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This work reports a platform based on ultrasound for mid-air particle manipulations using a 2×2 piezoelectric micromachined ultrasonic transducer (pMUT) array. Three achievements have been demonstrated as compared to the state-of-art: (1) high SPL (sound pressure level) of 120 dB at a distance 12 mm away by an individual lithium-niobate pMUT; (2) a numerically simulated and experimentally demonstrated 2D focal point control scheme by adjusting the phase-delay of individual pMUTs; and (3) the experimental demonstration of moving a 0.7 mg foam plastic particle of 12 mm away in the mid-air by ~1.8 mm. As such, this work shows the potential for practical applications in the broad fields of non-contact actuations, including particle manipulations in microfluidics, touchless haptic sensations, … etc. 

This work reports an engineered platform for the non-contact haptic stimulation on human skins by means of an array of piezoelectric micromachined ultrasonic transducer (pMUT) via the beamforming scheme. Compared to the state-of-art reports, three distinctive achievements have been demonstrated: (1) individual single pMUT unit based on lithium niobate (LN) with measured high SPL (sound pressure level) of 133 dB at 2 mm away; (2) a beamforming scheme simulated and experimentally proved to generate ~2.3x higher pressure near the focal point; and (3) the combination of auto-positioning and haptic stimulations on volunteers with the smallest reported physical device size to achieve haptic sensations. As such, this work could have practical applications in the broad areas to stimulate haptic sensations, such as AR (Augmented Reality), VR (Virtual Reality), and robotics. 

Optically active defects in 2D materials, such as hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDs), are an attractive class of single-photon emitters with high brightness, room-temperature operation, site-specific engineering of emitter arrays, and tunability with external strain and electric fields. In this work, we demonstrate a novel approach to precisely align and embed hBN and TMDs within background-free silicon nitride microring resonators. Through the Purcell effect, high-purity hBN emitters exhibit a cavity-enhanced spectral coupling efficiency up to 46% at room temperature, which exceeds the theoretical limit for cavity-free waveguide-emitter coupling and previous demonstrations by nearly an order-of-magnitude. The devices are fabricated with a CMOS-compatible process and exhibit no degradation of the 2D material optical properties, robustness to thermal annealing, and 100 nm positioning accuracy of quantum emitters within single-mode waveguides, opening a path for scalable quantum photonic chips with on-demand single-photon sources.