Author Correction: Optimal signal quality index for remote photoplethysmogram sensing
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Optimal signal quality index for remote photoplethysmogram sensing
Remote photoplethysmography (rPPG) enables non-invasive monitoring of circulatory signals using mobile devices, a crucial advancement in biosensing. Despite its potential, ensuring signal quality amidst noise and artifacts remains a significant challenge, particularly in healthcare applications. Addressing this, our study focuses on a singular signal quality index (SQI) for rPPG, aimed at simplifying high-quality video capture for heart rate detection and cardiac assessment. We introduce a practical threshold for this SQI, specifically the signal-to-noise ratio index (NSQI), optimized for straightforward implementation on portable devices for real-time video analysis. Employing (NSQI < 0.293) as our threshold, our methodology successfully identifies high-quality cardiac information in video frames, effectively mitigating the influence of noise and artifacts. Validated on publicly available datasets with advanced machine learning algorithms and leave-one-out cross-validation, our approach significantly reduces computational complexity. This innovation not only enhances efficiency in health monitoring applications but also offers a pragmatic solution for remote biosensing. Our findings constitute a notable advancement in rPPG signal quality assessment, marking a critical step forward in the development of remote cardiac monitoring technologies with extensive healthcare implications.
Recent advances in solid-liquid triboelectric nanogenerators for self-powered chemical and biological sensing
Solid-liquid triboelectric nanogenerators (SL-TENGs) exhibit significant potential in energy harvesting and sensing. This review explores SL-TENG development, focusing on chemical sensing and biosensing applications. Initially, the working mechanisms of various SL-TENG modes are described. Subsequently, an analysis of surface modifications of contact surfaces and liquids to functionalize chemical sensing and biosensing is explored, including their impact on surface properties and the corresponding effect on device performance related to sensing applications.
A computational unfolding-based design method for three-dimensional conformal electronic skin with adjustable mounting strain
Three-dimensional (3D) conformal electronic skins (E-skins) have been developed for matching the irregularly surfaces. The 3D conformal E-skins manufactured by direct-curved-surface or dimensional converting methods both need curved-surface calibration. With increase of units’ number and complication of mounting-surface morphology, curved-surface calibration becomes intricate. We report a universal cutting and distributing strategy for E-skins. The E-skin incorporates hierarchical and modular tactile sensors to match curvatures and sizes, thereby reducing mounting strain. This strategy enables curved-surface performance of 3D conformal E-skins to be characterized by flat-surface calibration results. An example is provided: Three-level sensors are utilized and calibrated on flat and curved surfaces. Performance variations reduce as sensor size decreases, and performance changes of level II and III sensing units are small after mounting. Their calibration results on curved surface are replaced by those on flat surface, proving low mounting strain facilitates 3D conformal E-skins to avoid complicated curved-surface calibration.
Biomolecule sensors based on organic electrochemical transistors
Biosensors based on organic electrochemical transistors (OECTs) have been a research highlight in recent years owing to their remarkable biocompatibility, low operating voltage, and substantial signal amplification capability. Especially, as an emerging fundamental device for biosensing, OECTs show great potential for pH, ions, molecules, and biomarker sensing. This review highlights the research progress of biomolecule sensors based on OECTs, focusing on recent publications in the past 5 years. Specifically, OECT-based biomolecule sensors for small molecules (glucose, dopamine, lactate, etc. that act as signals or effectors), and macromolecules (DNA, RNA, proteins, etc. that are often used as markers in physiology and medicine), are summarized. Additionally, emerging technologies and materials used to enhance sensitivity, detection limits, and detection ranges are described comprehensively. Last, aspects of OECT-based biomolecule sensors that need further improvement are discussed along with future opportunities and challenges.
A tip-tilt-piston electrothermal micromirror array with integrated position sensors
A tip-tilt-piston 3 × 3 electrothermal micromirror array (MMA) integrated with temperature field-based position sensors is designed and fabricated in this work. The size of the individual octagonal mirror plates is as large as 1.6 mm × 1.6 mm. Thermal isolation structures are embedded to reduce the thermal coupling among the micromirror units. Results show that each micromirror unit has a piston scan range of 218 μm and a tip-tilt optical scan angle of 21° at only 5 Vdc. The micromirrors also exhibit good dynamic performance with a rise time of 51.2 ms and a fall time of 53.6 ms. Moreover, the on-chip position sensors are proven to be capable for covering the full-range movement of the mirror plate, with the measured sensitivities of 1.5 mV/μm and 8.8 mV/° in piston sensing and tip-tilt sensing, respectively. Furthermore, the thermal crosstalk in an operating MMA has been experimentally studied. The measured results are promising thanks to the embedded thermal isolation structures.
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