RESUMEN

The introduction of flows within sessile droplets is highly effective for many lab-on-a-chip chemical and biomedical applications. However, generating such flows is difficult due to the typically small droplet volumes. Here, we present a simple, non-contact strategy to generate internal flows in sessile droplets for enhancing mixing and mass transport. The flows are driven by actuating a rigid substrate into oscillation with certain amplitude distributions without relying on the resonance of the droplet itself. Substrate oscillation characteristics and corresponding flow patterns are documented herein. Mixing indices and mass transfer coefficients of sessile droplets on the substrate surface are measured using optical and electrochemical methods. They demonstrate complete mixing within the droplets in 1.35 s and increases in mass transfer rates of more than seven times static values. Proof of concept was conducted with experiments of silver nanoparticle synthesis and with heavy metal ion sensing employing the sessile droplet as a microreactor for synthesis and an electrochemical cell for sensing. The degrees of enhancement of synthesis efficiency and detection sensitivity attributed to the internal flows are experimentally documented.

RESUMEN

There is a growing but unmet need for point-of-care detection of prostate-specific antigen (PSA) in body fluid which may facilitate early diagnosis and therapy of prostate cancer in a cost-effective and user-friendly way. Low sensitivity and narrow detection range limits applications of point-of-care testing in practice. Here, an immunosensor is first presented based on shrink polymer and integrated into a miniaturized electrochemical platform for detecting PSA in clinical samples. The sensing electrode was prepared by sputtering a gold film on shrink polymer, followed by heating to shrink the electrode to a small size with wrinkles from nano-scale to micro-scale. These wrinkles can be directly regulated by the thickness of the gold film with high specific areas for enhancement of antigen-antibody binding (3.9 times). A distinct difference between electrochemical active surface area (EASA) and response to PSA of shrink electrodes was observed and discussed. The electrode was treated with air plasma and modified with self-assembled graphene to further enhance the sensor's sensitivity (10.4 times). The shrink sensor with gold 200 nm thick integrated into the portable system was validated by a label-free immunoassay for detection of PSA in 20 µL serum within 35 mins. It exhibited a limit of detection of 0.38 fg/mL, the lowest among label-free PSA sensors, and a wide linear response from 10 fg/mL to 1000 ng/mL. Moreover, the sensor demonstrated reliable assay results in clinical serums, comparable to the commercial chemiluminescence instrument, confirming its feasibility for clinical diagnosis.

Asunto(s)

RESUMEN

Traditional lithography plays a significant role in the fabrication of micro- and nanostructures. Nevertheless, the fabrication process still suffers from the limitations of manufacturing devices with a high aspect ratio or three-dimensional structure. Recent findings have revealed that shrink polymers attain a certain potential in micro- and nanostructure manufacturing. This technique, denoted as heat-induced shrink lithography, exhibits inherent merits, including an improved fabrication resolution by shrinking, controllable shrinkage behavior, and surface wrinkles, and an efficient fabrication process. These merits unfold new avenues, compensating for the shortcomings of traditional technologies. Manufacturing using shrink polymers is investigated in regard to its mechanism and applications. This review classifies typical applications of shrink polymers in micro- and nanostructures into the size-contraction feature and surface wrinkles. Additionally, corresponding shrinkage mechanisms and models for shrinkage, and wrinkle parameter control are examined. Regarding the size-contraction feature, this paper summarizes the progress on high-aspect-ratio devices, microchannels, self-folding structures, optical antenna arrays, and nanowires. Regarding surface wrinkles, this paper evaluates the development of wearable sensors, electrochemical sensors, energy-conversion technology, cell-alignment structures, and antibacterial surfaces. Finally, the limitations and prospects of shrink lithography are analyzed.

RESUMEN

Dew water, mostly ignored until now, can provide clean freshwater resources, just by extracting the atmospheric vapor available in surrounding air. Inspired by silicon-based solar panels, the vapor can be harvested by a concept of water condensing panels. Efficient water harvesting requires not only a considerable yield but also a timely water removal from the surface since the very beginning of condensation to avoid the huge evaporation losses. This translates into strict surface properties, which are difficult to simultaneously realize. Herein, we study various functionalized silicon surfaces, including the so-called Black Silicon, which supports two droplet motion modes-out-of-plane jumping and in-plane sweeping, due to its unique surface morphology, synergistically leading to a pioneering combination of above two required characteristics. According to silicon material's scalability, the proposed silicon-based water panels would benefit from existing infrastructures toward dual functions of energy harvesting in daytime and water harvesting in nighttime.

RESUMEN

Micro-supercapacitors are promising miniaturized energy storage devices that have attracted considerable research interest. However, their widespread use is limited by inefficient microfabrication technologies and their low energy density. Here, a flexible, designable micro-supercapacitor can be fabricated by a single pulse laser photonic-reduction stamping. A thousand spatially shaped laser pulses can be generated in one second, and over 30,000 micro-supercapacitors are produced within 10 minutes. The micro-supercapacitor and narrow gaps were dozens of microns and 500 nm, respectively. With the unique three-dimensional structure of laser-induced graphene based electrode, a single micro-supercapacitor exhibits an ultra-high energy density (0.23 Wh cm-3), an ultra-small time constant (0.01 ms), outstanding specific capacitance (128 mF cm-2 and 426.7 F cm-3) and a long-term cyclability. The unique technique is desirable for a broad range of applications, which surmounts current limitations of high-throughput fabrication and low energy density of micro-supercapacitors.

RESUMEN

Early cancer diagnosis and treatment are crucial research fields of human health. One method that has proven efficient is biomarker detection which can provide real-time and accurate biological information for early diagnosis. This review presents several biomarker sensors based on electrochemistry, surface plasmon resonance (SPR), nanowires, other nanostructures, and, most recently, metamaterials which have also shown their mechanisms and prospects in application in recent years. Compared with previous reviews, electrochemistry-based biomarker sensors have been classified into three strategies according to their optimizing methods in this review. This makes it more convenient for researchers to find a specific fabrication method to improve the performance of their sensors. Besides that, as microfabrication technologies have improved and novel materials are explored, some novel biomarker sensors-such as nanowire-based and metamaterial-based biomarker sensors-have also been investigated and summarized in this review, which can exhibit ultrahigh resolution, sensitivity, and limit of detection (LoD) in a more complex detection environment. The purpose of this review is to understand the present by reviewing the past. Researchers can break through bottlenecks of existing biomarker sensors by reviewing previous works and finally meet the various complex detection needs for the early diagnosis of human cancer.

RESUMEN

The electrochemical sensing of dopamine is of great significance for studying and treating neurochemical diseases due to its potential feasibility for in vivo diagnostics. The commonly used sensors suffer from low sensitivity, the interference of ascorbic acid, and poor flexibility. In this paper, the function of electrode substrates including polyolefin, polystyrene, and polyethylene terephthalate films were investigated for their ability to improve electrochemical performances and provide favorable flexibility. The interference from ascorbic acid was cut down to a minimum by reducing the electrochemical resistance and the ascorbic acid diffusion current. The results demonstrate that gold electrodes prepared on polyolefin films exhibit a low charge transfer resistance of about 20 Ω, high sensitivity of dopamine detection (7.8 µA/µM), which is about 312 folds that of silicon electrode (0.025 µA/µM) and excellent flexibility. Having regulated the fabrication process of graphene by altering self-assembly layers and modification area, the sensor shows a dopamine detection limit of 0.11 µM in the presence of 500 µM ascorbic acid, and a sensitivity of 0.33 µA/µM. This work is valuable for the further improvement of the sensitivity and selectivity of the electrochemical sensor.

Asunto(s)

RESUMEN

Titanium dioxide (TiO2) is one of the most promising candidates for photoelectrochemistry applications. For a high photoelectrochemistry performance, the control of crystal structure and crystal facet is essential. The phase transformation of TiO2 is conventionally achieved by thermal annealing. Here, we report an approach for selective phase transformation of TiO2 containing exposed reactive facets with improved photoelectrochemistry performance. After femtosecond laser processing, TiO2 nanotubes with exposed reactive anatase {010} facets are prepared, and they have a maximum photocurrent density more than 5 times that of pure anatase. Additionally, this strategy can induce phase transformation in a selective area, which shows the advantages of patterning processing. Our method constructs a promising strategy for preparing functional nanomaterials with high performances and functionality.

RESUMEN

The composition and crystallization process are essential for high-quality perovskite films. Cesium (Cs) and methylammonium chlorine (MACl) were found to affect the crystallization kinetics of perovskite, and the performance and stability of corresponding devices were greatly improved. We adopted an ion exchange method to remove MACl vapor and add Cs to form a multiple-cation-based perovskite film. With the increase of annealing time, Cl- from cesium chloride (CsCl) and MA from methylammonium bromide (MABr) formed gradually MACl vapor, and the porosity of surface morphology improved accordingly. The highly crystallized and compact CsyMAx - yFA1 - xPbI3 - xBrx perovskite film with different compositions was eventually obtained. The effects of the amount of MABr on the property of perovskite films and on the performance of the corresponding perovskite solar cells (PerSCs) were systematically studied. The PerSCs derived from 12 mg of MABr exhibit the best photovoltaic performance with a power conversion efficiency of 21.57% under 1 sun illumination.

RESUMEN

Numerous valuable studies on electron dynamics have focussed on the extraordinary properties of molybdenum disulfide (MoS2); however, most of them were confined to the level below the damage threshold. Here the electron dynamics of MoS2 under intense ultrafast laser irradiation was investigated by experiments and simulations. Two kinds of ablation mechanisms were revealed, which led to two distinct types of electron dynamics and final ablation morphology. At a higher fluence, the emergence of superheated liquid induced a dramatic change in the transient reflectivity and micro-honeycomb structures. At a lower fluence, the material was just removed by sublimation, and the ablation structure was relatively flat. X-ray photoelectron spectroscopic (XPS) measurements demonstrated that thermal decomposition only occurred at the higher fluence. Furthermore, a theoretical model was developed to deeply reveal the ultrafast dynamics of MoS2 ablation. The simulation results were in good agreement with the temporal and spatial reflectivity distribution obtained from the experiment. The electron and lattice temperature evolution was also obtained to prove the ablation mechanism. Our results revealed ultrafast dynamics of MoS2 above the damage threshold and are helpful for understanding the interaction mechanism between MoS2 and intense ultrafast lasers, as well as for MoS2 processing applications.

RESUMEN

Blood-contacting medical devices that directly inhibit thrombosis and bacterial infection without using dangerous anticoagulant and antibacterial drugs can save countless lives but have proved extremely challenging. Here, a useful methodology is proposed that employs temporally shaped femtosecond laser ablation combined with fluorination to fabricate multifunctional three-dimensional (3D) micro-nanostructures with excellent hemocompatibility, zero cytotoxicity, outstanding biocompatibility, bacterial infection prevention, and long-term effectiveness on NiTi alloys. These multifunctional 3D micro-nanostructures present 0.1% hemolysis ratio and almost no platelet adhesion and activation, repel blood to inhibit blood coagulation in vitro, maintain 100% cell viability, and have exceptional stability over 6 months. Moreover, the multifunctional 3D micro-nanostructures simultaneously suppress bacterial colonization to form biofilm and kill 100% colonized Pseudomonas aeruginosa (P. aeruginosa) and 95.6% colonized Staphylococcus aureus (S. aureus) after 24 h of incubation, and bacterial residues can be easily removed. The fabrication method in this work has the advantages of simple processing, high efficiency, high quality, and high repeatability, and the new multifunctional 3D micro-nanostructures can effectively prevent thrombosis and bacterial infection, which can be widely applied to various clinical needs such as biomedical devices and implants.

Asunto(s)

RESUMEN

INTRODUCTION: Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) brings a serious impact on patients' quality of life, and has extremely high morbidity and mortality worldwide. Although there are many therapies being developed to alleviate symptoms and reduce mortality, a few studies have supported which treatment method is the best. Traditional Chinese medicine (TCM) has shown good potential in the prevention and treatment of AECOPD, especially in terms of supplementation and reduction of dosage and adverse effect of Western medicine. The purpose of this study is to compare the effectiveness of combination of TCM and Western medicine with conventional therapy alone for AECOPD, and to ensure whether the combined therapy may reduce the use of systemic glucocorticoid in AECOPD without influencing efficacy. METHODS AND ANALYSIS: A multicentre, randomised, double-blind, placebo-controlled study was conducted to enrol a total of 360 eligible patients who will be randomised into integrated Chinese and Western medicine group A, B and Western standard Medicine group C. After 5 days of intervention and 1 month of follow-up, the efficacy and safety of Xin Jia Xuan Bai Cheng Qi Decoction in patients with AECOPD will be observed. The results of evaluation indicators include: clinical symptoms, biochemical indicators such as blood gas analysis, inflammatory markers, hospitalisation time, TCM syndrome evaluation, biological indicators such as airway, intestinal flora sequencing. ETHICS AND DISSEMINATION: This trail has been approved by the Ethics Committee of China-Japan Friendship Hospital. The results will be disseminated in international peer-reviewed journals and be presented in academic conferences. The results will also be disseminated to patients by telephone, inquiring on patient's poststudy health status during the follow-up. TRIAL REGISTRATION NUMBER: ChiCTR1800016915.

Asunto(s)

RESUMEN

Raman spectroscopy plays a crucial role in biochemical analysis. Recently, superhydrophobic surface-enhanced Raman scattering (SERS) substrates have enhanced detection limits by concentrating target molecules into small areas. However, due to the wet transition phenomenon, further reduction of the droplet contact area is prevented, and the detection limit is restricted. This paper proposes a simple method involving femtosecond laser-induced forward transfer for preparing a hybrid superhydrophilic-superhydrophobic SERS (HS-SERS) substrate by introducing a superhydrophilic pattern to promote the target molecules to concentrate on it for ultratrace detection. Furthermore, the HS-SERS substrate is heated to promote a smaller concentrated area. The water vapor film formed by the contact of the solution with the substrate overcomes droplet collapse, and the target molecules are completely concentrated into the superhydrophilic region without loss during evaporation. Finally, the concentrated region is successfully reduced, and the detection limit is enhanced. The HS-SERS substrate achieved a final contact area of 0.013 mm2, a 12.1-fold decrease from the unheated case. The reduction of the contact area led to a detection limit concentration as low as 10-16 M for a Rhodamine 6G solution. In addition, the HS-SERS substrate accurately controlled the size of the concentrated areas through the superhydrophilic pattern, which can be attributed to the favorable repeatability of the droplet concentration results. In addition, the preparation method is flexible and has the potential for fluid mixing, fluid transport, and biochemical sensors, etc.

RESUMEN

During femtosecond laser fabrication, photons are mainly absorbed by electrons, and the subsequent energy transfer from electrons to ions is of picosecond order. Hence, lattice motion is negligible within the femtosecond pulse duration, whereas femtosecond photon-electron interactions dominate the entire fabrication process. Therefore, femtosecond laser fabrication must be improved by controlling localized transient electron dynamics, which poses a challenge for measuring and controlling at the electron level during fabrication processes. Pump-probe spectroscopy presents a viable solution, which can be used to observe electron dynamics during a chemical reaction. In fact, femtosecond pulse durations are shorter than many physical/chemical characteristic times, which permits manipulating, adjusting, or interfering with electron dynamics. Hence, we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses, and further to modify localized transient materials properties, and then to adjust material phase change, and eventually to implement a novel fabrication method. This review covers our progresses over the past decade regarding electrons dynamics control (EDC) by shaping femtosecond laser pulses in micro/nanomanufacturing: (1) Theoretical models were developed to prove EDC feasibility and reveal its mechanisms; (2) on the basis of the theoretical predictions, many experiments are conducted to validate our EDC-based femtosecond laser fabrication method. Seven examples are reported, which proves that the proposed method can significantly improve fabrication precision, quality, throughput and repeatability and effectively control micro/nanoscale structures; (3) a multiscale measurement system was proposed and developed to study the fundamentals of EDC from the femtosecond scale to the nanosecond scale and to the millisecond scale; and (4) As an example of practical applications, our method was employed to fabricate some key structures in one of the 16 Chinese National S&T Major Projects, for which electron dynamics were measured using our multiscale measurement system.

RESUMEN

A novel flexible mixed-potential-type (MPT) sensor was designed and fabricated for NO2 detection from 0 to 500 ppm at 200 °C. An ultra-thin Y2O3-doped ZrO2 (YSZ) ceramic film 20 µm thick was sandwiched between a heating electrode and reference/sensing electrodes. The heating electrode was fabricated by a conventional lift-off process, while the porous reference and the sensing electrodes were fabricated by a two-step patterning method using shadow masks. The sensor's sensitivity is achieved as 58.4 mV/decade at the working temperature of 200 °C, as well as a detection limit of 26.7 ppm and small response time of less than 10 s at 200 ppm. Additionally, the flexible MPT sensor demonstrates superior mechanical stability after bending over 50 times due to the mechanical stability of the YSZ ceramic film. This simply structured, but highly reliable flexible MPT NO2 sensor may lead to wide application in the automobile industry for vehicle emission systems to reduce NO2 emissions and improve fuel efficiency.

RESUMEN

Graphene biosensors reported so far are based on polycrystalline graphene flakes which are anchored on supporting substrates. The influence of grain boundary and the scattering from substrate drastically degrade the properties of graphene and conceal the performance of intrinsic graphene as a sensor. Here we report a label-free biosensor based on suspended single crystalline graphene (SCG), which can get rid of grain boundary and substrate scattering, revealing the biosensing mechanism of intrinsic graphene for the first time. Monolayer SCG flakes were derived from low pressure chemical vapor deposition (LPCVD) method. Multiplex detection of three different lung cancer tumor markers was realized. The suspended structure can largely improve the sensitivity and detection limit (0.1 pg/ml) of the sensor, and the single crystalline nature of SCG enable the biosensor to have superior uniformity compared to polycrystalline ones. The SCG sensors exhibit superb specificity and large linear detection range from 1 pg/ml to 1 µg/ml, showing the prominent advantages of graphene as a sensing material.

Asunto(s)