Electronic skin (e-skin) is able to monitor physiological signals, providing great potential in healthcare. This review briefly introduces the advanced information of e-skins for wearable sensors, such as their materials and integrate strategies.

The sensitivity and linearity are critical parameters that can preserve the high pressure‐resolution across a wide range and simplify the signal processing process of flexible tactile sensors. Although extensive micro‐structured dielectrics have been explored to improve the sensitivity of capacitive sensors, the attenuation of sensitivity with increasing pressure is yet to be fully resolved. Herein, a novel dielectric layer based on the gradient micro‐dome architecture (GDA) is presented to simultaneously realize the high sensitivity and ultrabroad linearity range of capacitive sensors. The gradient micro‐dome pixels with rationally collocated amount and height can effectively regulate the contact area and hence enable the linear variation in effective dielectric constant of the GDA dielectric layer under varying pressures. With systematical optimization, the sensor exhibits the high sensitivity of 0.065 kPa−1 in an ultrabroad linearity range up to 1700 kPa, which is first reported. Based on the excellent sensitivity and linearity, the high pressure‐resolution can be preserved across the full scale of pressure spectrum. Therefore, potential applications such as all‐round physiological signal detection in diverse scenarios, control instruction transmission with combinatorial force inputs, and convenient Morse code communication with non‐overlapping capacitance signals are successfully demonstrated through a single sensor device.

We present a waved microchannel for continuous focusing of microparticles and cells using negative direct current (dc) dielectrophoresis. The waved channel is composed of consecutive s-shaped curved channels in series to generate an electric field gradient required for the dielectrophoretic effect. When particles move electrokinetically through the channel, the experienced negative dielectrophoretic forces alternate directions within two adjacent semicircular microchannels, leading to a focused continuous-flow stream along the channel centerline. Both the experimentally observed and numerically simulated results of the focusing performance are reported, which coincide acceptably in proportion to the specified dimensions (i.e. inlet and outlet of the waved channel). How the applied electric field, particle size and medium concentration affect the performance was studied by focusing polystyrene microparticles of varying sizes. As an application in the field of biology, the focusing of yeast cells in the waved mcirochannel was tested. This waved microchannel shows a great potential for microflow cytometry applications and is expected to be widely used before different processing steps in lab-on-a-chip devices with integrated functions.

Flexible superhydrophobic surfaces have recently attracted extensive interest not only in the field of burgeoning flexible electronics, but also for the practicability toward various situations. Herein, a cost‐effective and environment‐friendly approach is demonstrated to realize the durable, flexible, and superhydrophobic film with optical transparency. Without sophisticated facilities, the essential hierarchical architecture to render a low‐adhesive surface is achieved via magnetic field‐assisted polydimethylsiloxane microcilia, followed with the swelling process to decorate nanoscaled particles with excellent robustness. This tight connection between the microcilia and decorated nanoparticles renders the mechanical robustness with resistance to ultrasonic treatment, sandpaper abrasion, and high‐speed water impact. The film further exhibits outstanding stabilities when exposed to organic contamination, hot water, and chemical corrosions. Water repellency is well preserved when the film is under various mechanical deformations including cyclic stretching, bending, and squeezing. For practical demonstrations, the film is applied as the protective film for touch screen owing to the intrinsic optical transmittance, or serves as the water‐proof covers for sorts of complex/curved surfaces. These stated features reveal the convincing potential of the methodology to be applied for the circumstances where simultaneous addressing of robustness, flexibility, and adaptability is highly appreciated.

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This article presents a dielectrophoresis (DEP)-based microfluidic device with the three-dimensional (3D) microelectrode configuration for concentrating and separating particles in a continuous throughflow. The 3D electrode structure, where microelectrode array are patterned on both the top and bottom surfaces of the microchannel, is composed of three units: focusing, aligning and trapping. As particles flowing through the microfluidic channel, they are firstly focused and aligned by the funnel-shaped and parallel electrode array, respectively, before being captured at the trapping unit due to negative DEP force. For a mixture of two particle populations of different sizes or dielectric properties, with a careful selection of suspending medium and applied field, the population exhibits stronger negative DEP manipulated by the microelectrode array and, therefore, separated from the other population which is easily carried away toward the outlet due to hydrodynamic force. The functionality of the proposed microdevice was verified by concentrating different-sized polystyrene (PS) microparticles and yeast cells dynamically flowing in the microchannel. Moreover, separation based on size and dielectric properties was achieved by sorting PS microparticles, and isolating 5 lm PS particles from yeast cells, respectively. The performance of the proposed microconcentrator and separator was also studied, including the threshold voltage at which particles begin to be trapped, variation of cell-trapping efficiency with respect to the applied voltage and flow rate, and the efficiency of separation experiments. The proposed microdevice has various advantages, including multi-functionality, improved manipulation efficiency and throughput, easy fabrication and operation, etc., which shows a great potential for biological, chemical and medical applications.

As crystallization processes are often rapid, it can be difficult to monitor their growth mechanisms. In this study, we made use of the fact that crystallization proceeds more slowly in small volumes than in bulk solution to investigate the effects of the soluble additives Mg2+ and poly(styrene sulfonate) (PSS) on the early stages of growth of calcite crystals. Using a “Crystal Hotel” microfluidic device to provide well‐defined, nanoliter volumes, we observed that calcite crystals form via an amorphous precursor phase. Surprisingly, the first calcite crystals formed are perfect rhombohedra, and the soluble additives have no influence on the morphology until the crystals reach sizes of 0.1–0.5 μm for Mg2+ and 1–2 μm for PSS. The crystals then continue to grow to develop morphologies characteristic of these additives. These results can be rationalized by considering additive binding to kink sites, which is consistent with crystal growth by a classical mechanism.

We report a simple, low-cost and detachable microfluidic chip incorporating easily accessible paper, glass slides or other polymer films as the chip materials along with adhesive wax as the recycling bonding material. We use a laser to cut through the paper or film to form patterns and then sandwich the paper and film between glass sheets or polymer membranes. The hot-melt adhesive wax can realize bridge bonding between various materials, for example, paper, polymethylmethacrylate (PMMA) film, glass sheets, or metal plate. The bonding process is reversible and the wax is reusable through a melting and cooling process. With this process, a three-dimensional (3D) microfluidic chip is achievable by vacuating and venting the chip in a hot-water bath. To study the biocompatibility and applicability of the wax-based microfluidic chip, we tested the PCR compatibility with the chip materials first. Then we applied the wax-paper based microfluidic chip to HeLa cell electroporation (EP). Subsequently, a prototype of a 5-layer 3D chip was fabricated by multilayer wax bonding. To check the sealing ability and the durability of the chip, green fluorescence protein (GFP) recombinant Escherichia coli (E. coli) bacteria were cultured, with which the chemotaxis of E. coli was studied in order to determine the influence of antibiotic ciprofloxacin concentration on the E. coli migration.