When blood vessels are injured, leader cells emerge in the endothelium to heal the wound and restore the vasculature integrity. The characteristics of leader cells during endothelial collective migration under diverse physiological conditions, however, are poorly understood. Here we investigate the regulation and function of endothelial leader cells by plasma lithography geometric confinement generated. Endothelial leader cells display an aggressive phenotype, connect to follower cells via peripheral actin cables and discontinuous adherens junctions, and lead migrating clusters near the leading edge. Time-lapse microscopy, immunostaining, and particle image velocimetry reveal that the density of leader cells and the speed of migrating clusters are tightly regulated in a wide range of geometric patterns. By challenging the cells with converging, diverging and competing patterns, we show that the density of leader cells correlates with the size and coherence of the migrating clusters. Collectively, our data provide evidence that leader cells control endothelial collective migration by regualting the migrating clusters.

A differential detection method (DDM) with a utility type and ease of realization for a micro-grating accelerometer is reported so as to reduce the common-mode noise and improve the sensitivity of the micro-grating accelerometer. The theoretical model is established, based on scalar diffraction theory for differential detection. According to the simulation and analysis of the DDM, the theoretical result shows that the sensitivity of the micro-grating accelerometer can be improved by at least a factor of 2. Based on the analysis, the detection circuit is designed with proper parameters and devices for the handheld experimental prototype, which is realized with our micro-grating acceleration sensor fabricated by inductively coupled plasma, lift-off, and anodic bonding of glass/silicon, etc. The prototype experiment is conducted with the turntable. Compared with the single-order detection method whose sensitivities are 6.797 V/g (zeroth order, 1 g=9.8 m/s²) and 7.767 V/g (first-order), the result of the DDM shows that the sensitivity of the micro-grating accelerometer is 18.61 V/g with an improvement of over two times. The overall signal-to-noise ratio improvement is 6.47 dB with the input of 0.86 g.

A novel out-of-plane MOEMS accelerometer based on near-field evanescent wave coupling by means of variable period subwavelength gratings has been proposed. First, the diffraction order number was calculated. Then, structure parameters were optimized by finite element analysis to achieve high sensitivity in an ideal vibration mode. Results show that the accelerometer has displacement sensitivity at 2033 nm/G with a measurement range of 0.12 G, corresponding to first diffraction beam optical sensitivity 0.46%/mG. Finally, we designed the fabrication method to form such MOEMS accelerometer and successfully fabricated the uniform and well-designed subwavelength gratings with the period of 1.0 µm by FIB/SEM dual beam system. The subwavelength gratings fabricated are very close to those designed within the experimental error to lay the foundation for the subsequent fabrication. These results provide a theoretical basis for design and fabrication of an out-of-plane MOEMS accelerometer with subwavelength gratings.Index Terms-Evanescent wave coupling, subwavelength gratings, MOEMS accelerometer, FIB/SEM dual beam system.

A combination of large mass, weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration. A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed. First, the numbers of diffraction orders are calculated. Then, structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode. Finally, we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm, crater of 451 nm by an FIB/SEM dual beam system. Based on the ANSYS simulation, a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of ±1 G, corresponding to zeroth diffraction beam optical sensitivity 1%/mG. The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication. These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.