Paper-based Sensor Research Articles

A rapid and sensitive paper-based sensor for sulfide ion detection in Chinese liquors

The accurate monitoring of sulfide ion concentrations is vital for ensuring food safety, but current detection methods are often cumbersome and confined to laboratories. This study introduces an innovative paper-based colorimetric sensor that leverages the peroxidase-like activity of cobalt tetrasulfonate phthalocyanine (CoTsPc) for rapid, sensitive, and selective sulfide ion quantification. The underlying mechanism relies on the interaction between cobalt and sulfide ions, modulating the catalytic efficiency of CoTsPc and triggering a visible color change when 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide are present. By controlling solvent evaporation, the reaction kinetics are standardized, enabling reproducible and accurate colorimetric measurements. Experimental results show that adding sulfide ions to the TMB-H₂O₂ reaction system causes a gradual decrease in color intensity on the paper substrate. This change verifies effectiveness of the sensor, highlighting its potential for reliable sulfide ion detection in food safety applications, while providing a simple and portable alternative to conventional methods.

Smartphone-integrated inkjet-printed paper sensor and UV/Vis spectrophotometric method for on-site detection of As3+ and L-cysteine in food samples using novel AMTPP-functionalized silver nanoparticles

The increasing prevalence of arsenic (As3+) in water and its health impacts necessitate advanced detection methods. Similarly, monitoring L-Cysteine, a vital thiol-containing amino acid, is crucial for assessing physiological processes and disorders. This study presents a novel method for detecting As3+ and L-Cysteine in food samples using 4-amino-3-(D-galactopentitol-1-yl)-5-mercapto-1,2,4-triazole (AMTPP) functionalized silver nanoparticles (AMTPP-AgNPs) by UV/Vis spectrophotometric method and smartphone-assisted inkjet-printed paper-based sensors. AMTPP-AgNPs, synthesized through a detailed process, show exceptional selectivity and sensitivity to As3+ and L-Cysteine, undisturbed by other metal ions and amino acids. Characterization techniques like FTIR, DLS, Zeta Potential, AFM, and SEM detailed their morphological and interaction properties. Optimizing detection parameters, such as response time, pH, and temperature, improved sensitivity and achieved low detection limits. The limits of detection (LODs) were 0.0052 μM for L-cysteine and 0.0092 μM for As3+, as calculated using UV–Vis spectrophotometric methods. The method also demonstrated high recovery rates in spiked meat and corn samples. This research offers a cost-effective, rapid method for on-site food analysis, significantly aiding environmental and public health monitoring.

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.

Vacuum Filtration-Coated Silver Electrodes Coupled with Stacked Conductive Multi-Walled Carbon Nanotubes/Mulberry Paper Sensing Layers for a Highly Sensitive and Wide-Range Flexible Pressure Sensor

Flexible pressure sensors based on paper have attracted considerable attention owing to their good performance, low cost, and environmental friendliness. However, effectively expanding the detection range of paper-based sensors with high sensitivities is still a challenge. Herein, we present a paper-based resistive pressure sensor with a sandwich structure consisting of two electrodes and three sensing layers. The silver nanowires were dispersed deposited on a filter paper substrate using the vacuum filtration coating method to prepare the electrode. And the sensing layer was fabricated by coating carbon nanotubes onto a mulberry paper substrate. Waterborne polyurethane was introduced in the process of preparing the sensing layers to enhance the strength of the interface between the carbon nanotubes and the mulberry paper substrate. Therefore, the designed sensor exhibits a good sensing performance by virtue of the rational structure design and proper material selection. Specifically, the rough surfaces of the sensing layers, porous conductive network of silver nanowires on the electrodes, and the multilayer stacked structure of the sensor collaboratively increase the change in the surface contact area under a pressure load, which improves the sensitivity and extends the sensing range simultaneously. Consequently, the designed sensor exhibits a high sensitivity (up to 6.26 kPa−1), wide measurement range (1000 kPa), low detection limit (~1 Pa), and excellent stability (1000 cycles). All these advantages guarantee that the sensor has potential for applications in smart wearable devices and the Internet of Things.

Portable alkaloid discrimination via nanozyme-mediated colorimetric paper-based sensor array integrated with smartphone detection.

Apaper-based colorimetric sensor array mediated by a novel nanozyme (CuCo2O4) was developed using a screen-printing technology. The aim was to facilitate the identification of different kinds of alkaloids. Typically, three chromogenic substrates (3,3',5,5'-tetramethylbenzidine, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), and o-phenylenediamine) were selected as sensing elements, which can be catalyzed by a CuCo2O4 nanozyme with peroxidase-like activity to yield corresponding oxidized products, thereby inducing color changes. Owing to the varying inhibitory ability of different alkaloids on acetylcholinesterase (AChE), a decrease in choline (Ch) concentration occurs and subsequently results in the restoration of color within the units of sensor array. Color data can be transformed into hue information with a smartphone. The above color variations generated a unique "fingerprint" pattern on five alkaloids (berberine, palmatine, jatrorrhizine, eserine, and harmane), which can be successfully discriminated through linear discriminant analysis in the range0.2 to 20µM. Furthermore, the sensor arrays allowed successful discrimination of the above five alkaloids in Chinese herbal medicine samples and recognition of 22 blind samples. This work presents a novel nanozyme-based paper sensor array, which is a user-friendly and reliable platform for probing different alkaloids. In addition, the developed sensing strategy enables the identification of AChE-related diseases, positively contributing to the screening available of AD-associated drugs.

E-waste driven eco-friendly highly sensitive wearable capacitive sensors for physical activity monitoring and sign language recognition

Owing to the continual and rapid advancement in technology, there has been a significant surge in electronic waste (e-waste) in recent decades, resulting in a harmful impact on our environment. Due to the growing demand for battery-powered devices, non-rechargeable batteries are a significant source of e-waste. This study describes fabricating a paper-based graphite strain sensor that is eco-friendly, inexpensive, biodegradable, and sensitive to the applied strain. Readily accessible materials are employed to design and fabricate MIDC strain sensors. The Modified Interdigital Capacitor (MIDC) structure is formed on basic printing paper, and the conductive substance made with the ink of a gel pen and graphite from a drained dry cell is painted on the paper and used as electrode material. The suggested sensor has a high gauge factor value of 1998.578 and fast response and recovery time of 112 ms and 100 ms, respectively. The proposed prototype has also been utilized to inspect fitness exercises and physical activities on the human body, inspiring the potential for its integration into wearable systems for various applications. Reliable detection and differentiation of finger positions are achieved, highlighting the sensor's potential for more advanced sign language applications. It’s a good option to integrate the suggested strain sensor in wearable systems, such as telemedicine systems, electromechanical detection, healthcare, and physical activity monitoring of humans.

Deep Learning-Enhanced Paper-Based Vertical Flow Assay for High-Sensitivity Troponin Detection Using Nanoparticle Amplification.

Successful integration of point-of-care testing (POCT) into clinical settings requires improved assay sensitivity and precision to match laboratory standards. Here, we show how innovations in amplified biosensing, imaging, and data processing, coupled with deep learning, can help improve POCT. To demonstrate the performance of our approach, we present a rapid and cost-effective paper-based high-sensitivity vertical flow assay (hs-VFA) for quantitative measurement of cardiac troponin I (cTnI), a biomarker widely used for measuring acute cardiac damage and assessing cardiovascular risk. The hs-VFA includes a colorimetric paper-based sensor, a portable reader with time-lapse imaging, and computational algorithms for digital assay validation and outlier detection. Operating at the level of a rapid at-home test, the hs-VFA enabled the accurate quantification of cTnI using 50 μL of serum within 15 min per test and achieved a detection limit of 0.2 pg/mL, enabled by gold ion amplification chemistry and time-lapse imaging. It also achieved high precision with a coefficient of variation of <7% and a very large dynamic range, covering cTnI concentrations over 6 orders of magnitude, up to 100 ng/mL, satisfying clinical requirements. In blinded testing, this computational hs-VFA platform accurately quantified cTnI levels in patient samples and showed a strong correlation with the ground truth values obtained by a benchtop clinical analyzer. This nanoparticle amplification-based computational hs-VFA platform can democratize access to high-sensitivity point-of-care diagnostics and provide a cost-effective alternative to laboratory-based biomarker testing.

Portable paper-based multicolor sensor for sensitive on-site detection of organophosphorus pesticides using a high-efficiency Au+-induced gold nanobipyramids aspect ratio regulation strategy

On-site visual detection of organophosphorus pesticides (OPs) is crucial for safeguarding environmental and food safety. This study presents a robust, sensitive, and portable paper-based multicolor sensor (PMS) for the on-site detection of OPs. The PMS involves a novel Au+-induced gold nanobipyramids (AuNBPs) morphology transformation reaction within a paper-based analytical device (PAD) coupled with a bienzymatic hydrolysis system. The Au+-induced reaction sensitively regulates the aspect ratio of AuNBPs through Au+ disproportionation, which decreases the length of AuNBPs and simultaneously increases the width, accompanied by distinct multicolor changes. Upon performing in the PAD incorporating easily-prepared AuNBPs-deposited nylon membranes, a metal heater, and an oscillator, the Au+-induced reaction exhibits excellent reaction sensitivity, efficiency, reproducibility, AuNBPs stability, and color uniformity. In the bienzymatic hydrolysis system, acetylcholinesterase (AChE) and choline oxidase hydrolyze acetylcholine to product H2O2, which consumes tris(2-carboxyethyl)phosphine hydrochloride (TCEP), maintaining free Au+ for the disproportionation in the Au+-induced system, while the presence of OPs inhibits AChE activity, preserving TCEP to chelate Au+ and hindering the disproportionation. Under optimized conditions, the PMS exhibited eight dichlorvos concentration-corresponding color changes with a visual detection limit of 30 μg/L and a spectrometry detection limit of 8.1 μg/L. It achieved recoveries of 85.4–101.9 % in river water, drinking water, rice, and Chinese cabbage samples with relative standard deviations (n = 5) < 6 %. Thus, this study offers a portable, sensitive, reliable, and practical on-site detection method for OPs. Additionally, the proposed Au+-induced AuNBPs morphology transformation system within the PAD offers promising alternative strategies for developing other AuNBPs-based colorimetric sensors.

Classification of Sesame Oil Based on Processing-Originated Differences in the Volatile Organic Compound Profile by a Colorimetric Sensor.

Fragrant edible sesame oil is popular for its unique aroma. The aroma of sesame oil is determined by its volatile organic compound (VOC) profile. Sesame oils produced by different techniques could have different VOC profiles. In addition, blending fragrant sesame oil with refined oil could also alter the VOC profile of the final product. Current practices in aroma analysis, such as sensory evaluation and gas chromatography (GC), still face many restraints. Hence, there is a need for alternatives. We present a novel 14-unit multiplexed paper-based colorimetric sensor for fragrant sesame oil VOC analysis. The sensor was designed to visualize the VOC profile as a color "fingerprint". The sensor was validated with 55 branded sesame oil samples produced by two different techniques, i.e., hot pressing and small milling; the experimental results suggested a processing dependency in color VOC fingerprints. The sensor also demonstrated the potential to detect the change in sesame oil VOC profile due to blending with refined oil, with an estimated limit of detection down to 20% v/v of the refined oil. The colorimetric sensor might be used as a simple, rapid, and cost-effective analytical tool in the production and quality control of fragrant sesame oil.

Flexible paper-based AuNP sensor for rapid detection of diabenz (a,h)anthracene (DbA) and benzo(b)fluoranthene (BbF) in mussels coupled with deep learning algorithms

Flexible paper-based AuNP sensor for rapid detection of diabenz (a,h)anthracene (DbA) and benzo(b)fluoranthene (BbF) in mussels coupled with deep learning algorithms

MnO4−-triggered wavelength-changeable and rapid-response fluorescence sensor for paper-based on-site sensing of tyrosinase activity in potato

Rapid-response in situ fluorogenic reactions in aqueous solution are important for designing sensitive and stable sensing platforms. Herein, a wavelength-changeable and rapid-response (within 5 s) fluorescence sensing platform for monitoring tyrosinase (TYR) activity is constructed. The developed assay is based on TYR catalyzing the hydroxylation of mono-phenol to o-diphenol and MnO4−-triggered fluorogenic between dopamine (DA) and phenol derivatives in aqueous solution. The fluorescence wavelength can be changeable from 470 to 550 nm with strong fluorescence according to different phenol derivatives. Our proposed sensor not only exhibits a good recovery for TYR in high serum concentration (20 %), but also has been successfully applied to the screening of TYR inhibitors modeled on kojic acid. Furthermore, a paper-based wavelength-changeable fluorescence sensor was developed for on-site detection of TYR activity in potatoes with high recovery, which is consistent with our previously reported method. Consequently, the proposed sensing system has broad prospects in the practical application of TYR-associated food monitoring and clinical diagnosis.

High sensitivity distinguishing detection of fluoroquinolones with a cage-based lanthanide metal-organic framework in food

Sensitive and selective detection of fluoroquinolones, especially from different sources, is challenging. This study reported an uncommon three-cage lanthanide metal-organic framework (1-Eu) with a Eu3+ cluster as its structural primitive using a C2-symmetric 5,5-(Pyrazine-2,6-diyl) diisophthalic acid ligand. The 1-Eu probe effectively detected four fluoroquinolones through distinct color changes and spectral emission bands, demonstrating excellent performance with low detection limits: moxifloxacin (LOD: 9.3 nM), danofloxacin (LOD: 33.7 nM), gatifloxacin (LOD: 67.9 nM), and ofloxacin (LOD: 238.6 nM). Mechanistic studies revealed that internal filtration and photoinduced electron transfer (a-PET) effects were key factors. Furthermore, 1-Eu was successfully used to detect fluoroquinolones in food samples. Additionally, portable paper-based sensors were developed to quickly semi-quantify analyte concentrations using a smartphone color recognition app, underscoring the practical potential of this probe. This study introduces a novel methodology for the identification and detection of fluoroquinolones to enhance food safety.

Specific and enzyme-free monitoring of propiconazole pesticide residues in vegetables with a portable nanozyme-based paper sensor

The nanozyme-based colorimetric sensor shows promise for rapid pesticide detection but struggles with non-specific enzyme inhibition. This study developed a portable paper-based sensor for detecting the propiconazole (PC) pesticide using Fe@PCN-224 nanocubes (NCs). Characterization confirmed the successful synthesis of Fe@PCN-224 NCs, which displayed peroxidase-like activity. The specific interaction between PC's triazole ring and the Fe active site inhibited their activity, enabling selective detection with a limit of 8 × 10−9 mol L−1 and a linear range of 0.03 × 10−6 to 0.90 × 10−6 mol L−1. Kinetic studies revealed a Michaelis-Menten constants (Km) of 0.68 × 10−3 mol L−1 for TMB, indicating higher affinity in Fe@PCN-224 NCs. The electron paramagnetic resonance (EPR) analysis revealed the production of •OH, 1O2, O2•− during the catalytic reactions. By integrating smartphone technology, this portable sensor achieved recoveries from vegetable samples between 94.6 % and 109.2 %, demonstrating its potential as an accurate, cost-effective analytical tool for food safety and advancing nanozyme applications.

Copper nano metal-organic framework paper-based sensor for dual optical detection of biogenic amines to evaluate the food freshness

The improvement of food safety and the reduction of food loss and waste require the development of new bioanalytical tools that provide chemical information about the composition of food that is of great value for improving traceability and extending the shelf life of food. Herein, a Cu-based metal-organic framework has been synthesized and immobilized onto cellulose paper disks for colorimetric and fluorescent detection and quantification of biogenic amines in food. The color of the nano metal-organic framework changes from green to brown in the presence of low amounts of biogenic amine vapors. Also, the fluorescence emission of the nano metal-organic framework greatly decreases after exposing the cellulose disks to amine vapors. The developed sensing paper disk exhibits a quick response to the presence of volatile biogenic amines, very low detection limits, and great selectivity. Also, the paper sensor was used for real-time monitoring of biogenic amines in bass samples at different temperature conditions, being a highly valuable method for evaluating food freshness and safeguarding food safety.

Ultra-low cost and high-performance paper-based flexible pressure sensor for artificial intelligent E-skin

E-skin driven by artificial intelligence algorithms enables the innovation of future technologies such as IoT, intelligent manufacturing, health monitoring and human–machine interfaces for VR/AR. Although many flexible pressure sensors have been reported, the development of sensors that combine low-cost and high performance remains a huge challenge. Herein, we propose an all-paper-based pressure sensor with water-soluble graphite functional layer and carbon interdigital electrodes obtained by friction coating and screen printing, respectively. The sensor boasts a rectangular design measuring 1 cm × 2.15 cm, with a remarkably thin profile of only 71 μm and an ultra-light weight of 6 mg, and the cost of a single sensor is extremely low. Specifically, the sensor achieved a lower detection limit of 0.98 Pa and an upper detection limit of 2000 kPa, which represents a new benchmark among paper-based pressure sensors. It demonstrated high sensitivity across various pressure ranges: 319.94 kPa−1 (0–1 kPa), 97.63 kPa−1 (1–40 kPa), 18.75 kPa−1 (40–200 kPa), and 2.72 kPa−1 (200–2000 kPa). The sensor also exhibited a rapid response and recovery time of 8 ms and 9 ms, respectively, along with excellent durability (>20,000 fatigue tests, 10,000 cycles at 2 kPa and 10,000 cycles at 100 kPa) and high pressure stability. Furthermore, the eco-friendly sensor can identify eight surface textures with a recognition accuracy of 98.33% after training with a 2D convolutional neural network (2D CNN). Finally, a portable wireless wearable device with dimensions of 38 mm × 26 mm × 14 mm and a weight of only 11.265 g has been developed for pressure recognition, breathing, pulse, and heartbeat detection.

Colorimetric sensing of fatty acids in organic solvents using polydiacetylene-based nanocomposites

Colorimetric detection of long chain fatty acids by polydiacetylenes (PDAs)-based sensors is quite a challenge, mainly due to their relatively low solubility in aqueous media. In this study, we developed PDA/Zn2+/ZnO nanocomposites in various organic solvents for detecting fatty acids. Oleic acid and steric acid were used as representatives of fatty acids with bent and linear structures, respectively. The nanocomposites dispersed in ethanol exhibited blue-to-red color transition upon increasing the concentration of oleic acid. The use of other solvents including 1-butanol, 1-hexanol, 1-octanol, 1,4-dioxane, hexane, octane and toluene affected the sensitivity of nanocomposites. Furthermore, incorporating cetyltrimethylammonium bromide (CTAB) into the structure of the nanocomposites resulted in a systematic increase of sensitivity. The use of organic solvents simplified the method and allowed direct sensing of the fatty acids. Paper-based sensor was fabricated and utilized as a mobile test kit. This class of colorimetric sensors can also distinguish the bent and linear structures of fatty acids. Our study extends the utilization of PDA-based materials as colorimetric sensors of fatty acids in food industries.

Paper-based colorimetric sensor using a single-atom nanozyme for the ultrasensitive detection of Cr(VI) in short-necked clams.

Single-atom nanozymes (SAzymes) as a class of highly active nanozymes with the advantages of high atom utilization, high catalytic activity and stability have attracted great attention. In this work, Fe-N-C SAzymes with exceptional oxidase (OXD)-like activity were achieved utilizing polyvinylpyrrolidone (PVP) as a template. The Fe-N-C SAzymes with remarkable OXD-like activity could oxidize TMB to blue oxTMB, but 8-hydroxyquinoline (8-HQ) as a metal chelator is capable of discoloring oxTMB. Thus, the addition of 8-HQ decolorized the solution. However, upon the introduction of Cr(VI) ions, 8-HQ preferentially chelated with the Cr(VI) ions, reversing the inhibition of the color reaction and restoring the blue color. Based on this phenomenon, we constructed a novel paper-based analytical device (PAD) that exhibited a linear range of 5-1000 μM and an LOD of 1.2 μM. Importantly, the PAD used in this study shows the merits of simplicity, low preparation costs, and rapid reaction times. When combined with smartphone RGB analysis, it enables the simultaneous analysis of eight different Cr(VI) concentrations without the need for large-scale instrumentation. Moreover, the proposed PAD displays high selectivity, accuracy and utility in testing actual short-necked clam samples. This work not only provides a simple and cost-effective method to detect Cr(VI) but also makes a contribution to rapid food testing.

Multiwalled Carbon Nanotube-Templated Nickel Porphyrin Covalent Organic Framework for Pencil-Drawn Noninvasive Respiration Sensors.

Paper-integrated configuration with miniaturized functionality represents one of the future main green electronics. In this study, a paper-based respiration sensor was prepared using a multiwalled carbon nanotube-templated nickel porphyrin covalent organic framework (MWCNTs@COFNiP-Ph) as an electrical identification component and pencil-drawn graphite electric circuits as interdigitated electrodes (IDEs). The MWCNTs@COFNiP-Ph not only inherited the high gas sensing performance of porphyrin and the aperture induction effect of COFs but also overcame the shielding effect between phases through the MWCNT template. Furthermore, it possessed highly exposed M-N4 metallic active sites and unique periodic porosity, thereby effectively addressing the key technical issue of room-temperature sensing for the respiration sensor. Meanwhile, the introduction of a pencil-drawing approach on common printing papers facilitates the inexpensive and simple manufacturing of the as-fabricated graphite IDE. Based on the above advantages, the MWCNTs@COFNiP-Ph respiration sensor had the characteristics of wide detection range (1-500 ppm), low detection limit (30 ppb), acceptable flexibility for toluene, and rapid response/recovery time (32 s/116 s). These advancements facilitated the integration of the respiration sensor into surgical masks and clothes with maximum functionality at a minimized size and weight. Moreover, the primary internal mechanism of COFNiP-Ph for this efficient toluene detection was investigated through in situ FTIR spectra, thereby directly elucidating that the chemisorption interaction of oxygen modulated the depletion layers, resulting in alterations in sensor resistance upon exposure to the target gas. The encouraging results revealed the feasibility of employing a paper-sensing system as a wearable platform in green electronics.

Drone-Based Localization of Hazardous Chemicals by Passive Smart Dust

The distribution of tiny sensors over a specific area was first proposed in the late 1990s as a concept known as smart dust. Several efforts focused primarily on computing and networking capabilities, but quickly ran into problems related to power supply, cost, data transmission, and environmental pollution. To overcome these limitations, we propose using paper-based (confetti-like) chemosensors that exploit the inherent selectivity of chemical reagents, such as colorimetric indicators. In this work, cheap and biodegradable passive sensors made from cellulose could successfully indicate the presence of hazardous chemicals, e.g., strong acids, by a significant color change. A conventional color digital camera attached to a drone could easily detect this from a safe distance. The collected data were processed to define the hazardous area. Our work presents a combination of the smart dust concept, chemosensing, paper-based sensor technology, and low-cost drones for flexible, sensitive, economical, and rapid detection of hazardous chemicals in high-risk scenarios.

Fill, Fold, Photo: Preconcentration and Multiplex Detection of Trace Level Heavy Metals in Water.

Heavy metal contamination is an increasing global threat to human and environmental health, particularly in resource-limited areas. Traditional platforms for heavy metal detection are labor intensive and expensive and require lab facilities. While paper-based colorimetric sensors offer a simpler approach, their sensitivity limitations prevent them from meeting legislative requirements for many metals. Existing preconcentration systems, on the other hand, can achieve lower detection limits but typically focus on analyzing only one metal, making comprehensive monitoring difficult. We address these limitations by introducing a low-cost preconcentration system coupled with colorimetric analysis for the simultaneous detection of seven metal ions at low ppb levels without the need for external equipment outside a smartphone. The system achieved detection limits of 15 ppb (Ni(II)), 7 ppb (Cu(II)), 2 ppb (Fe(III)), 20 ppb (Cr(VI)), 13 ppb (Pb(II)), 26 ppb (Hg(II)), and 15 ppb (Mn(II)) with six out of seven limits of detection values falling well below EPA regulatory guidelines for drinking water. The user-friendly Fill, Fold, Photo approach eliminates complex pretreatment steps. Smartphone-based detection offers portable quantification within seconds. Employing masking strategies ensured higher selectivity for each assay on the card, while our packaging protocols enable system stability for over 4 weeks of study, facilitating mass production and deployment within a realistic time frame. To validate the sensor's performance in real-world scenarios, the sensor was tested with environmental water samples. The sensor demonstrated good recovery, ranging from 77% to 94% compared to the standard ICP-MS method. Furthermore, spike recovery analysis confirmed the sensor's accuracy, with a relative standard deviation (RSD) of less than 15%. This technology holds significant promise for future development as a convenient, portable solution for field-based monitoring of a broad spectrum of water contaminants, including pesticides, PFAS, fertilizers, and beyond.