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ObjectiveChlorophyll fluorescence (ChlF) emission from photosystem II (PSII) is closely coupled with photochemical reactions. As an efficient and non-destructive means of obtaining plant photosynthesis efficiency and physiological state information, the collection of fluorescence signals is often used in many fields such as plant physiological research, smart agricultural information sensing, etc. Chlorophyll fluorescence imaging systems, which is the experimental device for collecting the fluorescence signal, have difficulties in application due to their high price and complex structure. In order to solve the issues, this paper investigates and constructs a low-cost chlorophyll fluorescence imaging system based on a micro complementary metal oxide semiconductor (CMOS) camera and a smartphone, and carries out experimental verifications and applications on it.MethodThe chlorophyll fluorescence imaging system is mainly composed of three parts: excitation light, CMOS camera and its control circuit, and a upper computer based on a smartphone. The light source of the excitation light group is based on the principle and characteristics of chlorophyll fluorescence, and uses a blue light source of 460 nm band to achieve the best fluorescence excitation effect. In terms of structure, the principle of integrating sphere was borrowed, the bowl-shaped light source structure was adopted, and the design of the LED surface light source was used to meet the requirements of chlorophyll fluorescence signal measurement for the uniformity of the excitation light field. For the adjustment of light source intensity, the control scheme of pulse width modulation was adopted, which could realize sequential control of different intensities of excitation light. Through the simulation analysis of the light field, the light intensity and distribution characteristics of the light field were stuidied, and the calibration of the excitation light group was completed according to the simulation results. The OV5640 micro CMOS camera was used to collect fluorescence images. Combined with the imaging principle of the CMOS camera, the fluorescence imaging intensity of the CMOS camera was calculated, and its ability to collect chlorophyll fluorescence was analyzed and discussed. The control circuit of the CMOS camera uses an STM32 microcontroller as the microcontroller unit, and completes the data communication between the synchronous light group control circuit and the smartphone through the RS232 to TTL serial communication module and the full-speed universal serial bus, respectively. The smartphone upper computer software is the operating software of the chlorophyll fluorescence imaging system user terminal and the overall control program for fluorescence image acquisition. The overall workflow could be summarized as the user sets the relevant excitation light parameters and camera shooting instructions in the upper computer as needed, sends the instructions to the control circuit through the universal serial bus and serial port, and completes the control of excitation light and CMOS camera image acquisition. After the chlorophyll fluorescence image collection was completed, the data would be sent back to the smart phone or server for analysis, processing, storage, and display. In order to verify the design of the proposed scheme, a prototype of the chlorophyll fluorescence imaging system based on this scheme was made for experimental verification. Firstly, the uniformity of the light field was measured on the excitation light to test the actual performance of the excitation light designed in this article. On this basis, a chlorophyll fluorescence imaging experiment under continuous light excitation and modulated pulse light protocols was completed. Through the analysis and processing of the experimental results and comparison with mainstream chlorophyll fluorometers, the fluorescence imaging capabilities and low-cost advantages of this chlorophyll fluorometer were further verified.Results and DiscussionsThe maximum excitation light intensity of the chlorophyll fluorescence imaging system designed in this article was 6250 µmol/(m2·s). Through the simulation analysis of the light field and the calculation and analysis of the fluorescence imaging intensity of the CMOS camera, the feasibility of collecting chlorophyll fluorescence images by the OV5640 micro CMOS camera was demonstrated, which provided a basis for the specific design and implementation of the fluorometer. In terms of hardware circuits, it made full use of the software and hardware advantages of smartphones, and only consisted of the control circuits of the excitation light and CMOS camera and the corresponding communication modules to complete the fluorescence image collection work, simplifying the circuit structure and reducing hardware costs to the greatest extent. The final fluorescence instrument achieved a collection resolution of 5 million pixels, a spectral range of 400~1000 nm, and a stable acquisition frequency of up to 42 f/s. Experimental results showed that the measured data was consistent with theoretical analysis and simulation, which could meet the requirements of fluorescence detection. The instrument was capable of collecting images of chlorophyll fluorescence under continuous light excitation or the protocol of modulated pulsed light. The acquired chlorophyll fluorescence images could reflect the two-dimensional heterogeneity of leaves and could effectively distinguish the photosynthetic characteristics of different leaves. Typical chlorophyll fluorescence parameter images of Fv/Fm, Rfd, etc. were in line with expectations. Compared with the existing chlorophyll fluorescence imaging system, the chlorophyll fluorescence imaging system designed in this article has obvious cost advantages while realizing the rapid detection function of chlorophyll fluorescence.ConclusionsThe instrument is with a simple structure and low cost, and has good application value for the detection of plant physiology and environmental changes. The system is useful for developing other fluorescence instruments.

Driven by the development of innovative electrode materials, the brain-machine interface (BMI) has witnessed significant advancements in recent years. However, traditional implantable electrodes, such as metal-based and polymer-based electrodes, often face limitations in terms of flexibility, chronic stability, and long-term biocompatibility. Liquid metal-based electrodes have emerged as a promising alternative to traditional electrode materials, offering unique properties and numerous advantages for BMI applications. In this Review, we provided an in-depth overview of liquid metal-based electrodes. Liquid metal-based electrodes demonstrate several desirable features, including high electrical conductivity, flexibility, biocompatibility, and the ability to conform to the irregular and delicate structures of the brain. We also systematically and thematically discussed their material properties, biocompatibility considerations, performance characteristics, and assorted applications in neural recording, stimulation, brain-machine interfaces, closed-loop feedback systems, and neuroprosthetics. Meanwhile, long-term stability, biocompatibility, electrode-tissue interface, miniaturization, signal processing, and ethical considerations are areas that require further research and innovation. Addressing these challenges will contribute to the successful integration and widespread use of liquid metal-based electrodes in BMI systems.

This study explored the effect of individualised nutritional intervention on the postpartum nutritional status of patients with the growth and development of their offspring. This study included pregnant women with gestational diabetes mellitus (GDM) at Hangzhou Women’s Hospital in 2019. At 42 days after childbirth, the HbA1c (95% CI: 0.44-0.56%, p 0.05). There were significant differences in the number of macrosomia and neonatal weight between the two groups (both p 0.05). Individualised nutritional intervention could improve blood glucose levels 42 days after childbirth and reduce macrosomia incidence in pregnant women with GDM.Impact statement What is already known on this subject? Individualised nutrition intervention can improve blood glucose status and complications during pregnancy, thus improving pregnancy outcomes. What the results of this study add? Individual nutrition intervention improved the blood glucose and nutritional status of patients at 42 days postpartum, but there was no difference in the growth and development indicators of their offspring at 0–24 months. What the implications are of these findings for clinical practice and/or further research? Improve nutritional intervention programs for gestational diabetes, improve blood glucose during pregnancy and postpartum, to improve pregnancy outcomes and reduce the occurrence of type 2 diabetes and other metabolic diseases; Extend the monitoring range of the growth and development of the offspring of gestational diabetes, find the problems and timely carry out the nutritional intervention, to improve the development of the offspring.