Flexible capacitive pressure sensors with simple structure and low power consumption have attracted great interest because of their promising applications in wearable electronics. However, assembling a pressure sensor with high sensitivity, low detection limit, and wide dynamic range is still a big challenge. Here, a sandwich‐like, flexible capacitive pressure sensor is reported with micropyramid array electrode and porous dielectric layer. Under external stimulus pressure, the distance between two electrodes, and dielectric constant of dielectric layer will change simultaneously, resulting in high sensitivity (2.51 kPa−1) of the sensor. Due to the micropyramid array electrode, the sensor exhibits low detection limit (2.0 Pa), fast response speed (84 ms), wide working range (>10 kPa), and high stability (>5000 dynamic cycles). Finite‐element analysis also reveals that the larger duty ratio and altitude of micropyramid arrays lead to higher sensor sensitivity. By depicting the deformation of micropyramid during compression, the sensing mechanism of these sensors is discovered, providing a potential direction for developing sensitivity and linear range. Additionally, the sensor has been demonstrated to be efficient in monitoring human motion, such as muscle activation and rope skipping, showing high potential in the field of sport wearable equipment.

Contact angle is an essential characteristic in wetting, capillarity and moving contact line; however, although contact angle phenomena are effectively simulated, an accurate and real-time measurement for contact angle has not been well studied in computational fluid dynamics, especially in dynamic environments. Here, we design a geometry-based mesoscopic scheme for on-the-spot measurement of the contact angle in the lattice Boltzmann method. The measuring results without gravity effect are in good agreement with the benchmarks from the spherical cap method. The performances of the scheme are further verified in gravitational environments by simulating sessile and pendent droplets on smooth solid surfaces and dynamic contact angle hysteresis on chemically heterogeneous surfaces. This scheme is simple and computationally efficient. It requires only the local data and is independent of multiphase models.

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The precise and effective generation of micron-sized droplets is one of the most common and important issues for droplet-based microfluidics. Active droplet generation makes use of additional energy input in promoting interfacial instabilities for droplet generation. Here, we report a new technique for the active generation of femtoliter droplets in microfluidic systems using confined interfacial vibration (CIV). The CIV is formed at the orifice of a traditional inkjet nozzle first by pushing the liquid out and then pulling it back. Droplets are pinched off during the withdrawal process, and this is different from the current active droplet generation techniques, which only monodirectionally push the liquid out. Droplets with radius ranging from ca. 1 to 28 μm can be actively generated by CIV at an orifice with radius 30 μm, distinguishing from conventional active generation techniques in which the droplets are always comparable or slightly bigger than the orifice. Experimental results showed that the droplet volume can be customized by controlling the intensity of the CIV. The inherent digital nature of the inkjet technique enables easy and precise regulating of the droplet volume, making it seamlessly compatible with the digital microfluidic systems.

The precise and effective generation and manipulation of micron-sized droplets is crucial for chemical and biological research and applications. Normally, droplets generation and manipulation are achieved by two separate devices/systems with their respective operation strategies. Pipette, inkjet nozzle, and microfluidic channels equipped with programed syringes are commonly used for droplets generation whereas the subsequent manipulation is normally achieved by leveraging of forces originating either from optical, electric, magnetic or acoustic field and the corresponding complicated devices. Here we report a new paradigm that can realize simultaneous droplets generation and manipulation in an immiscible liquid environment using only the confined interface vibration generated by the ordinary inkjet nozzle. Droplets, ranging from femtoliter to picoliter, can be generated and manipulated without interruption since they are actuated by the same nozzle. Our strategy provides a platform for precise generation and manipulating the micro-sized droplets that may be valuable for applications requiring simple setups and seamless connection between droplets generation and droplets manipulation.