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Microfluidic devices have become a powerful tool for chemical and biologic applications. To control different functional parts on the microchip, valve plays a key role in the device. In conventional methods, physio-mechanical valves are usually used on microfluidic chip. Herein, we reported a chemo-mechanical switchable valve on microfluidic chip by using a thermally responsive block copolymer. The wettability changes of capillary with copolymer modification on inner surface were investigated to verify the function as a valve. Capillaries with modification of poly-(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate) (P(NIPAAm-co-HFIPA)) with a 20% HFIPA was demonstrated capable of control aqueous solution stop or go through. Then short capillaries with copolymer modification were integrated in microchannels as valves. With the temperature changing around lower critical solution temperature (LCST), the integrated chemo-mechanical switchable valve exhibited excellent “OPEN–CLOSE’’ behavior for microflow control. After optimization of the block copolymer sequences and molar ratio, a switching time as low as 20 s was achieved. The developed micro valve was demonstrated effective for flow control on microchip. more...

Metabolism of a single cell, even within the same organization, differs from other cells by orders of magnitude. Single-cell analysis provides key information for early diagnosis of cancer as well as drug screening. Any slight change in the microenvironment may affect the state of a single cell. Timely and effective cell monitoring is conducive to better understand the behavior of single cells. The immediate response of a single cell described in this study is a liquid transfer-based approach for real-time electrochemical detection. The cell was in situ stimulated by continuous flow with glucose, and lactate secreted from the cell would diffuse into the microflow. The microflow was aspirated into the detection channel where lactate was then decomposed by coupled enzyme reactions and detected by an electrode. This work provides a novel approach for detecting lactate response from a single cell by noninvasive measurements, and the position resolution of the microfluidic probe reaches the level of a single cell and permits individual heterogeneity in cells to be explored in the diagnosis and treatment of cancer as well as in many other situations. more...

An innovative technique is proposed for forming silver thin films of nanometer-order thickness via a silver-mirror reaction. This approach is made possible by the real-time monitoring of the thickness of a silver thin film formed on the edge surface of a fiber core during the silver-mirror reaction using a homemade absorbance measurement system. The monitored absorbance value increases as silver plating progresses, and the relationship between the absorbance values and the thickness of the silver thin film is linear in the thickness range from approximately 30 to 60 nm. This technique was applied to the preparation of a fiber-optic surface plasmon resonance (FO-SPR) sensor. The sensor was successfully used to measure sucrose solutions with concentrations of less than 16% (w/v). The sensitivity of the sensor probe was estimated to be 2205 nm/RIU in the refractive index range of 1.333 - 1.357. The relative standard deviation of the wavelength shift obtained from measurements using different sensor probes was estimated to be less than 3.3%. more...

Gold nanowires are expected to be applied to biosensing due to their advantages, such as high stability and biocompatibility. However, it is still inconvenient to fabricate a single gold nanowire at a precise position, and without a special demanding environment. In this study, we present an open-space laminar flow approach for fabricating a single gold nanowire at a precise position under normal conditions. The fabricated gold nanowire demonstrated excellent biosensing of IgA with an extremely low limit of detection (1 aM). more...

A simple and low-cost method of fabricating an optical fiber for a surface plasmon resonance (SPR) sensor was proposed. The method is based on the electroless nickel plating and subsequent displacement gold plating of the core of the optical fiber. The thickness of the nickel and gold thin films deposited on the core of the optical fiber could be controlled by measuring the reflected light intensity from the tip of the optical fiber during the plating processes. The sensitivity and resolution of the SPR sensor with the fabricated optical fiber in the refractive index range from 1.333 to 1.348 were 1324.3 nm/RIU and 7.6 × 10 more...

The selective fabrication of highly ordered nanowires with high aspect ratios was of low reproducibility, which remains a challenge for laboratory research. In this paper, we report a novel approach for selective fabrication of conductive nanowires on a solid surface via diffusion mixing reaction system formed by a chemical pen. The nanoscale-mixing region was achieved by appropriately adjusting the viscosity of the solution and other parameters with the aid of dyes functioned as a flow boundary indicator. Finite element simulations and analysis were performed to understand the generation of mixing regions and guide the improvement of the chemical pen design. Under the optimal parameters, high aspect ratio silver nanowires (aspect ratio ≈ 1800) were obtained. Silver nanowire arrays with uniform width, gradient width and complex patterns were successfully fabricated. The theoretical value of the temperature coefficient of resistance (TCR) for silver was 0.0038 Ω/°C. A single silver wire temperature sensor with 7-fold increase in temperature coefficient resistance (0.0261 Ω/°C) was fabricated to show the advantages of the chemical pen in the fabrication of nanosensors. With the freedom of the region, simple operability and applicability, the chemical pen was expected to a potential and advanced method for selective nanomodification and processing on subcellular interfaces. more...

The nitrogen doped carbon dots (N-CDs) produces strong chemiluminescence (CL)-emission due to hydroxyl radical (•OH) induced electron-hole transition in N-CDs. The Fe2+ has the ability to generate •OH from available hydrogen peroxide (H2O2). Therefore, a pre-mixed N-CDs/H2O2 solution was utilized for selective quantification of Fe2+ in solution via CL-emission. A linear increase in the CL-emission intensity was observed within increase in Fe2+ concentration. The N-CDs/H2O2 system enabled the detection of Fe2+ up to lower concentration of 0.2 × 10−9 M with a linear dynamic range of 1.0 × 10−9–1.0 × 10−6 M. Significantly, no CL-emission was observed when other divalent cations, Al3+, Fe3+, or Cr3+ were injected to this system. Moreover, no interference was observed when a mixed solution of Fe2+ and other cations were introduced to N-CDs/H2O2. The practical evaluation of N-CDs/H2O2 system was demonstrated for detection of Fe2+ in tap, lotus pond, and canal water samples. The easy detection, high sensitivity, and selectivity make this method a significant tool for analysis of Fe2+ in solution. more...

The microwell plate/microtiter plate is among the most widely used tools in immune assays. In this paper, we report on a sensitive method for enhancing fluorescence emission detection by simply adding several droplets of an immiscible organic compound into the microwells before detection. To prove the concept, human IgA was determined on a microwell plate using this droplet enhanced fluorescence (DEF) detection method. An obvious enhancement in fluorescence was observed. The detection limit (LOD) was about 1/20 times and the sensitivity was 4 times greater than that without droplets. To prove the use of the method for disease diagnosis, the IgG of measles in human plasma was determined using the proposed DEF method. A LOD of around 1/5 times and a sensitivity of 4 times the DEF were easily achieved compared to ELISA with a conventional fluorescence detection. more...

The far-field fluorescence amplification, the intense fluorescence emission addresses the great potential in sensitive detection to large biomolecules, was seriously ignored for the failure in amplifying the weak fluorescence excepting the electromagnetic field (EM) induced fluorescence amplification on the metallic surfaces. Here, a microsphere in hundreds of micrometers was adopted to proceed with the fluorescence amplification via building up a local dielectric surrounding for fluorophore. The wide range of contribution-angle fluorescence could be efficiently restricted within the microsphere by facilitating the energy of reflection restraining and declining the energy of refraction decaying and the intense fluorescence emission confined within the microsphere could be directly observed. The proposed microsphere amplified fluorescence was demonstrated to induce about 2600 times of improved sensitivity in the detection of the fluorescent resorufin referring that of the original resorufin solution through the laser induced fluorescence (LIF). Furthermore, the limit of detection (LOD) of human IgA was successfully obtained to 3.25 fM through the microsphere in 47.7 pL when the microsphere amplified fluorescence was utilized in the fluoroimmunoassay. We believe the microsphere amplified fluorescence would be a potential strategy to implement the sensitive fluorescence sensing. more...

Affordable methods for ultra-sensitive biomarkers detection may improve the standard of living in resource-constrained countries. Nanowire biosensor is preponderant in ultra-sensitive protein detection. However, current strategies for nanowire sensor (NWS) fabrication often require sophisticated instruments, being inaccessible in less-resourced laboratories. Herein, we circumvent this challenge by developing a simple methodology, localized hydrodynamic flow confinement assisted nanowire sensor fabrication, enable the detection with limits of detection (LOD) for IgA and IgG measurement were 0.089 fg/mL and 0.93 fg/mL, respectively, demonstrating a 10-fold increase in detection sensitivity compared with the published NWS. Noteworthy, an X-Y positioner combined with a homemade microchemical pen (MCP) for tunable chemical deposition were sufficient to complete the fabrication of the nanowire biosensor without other expensive and demanding equipment. Overall, a particularly accessible, competitive, and low-cost approach of nanowire sensor fabrication for ultra-sensitive protein detection was developed, which could widely facilitate the application of nanowire biosensors. Besides, the nanowire sensor can also be employed to detect other analytes of interest by the use of different stimuli-responsive biosystems. more...

Pipes are the primary structural elements used for transporting fluid in various industries. The most common damage mechanism is corrosion, which occurs in pipes surface of turbine. The corrosive compounds for pipes are inorganic ion (Na+ , Cl- , NH4+ , NO3- , etc.) and grinding oil. For rapid and quantitative detection of inorganic ions on site, more reliable and reproducible analytical methods are demanded. A highly efficient solid-liquid sampling collection system is introduced in this work. Papering on the sample surface, inorganic cations and anions were simultaneously collected and analyzed by capillary electrophoresis with indirect ultraviolet detection. As a result, five cations (Na+ , K+ , NH4+ , Ca2+ , Mg2+ ) and three anions (Cl- , NO3- , SO42- ) were completely separated. The efficiency of the sampling and ability of capillary electrophoresis analysis were presented by the determination of trace-level (mg/m2 ) contaminants. The recoveries of cations and anions on the paper from metal surface were between 86.6 and 107.2%, and the relative standard deviations were less than 12.85%. more...

A novel method was developed for determination of aflatoxin B1, B2, G1, and G2 (AFB1, AFB2, AFG1, and AFG2) in wheat using inkjet-based dispersive liquid-liquid microextraction (DLLME) coupled with ultrahigh-pressure liquid chromatography-tandem mass spectrometry. A drop-on-demand jetting device was used to form a cloudy solution in traditional DLLME by injecting extraction solvent (10 μL) as ultrafine droplets (∼20 μm diameter) at high frequency into sample solution. The method was validated using wheat as a representative matrix, which was pretreated with acetonitrile/water solution. Good linearity was observed over the studied range (0.06-6 μg/kg), and the limits of quantification (0.06-0.18 μg/kg) were below the maximum level established by the European Union for cereal. Satisfactory recoveries, ranging from 83.2% to 93.0% with relative standard deviations below 4.6%, were obtained for all compounds. The method, which is convenient and reliable and has low solvent consumption, represents a new direction for the development of traditional DLLME technology. more...

Reactive oxygen species (ROS) generation is of intense interest because of its crucial role in many fields. Here we demonstrate that MoS2-QDs exhibit a promising capability for the generation of reactive oxygen species, which leads to enhanced chemiluminescence. We discovered that the unique performance is due to hydroxyl radical activation increasing the active catalytic sites on molybdenum sulphide quantum dots (MoS2-QDs). The reactive oxygen species, such as hydroxyl radicals (˙OH), superoxide radicals (˙O2−) and singlet oxygen (1O2) have been efficiently generated from H2O2 solution in alkaline conditions. In particular, the maximum ˙OH yield was enhanced significantly (9.18 times) compared to the Fe(II)/H2O2 Fenton system under neutral conditions. These findings not only enrich our understanding of the fascinating performance of MoS2 QDs, but also provide a new pathway for ROS generation in all kinds of pH environment. more...

A controlled drug delivery system (DDS) was designed by integrating the thermoresponsive copolymer poly(N-isopropylacrylamide-co-methacrylic acid) (poly(NIPAAm-co-MAA)) with core–shell 1,6-hexanediol diacrylate (HDDA) microparticles. The monodisperse HDDA particles with a hollow core and a nanoporous shell were fabricated in a continuous manner by an initially proposed inkjet printing process combined with UV polymerization. The thermoresponsive poly(NIPAAm-co-MAA) copolymer was grafted onto the surface of HDDA microcapsules by free radical initiated polymerization. Particularly, the lower critical solution temperature (LCST) of the copolymer was adjusted to human physiological temperature by the optimal comonomer ratio of MAA. With temperature changes at around the LCST, the copolymer, which was modified on the internal nanopore, served as a “retractable gate” by virtue of its changes in conformation between swollen and collapsed structures. Thus, controlled drug release was achieved by the reversible “open–close” transition characteristics of the nanopores. Fluorescein as a hypothetical drug molecule was loaded in the microcapsules and used to investigate the controlled release of the material. The results confirmed that this system represents a promising candidate for use in preparing controlled DDSs. more...

This article presents sequential inkjet-based method to produce double emulsions as templates to fabricate morphology-controlled and inner-modified hole-shell microparticles. This sequential printing strategy for producing double emulsions circumvents complex wettability modification of the microchannels in lithography-based microfluidic device and largely saves the reagent in comparison to the coaxial two-phase jet in glass capillary. The formation of hole-shell structures is attributed to the diffusion of solvent out of droplets into butanol at the interface between oil and extract phase. The change of hole size is controlled by different diffusion rate, which is determined by changing the volume ratio of butanol and alcohol in extract phase. This presented flexible method can fabricate some functionalized microparticles in our future work. more...

Cell adhesion is essential for a cell to maintain its functions, and biomaterials acting as the extracellular matrix (ECM) play a vital role. However, conventional methods for evaluating the functions of biomaterials become insufficient and sometimes incorrect when we give a deeper insight into single-cell research. In this work, we reported a novel methodology for the measurement of cell-matrix adhesion at single-cell resolution that could precisely evaluate the functions of biomaterials for adherent cell culture. A microfludic device, a live single-cell extractor (LSCE), was used for cell extraction. We applied this method to evaluate various modified biomaterials. The results indicated that poly(l-polylysine) (PLL)-coated glass and fibronection (FN)-coated glass slides showed the best biocompatibility for adherent cell culture following by the (3-aminopropyl)triethoxysilane (APTES)-coated glass, while piranha solution treated glass slide and octadecyltrichlorosilane (OTS)-coated glass showed weak biocompatibilities. Furthermore, APTES, PLL, and FN modifications enhanced the cell heterogeneity, while the OTS modification weakened the cell heterogeneity compare to the initial piranha solution treated glass. The method not only clarified the cell-matrix adhesion strength at single-cell resolution but also revealed the influences of biomaterials on cell-matrix adhesion and heterogeneity of cell-matrix adhesion for adherent cell culture. It might be a general strategy for precise evaluation of biomaterials. more...

Manipulation of light transmission/absorbance and reflection/emission has a great significance in smart windows and displaying media like liquid crystal. Here, we report the usage of an external electric field to reversibly switch the molecular spectra of a model molecule on the basis of its interaction with an electroresponsible polymer brush. Both the UV-vis absorbance spectrum and the fluorescence emission spectrum of the model molecule were confirmed to be electroswitchable. The electroswitchable spectra were experimentally demonstrated to be induced by the electroswitchable statuses of medium anionic poly-allyloxy hydroxypropyl sulfonate (poly-AHPS) brush. Insightfully, the molecular aggregated status of model proflavine molecules could be electrically controlled via the electroresponsible poly-AHPS brushes and then the molecular spectra of the model proflavine molecule also could be electrically and controllably shifted. The success in the manipulation of molecular spectra opens up a wide range of applications not only for displaying but also for nonlinear optics, in vivo imaging, sensors, and environmental inspection. more...

We developed a small fluorescence microplate reader with an organic photodiode (OPD) array. The OPD array has nine OPDs that have a large light receiving area (9.62 mm2 per one OPD). Since the OPD array is fabricated on a flat glass plate, it can be placed just below microwells and can detect fluorescence emitted through the entire surface of the microwell bottom. The analytical performance of the developed plate reader was evaluated by measuring an aqueous solution of resorufin. The limit of detection (LOD) for resorufin (0.01–0.05 μM) was lower than that obtained with a plate reader equipped with nine inorganic photodiodes developed in a previous study (0.30 μM) and a commercially available microplate reader (0.16 μM). These results indicate that the large light receiving area improves the detection performance of the system. In addition, the developed reader was successfully used to quantify immunoglobulin A (IgA) in human saliva. The LOD for IgA was estimated to be 1.2 ng/mL, which is low enough to objectively evaluate human stress. more...

We report on the development of a novel and flexible online digital polymerase chain reaction (dPCR) system. The system was composed of three parts: an inkjet for generating the droplets, a coiled fused-silica capillary for thermal cycling, and a laser-induced fluorescence detector (LIFD) for positive droplet counting. Upon inkjet printing, monodisperse droplets were continuously generated in the oil phase and then introduced into the capillary in the form of a stable dispersion. The droplets containing one or zero molecules of target DNA passed through the helical capillary that was attached to a cylindrical thermal cycler for PCR amplification, resulting in the generation of fluorescence for the DNA-positive droplet. After 36 PCR cycles, the fluorescence signal intensity was detected by laser-induced fluorescence located at the downstream of the capillary, followed by a positive/negative counting. The present system was successfully applied to the absolute quantification of the HPV sequence in Caski cells with dynamic ranges spanning 4 orders of magnitude. more...

For high sensitivity and rapid reaction of enzyme-linked immunosorbent assay (ELISA), the film-stack reaction field with micro-pillars array was designed and developed. The film-stack reaction field was fabricated by a nanoimprint process and an automatic punch-press process. The films with different gaps between micro-pillars (5, 10 and 50 μm) were prepared. These reaction fields were evaluated by IgA ELISA using 96-well microtitre plates and the computational simulation analysis of the fluid flow and the particle trajectory. Compared with ELISA using only the microtitre plate, higher detection sensitivity and shorter incubation time were achieved using the film-stack reaction field due to the increased surface area and the circulating flow through the space between films in a well by the rotation of the film-stack reaction field. Furthermore, in the ELISA results obtained using the film-stack reaction fields, the fluorescence intensities in 10-μm and 50-μm pillar gaps were the minimum and maximum values, respectively. This trend was due to the flow rate between micro-pillars, and the number and the diffusion distance of supplied biomolecules to the inertial space in the film-stack reaction field. In simulation results, the trend of the number of adsorbed biomolecule particles with different gaps between micro-pillars was in agreement with the trend in the ELISA results. Hence, these simulation analyses were validated in the quantitative evaluation of this reaction field and could be applied in the design of this reaction field as an effective design tool. more...

Elaborately programmed silver nanowire arrays can be prepared using a tapered push-pull nozzle system (TPPNS), which is used to directly write micro-nano wires on a substrate via a two-reagent reaction in the diffusion mixing region. The wires could be precisely positioned on the substrate and their width could be freely controlled from the micro to the nano scale, indicating an advance in the methodologies of controlling and fabricating nanowires. The as-prepared silver three-electrode device can serve as a three-electrode sensor. more...

An anion-terminated branched brush was designed, and confirmed to have reversibly electrical field responsive characters, which enables the stable and reversible manipulation of the adhesion behaviors of proteins and cells in a controllable manner. To proof the concept, poly sodium allyloxy hydroxypropyl sulfonate (poly-AHPS) branched brush was grafted from electrically conductive indium tin oxide (ITO) glass slide, and was demonstrated having two states: the stretched polymer brush under negatively charged and the rolled contractive polymer structure under positively charged. The electrical capture and release of anti-Ig G via the above poly-AHPS polymer branched brushes were successfully implemented, which indicated a potential in the disease diagnosis. The electrical capture and release of K562 cells were also accomplished through the poly-AHPS polymer branched brushes, which announced a possibility in the diagnosis of myelogenous leukemia. We anticipate the electro-switchable polymer branched brushes would be adopted in the electrical manipulation of adhesion behaviors of proteins and cells, and facilitate the applications in construction of micro-sensors and micro-actuators. more...

This study describes a method to investigate the separation of cells by capillary electrophoresis (CE) coupled with inkjet printing system. The results validated the feasibility of inkjet printing for mammalian cells to achieve the drop-on-demand and convenient sampling into capillary then zone electrophoresis was applied to separate different cells according to their electrophoretic mobility, finally the peak signal were measured by UV detector. Linear relationship between the peak area and the droplet number was obtained within the range of 25-400 drops (R2 = 0.996) at a fixed cell concentration 106/mL, indicating that this system could be used for rapid and accurate quantification of cells. more...

A four-aperture microchemical pen was used to produce a stable convection-diffusion layer in an "open space" for microreactions and microfabrication. The process represents a new method for microreactions and microfabrication in a convection-diffusion layer. To prove the concept of a convection-diffusion layer in an "open space", bovine serum albumin was labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole to confirm that the small convection-diffusion layer was effective for local surface treatment. To demonstrate the potential for microfabrication, silver patterns were fabricated on a glass surface with a convection-diffusion layer by using the silver-mirror reaction. The widths of each silver pattern could be easily controlled from 10 to 60 μm. Patterned silver lines with uniform widths or gradient widths were prepared. This is the first proof of concept study of a convection-diffusion layer in an "open space" used in local surface treatment and microfabrication on a surface. The microchemical pen represents a potential method for the region-selective microtreatment of tissues, cells, and other biological interfaces. more...

Surface patterning and modification are common approaches to deriving different functions in distinct areas on the sample surface. The development of a flexible, region-selective, controllable method capable of localized patterning and modification in high spatial resolution requires a new principle to generate micro and nano-scale reagent areas. In this work, we report a high viscosity-induced nano diffusive layer for locally printing nano polymer wires onto a substrate. Using a millimeter-sized fluidic device, a reduced diffusive layer on the nanoscale was achieved by increasing the viscosities of injected solutions. The reduced diffusive layer, which functioned as an open reactor, is successfully explored in micro and nano-polymer wire fabrication. Multiple dominant parameters were explored, and consequently, a resolution as small as 800 nm was attained. The nano diffusive layer in the open environment was demonstrated to be a useful tool for localized chemistry. Furthermore, it has potential in nano-electrode assembly, nano-circuit manufacture, localized chemical modification and subcellular treatment. more...

The ability of single or several cells introduction onto substrate simply would be a useful tool for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). In this study, we aimed to establish a sample introduction method for pattering cells to the substrate by inkjet technology. Inkjet driving, substrate surface and relative humidity were optimized for single or several cells introduction. Single type cell solution and MALDI matrix solution were automatically printed onto ITO glass substrate which was hydrophobic modified under humidity controlled condition. Then the substrate was inserted to MALDI-MS and cells sample solution provided several peaks from phospholipids. The inkjet technique enables us to print single and subcellular on the substrate with the range of a few hundred micrometers. This diameter would be useful for targeting by laser of MALDI-MS. Our technique provides a new platform for MALDI-MS analysis in single or several cells to get a wide information from one sample. more...

We report electrically switchable friction, which is reversibly manipulated by an external electric field via an electro-controllable polymer branched brush. The electro-controllable polymer branched brush, poly-sodium allyloxy hydroxypropyl sulfonate (poly-AHPS), was grafted onto an electrically conductive indium tin oxide (ITO) glass, and it demonstrated the capability of switching states by responding to the external electric field in a controllable manner. The two states of poly-AHPS branched brushes – stretched polymer brush arrays when negatively charged and rolled polymer knolls when positively charged – correspond to two different friction factors. Meanwhile, the shifting span for friction factors would be compressed by sandwiching a polar molecule medium or a nonpolar molecule medium, and exhibited a medium-controllable character. The proposed electric-field-responsive polymer brush is expected to be a manoeuvrable matrix for automatic control of friction, and to find wide application in automatization, intelligent manipulation and actuators. more...

The paper describes a new online quantitative electrophoretically mediated microanalysis (EMMA) for use in immunoassays based on the unique drop-by-drop introduction of a sample by means of an inkjet for capillary electrophoresis (CE). Plugs of a fluorescein-labeled antibody (Anti-humanIgG-DyL550) and human IgG were alternately injected into a capillary using the inkjet, followed by the merging of the plugs and the subsequent immune reaction. The antigen-antibody complex that was formed in the merged zone was then separated by CE. As a proof-of-concept, the method was used to determine human IgG. As a result, both the consumption of the reaction solution and the analysis time were significantly reduced. The method showed a wide linear range (10–2000 ng mL−1, R2 = 0.9912) of calibration and the detection limit (5 ng mL−1) was substantially lower than that by for conventional methods. more...

A fluorescence enhanced phenomenon was found within a micrometer-sized liquid droplet, and it was adopted to construct droplet enhanced fluorescence (DEF) for ultrasensitive fluorescence detection. In this paper, an inkjet was utilized to eject perfect spherical droplets to construct a microspherical resonator and to develop a DEF system. It was utilized to implement ultrasensitive fluorescence detection in a liquid specimen with a volume of several microliters. The DEF detection of fluorescent molecules, fluorescein sodium, was used as a model to validate the proposed enhanced fluorescence detection method. A low limit of detection (LOD) for fluorescein sodium of 124 pM was obtained. The sensitive detection of single stranded DNA (ssDNA) was experimentally completed, with a wide range of linearity with a LOD of 312 pM. The proposed mechanism can be used as an ultrasensitive detection technique for analyzing microliters of liquid samples. more...

We have found that HEWL (hen egg white lysozyme) is effectively immobilized on biochar through adsorption, and the amount of HEWL adsorbed on biochar is strongly dependent on the pH value of adsorption solutions. The structure of HEWL adsorbed on biochar changed by the pH value of adsorption solutions and became similar to that of native HEWL at acidic pH value, although the structure of HEWL solubilized in the solution was the same in the range between pH 4 and 9. On the other hand, the lytic activity of biochar-adsorbed HEWL toward Micrococcus lysodeikticus was markedly influenced by the pH value of adsorption solutions and increased with decreasing the pH value. Moreover, the addition of KCl to adsorption solutions enhanced the lytic activity of biochar-adsorbed HEWL. more...

We report a laminar flow based approach that is capable of precisely cutting off or treating a portion of a single cell from its remaining portion in its original adherent state., Single cells are increasingly recognized to be capable of wound repair that is important for our mechanistic understanding of cell biology. The lack of flexible, facile, and friendly subcellular treatment methods has hindered single-cell wound repair studies and organelle transport analyses. Here we report a laminar flow based approach, we call it fluid cell knife (Fluid CK), that is capable of precisely cutting off or treating a portion of a single cell from its remaining portion in its original adherent state. Local operations on portions of a living single cell in its adherent culture state were applied to various types of cells. Temporal wound repair was successfully observed. Moreover, we successfully stained portions of a living single cell to measure the organelle transport speed (mitochondria as a model) inside a cell. This technique opens up new avenues for cellular wound repair and subcellular behavior analyses. more...

The nitrogen doped carbon dots (N-CDs) produces strong chemiluminescence (CL)-emission due to hydroxyl radical (

The principle of the generation of liquid droplets in liquids by inkjet was discussed in this paper. As a liquid/liquid droplet generator, inkjet was used to produce monodisperse water droplets in oil (W/O) and oil droplets in water (O/W). Strategies for regulating droplet generation in various liquids were experimentally explored. The diameter of the generated monodisperse droplet also could be accurately tuned by varying the driving voltage and pulse width exerted on the miniature piezo ceramic slide of inkjet device. Experimentally, limitations of generation monodisperse droplets were discussed for both W/O and O/W. The work could be a guidance to generate monodisperse droplets in liquids by inkjet aiming at wide applications of simple droplets generation in liquids. more...

A quantitative sample introduction method based upon inkjet injection was applied to capillary electrophoresis coupled with stacking and sweeping on-line concentration techniques. Methylxanthines were used as model compounds for the proof-of-concept of the method. The volume of injected sample could be easily manipulated by controlling the number of ejected droplets in the injection procedure. Under optimized conditions, a linear relationship between the ejected droplet number and peak area was obtained when the droplet number introduced into the capillary was less than 100. Under optimized quantitative on-line concentration conditions, the limits of detection for theobromine, caffeine, and theophylline were 1.0, 2.0, and 1.0 μM, respectively. The inkjet injection system was evaluated by comparing it with conventional injection methods. The electropherogram of the inkjet injection mode was the same as that for hydrodynamic injection mode, and no sample discrimination was observed compared with the electrokinetic injection mode. The established method was applied to the determination of methylxanthines in bottled green tea. The recoveries of theobromine, caffeine, and theophylline were 94.1, 110.6, and 86.8%, respectively. We conclude that proposed method can be used for quantitative concentration for capillary electrophoresis, thus resulting in an improved accuracy. more...

Push-pull cannula system, which was first proposed by Gaddum, has grown to be an important method for the perfusion of brain and region-selective surface treatment. However, reported push-pull cannula systems only concerned on single reagent applications. Microfluidic system was then an exciting tool for multi-reagent treatment on substrate in closed microchannels. Nowadays, it is still a challenge to apply online mixing and reaction for surface pattern in an open environment. Here, we present a novel method using a chemical pen that enables region-selective online chemical reactions for the micro-surface modification/patterning. We utilized this method to fabricate labeling protein array using an online labeling strategy. Moreover, the device was applied for local modification of biomaterials surface by using a three-component reaction at precise position. This tool was the first demonstration of design to perform online reaction of two different reagents on a real solid sample in an open environment. It was demonstrated a useful method for protein array fabrication with online labeled protein. more...

A straightforward approach for the preparation of monodisperse porous polymer particles by inkjet technology is reported. Uniform droplets of an aqueous polymer solution were ejected from an inkjet, the nozzle of which was immersed in an organic phase. The subsequent dehydration of the droplets by solvent extraction resulted in the formation of porous polymer microspheres. Particles with a narrow size distribution could be obtained using the present system in a single step. Parameters for polymer droplet generation in an organic phase, including polymer properties, organic solvent, and inkjet waveform, were investigated. The relationship between the final particle diameter and the initial polymer droplet size were also examined. The diameters of the particles could be precisely controlled by changing the waveform exerted on the inkjet, thus producing particles with diameters in the range of 15 μm–60 μm with a coefficient of variation (CV) in the range of 2.7–4.8%. It was also possible to produce hollow porous polymer particles by simply decreasing the concentration of the polymer solution. The results demonstrate the merit of the inkjet-based method for the generation of monodisperse porous polymer particles. The method has the potential for producing functional polymer particles via the incorporation of functional or smart materials. more...

Single-cell biology provides insights into some of the most fundamental processes in biology and promotes the understanding of life's mysteries. As the technologies to study single-cells expand, they will require sophisticated analytical tools to make sense of various behaviors and components of single-cells as well as their relations in the adherent tissue culture. In this paper, we revealed cell heterogeneity and uncovered the connections between cell adhesion strength and cell viability at single-cell resolution by extracting single adherent cells of interest from a standard tissue culture by using a microfluidic chip-based live single-cell extractor (LSCE). We believe that this method will provide a valuable new tool for single-cell biology. more...

Cellular membranes are composed of a variety of lipids in different amounts and proportions, and alterations of them are usually closely related to various diseases. To reveal the intercellular heterogeneity of the lipid variation, an integrated microfluidic system is designed, which consists of droplet-based inkjet printing, dielectrophoretic electrodes, and de-emulsification interface to achieve on-line single-cell encapsulation, manipulation, and mass spectrometry (MS) detection. This integrated system effectively improves the single-cell encapsulation rate, and meanwhile reduces the matrix interference and continuous oil phase interference to the MS detection. Using this system, the heterogeneities between the normal and cancer cells are compared, and the heterogeneity of the same cells before and after the drug treatment changed obviously, indicating that this system can be used as a promising tool for studying the link between the alterations of lipid homeostasis and various diseases. more...

We have found that the heat stress tolerance of hen egg white lysozyme (HEWL) is markedly enhanced by the adsorption of HEWL on bamboo charcoal powder (BCP), which is a kind of biochar. HEWL was firmly adsorbed on BCP even at high temperatures. The secondary structure of HEWL was altered to some extent by the adsorption of HEWL on BCP. The remaining activity of BCP-adsorbed HEWL exhibited more than 20% after the incubation for 30 min at 900C although that of free one was hardly observed. Moreover, the half-life of BCP-adsorbed HEWL was 13 min at 900C while that of free one was 4 min. more...

A smart and reversible chemo-mechanical switch was developed by synthesis of a thermally responsive block copolymer brush poly(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate) (P(NIPAAm-co-HFIPA)) on a capillary plate. With the temperature changing around lower critical solution temperature (LCST), the designed chemo-mechanical switch exhibited excellent "ON-OFF" behavior for water transportation. more...