact sites and contact areas, which can significantly enhance the sensitivity and operating range of the obtained sensor. More impressively, the multilevel sensing paths comprising both interlaminar and intrastratal signal transmissions fulfill the simultaneous and precise detection of pressure-temperature stimuli without interference with each other. The obtained sensor ultimately shows an ultrahigh pressure sensitivity of 1185.8 kPa-1 and superior reliability, enabling the rapid detection of a subtle stimulus as low as 2.4 Pa and superior response behavior under 5000 cyclic loading tests. Besides, high linearity and stability are achieved for the temperature sensing characteristic even under various pressure loadings. These outstanding performances are further evaluated by preparing a 4 × 5 bimodal sensor array to synchronously monitor multiple signals, consequently demonstrating precise sensing capability with negligible interference and providing an effective approach for developing multiparametric sensing platforms and wearable devices.

Thermal and Energy Management Based on Bimodal Airflow-Temperature Sensing and Reinforcement Learning

Multi-physical field sensing and machine learning have drawn great attention in various fields such as sensor networks, robotics, energy devices, smart buildings, intelligent system and so on. In this paper, we present a novel efficient method for thermal and energy management based on bimodal airflow-temperature sensing and reinforcement learning, which expedites an exploration process by self-learning and adjusts action policy only through actuators interacting with the environment, being free of the controlled object model and priori experiences. In general, training of reinforcement learning requires a large amount of data iterations, which takes a long time and is not suitable for real-time control. Here, we propose an approach to speed up the learning process by indicating the action adjustment direction. We adopt tailor-designed bimodal sensors to simultaneously detect airflow and temperature field, which provides comprehensive information for reinforcement learning. The proposed thermal and energy management incorporates bimodal parametric sensing with an improved actor-critic algorithm to realize self-learning control. Experiments of thermal and energy management in a multi-module integrated system validate the effectiveness of the proposed methodology, which demonstrate high efficiency, fast response, and good robustness in various control scenarios. The proposed methodology can be widely applied to thermal and energy management of diverse integrated systems.

AuNS@Ag core-shell nanocubes grafted with rhodamine for concurrent metal-enhanced fluorescence and surfaced enhanced Raman determination of mercury ions

Mercury ion (Hg2+) is a highly hazardous and widespread pollutant with bio-accumulative properties. Although the existing Hg2+ detection methods have high sensitivity and reliability, whereas there have few reports concerning bimodal detection for Hg2+ with one sensor. Toward this goal, a novel sensor based on rhodamine derivatives (RhD) grafted AuNS@Ag core-shell nanocubes (CSN) has been synthesized and shown the bimodal detection capabilities with metal enhanced fluorescence (MEF) and surface enhanced Raman scattering (SERS) for Hg2+. Herein, resultant CSN acts as the signal enhancing material; RhD was modified on the outside of the shell to ensure the signal sensitive of the CSN-RhD hybrids. In this work, we investigate the size- and shape-dependent SERS activity of plasmonic CSN comprised of AuNS as cores and Ag cuboids as shells. The SERS activity of CSN with spherical core was found to increase with the increasing thickness of the Ag cubic shell. Sequel, under an optimized condition, a display of strong MEF and SERS signals of the resulting mixtures with increasing of Hg2+ concentrations was observed. The proposed bimodal sensor showed excellent performances for Hg2+ along with wide linear range of 0.001–1000 ppm and 0.01–1000 ppm as well as the relatively low detection limit of 0.94 and 5.16 ppb for MEF and SERS assays, respectively. Furthermore, the ability of the sensor to detect Hg2+was also confirmed in adulterated milk samples.

Biomimetic Mineralization Guided One-Pot Preparation of Gold Clusters Anchored Two-Dimensional MnO2 Nanosheets for Fluorometric/Magnetic Bimodal Sensing.

A novel fluorometric/magnetic bimodal sensor is reported based on gold nanoclusters (Au NCs)-anchored two-dimensional (2D) MnO2 nanosheets (Au NCs-MnO2) that are synthesized through a one-pot biomimetic mineralization process. Bovine serum albumin (BSA) was used as the template to guide the formation and assembly of the Au NCs-MnO2 under physiological conditions and without use of any strong oxidizing agent and toxic surfactants as well as organic solvent. The fluorescence of Au NCs was first quenched by MnO2 nanosheets, while upon H2O2 introduction, the MnO2 nanosheets can be sensitively and selectively reduced to Mn2+ with enhanced magnetic resonance (MR) signal and rapid recovery of Au NCs fluorescence simultaneously. This dual-modal strategy can overcome the weakness of a single-fluorescence detection mode. A linear range of 0.06-2 μM toward H2O2 was obtained for the fluorescence mode, whereas the MR mode also allowed detection of H2O2 at a concentration that ranged from 0.01 to 0.2 mM. Benefiting from the BSA molecule residual on the product surface, the as-prepared Au NCs-MnO2 displays low cytotoxicity and good biocompatibility. Importantly, the successful application of Au NCs-MnO2 for analysis of H2O2 in biological samples and cells indicates that the integration of Au NCs fluorescence with Mn2+ MR response provides a promising bimodal sensing platform for H2O2 in vivo monitoring.

Multifunctional Sensor Based on Porous Carbon Derived from Metal-Organic Frameworks for Real Time Health Monitoring.

Flexible and sensitive sensors that can detect external stimuli such as pressure, temperature, and strain are essential components for applications in health diagnosis and artificial intelligence. Multifunctional sensors with the capabilities of sensing pressure and temperature simultaneously are highly desirable for health monitoring. Here, we have successfully fabricated a flexible and simply structured bimodal sensor based on metal-organic frameworks (MOFs) derived porous carbon (PC) and polydimethylsiloxane (PDMS) composite. Attributed to the porous structure of PC/PDMS composite, the fabricated sensor exhibits high sensitivity (15.63 kPa-1), fast response time (<65 ms), and high durability (∼2000 cycles) for pressure sensing. Additionally, its application in detecting human motions such as subtle wrist pulses in real time has been demonstrated. Furthermore, the as-prepared device based on the PC/PDMS composite exhibits a good sensitivity (>0.11 °C-1) and fast response time (∼100 ms), indicating its potential application in sensing temperature. All of these capabilities indicate its great potential in the applications of health monitoring and artificial skin for artificial intelligence system.

Affordable Bimodal Optical Sensors to Spread the Use of Automated Insect Monitoring

We present a novel bimodal optoelectronic sensor based on Fresnel lenses and the associated stereo-recording device that records the wingbeat event of an insect in flight as backscattered and extinction light. We investigate the complementary information of these two sources of biometric evidence and we finally embed part of this technology in an electronic e-trap for fruit flies. The e-trap examines the spectral content of the wingbeat of the insect flying in and reports wirelessly counts and species identity. We design our devices so that they are optimized in terms of detection accuracy and power consumption, but above all, we ensure that they are affordable. Our aim is to make more widespread the use of electronic insect traps that report in virtually real time the level of the pest population from the field straight to a human controlled agency. We have the vision to establish remote automated monitoring for all insects of economic and hygienic importance at large spatial scales, using their wingbeat as biometric evidence. To this end, we provide open access to the implementation details, recordings, and classification code we developed.

Self-powered pressure and light sensitive bimodal sensors based on long-term stable piezo-photoelectric MAPbI3 thin films

Schematic of the output current measurement for light sensitive effect of different light powers using piezoelectric sensors and output current patterns measured at 3000 lx under an applied pressure of 30 kPa.

Tactile Sensors: Flexible Bimodal Sensor for Simultaneous and Independent Perceiving of Pressure and Temperature Stimuli (Adv. Mater. Technol. 11/2017)

Tactile Sensors: Flexible Bimodal Sensor for Simultaneous and Independent Perceiving of Pressure and Temperature Stimuli (Adv. Mater. Technol. 11/2017)

Low-voltage, high-sensitivity and high-reliability bimodal sensor array with fully inkjet-printed flexible conducting electrode for low power consumption electronic skin

Electronic skin, which has pixels composed of various functional sensors and can be applied to robots and various medical devices by mimicking the human skin, requires flexible, multi-mode, high-sensitivity, and low-interference sensors. In this study, we used a flexible electrode material comprised of organic conductor-elastomer-metal nanoparticles, as the core material and the inkjet printing method as the core process. These were used to form a flexible sensor for electronic skin applications, which involved vertically laminated sensors that utilize different sensing principles, thus enabling the realization of a flexible bimodal sensor with negligible interference. The pressure sensor with low resistivity and a flexible electrode, which was implemented using the sophisticated synthesis method, performed well under low-voltage (0.5mV) operation conditions, exhibited pressure sensitivity over a wide range (3Pa to 5kPa), and showed excellent reliability characteristics (100,000 cycles) that can withstand severe mechanical stress. The temperature sensor, which was formed by a long bent organic conductor-metal line, changes its resistance with temperature, has a resistance change sensitivity of 0.32% per degree of temperature change, and exhibits a hysteresis-free temperature sensing capability. In particular, this device has maintained its robustness even over 5000 bending cycles. The 25 pixels temperature-pressure bimodal sensor array demonstrates very fast response rates, high sensitivity, and negligible interference performance. The low-resistivity/high-flexibility conducting electrode, inkjet printing process, device architecture, and integration scheme proposed in this study are expected to be widely used for electronic skin, multi-mode sensors, and flexible devices.

Flexible Bimodal Sensor for Simultaneous and Independent Perceiving of Pressure and Temperature Stimuli

AbstractSimultaneous bimodal perceiving of pressure and temperature stimuli is widely desired for artificial intelligence electronics, such as electronic skin and health monitoring. In multiparametric sensing, it is a challenge to detect different stimuli independently and expediently without cross coupling. Here, this study reports a pressure–temperature bimodal tactile sensor composed of two sinuous thermosensitive platinum (Pt) ribbons fabricated on a flexible polyimide substrate, which is covered by a porous elastomer membrane to provide a handy solution for multimodal detection. By operating two Pt ribbons in a constant temperature difference feedback circuit, the sensor implements simultaneous and independent detections of pressure and temperature stimuli automatically and efficiently. High sensitivity, lower detection limit, high resolution, good stability, and low hysteresis are achieved for dual parametric sensing. The sensor shows competence in health monitoring for bimodal perceiving of wrist pulse and artery temperature simultaneously and independently. The smart sensing design and self‐sustained circuit simplify the bimodal sensor, and thus provide a fast and expedient approach for multimodal sensation applications.

Paper-Based Bimodal Sensor for Electronic Skin Applications.

We present the development of a flexible bimodal sensor using a paper platform and inkjet printing method, which are suited for low-cost fabrication processes and realization of flexible devices. In this study, we employed a vertically stacked bimodal device architecture in which a temperature sensor is stacked on top of a pressure sensor and operated on different principles, allowing the minimization of interference effects. For the temperature sensor placed in the top layer, we used the thermoelectric effect and formed a closed-loop thermocouple composed of two different printable inks (conductive PEDOT:PSS and silver nanoparticles on a flexible paper platform) and obtained temperature-sensing capability over a wide range (150 °C). For the pressure sensor positioned in the bottom layer, we used microdimensional pyramid-structured poly(dimethylsiloxane) coated with multiwall carbon nanotube conducting ink. Our pressure sensor exhibits a high-pressure sensitivity over a wide range (100 Pa to 5 kPa) and high-endurance characteristics of 105. Our 5 × 5 bimodal sensor array demonstrates negligible interference, high-speed responsivity, and robust sensing characteristics. We believe that the material, process, two-terminal device, and integration scheme developed in this study have a great value that can be widely applied to electronic skin.

A magnetic/fluorometric bimodal sensor based on a carbon dots-MnO2 platform for glutathione detection.

A novel magnetic/fluorometric bimodal sensor was built from carbon dots (CDs) and MnO2. The resulting sensor was sensitive to glutathione (GSH), leading to apparent enhancement of magnetic resonance (MR) and fluorescence signals along with visual changes. The bimodal detection strategy is based on the decomposition of the CDs-MnO2 through a redox reaction between GSH and MnO2. This process causes the transformation from non-MR-active MnO2 to MR-active Mn(2+), and is accompanied by fluorescence restoration of CDs. Compared with a range of other CDs, the polyethylenimine (PEI) passivated CDs (denoted as pCDs) were suitable for detection due to their positive surface potential. Cross-validation between MR and fluorescence provided detailed information regarding the MnO2 reduction process, and revealed the three distinct stages of the redox process. Thus, the design of a CD-based sensor for the magnetic/fluorometric bimodal detection of GSH was emphasized for the first time. This platform showed a detection limit of 0.6 μM with a linear range of 1-200 μM in the fluorescence mode, while the MR mode exhibited a linear range of 5-200 μM and a GSH detection limit of 2.8 μM with a visible change being observed rapidly at 1 μM in the MR images. Furthermore, the introduction of the MR mode allowed the biothiols to be easily identified. The integration of CD fluorescence with an MR response was demonstrated to be promising for providing detailed information and discriminating power, and therefore extend the application of CDs in sensing and imaging.

Functionalized Au-Fe3O4 nanocomposites as a magnetic and colorimetric bimodal sensor for melamine

Au-Fe3O4 nanocomposites were synthesized and modified with l-(2-mercaptoethyl)-1,2,3,4,5,6-hexanhydro-s-triazine-2,4,6-trione (MTT) for the bimodal detection of melamine. The bimodal detection is based on the aggregation of Au-Fe3O4@MTT nanoparticles (NPs) from the dispersed state upon the formation of special triple hydrogen bonds between melamine and MTT. This phenomenon causes the red shift of the absorption peak and the increase of the spin–spin relaxation time (T2) of the water protons upon addition of melamine at different concentrations to an aqueous solution of Au-Fe3O4@MTT NPs. Furthermore, the dual-modal method exhibits a clear selectivity toward melamine.

Bimodal wireless sensing with dual-channel wide bandgap heterostructure varactors

A capacitive wireless sensing scheme is developed that utilizes an AlN/GaN-based dual-channel varactor. The dual-channel heterostructure affords two capacitance plateaus within the capacitance-voltage (CV) characteristic, owing to the two parallel two-dimensional electron gases (2DEGs) located at respective AlN/GaN interfaces. The capacitance plateaus are leveraged for the definition of two resonant states of the sensor when implemented in an inductively-coupled resonant LRC network for wireless readout. The physics-based CV model is compared with published experimental results, which serve as a basis for the sensor embodiment. The bimodal resonant sensor is befitting for a broad application space ranging from gas, electrostatic, and piezoelectric sensors to biological and chemical detection.