Strip Sensors Research Articles

M13mp18 nanoscaffold-based strip sensor for detecting influenza A virus (H1N1)

We report the development of an amplification-free nucleic acid assay using lateral flow test strips. M13mp18 nanoscaffold signal amplification permitted the visual detection of H1N1 RNA in 20 min. M13mp18 nanoscaffold supported a set of backbone, variable, detection, and modified oligonucleotides. A bridging-type FAM probe/H1N1 RNA/M13mp18 was used in the lateral flow test strip format. The bridging-type complexes were captured on the test zone. The lower limit of detection of specific H1N1 RNA was 1 pM. The method directly detected H1N1 RNA without amplification, eliminating the risk of amplicon contamination and lessening the chance of false positives. This biosensor has potential value for field testing in resource-limited settings and monitoring viral loads in recovering patients. The amplification-free lateral flow detection of RNA provides an alternative between amplification-based RNA assays and protein antigen assays for facilitating the rapid identification of H1N1 virus during point-of-care testing.

Lateral Flow Assay for Cattle Age Determination: Implications for Diagnosing Bovine Spongiform Encephalopathy

Quarantine authorities in East Asia prohibit the import of cattle over 30 months old due to concerns about bovine spongiform encephalopathy (BSE). Accurately determining the age of cattle is critical for complying with these regulations. However, current methods for determining cattle age are time-consuming and require laboratory analysis, making them impractical for real-time use during import inspections. This creates a pressing need for a point-of-care test (POCT) method that can rapidly determine cattle age from beef samples in the field. 4To develop a portable POCT method capable of quickly and accurately determining the age of cattle from beef samples in the field. We investigated the expression of cell cycle proteins p53 and p21, and based on these findings, designed a lateral flow assay (LFA) to measure cattle age using the expression patterns of these proteins.We investigated the expression of cell cycle proteins p53 and p21 using immunoblot analysis to determine the age of beef and applied these findings to lateral flow assay (LFA). The expression pattern of p53 remains at baseline levels up to 28 months and then increases sharply after 35 months. In contrast, p21 expression gradually decreases, reaching baseline levels after 30 months. The SPR sensogram of p21 using surface plasmon resonance (SPR) clearly distinguished beef samples between 27-month-old and 31-month-old cattle. We constructed a calibration curve using recombinant p21 protein to determine the age of beef samples from cattle aged 9 to 33 months. The LFA sensor strip, designed with bovine p21 epitope-based peptide antibody, improved sensitivity and limit of detection (LOD) by more than 10 times.

Affordable paper-based strips: A breakthrough in phenol detection for water samples

Phenols are pollutants prevalent in industries such as pharmaceuticals, pulp and paper, petrochemicals, coal, agriculture, and plastics, often released untreated. Detecting and measuring phenols is essential, typically achieved through spectrophotometry, chromatography, electrochemical, and immunochemical biosensors. These methods, however, are expensive and require skilled operators. Thus, developing an efficient, user-friendly, affordable, and environmentally sustainable method is crucial. This study introduces inexpensive colorimetric paper-based sensor strips for detecting phenolic contaminants in water samples using the Folin–Ciocalteu (FC) reagent as the chromogenic probe. Whatman #1 and #4 filter papers were used to construct the prototypes, WFP-1 and WFP-4. The limit of detection (LOD) for five phenols (pyrogallol, gallic acid, resorcinol, vanillin, and hydroquinone) was 6.01 mg/L and 9.66 mg/L, respectively. ImageJ software analyzed the color intensity of each phenol, revealing a detection order of pyrogallol > resorcinol > gallic acid > hydroquinone > vanillin, attributed to the reactivity of phenolic hydroxyl groups with FC reagent. Recovery tests with water samples containing resorcinol showed WFP-1 sensors achieving 90 %–98.50 % recovery and WFP-4 sensors achieving 97.50 %–101.69 % recovery. These results highlight the sensor’s simplicity, cost-effectiveness, and potential for widespread application in phenolic contaminant detection and quantification.

Development of microfibrillated cellulose-reinforced carboxymethyl cellulose dipstick imprinted with benzotrifluoride-bearing hydrazone sensor for colorimetric detection of organophosphonate.

The colorless and odorless nerve agents can cause paralysis and even death. The development of novel composite-based microporous strips has allowed for the rapid and visual detection of diisopropyl phosphorofluoridate (DIPF) nerve agent mimics. The active methyl-containing tricyanofuran and 4-aminobenzotrifluoride diazonium salt were azo-coupled in a straightforward manner to produce a new benzotrifluoride (BFT)-comprising tricyanofuran (TCF) hydrazone colorimetric probe. The molecular structure of the benzotrifluoride-bearing hydrazone (BFTH) was explored by different spectroscopic techniques. Microfibrillated cellulose (MFC) was produced using a green process from sugarcane bagasse, an agriculture waste that is notorious for being a solid pollution. Consequently, discovering a straightforward procedure to convert bagasse into valuable materials has been of utmost importance. MFC displayed diameters of 0.25-2 μm, whereas the sensory films exhibited pore diameters of 0.5-2.25 μm. Various quantities of the BFTH chromophore were used to create benzotrifluoride-bearing hydrazone/microfibrillated cellulose/carboxymethyl cellulose (BFTH/MFC@CMC) composites. The absorbance band of the hydrazone-immobilized composite increased from 435 nm to 580 nm as the content of DIPF was raised. When exposed to DIPF, the dipstick color shifted from orange to pink, according to the CIE Lab measurements. The sensor strip showed a detection limit to DIPF between 5 and 200 ppm.

Performance of AC-LGAD strip sensors designed for the DarkSHINE experiment

Performance of AC-LGAD strip sensors designed for the DarkSHINE experiment

Investigating the mechanical properties of composites containing exfoliated graphite/epoxy sensors: Experimental testing and simulation

One approach to structural health monitoring (SHM) involves embedding sensors within a composite material. However, the integration of these sensors can potentially introduce flaws that might affect the composite’s mechanical properties. This research aims to explore the impact of embedding exfoliated graphite (EG)/epoxy sensors on the mechanical characteristics of composite systems through laboratory experiments and numerical simulations. Sensor strips composed of varying volume fractions of EG/epoxy were fabricated. Tensile test specimens were prepared by embedding these sensors in the epoxy matrix oriented both lengthwise and widthwise. Baseline specimens of EG/epoxy without sensors were also created for comparison. Tensile tests were performed on the samples to evaluate the effects of the embedded sensors on the composite’s elastic modulus and tensile strength. The results indicated a slight improvement in both elastic modulus and tensile strength with the introduction of EG. Crucially, the orientation of the sensors within the samples had a significant impact on the composite’s mechanical properties. Samples with widthwise-aligned sensors showed reduced tensile strength due to delamination along the sensor edges. Finite element simulations using a viscoelastic model based on the experimental data were conducted to analyze the effect of sensor alignment on mechanical properties. The findings revealed that a grid pattern alignment of sensors significantly enhanced mechanical performance compared to lengthwise or widthwise alignment, particularly at 0.1% and 0.3% EG volume fractions, highlighting the effectiveness of a grid pattern for embedding sensors in SHM applications.

A spectroscopy-based proof-of-concept (POC) for developing loading of pathogen analyzer (LOPA) for dairy products

Detection of bacterial contamination in dairy products of daily use is a challenge worldwide. We have utilized Methylene Blue Reduction Test (MBRT) for quantification of the microbial count in dairy products (milk) and developed a proof-of-concept (POC) based on this for in-filed applications. In this study, we have used pasteurized milk contaminated with model bacteria Escherichia coli, and Staphylococcus aureus for the calibration and validation of the developed POC. The conversion of MB to Leuco-MB i.e., the colorimetric change due to the reduction of MB to Leuco-MB in presence of microbes has been utilized as the tool to detect presence of microbes in milk. The absorbance peak for methylene blue (MB) at 664 nm decreases significantly in presence of microbes and the blue color becomes faded. In our study, we have employed methylene blue (MB) discolouration phenomenon to estimate the microbial count in milk samples using our developed spectroscopy based POC. The limit of detection (LOD) and the limit of quantitation (LOQ) of the POC were found to be 0.32 CFU/mL and 0.97 CFU/mL. The end users of the developed POC are primarily those involved in the production, processing, testing, regulation, and research of dairy products to ensure they meet safety standards and protect public health. These include retailers, dairy farmers, dairy processors, quality control laboratories, regulatory agencies and research institutions. In our experiment, we have observed a significant change in MB absorption in the milk contaminated with microbes. The indigenously developed sensor strips designed for the working of the POC turn to colorless Leuco-MB compared to milk without the microbes. The analysis of the strips has been measured in the developed device.

Monitoring electron and proton beam profiles with segmented silicon sensors

The FRIDA INFN project characterized thin silicon sensors for monitoring electron FLASH beams, showing a response linearity up to ∼10 Gy/pulse on 9 MeV electrons. The use of segmented silicon configurations could provide the spatial resolution useful in Spatially Fractionated Radiotherapy (SFRT). Within the MIRO INFN project, a strip sensor integrated with a multichannel readout chip is being developed and tested for monitoring FLASH and SFRT electron and proton beams. One hundred and twenty-eight strips are independently read by two front-end TERA chips. Preliminary tests were performed on 6–10 MeV electron beams at the LINAC at Physics Department of the University of Torino, with and without using a tungsten minibeam collimator, and on 62–226 MeV proton beams at CNAO (Pavia). The capability to spatially resolve electron and proton beams at conventional dose-rates has been proved.

AuNP@Self-assembled 4H-Chromene-Enhanced colorimetric detection of ganciclovir using smartphone Technology: Portable solutions for healthcare

Any substance, radiation, or radionuclide in our environment that promotes carcinogenesis is a cancerogen. In the current work, we modified the 4H-chromene derivative by covering its surface with a shell of gold nanoparticles. Interestingly, ganciclovir (GCV) formed a bridge between the Nap-group of 4H-chromene and gold nanoparticles to display surface charge reduction properties in AuNP@Self-assembled 4H-Chromene. The surface charge of AuNPs is reduced as a result of the electron transfer mechanism brought on by the creation of the Nap-GCV-AuNP link, which leads to agglomeration. This led to the development of a dual-mode colorimetric sensor for GCV that incorporates solution form and portable sensor strip. The probe showed a linear range of 0–74 nM under ideal circumstances, with a detection limit of 4 nM in solution and 3 nM on paper strip detection. An evaluation of the practical utility in human serum using a portable visual read-out produced satisfactory findings, with a recovery percentage of 102.1 % and a standard deviation of ± 4 %. Surprisingly, this is the first work on the colorimetric detection of Ganciclovir that we are aware of.

A Passive Perspiration Inspired Wearable Platform for Continuous Glucose Monitoring.

The demand for glucose monitoring devices has witnessed continuous growth from the rising diabetic population. The traditional approach of blood glucose (BG) sensor strip testing generates only intermittent glucose readings. Interstitial fluid-based devices measure glucose dynamically, but their sensing approaches remain either minimally invasive or prone to skin irritation. Here, a sweat glucose monitoring system is presented, which completely operates under rest with no sweat stimulation and can generate real-time BG dynamics. Osmotically driven hydrogels, capillary action with paper microfluidics, and self-powered enzymatic biochemical sensor are used for simultaneous sweat extraction, transport, and glucose monitoring, respectively. The osmotic forces facilitate greater flux inflow and minimize sweat rate fluctuations compared to natural perspiration-based sampling. The epidermal platform is tested on fingertip and forearm under varying physiological conditions. Personalized calibration models are developed and validated to obtain real-time BG information from sweat. The estimated BG concentration showed a good correlation with measured BG concentration, with all values lying in the A+B region of consensus error grid (MARD = 10.56% (fingertip) and 13.17% (forearm)). Overall, the successful execution of such osmotically driven continuous BG monitoring system from passive sweat can be a useful addition to the next-generation continuous sweat glucose monitors.

Label free immunochromatographic sensor based on TCBPE for the detection of Acidovorax citrulli in Cucurbitaceae plants

The presence of Acidovorax citrulli (Ac), the etiological agent responsible for bacterial fruit blotch (BFB), exerts a profound impact on the growth and development of cucurbit plants. Therefore, it is imperative to promptly detect Ac to effectively mitigate the widespread dissemination of this disease among cucurbit crops. The present study describes the development of a novel label-free immunochromatographic strip (ICTS) sensor for the detection of Ac in cucurbit samples. This was achieved by utilizing 4’,4’’’,4’’’’’,4’’’’’’’-(ethene-1,1,2,2-tetrayl) tetrabiphenyl-4-carboxylic acid (TCBPE) carboxyl activation product (CA-TCBPE) as a fluorescent probe. The CA-TCBPE@Ac complex is captured at the detection site through the immobilization of a monoclonal antibody monoclonal antibody (mAb) targeting Ac in this sensor. Under the excitation of 365 nm ultraviolet (UV) light, the detection of Ac in the concentration range of 105-108 CFU/mL was successfully achieved, with a visual detection limit of 105 CFU/mL. The accuracy of the sensor was further validated through experimentation with real samples, including watermelon, cantaloupe, cucumber, and zucchini. This study presents the pioneering development of a label-free ICTS sensor, utilizing TCBPE material markers, for rapid and sensitive detection of Ac. This innovative approach offers a robust solution for the swift detecting of Ac in cucurbits and other samples, thereby holding great promise for future applications.

Highly sensitive disposable test strips for sweat chloride detection using silver nanoparticles decorated reduced graphene oxide

The quantification of chloride ions in sweat by a point-of-care test system is a useful strategy in the early screening of cystic fibrosis. In this context, silver nanoparticles decorated reduced graphene oxide were synthesized by one-pot reduction method in this work. This reaction in situ produces silver nanoparticles spread across thin sheets of rGO with high surface area. This helps in the electrochemical detection of chloride ions by conversion of silver to silver chloride and formation of a thin layer of silver chloride on the surface of nanocomposite. The validity of this strategy has been demonstrated by voltammetric analysis of chloride ions using the screen-printed Ag-rGO nanocomposite. For electrodes tested in buffer, the sensitivity was 37.66 ± 0.99 mA (log mM)−1 cm−2 with a high selectivity and detection range from 30 to 400 mM chloride concentration. The lower detection limit is 1.02 mM (S/N = 3), and the relative standard deviation (RSD) of sensor response is 4.77 %. Disposable sensor test strips fabricated with screen printing of the catalyst followed by layer by layer array of electrolyte and hydrophilic membrane shows a sensitivity of 165.2 ± 4.3 µA mM−1 cm−2, a linear detection range upto 210 mM, and a LOD of 2.46 ± 0.06 µM. The quantification of the developed sensor strips were confirmed by comparing the values from clinical laboratories. This finding confirms the potentiality of the developed method and its possible application in the rapid and easy-to-use point-of-care devices. Notable advantages of the Ag-rGO nanocomposite is its reversibility due to the regeneration of fresh silver nanoparticles on the rGO surface and increased electrochemical response. This feature realizes a high stability even at multiple trials with a RSD of 2.63 % and long-time storage tested upto 3 months. Using this superior performance, the developed sensor test strip demonstrates a disposable, non-invasive, reproducible, reversible, highly selective, and sensitive monitoring of chloride ions.

Laser-Induced Graphene for Electrochemical Analysis of Food and Agricultural Contaminants

Carbon-nanomaterial sensors offer promising routes toward low-cost, high-throughput electrochemical sensors. Carbon nanomaterials, such as graphene and carbon nanotube (CNT), have been studied with various fabrication methods to produce sensors, including high-quality thin film graphene and CNT by chemical vapor deposition. However, the complexity and cost associated with their fabrication have hindered their implementation into single-use test strip sensors. Even high-yield mechanical and/or chemical exfoliation of graphene from graphite followed by solution phase printing of electrodes can be costly due to the complexity of ink formulation and the need for post-print annealing requirements. However, laser-induced graphene (LIG) avoids the need to exfoliate graphene from graphite or to create a solution-phase graphene ink by converting sp3 carbon found in carbon-rich substrates into conductive sp2-hybridized carbon found in graphene through a laser scribing technique. The resulting LIG also exhibits a high surface area and is porous with a high density of edge plane sites, which are beneficial for biofunctionalization and heterogeneous charge transport during electrochemical sensing. Furthermore, we have demonstrated that the surface area and wettability of the LIG can be tuned to greatly improve the sensitivity of electrochemical enzymatic biosensors (detection limits down to the picomolar range) and reduce the water layer buildup between the ion-selective membrane and the electrode, which improves the accuracy of the sensor readings. The fabricated LIG electrodes have been used in a wide variety of electrochemical sensing applications, including in food safety (foodborne pathogens and other contaminants), environmental monitoring (agrochemicals), and health monitoring sensors (salivary potassium and lactate, and urinary potassium and ammonium). Different electroanalytical methods are used, including amperometric, potentiometric, coulometric, and impedimetric, to quantify the analytes. We demonstrate how the ISE (ion-selective electrodes) can be functionalized with PVC-based ion-selective membranes for potassium, nitrate, nitrite, ammonium, sodium, and pH in various biological solutions, including soil and water for nutrient/fertilizer monitoring in farm fields. Additionally, we demonstrate how the hydrophilic LIG graphene can be used to create other highly sensitive electrochemical biosensors including enzymatic pesticide biosensors and Salmonella spp. immunosensors. All these electroanalytical sensors were validated in real-world samples and demonstrated to have limits of detection and linear sensing ranges that are relevant to their sensing applications. Results demonstrate the utility of LIG-based sensors for rapid and sensitive electrochemical measurement of contaminants as a readily modified platform for scalable production of electroanalytical devices applied toward point-of-service environmental and food monitoring.

Flexible Graphene-Based Sensors for Electrochemical Analysis of Human Saliva and Sweat

Flexible carbon nanomaterial sensors offer a low-cost, facile fabrication approach toward producing sensors at an industrial scale for electrochemical sensing. Graphene and carbon nanotube (CNT) based sensors have been studied, with various fabrication methods available, including producing high-quality thin film graphene and CNTs via chemical vapor deposition (CVD). However, CVD is a high-temperature vacuum process that is low-yielding and consequently costly, hindering its implementation into single-use test strip sensors. Other methods, such as inkjet or aerosol printing, are more cost-effective as they print graphene inks obtained from liquid-phase exfoliation of graphite, which can be performed using large batch processing techniques. Additionally, the laser-induced graphene (LIG) technique directly converts sp3 carbon found in carbon-rich substrates, such as polyimide, into conductive sp2-hybridized carbon found in graphene through a laser scribing technique. Saliva and sweat offer promising biological fluids for precision health monitoring and diagnostics due to the non-invasive nature of their sampling (no need for a blood draw at a laboratory or a fingerstick at home) and due to the abundance of medically relevant analytes. Saliva can also be used for monitoring infections such as COVID-19 infection. Herein, we introduce graphene-based flexible sensors fabricated using scalable manufacturing based on aerosol jet printing (AJP) using custom-formulated graphene inks and laser-induced graphene via direct writing. We report a label-free, high-sensitivity, and rapid-response-time graphene-based electrochemical immunosensor for quantitatively detecting the SARS-CoV-2 Spike Receptor-Binding Domain (RBD) as well as SARS-CoV-2 Spike S1 protein. We demonstrate LIG-based electrochemical sensors for real-time monitoring of glucose, lactate, and sodium in sweat, and potassium and lactate in saliva. Different electrochemical methods are used, including amperometric, potentiometric, coulometric, and impedimetric, to quantify the analytes. All these electrochemical sensors were validated in human saliva and sweat and demonstrated to have limits of detection and linear sensing ranges that are relevant to their sensing applications. Flexibility studies were also performed to evaluate the ability of the sensors to operate under stresses caused by bending, such as those that would be encountered by skin and implanted oral sensors. Results demonstrate the utility of AJP-graphene and LIG for rapid and sensitive measurement of biological analytes and pathogen infection as simple methods for scalable production of non-invasive salivary and perspiration (sweat) health sensors.

Trimetallic FeCoNi Metal-Organic Framework with Enhanced Peroxidase-like Activity for the Construction of a Colorimetric Sensor for Rapid Detection of Thiophenol in Water Samples.

In recent years, nanozymes have attracted particular interest and attention as catalysts because of their high catalytic efficiency and stability compared with natural enzymes, whereas how to use simple methods to further improve the catalytic activity of nanozymes is still challenging. In this work, we report a trimetallic metal-organic framework (MOF) based on Fe, Co and Ni, which was prepared by replacing partial original Fe nodes of the Fe-MOF with Co and Ni nodes. The obtained FeCoNi-MOF shows both oxidase-like activity and peroxidase-like activity. FeCoNi-MOF can not only oxidize the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) to its blue oxidation product oxTMB directly, but also catalyze the activation of H2O2 to oxidize the TMB. Compared with corresponding monometallic/bimetallic MOFs, the FeCoNi-MOF with equimolar metals hereby prepared exhibited higher peroxidase-like activity, faster colorimetric reaction speed (1.26-2.57 folds), shorter reaction time (20 min) and stronger affinity with TMB (2.50-5.89 folds) and H2O2 (1.73-3.94 folds), owing to the splendid synergistic electron transfer effect between Fe, Co and Ni. Considering its outstanding advantages, a promising FeCoNi-MOF-based sensing platform has been designated for the colorimetric detection of the biomarker H2O2 and environmental pollutant TP, and lower limits of detection (LODs) (1.75 μM for H2O2 and 0.045 μM for TP) and wider linear ranges (6-800 μM for H2O2 and 0.5-80 μM for TP) were obtained. In addition, the newly constructed colorimetric platform for TP has been applied successfully for the determination of TP in real water samples with average recoveries ranging from 94.6% to 112.1%. Finally, the colorimetric sensing platform based on FeCoNi-MOF is converted to a cost-effective paper strip sensor, which renders the detection of TP more rapid and convenient.

A fast and sensitive colorimetric sensor for residual chlorine detection made with oxidized cellulose

Residual chlorine from widespread disinfection processes forms byproducts in water that are harmful to humans and ecosystems. Portable sensors are essential tools for the on-site monitoring of residual chlorine in environmental samples. Here, an inexpensive colorimetric sensor was developed by grafting via amidation the chromogen orthotolidine (OTO) to the surface of a TEMPO-oxidized cellulose filter paper (O-TOFP). A thorough characterization of the sensor strip demonstrated that it was highly stable and that it could be stored for a long period before usage. O-TOFP had a fast response time of 30 s, was highly selective for residual chlorine ions (ClO−) with an accuracy of at least 95 %, and exhibited an excellent limit of detection of only 0.045 mg/L when combined with smartphone image acquisition. With its many positive features, the easy-to-use and robust O-TOFP sensor described here could become a useful tool for the determination of residual chlorine in different water samples.

Magnetostrictive Strip Sensors to Identify the Nonlinearity of Viscosity

Magnetostrictive Strip Sensors to Identify the Nonlinearity of Viscosity

Characterization of Tracking Modules Based on DSSD Sensors at the SC-1000 Accelerator for the BM@N Project

The results of studying characteristics of modules based on double-sided microstrip silicon sensors, which are designed to create the wide-aperture Silicon Tracking System for the BM@N facility, are presented. The main module features are the use of fast readout electronics based on the STS-XYTER chip and the application of ultralight (0.23% X0) aluminum microcables for transmitting analog signals from the sensor strips to the input channels of the readout electronics. The results of testing different configurations of tracking modules on the extracted beam of protons at the SC-1000 accelerator in the PNPI are presented. The stable operation of readout electronics is demonstrated at loads close to the maximum values of 360 kHz s–1 cm–2. The signal-to-noise ratio was no less than 23. The measured coordinate resolution of the modules within the beam telescope was 17 ± 0.4 μm, and the detector efficiency of recording for protons with energy of 1 GeV was no less than 99%.

Unobtrusive Skin Temperature Estimation on a Smart Bed.

The transition from wakefulness to sleep occurs when the core body temperature decreases. The latter is facilitated by an increase in the cutaneous blood flow, which dissipates internal heat into the micro-environment surrounding the sleeper's body. The rise in cutaneous blood flow near sleep onset causes the distal (hands and feet) and proximal (abdomen) temperatures to increase by about 1 °C and 0.5 °C, respectively. Characterizing the dynamics of skin temperature changes throughout sleep phases and understanding its relationship with sleep quality requires a means to unobtrusively and longitudinally estimate the skin temperature. Leveraging the data from a temperature sensor strip (TSS) with five individual temperature sensors embedded near the surface of a smart bed's mattress, we have developed an algorithm to estimate the distal skin temperature with a minute-long temporal resolution. The data from 18 participants who recorded TSS and ground-truth temperature data from sleep during 14 nights at home and 2 nights in a lab were used to develop an algorithm that uses a two-stage regression model (gradient boosted tree followed by a random forest) to estimate the distal skin temperature. A five-fold cross-validation procedure was applied to train and validate the model such that the data from a participant could only be either in the training or validation set but not in both. The algorithm verification was performed with the in-lab data. The algorithm presented in this research can estimate the distal skin temperature at a minute-level resolution, with accuracy characterized by the mean limits of agreement [-0.79 to +0.79 °C] and mean coefficient of determination R2=0.87. This method may enable the unobtrusive, longitudinal and ecologically valid collection of distal skin temperature values during sleep. Therelatively small sample size motivates the need for further validation efforts.

Eco-friendly fluorescent detection method for Cu2+ ions combined with smartphone-integrated paper strip sensors based on highly fluorescent 2-aminoterephthalic acid in milk samples

The creation of smart, real-time sensing devices is crucial in food monitoring, though it continues to be a major challenge. Here, we report an eco-friendly fluorescent detection method for Cu2+ ions using 2-aminoterephthalic acid (NH2-H2BDC). Fluorescence (FL) quenching occurs at 425 nm under excitation at 330 nm, with detection limits (LOD) as low as 16.25 nM for Cu2+ ions. Additionally, a smartphone can visually and quantitatively detect Cu2+ ions by analyzing the RGB values on test paper. The results show high sensitivity, with a LOD of 11.07 μM. This work not only reveals fluorescent detection methods but also develops a convenient, low-cost, and portable smartphone-integrated paper strip for Cu2+ ion sensing. Two metrics, AGREEprep and BAGI, were employed to assess the method's environmental friendliness. The evaluation confirmed its exceptional eco-friendliness. This method marks a significant advancement for Cu2+ ion monitoring in diverse fields, especially food monitoring.