Analytical quality by design in the development of a paper-based microfluidic device for iron (II) determination as an impurity in iron (III) pharmaceuticals.

Blue-for-Positive: Colorimetric LAMP detection on paper-based microfluidic devices using a blue-shift indicator for instrument-free naked-eye readout.

Microfluidic synthesis of carbon quantum dots and detection of iron ions using paper-based chip devices

A novel approach for the extraction of nucleic acids using a hybrid paper-plastic device.

Paper-based microfluidic devices (μPADs) have attracted significant attention for point-of-care testing (POCT), environmental monitoring, and food safety due to their low cost, ease of use, and minimal instrument dependence. However, fabricating high-resolution and reproducible microchannels on paper remains challenging. Conventional methods such as wax printing, photolithography, and inkjet printing are limited by resolution or equipment cost. Here, we present a low-cost, high-resolution fabrication method for μPADs, termed wax soft lithography, which combines wax printing with soft lithography. Through this method, microchannels with a minimum width of 234 ± 62 μm were consistently produced, and complex patterns were successfully fabricated, demonstrating high precision and reproducibility. As a proof-of-concept demonstration of device functionality, the fabricated μPADs were used to detect glucose in spiked urine samples, showing a concentration-dependent colorimetric response. This method provides an effective route for rapid production of high-resolution μPADs in resource-limited settings. With further validation before practical applications, this method shows promise for future development in POCT.

Cell-free protein synthesis (CFPS) is an in vitro platform that enables rapid protein production using cell extracts, energy sources, and genetic templates. Owing to its fast response, elimination of cell culture, open reaction environment, lyophilization compatibility, and high programmability, CFPS has emerged as a versatile engine for diagnostic sensing. Recent advances have integrated CFPS with modular genetic circuits, CRISPR-based detection, isothermal amplification, and portable formats such as paper-based devices and microfluidic chips, enabling sensitive and specific detection of viral nucleic acids, pathogen antigens, and small-molecule targets. These platforms further support multiplexed and point-of-care testing, substantially reducing assay time, cost, and infrastructure requirements. Despite remaining challenges in biosensor design for novel targets, analytical sensitivity in complex samples, batch-to-batch reproducibility, and clinical translation, continued engineering optimization is rapidly improving CFPS performance and robustness. This review summarizes the fundamental principles of CFPS, its major technological platforms, recent progress in diagnostic applications, and key challenges and opportunities for future development.

User-friendly and timely biomarker monitoring is essential for metabolic disease diagnosis and management. The aptameric switch has emerged as a promising tool in metabolite sensing but is limited in point-of-care (POC) diagnostics due to the lack of fast response capacity. Here, we report a rapid, generalizable aptaswitch that leverages the flanking region to accelerate switching kinetics via decreasing the reaction energy barrier for the metabolite assay and further develop two portable, affordable POC devices comprising the aptaswitch and paper-based assays including lateral flow strips and paper disc arrays for fast and accurate diagnostic tests of clinical samples. We demonstrate tunability and universality of the flanking aptaswitch using four affinity binders against different metabolites, exhibiting its easy reprogramming and modular plug-and-play capability for distinct target analytes. This aptaswitch outperforms conventional aptameric designs, achieving up to 5-fold and 4.6-fold improvements in reaction speed and sensitivity, respectively. In addition, the paper-based POC tests require 20-fold less sample volume compared to the analogous solution-based assay while keeping excellent sensitivity, specificity, and storage and batch stability. We also demonstrate high diagnostic accuracy (100%) of the paper-based POC device for phenylketonuria screening using both mouse model and human clinical samples, and the visually read, user-friendly result within 20 min highlights its potential for rapid POC diagnostics. This work advances aptamer sensing toward POC accessibility and represents a significant improvement toward cost-effective, widely applicable, more usable paper-based biosensors or POC tools.

The demand for point-of-care (POC) diagnostics is driving portable analytical innovation. Despite advances, precise optical tag control remains a key challenge limiting diagnostic accuracy. Here, we present a vertically stacked microarray paper-based device (µAPAD) enabling high-throughput surface-enhanced Raman scattering (SERS) immunoassays for multiplex biomarker detection. The 16-layer wax-patterned architecture integrates sample migration, reaction, and capture within one platform. Optimized microfluidic channels ensure uniform nanotag distribution, reducing signal variation from 36.6% to 6.69%, while an agarose hydrogel layer regulates flow to improve immunocapture efficiency. The µAPAD simultaneously analyzes 14 samples for two biomarkers within 30min. Using carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) as models, it achieves detection limits of 0.34 and 0.69ng/mL, outperforming conventional ELISA. Tests with spiked serum confirm high analytical accuracy, showing recoveries of 80.3%-139% and RSDs of 6.30%-10.8%. With its high sensitivity, flow precision, scalability, and true multiplexing capability, this low-cost platform offers great potential for next-generation POC diagnostics and large-scale health monitoring.

Integrating passive haptic learning (PHL) into paper-based devices offers significant potential for enhancing user immersion and skill acquisition. Herein, we present a compact audio-haptic-coupled paper-based device constructed from flexible, readily available, and eco-friendly materials. The device generates mechanical vibration under low-frequency excitation (~200 Hz), serving as a PHL indicator that can be easily sensed by humans, while higher-frequency excitation (>1,000 Hz) enables the production of diverse musical scales. The device achieves a sound pressure level of 70 dB, which is clearly perceived by audiences. Moreover, it exhibits excellent fatigue resistance, displaying negligible performance degradation even after 43,200 cycles of continuous compression. To improve portability, two compact circuit boards enabling the device to operate in various environments were developed. In practice, volunteers demonstrated improved learning efficiency when using the device integrated with PHL, achieving a ~35% reduction in learning time and 100% performance accuracy.

Rapid detection of hexavalent chromium using CuO/CN/LDH as an oxidase mimetic and the construction of a paper-based device.

In this work, we report the development of an integrated, multi-folding paper-based device for the quantum-dot (QD)-based simultaneous detection of two cancer biomarkers—carcinoembryonic antigen (CEA) and cancer antigen 125 (CA125)—in serum using dual-mode fluorescence–voltammetric sensing. The device comprises a fluidic conduit with a single sample zone connected to two spatially separated assay zones, positioned adjacent to a circular three-electrode electrochemical cell. Two sandwich immunoassay formats are implemented in the assay zones using PbS- and CdS-based QD–labeled reporter antibodies as barcode probes. Fluorescence readout is performed in situ under UV illumination with smartphone-based image acquisition. For electrochemical readout, the immunocomplexes are dissolved to release Pb(II) and Cd(II) ions; the assay zones are subsequently folded onto the adjacent electrochemical cell, enabling vertical elution of the metal ions, which are detected by anodic stripping voltammetry. By synergistically integrating the origami-inspired folding with vertical elution, the dual optical and electrochemical activity of QD barcode labels, and a bismuth-modified transducer, this work establishes the first bimodal quantum dot–linked duplex paper-based immunosensing platform. The device offers clear advantages over existing paper-based immunosensors, underscoring its potential for point-of-care (PoC) diagnostic applications. • The first bimodal quantum-dot linked duplex paper-based immunosensor for CEA and CA 125 in serum is developed • The paper device consists of a fluidic conduit adjacent to a circular 3-electrode electrochemical cell. • Two sandwich immunoassay protocols are implemented in the two spatially separated assay zones • Fluorescence detection is performed in situ by UV illumination and smartphone image capture. • For electrochemical detection, the device is folded, the quantum dots are dissolved and the metals are measured by stripping voltammetry

A foldable and paper-based microfluidic device integrated with LIBS and colorimetric for accurate heavy metals detection

Paper-based reaction devices as accelerated platforms in forced degradation studies.

Trends of microextraction methods for opioids in complex samples.

Portable origami paper-based photoacoustic-photothermal dual-mode device for on-site antioxidants detection.

The performance and scalability of electrochromic devices (ECDs) are highly dependent on the architecture and uniformity of their electrodes. However, conventional coating or printing approaches restrict the controllable patterning and large-scale fabrication required for sustainable paper-based ECDs. In this study, a high-quality PEDOT:PSS electrode was fabricated using roll-to-roll (R2R) flexographic printing, offering a scalable and low-cost route for flexible electrochromic manufacturing. The rheological behavior of the ink was characterized to elucidate its influence on film formation and electrical conductivity on biodegradable paper substrates. The assembled self-powered paper-based ECD exhibited a maximum optical contrast of 0.27 at 650 nm, a coloration efficiency of 70.4 cm2 C–1, and excellent cycling durability with 97.7% optical stability after 12,000 s of switching. Moreover, the printed electrodes enabled precise and uniform patterning with reversible deep-to-light blue transitions. This work establishes a green and designable fabrication strategy for sustainable, high-performance paper-based ECDs, paving the way for next-generation flexible and eco-friendly optoelectronic systems.

Increasing drug-facilitated crimes, mainly sexual assaults have intensified the necessity of accessible and efficient methods for club drugs detection especially in biological matrices and beverages that are served at parties and clubs. The recent development of 3D printing technology has markedly accelerated. One prominent application is the fabrication of wearable electrochemical sensors for the selective and sensitive detection of club drugs such as amphetamine. This class of drug is used as a stimulant in the treatment of conditions including attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity. Monitoring amphetamine type drugs level in human body is critical due to the risks associated with its possible misuses and related health concerns. By employing the use of 3D printing, makers can create complex and customized sensors specially intended for drug detection. This compliance facilitates integrating diverse type of sensors, thereby improving detection accuracy also. Conventional diagnostic methods are frequently labor-intensive and time-consuming, positioning 3D printed sensors as an innovative approach for real-time monitoring applications. Integrating 3D printing technology in sensor development holds significant potential to transform personalized healthcare by enabling accurate, rapid, and safe detection of amphetamine. This novel study shows the development of a screen-printed paper based electrochemical device with a 3D printed wristband cassette design named "3DP-PWC". This 3D printed paper based wristband cassette (3DP-PWC) features modified electrodes with amphetamine binding aptamer and copper nanoparticles (CuNPs). For electrochemical study, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were used and further validated the sensor's performance. Developed sensor demonstrated versatility across various beverage types (alcoholic and non-alcoholic) and biological matrices such as synthetic urine. The developed sensor achieved a low detection limit (LOD) of ~0.02μg/mL with a linear range between 0.01 to 7μg/mL. Promising results were obtained at an optimum response time of approximately 25seconds.

Herein, we report a non-enzymatic paper-based device for selective electrochemical detection of creatinine. This work demonstrates three modification strategies adopted for the paper-based electrochemical sensing device (PESD) for the detection of creatinine. Copper, a non-enzymatic metal electrode, was fabricated on the Whatman paper without sophisticated instrumentation. The fabricated pristine non-enzymatic PESD could detect creatinine in the linear range 10 µM to 90 µM with a detection limit of 6.6 µM. Further, the electrode and Whatman paper were modified with silver to improve the sensitivity of PESD towards creatinine. Firstly, the working electrodes were modified by the Scotch tape strategy via galvanic displacement of Ag on Cu. The Ag-modified Cu electrodes were stuck on the Whatman paper, which sensitized the creatinine in the linear range 10 nM to 240 nM with a detection limit of 0.089 nM. Secondly, the Whatman paper was modified by mussel-inspired soak, polymerize, and then reduction of silver on the paper. The modified paper works similarly to the modified electrode with Ag in the linear range 10 nM to 90 nM with a detection limit of 2.5 nM. Further, the fabricated pristine PESD was tested for Jaffe's inspired indirect electrochemical detection of creatinine in the linear range 10 µM to 100 µM with a detection limit of 6.4 µM. The sensitivity of the fabricated pristine PESD was improved from µM to nM by adopting modification strategies. The reported PESD with the least interference from the co-existing biomolecules has the potential applicability of monitoring creatinine in urine sample analysis.

Microfluidic paper-based analytical devices (µPADs) convert ordinary cellulose into an active analytical platform where capillary gradients shape transport, surface chemistry guides recognition, and embedded electrodes or optical probes translate biochemical events into readable signals. Progress in fabrication-from wax and stencil barriers to laser-defined grooves, inkjet-printed conductive lattices, and 3D-structured multilayers-has expanded reaction capacity while preserving portability. Detection strategies span colorimetric fields that respond within porous fibers, fluorescence and ratiometric architectures tuned for low abundance biomarkers, and electrochemical interfaces resilient to turbidity, salinity, and biological noise. Applications now include diagnosing human body fluids, checking food safety, monitoring the environment, and testing for pesticides and illegal drugs, often in places with limited resources. Researchers are now using learning algorithms to read minute gradients or currents imperceptible to the human eye, effectively enhancing and assisting the measurement process. This perspective article focuses on the newest advancements in the design, fabrication, material selection, testing methods, and applications of µPADs, and it explains how they work, where they can be used, and what their future might hold.

Less expensive, faster, and laborious protocols are needed for protein and peptide mass spectrometry (MS) for therapeutic protein characterization. This work describes a simple paper-based device that couples electrokinetic (EK) stacking via faradaic ion concentration polarization (f-ICP) with paper spray (PS) MS to enrich proteins and peptides on paper in minutes. The EK-PS device consists of a three-dimensional (3D)-printed holder with two polytetrafluoroethylene (PTFE) filter papers that act both as the media for electrokinetic stacking by f-ICP and as the supports for paper spray ionization. Modification of the PTFE filters via silanization improves MS ionization and imparts a positive surface charge to enable electro-osmotic flow. A potential of ∼280 V along the length of the papers induces electrokinetic stacking, whereas simultaneously floating the device at 4000 V generates online ionization via paper spray. Stacking and elution of proteins and peptides, which occurs by a combination of electro-osmotic flow and electrophoresis, takes ∼5-10 min and improves detection sensitivity by over 10-fold. In the analysis of tryptic protein digests and glycosylation profiling of monoclonal antibodies, electrokinetic stacking increases peptide identifications ∼9-fold and enables the detection of glycoforms above 3% relative abundance. The method is relatively simple and rapid, which may be useful for monitoring protein manufacturing.