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Droplet-based transport driven by surface tension has been explored as an automated pumping source for several biomedical applications. This paper presented a simple and fast superhydrophobic modify and patterning approach to fabricate various open-surface platforms to manipulate droplets to achieve transport, mixing, concentration, and rebounding control. Several commercial reagents were tested in our approach, and the Glaco reagent was selected to create a superhydrophobic layer; laser cutters are utilized to scan on these superhydrophobic surface to create gradient hydrophilic micro-patterns. Implementing back-and-forth vibrations on the predetermined parallel patterns, droplets can be transported and mixed successfully. Colorimetry of horseradish peroxidase (HRP) mixing with substrates also reduced the reaction time by more than 5-times with the help of superhydrophobic patterned chips. Besides, patterned superhydrophobic chips can significantly improve the sensitivity of colorimetric glucose-sensing by more than 10 times. Moreover, all bioassays were distributed homogeneously within the region of hydrophilic micropatterns without the coffee-ring effect. In addition, to discuss further applications of the surface wettability, the way of controlling the droplet impacting and rebounding phenomenon was also demonstrated. This work reports a rapid approach to modify and pattering superhydrophobic films to perform droplet-based manipulations with a lower technical barrier, higher efficiency, and easier operation. It holds the potential to broaden the applications of open microfluidics in the future.

In this study, a novel gradient grating period guided-mode resonance (GGP-GMR) biosensor is proposed, and albumin was successfully detected as a test model. The GGP-GMR sensor exhibits a gradient resonant wavelength along the device. At a fixed incident wavelength, light resonates at a specific period such that the light is reflected at this period (or resonant period) and transmitted to other periods. Thus, for a charge-coupled device under the GGP-GMR sensor, a dip-like intensity distribution was measured with a specific pixel of minimum intensity corresponding to the resonant period. The variation in sample concentrations caused changes in the refractive index (RI) on the sensor surface, which induced a shift in the resonant period and in the pixel corresponding to the minimum intensity. A GGP-GMR sensor can achieve a limit of detection of $8.58\times 10^{{-4}}$ RIU within a detection range of sucrose solutions of 0%–60% concentrations that corresponds to the RI from 1.333 to 1.442. In a buffer solution, albumin was successfully detected to measure the clinically relevant concentration. The simple design and easy fabrication of the GGP-GMR sensor combined with its simple readout and optical path design facilitates system miniaturization for handheld devices and its integration with smartphones, which could be beneficial for future point-of-care applications.

Enzyme-linked immunosorbent assays (ELISAs) are tests that uses antibody recognition and enzyme catalytic activity to identify a substance, and they have been widely used as a diagnostic tool in the clinic.

Proper orientation of probes and the binding capacity of surfaces will determine the performance of bio-applications. It has been reported that immobilizing through bio-/chemical affinity is an efficient but gentle strategy to solve the above-mentioned issue. Herein, we introduce a total self-assembly approach

Since nucleic acid amplification technology has become a vital tool for disease diagnosis, the development of precise applied nucleic acid detection technologies in point-of care testing (POCT) has become more significant. The microfluidic-based nucleic acid detection platform offers a great opportunity for on-site diagnosis efficiency, and the system is aimed at user-friendly access. Herein, we demonstrate a microfluidic system with simple operation that provides reliable nucleic acid results from 18 uniform droplets via LAMP detection. By using only micropipette regulation, users are able to control the nanoliter scale of the droplets in this valve-free and pump-free microfluidic (MF) chip. Based on the oil enclosure method and impermeable fabrication, we successfully preserved the reagent inside the microfluidic system, which significantly reduced the fluid loss and condensation. The relative standard deviation (RSD) of the fluorescence intensity between the droplets and during the heating process was

Open-surface microfluidics is promising in terms of enabling economical and rapid biochemical analysis for addressing challenges associated with medical diagnosis and food safety. To this end, we present a simple and economical approach to develop an open-surface microfluidic platform suitable for facile liquid transport and mixing. Customizable patterns with tailored wettability are deposited using a plasma-assisted deposition technique under atmospheric pressure. The flow of the dispensed liquid is driven by gravity, and the tilting angle of the device determines the extent of mixing. First, a hexamethyldisiloxane film was deposited to create hydrophobic patterns on glass, and then, hydrophilic acrylic acid was deposited by a patterned cardboard mask to construct a channel suitable for forming channels to transport aqueous liquids without the need of an external energy input; the liquid can be confined to designated pathways. Several designs including Y-junctions, serpentine-shaped patterns, splitting channels, and concentration gradient generation patterns are presented. The proposed method can spatially pattern a surface with a hydrophobic/hydrophilic area, which can function as a microfluidic channel, and the surface can be applied in microfluidic devices with other types of substrates.

In this study, the surface properties of iron microparticles were modified for the manipulation of liquid droplets using atmospheric pressure plasma jets. These modified hydrophobic iron microparticles were prepared by synthesizing fluorinated silica nanocomposites on the surfaces of iron microparticles under atmospheric pressure plasma. The compositions of the silica nanocomposites were controlled by the deposition of hexamethyldisiloxane and fluoroalkylsilane precursors. The fluorinated silica nanocomposites were then used with iron microparticles to prepare magnetic liquid marbles. The contact angles of the iron microparticles and the fluorinated silica nanoparticle coating on the glass surface were both 154°, which indicated that the surfaces of these particles were superhydrophobic. Higher hexamethyldisiloxane precursor flow rates produced more silica nanocomposites and resulted in greater roughness and larger contact angles. Changes in surface roughness were characterized by atomic force microscopy. X-ray photoelectron spectroscopy showed that C–F bonds were present on the modified glass surface. The presented approach allows rapid and highly efficient modification of uneven surfaces and can therefore be employed to render hydrophilic, superhydrophobic, and oleophilic surfaces. Moreover, the described hydrophobic iron microparticles can be used for the controlled magnetic manipulation of water droplets and oil–water separation.

A biosensor is generally defined as an analytical device, which converts the biochemical responses into the quantifiable electronic signals. Its extensive utilities in medical diagnosis, toxicity testing, chemical analysis, food industry, and many other areas for quantitative assessments has appeared. Quartz crystal microbalance and field-effect transistor based devices have been demonstrated to possess exceptional characteristics and outstanding performance while conjugated with the advanced nanotechnology. However, both devices still have to face the nonspecific binding issue, which is a headache for researchers on all biosensor platforms. In our research, we have efficaciously reduce 95% nonspecific binding via immobilize the zwitterionic layer on the surface of the chip. Moreover, we integrate microfluidics, nanoparticles, rapid surface modification on several bio-sensing platforms to efficiently pretreat specimens and detect target biomolecules. In addition, a series advanced microfluidic ships are designed for lymphocyte isolation, active sperm sorting, and nanoparticle synthesis. Figure 1

Blood tests provide crucial diagnostic information regarding several diseases. A key factor that affects the precision and accuracy of blood tests is the interference of red blood cells; however, the conventional methods of blood separation are often complicated and time consuming. In this study, we devised a simple but high-efficiency blood separation system on a self-strained microfluidic device that separates 99.7% of the plasma in only 6 min. Parameters, such as flow rate, design of the filter trench, and the relative positions of the filter trench and channel, were optimized through microscopic monitoring. Moreover, this air-difference-driven device uses a cost-effective and easy-to-use heater strip that creates a low-pressure environment in the microchannel within minutes. With the aforementioned advantages, this blood separation device could be another platform choice for point-of-care testing.

Diabetes has become a chronic metabolic disorder, and the growing diabetes population makes medical care more important. We investigated using a portable and noninvasive contact lens as an ideal sensor for diabetes patients whose tear fluid contains glucose. The key feature is the reversible covalent interaction between boronic acid and glucose, which can provide a noninvasive glucose sensor for diabetes patients. We present a phenylboronic acid (PBA)-based HEMA contact lens that exhibits a reversible swelling/shrinking effect to change its thickness. The difference in thickness can be detected in a picture taken with a smartphone and analyzed using software. Our novel technique offers the following capabilities: (i) non-enzymatic and continuous glucose detection with the contact lens, (ii) no need for an embedded circuit and power source for the glucose sensor, and (iii) the use of a smartphone to detect the change in thickness of the contact lens with no need for additional photo-sensors. This technique is promising for a noninvasive measurement of the glucose level and simple implementation of glucose sensing with a smartphone.

In applications of silicon nanowire field-effect transistors (SiNW-FETs) as biosensors, the SiNW-FETs conventionally are all area modified (AAM), with receptors covering not only the minute SiNW surface area but also the relatively large surrounding substrate area. In this study, using a bottom-up technique, we successfully fabricated selective surface modified (SSM) SiNW-FETs with the receptors on the SiNW sensing surface only. In this approach, the strategy was to modify the SiNWs with a chemical linker of 3-aminopropyltrimethoxysilane (APTMS) prior to photolithographic fabrication of the device. The APTMS molecules modifying the SiNWs survived the harsh photolithographic processes, including coating with photoresist, washing with organic solvent, and thermal annealing. These SSM SiNW-FETs also exhibited desirable electrical characteristics such as ohmic contact and high transconductance. Using the biotin-avidin binding system, we showed that the faster response time and smaller sample requirements of the SSM SiNW-FETs, relative to the conventional AAM SiNW-FETs, clearly show that restricting the surface modification of the SiNW-FETs substantially improves their detection sensitivity. Detection with a SSM boronic acid-modified SiNW-FET of the dopamine released under high-K(+) buffer stimulation from living PC12 cells also demonstrates that SiNW-FETs can serve as highly sensitive biosensors for biomedical diagnosis. In binding affinity measurements with SiNW-FETs, the dissociation constants (Kd) of the biotin-avidin and dopamine-boronic acid complexes were determined to be 15 ± 1 fM and 33 ± 8 fM, respectively.

Summary Silicon nanowire field-effect transistors (SiNW-FETs) have recently drawn tremendous attention as a promising tool in biosensor design because of their ultrasensitivity, selectivity, and label-free and real-time detection capabilities. Here, we review the recently published literature that describes the device fabrication and biomedical applications of SiNW-FET sensors. For practical uses, SiNW-FETs can be delicately designed to be a reusable device via a reversible surface functionalization method. In the fields of biological research, SiNW-FETs are employed in the detections of proteins, DNA sequences, small molecules, cancer biomarkers, and viruses. The methods by which the SiNW-FET devices were integrated with these representative examples and advanced to virus infection diagnosis or early cancer detection will be discussed. In addition, the utilization of SiNW-FETs in recording the physiological responses from cells or tissues will also be reviewed. Finally, the novel design of a three dimensional (3D) nano-FET probe with kinked SiNWs for recording intracellular signals will be highlighted in this review.

Boronic acids (BAs) provide strong potential in orientation immobilization of antibody and the modification method is crucial for efficiency optimization. A highly effective method has been developed for rapid antibody immobilization on gold electrodes through the electrodeposition of a BA–containing linker in this study. Aniline-based BA forms a condense layer while antibody could automatically immobilize on the surface of the electrode. Compare to traditional self-assembled monolayer method, the electrodeposition process dramatically reduces the modification time from days to seconds. It also enhances the immobilized efficiency from 95 to 408 (ng/cm2) with a strong preference being exhibited for shorter aniline-based linkers.

Silicon nanowire field effect transistors (SiNW-FETs) have shown great promise as biosensors in highly sensitive, selective, real-time and label-free measurements. While applications of SiNW-FETs for detection of biological species have been described in several publications, less attention has been devoted to summarize the conjugating methods involved in linking organic bio-receptors with the inorganic transducer and the strategies of improving the sensitivity of devices. This article attempts to focus on summarizing the various organic immobilization approaches and discussing various sensitivity improving strategies, that include (I) reducing non-specific binding, (II) alignment of the probes, (III) enhancing signals by charge reporter, (IV) novel architecture structures, and (V) sensing in the sub-threshold regime.