We conducted a scoping review to identify and describe trends in the use of social media images as data sources to inform social science research in published articles from 2015 to 2019. The identified trends include the following: (1) there is increasing interest in social media images as research data, especially in disciplines like sociology, cultural studies, communication and environmental studies; (2) the photo sample size is often smaller than that is typically used in text-based social media analysis and usually is collected manually; (3) thematic coding, object recognition and narrative analysis are the most popular analysis methods that are often conducted manually; (4) computer vision and machine-learning technologies have been increasingly but still infrequently used and are not fit for all purposes; and (5) relatively few papers mention ethics and privacy issues, or apply strategies to address ethical issues. We identify noteworthy research gaps, and opportunities to address limitations and challenges.

Current circulating tumor cells (CTCs) detection strategies based on surface epithelial markers suffer from low specificity in distinguishing between CTCs and epithelial cells in hematopoietic cell population. Tumor‐associated miRNAs within CTCs are emerging as new biomarkers due to their high correlation with tumor development and progress. However, in‐situ simultaneous analysis of multiple miRNAs in single CTC cell is still challenging. To overcome this limitation, a digital droplet microfluidic flow cytometry based on biofunctionalized 2D metal‐organic framework nanosensor (Nano‐DMFC) is developed for in situ detection of dual miRNAs simultaneously in single living breast cancer cells. Here, 2D MOF‐based fluorescent resonance energy transfer (FRET) nanosensors are established by conjugating dual‐color fluorescence dye‐labeled DNA probes on MOF nanosheet surface. In the Nano‐DMFC, 2D MOF‐based nanoprobes are precisely microinjected into each single‐cell encapsulated droplets to achieve dual miRNA characterization in single cancer cell. This Nano‐DMFC platform successfully detects dual miRNAs at single‐cell resolution in 10 mixed positive MCF‐7 cells out of 10 000 negative epithelial cells in serum biomimic samples. Moreover, this Nano‐DMFC platform shows good reproductivity in the recovery experiment of spiked blood samples, which demonstrate the high potential for CTC‐based cancer early diagnosis and prognosis.

In this work, we proposed a novel ultrasonic transducer array based on an array of 50 × 50 piezoelectric micromachined ultrasonic transducers (pMUTs). The structure was specially designed for fingerprint imaging application. The pMUTs array were fabricated with isolated piezoelectric lead zirconate titanate (PZT) cells to reduce the crosstalk between adjacent units, and released by deepsilicon etching from the back side. The cell size and pitch of pMUTs were 50 μm and 100 μm, respectively. Layer-by-layer annealing method was used instead of one-time annealing during the fabrication of sol-gel based PZT film. The resonance frequency of the pMUT was about 24.82 MHz which agreed well with simulated 25.02 MHz. Besides, the effective electro-mechanical coupling coefficient (k eff ) and mechanical quality factor (Q factor) of the transducer were 0.1293 and 198, respectively. The equivalent circuit of the transducer was established and analyzed. The fitted admittance circle agreed well with the experimental result. This demonstration of pMUTs array has profound potential for large-scale, high-density, and high-frequency fingerprint imaging. Optical, capacitive, piezoelectric and acoustic mechanisms based sensors have been developed to capture the electronic images of human fingerprints in the last twenty years.1 The capacitive fingerprint sensors are the most widely used in consumer electronics, duo to their high array density and complementary metal-oxide-semiconductor transistor (CMOS) compatibility.2-4 However, the image captured by capacitive fingerprint sensor is two-dimensional, which can be spoofed easily by a printed template. And capacitive fingerprint sensors are extremely sensitive to contamination and moisture on the finger, which may lead to false recognition. Ultrasonic transducer array provides a potential solution to these problems. The acoustic impedances of valleys and ridges on fingerprints are greatly different, and can be easily distinguished by ultrasonic transducer.5 Thus, the ultrasonic pulse-echo imaging technology can be applied to imaging the ridges, valleys of the fingerprints, and even the tissue beneath. The three-dimensional images captured by ultrasonic fingerprint sensor eliminates the risks of failure and spoof.6 Large-scale, high-density pMUTs array based on AlN were used in high resolution fingerprint imaging with small size, high frame-rate and low cost. 7,8 The lead zirconate titanate (PZT) has piezoelectric coefficient that is generally two-orders-of-magnitude higher than AlN, 9-11 which can be used to fabricate fingerprint sensor with better performance. A PZT based fingerprint sensor was reported with single-pixel and mechanicalscanning working mode, which was large size, low frame-rate, and high cost. 12In this report, we demonstrate an ultrasound transducers array for fingerprint imaging based on sol-gel PZT technique. We designed the structures and parameters of the transducer by simulation, and fabricated the arrays of pMUTs based on the sol-gel PZT techniques. 13 The isolat...