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With the flourishing development of artificial intelligence, lasing with tailored features generated by photonic crystal (PhC) lasers has been playing a more important part in the optics field and in potential applications of self‐control, light detection and ranging, telecommunications, and holography imaging. As an information vehicle, the optical beam's maneuverability is influenced by the working wavelength, direction, and efficiency of the laser. Liquid crystal (LC)‐based mirrorless lasers are widely investigated in manipulating the tuning of emission wavelength. Realizing fast self‐steering of the laser beam to tune the emission direction is challenging because of the limitation on the complex and expensive inorganic fabrication and circuit design. In this work, a self‐steered lasing from a defect‐mode sandwich film composed of photomechanical deformable azobenzene cholesteric LC elastomer (CLCE) PhC layers and an isotropic gain interlayer is demonstrated. On the basis of the great light‐deformability of the CLCE, the output single‐mode lasing emission of the sandwich‐film laser can be steered quickly by UV irradiation in a wide angular tuning range of ≈±57°. This flexible, portable, and durable laser system with controllable beam‐steering and mechanical robustness is envisioned to open a gate for autonomous vehicles, self‐sustaining machines, and optical devices with the core feature of photomechanical conversion. [ABSTRACT FROM AUTHOR]

A polarization controllable band‐edge liquid crystal (LC) laser configuration is presented that provides on‐demand control of the polarization state of the laser using a four electrode in‐plane configuration to drive a nematic LC layer. By controlling the orientation of the electric field, and thus the orientation of the optic axis of the nematic LC, as well as the retardance, any laser polarization state (e.g., circular, elliptical) can, in principle, be created that is aligned along any desired direction in a plane perpendicular to the propagation direction. After calibrating the tuneable nematic device with a He‐Ne laser that has a well‐defined polarization state, control of the LC laser polarization is then demonstrated, where it is shown that different polarization states and orientations thereof can be obtained by changing the relative combination and amplitudes of the voltages applied to each of the four electrodes. It is found, however, that achieving a pure linear polarization state is challenging, which may indicate that the polarization from the LC laser is not a well‐defined circularly polarized state. These thin‐film LC lasers with full polarization control are potentially important for a variety of different applications ranging from the biomedical to the display industries. [ABSTRACT FROM AUTHOR]

This study employed wearable inertial sensors integrated with an activity-recognition algorithm to recognize six types of daily activities performed by humans, namely walking, ascending stairs, descending stairs, sitting, standing, and lying. The sensor system consisted of a microcontroller, a three-axis accelerometer, and a three-axis gyro; the algorithm involved collecting and normalizing the activity signals. To simplify the calculation process and to maximize the recognition accuracy, the data were preprocessed through linear discriminant analysis; this reduced their dimensionality and captured their features, thereby reducing the feature space of the accelerometer and gyro signals; they were then verified through the use of six classification algorithms. The new contribution is that after feature extraction, data classification results indicated that an artificial neural network was the most stable and effective of the six algorithms. In the experiment, 20 participants equipped the wearable sensors on their waists to record the aforementioned six types of daily activities and to verify the effectiveness of the sensors. According to the cross-validation results, the combination of linear discriminant analysis and an artificial neural network was the most stable classification algorithm for data generalization; its activity-recognition accuracy was 87.37% on the training data and 80.96% on the test data. [ABSTRACT FROM AUTHOR]

Nano‐ and microscale morphology endows surfaces that play conspicuous roles in natural or artificial objects with unique functions. Surfaces with dynamic regulating features capable of switching the structures, patterns, and even dimensions of their surface profiles can control friction and wettability, thus having potential applications in antibacterial, haptics, and fluid dynamics. Here, a freestanding film with light‐switchable surface based on cholesteric liquid crystal networks is presented to translate 2D flat plane into a 3D nanometer‐scale topography. The wettability of the interface can be controlled by hiding or revealing the geometrical features of the surfaces with light. This reversible dynamic actuation is obtained through the order parameter change of the periodic cholesteric organization under a photoalignment procedure and lithography‐free mode. Complex tailored structures can be used to encrypt tactile information and improve wettability by predesigning the orientation distribution of liquid crystal director. This rapid switching nanoprecision smart surface provides a novel platform for artificial skin, optics, and functional coatings. [ABSTRACT FROM AUTHOR]

Conventional polymer dispersed liquid crystal (PDLC) films have been successful as electrically‐switchable screens for privacy applications. However, spatial patterning of the films so as to generate a visually appealing design, logo, or image typically requires intricate fabrication processes, such as the use of prefabricated photomasks that do not allow for on‐demand designs. Herein is reported on the fabrication and characterization of spatially patterned PDLC "pixels" using drop‐on‐demand inkjet printing, and it is demonstrated how these materials can be used to form a new generation of smart windows that consist of embedded images or company logos, which can be made to disappear with the application of a voltage. Following refinements to the material rheology and the subsequent successful deposition of individual PDLC droplets, arrays of PDLC pixels are printed at a resolution of 250 pixels per inch with an individual pixel size of 130 µm operating at an electric field strength (E) of E = 1.4 V μm−1. Finally, using the approach developed herein, these printed PDLC pixels are arranged to form a college emblem that is embedded within a smart window that can be made to disappear with the application of a voltage. [ABSTRACT FROM AUTHOR]