Ionic transition-metal complex (iTMCs)-based electro-luminescent nanofibers (TELFs) are developed by using coelectrospinning. A single TELF consists of a Galistan liquid metal core (cathode), an iTMC-based polymer shell, and an ITO thin film coating (anode). Lights emitted from the TELFs can be detected by a CCD camera at 4.2 V and seen by naked eyes at 5.6 V in nitrogen. The TELFs are structurally self-supporting but do not require a physical substrate (generally relatively bulky and heavy) to support them, rendering one-dimensional light sources more flexible, lightweight, and conformable. This technology can be beneficial to many research and development areas such as optoelectronic textile, bioimaging, chemical and biological sensing, high-resolution microscopy, and flexible panel displays, particularly as iTMCs with emission at different wavelengths are available.

We report on a label-free microfluidic immunosensor with femtomolar sensitivity and high selectivity for early detection of epidermal growth factor receptor 2 (EGFR2 or ErbB2) proteins. This sensor utilizes a uniquely structured immunoelectrode made of porous hierarchical graphene foam (GF) modified with electrospun carbon-doped titanium dioxide nanofibers (nTiO2) as an electrochemical working electrode. Due to excellent biocompatibility, intrinsic surface defects, high reaction kinetics, and good stability for proteins, anatase nTiO2 are ideal for electrochemical sensor applications. The three-dimensional and porous features of GF allow nTiO2 to penetrate and attach to the surface of the GF by physical adsorption. Combining GF with functional nTiO2 yields high charge transfer resistance, large surface area, and porous access to the sensing surface by the analyte, resulting in new possibilities for the development of electrochemical immunosensors. Here, the enabling of EDC-NHS chemistry covalently immobilized the antibody of ErbB2 (anti-ErbB2) on the GF-nTiO2 composite. To obtain a compact sensor architecture, the composite working electrode was designed to hang above the gold counter electrode in a microfluidic channel. The sensor underwent differential pulse voltammetry and electrochemical impedance spectroscopy to quantify breast cancer biomarkers. The two methods had high sensitivities of 0.585 μA μM(-1) cm(-2) and 43.7 kΩ μM(-1) cm(-2) in a wide concentration range of target ErbB2 antigen from 1 × 10(-15) M (1.0 fM) to 0.1 × 10(-6) M (0.1 μM) and from 1 × 10(-13) M (0.1 pM) to 0.1 × 10(-6) M (0.1 μM), respectively. Utilization of the specific recognition element, i.e., anti-ErbB2, results in high specificity, even in the presence of identical members of the EGFR family of receptor tyrosine kinases, such as ErbB3 and ErbB4. Many promising applications in the field of electrochemical detection of chemical and biological species will derive from the integration of the porous GF-nTiO2 composite into microfluidic devices.

nonconventional substrates (e.g., paper, tape, and cloth) [7][8][9][10] have been widely utilized as the base materials of flexible electronic devices. Conductive nanomaterials, such as carbon nanotubes, metal oxide nanowires, and graphene, have also attracted considerable attention as functional materials for applications ranging from transistors, to sensors, to energy harvesting and storage devices. [11][12][13][14][15][16][17][18][19][20][21][22] Among these conductive nanomaterials, graphene plays a key role in producing next-generation sensors owing to its unique properties, including atomic thickness, large surface area, fast electron mobility, good piezoresistivity, and high mechanical flexibility. [23][24][25][26][27] As a result, integrations between flexible substrate materials and graphene-based nanomaterials have led to a variety of sensors and other electronic devices through development of novel fabrication processes, advancing emerging and significant fields such as real-time motion tracking, [28] structural and human health monitoring, [29][30][31] electronic skin sensing, [32][33][34][35][36] and humanized robotic manipulation. [37] It is well known that repeated mechanical exfoliation to peel single-or few-layer graphene from bulk graphite using sticky tape and transfer it to another surface is rather uncontrollable in terms of the number of graphene layers, location, and size of the peeled graphene. [38] Recently, graphene film electrodes at centimeter scale have been fabricated by peeling tape from a commercial graphite foil for the detection of glucose, [39] but the obtained electrodes did not have well-defined shapes or control over thickness. Physically rubbed graphene electrodes have also been produced by directly placing solid-state graphene powders at a channeled adhesive surface and then rubbing against the surface. [40] The resulting graphene patterns, however, have poor feature resolution. Photolithography-based microfabrication for graphene patterning [41][42][43][44][45][46][47][48][49] is relatively complex and requires multiple steps such as film deposition, lithography, and etching. Recently, various interesting methods have been developed for patterning and transferring graphene-based materials onto different substrates. For example, laser printing of graphene has been studied with variable laser energy, spot size, and pulse duration. [50][51][52][53][54] This method, however, requires sophisticated lasers and is limited to producing patterns with minimum feature size of several tens of micrometers. An ink-jet printing This paper reports on a simple and versatile method for patterning and transferring graphene-based nanomaterials onto various types of tape to realize flexible microscale sensors. The method involves drop-casting a graphene film on a prepatterned polydimethylsiloxane (PDMS) surface containing negative features by graphene suspensions, applying Scotch tape to remove the excess graphene from the nonpatterned areas of the PDMS surface, and then transferring the patte...

We present a microelectromechanical system (MEMS) graphene-based pressure sensor realized by transferring a large area, few-layered graphene on a suspended silicon nitride thin membrane perforated by a periodic array of micro-through-holes. Each through-hole is covered by a circular drum-like graphene layer, namely a graphene "microdrum". The uniqueness of the sensor design is the fact that introducing the through-hole arrays into the supporting nitride membrane allows generating an increased strain in the graphene membrane over the through-hole array by local deformations of the holes under an applied differential pressure. Further reasons contributing to the increased strain in the devised sensitive membrane include larger deflection of the membrane than that of its imperforated counterpart membrane, and direct bulging of the graphene microdrum under an applied pressure. Electromechanical measurements show a gauge factor of 4.4 for the graphene membrane and a sensitivity of 2.8 × 10(-5) mbar(-1) for the pressure sensor with a good linearity over a wide pressure range. The present sensor outperforms most existing MEMS-based small footprint pressure sensors using graphene, silicon, and carbon nanotubes as sensitive materials, due to the high sensitivity.

No abstract

There is an unmet need for improved fertilizer management in agriculture. Continuous monitoring of soil nitrate would address this need. This paper reports an all-solid-state miniature potentiometric soil sensor that works in direct contact with soils to monitor nitrate-nitrogen (NO3-N) in soil solution with parts-permillion (ppm) resolution. A working electrode is formed from a novel nanocomposite of poly(3-octylthiophene) and molybdenum disulfide (POT-MoS2) coated on a patterned Au electrode and covered with a nitrate-selective membrane using a robotic dispenser. The POT-MoS2 layer acts as an ion-to-electron transducing layer with high hydrophobicity and redox properties. The modification of the POT chain with MoS2 increases both conductivity and anion exchange, while minimizing the formation of a thin water layer at the interface between the Au electrode and the ion-selective membrane, which is notorious for solid-state potentiometric ion sensors. Therefore, the use of POT-MoS2 results in an improved sensitivity and selectivity of the working electrode. The reference electrode comprises a screen-printed silver/silver chloride (Ag/AgCl) electrode covered by a protonated Nafion layer to prevent chloride (Cl-) leaching in long-term measurements. This sensor was calibrated using both standard and extracted soil solutions, exhibiting a dynamic range that includes all concentrations relevant for agricultural applications (1-1500 ppm NO3-N). With the POT-MoS2 nanocomposite, the sensor offers a sensitivity of 64 mV/decade for nitrate detection, compared to 48 and 38 mV/decade for POT and MoS2 alone, respectively. The sensor was embedded into soil slurries where it accurately monitored nitrate for a duration of 27 days.

We report on the development of a vertical and transparent microfluidic chip for high-throughput phenotyping of Arabidopsis thaliana plants. Multiple Arabidopsis seeds can be germinated and grown hydroponically over more than two weeks in the chip, thus enabling large-scale and quantitative monitoring of plant phenotypes. The novel vertical arrangement of this microfluidic device not only allows for normal gravitropic growth of the plants but also, more importantly, makes it convenient to continuously monitor phenotypic changes in plants at the whole organismal level, including seed germination and root and shoot growth (hypocotyls, cotyledons, and leaves), as well as at the cellular level. We also developed a hydrodynamic trapping method to automatically place single seeds into seed holding sites of the device and to avoid potential damage to seeds that might occur during manual loading. We demonstrated general utility of this microfluidic device by showing clear visible phenotypes of the immutans mutant of Arabidopsis, and we also showed changes occurring during plant-pathogen interactions at different developmental stages. Arabidopsis plants grown in the device maintained normal morphological and physiological behaviour, and distinct phenotypic variations consistent with a priori data were observed via high-resolution images taken in real time. Moreover, the timeline for different developmental stages for plants grown in this device was highly comparable to growth using a conventional agar plate method. This prototype plant chip technology is expected to lead to the establishment of a powerful experimental and cost-effective framework for high-throughput and precise plant phenotyping.

Soil monitoring is emerging as a key factor to manage smart farming which has been recommended to have economical food safety and security. Among various development for example internet of things assisted farming, electrochemical sensing system are getting popularity via detecting one or multiple soil component effectively, efficiently, and selectively for soil quality assessment remotely via data sharing and site of location just like point-of-care soil heath care. Considering scenarios, this perspective is designed to describe state-of-the art electrochemical sensing technology developed for soil quality. The associated challenges, possible alternatives, and potential prospects are also discussed in this perspective.