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A novel microfluidic droplet generator is proposed, which can control the droplet size through turning an integrated micrometer head with ease, and the size of the produced micro-droplet can be automatically and real-time monitored by an open-sourced software and off-the-shelf hardware.

Recent advances in the development of hybrid organic–inorganic halide perovskite quantum dots (HP-QDs) have proven their versatility and potential applications in photovoltaics and light sources through compositional tuning. However, the compositional complexity for mixed-cation and/or mixed-halide HP-QDs would require repetitive optimization processes to obtain the desired perovskite crystals via traditional batch-scale chemistry, causing prolonged time, labor, and cost. To address this issue, we herein report a dynamic flow chemistry synthetic system operated with the on-and-off feedback control with hysteresis algorithm to produce methylammonium lead trihalide perovskite quantum dots (MAPbBrXI3-X QDs with 0 ≤ X ≤ 3), automatically showing a target emission wavelength. We set up the target photoluminescent (PL) emission wavelength of the MAPbBrXI3-X QDs and started with an arbitrary flow rate of the bromide and iodide precursor solution. The PL emission wavelength of the synthesized perovskites was in-situ monitored in the flow cell equipped with a miniaturized optical detector. By comparing the measured wavelength with the target one, the controlling algorithm recalculated to adjust the flow rates of the bromide and iodide precursor solution accordingly. Then, the PL emission wavelength of the newly synthesized MAPbBrXI3-X QDs was detected again in real-time, and the iterative feedback control process was repeated until the observed wavelength was matched with the user-defined emission target. Thus, the desired MAPbBrXI3-X QDs could be obtained eventually through the feedback control in an automatic manner, suggesting an advanced flow chemistry synthetic platform to produce on-demanded nanomaterials with high efficiency.

Rapid and accurate testing tools for SARS-CoV-2 detection are urgently needed to prevent the spreading of the virus and to take timely governmental actions. Internet of things (IoT)-based diagnostic devices would be an ideal platform for point-of-care (POC) screening of COVID-19 and ubiquitous healthcare monitoring for patients. Herein, we present an advanced IoT-based POC device for real-time direct reverse-transcription-loop mediated isothermal amplification assay to detect SARS-CoV-2. The diagnostic system is miniaturized (10 cm [height] × 9 cm [width] × 5.5 cm [length]) and lightweight (320 g), which can be operated with a portable battery and a smartphone. Once a liquid sample was loaded into an integrated microfluidic chip, a series of sample lysis, nucleic amplification, and real-time monitoring of the fluorescent signals of amplicons were automatically performed. Four reaction chambers were patterned on the chip, targeting As1e, N, E genes and a negative control, so multiple genes of SARS-CoV-2 could be simultaneously analyzed. The fluorescence intensities in each chamber were measured by a CMOS camera upon excitation with a 488 nm LED light source. The recorded data were processed by a microprocessor inside the IoT-based POC device and transferred and displayed on the wirelessly connected smartphone in real-time. The positive results could be obtained using three primer sets of SARS-CoV-2 with a limit of detection of 2 × 101 genome copies/μL, and the clinical sample of SARS-CoV-2 was successfully analyzed with high sensitivity and accuracy. Our platform could provide an advanced molecular diagnostic tool to test SARS-CoV-2 anytime and anywhere.