Fabrication and Characterization of Paper-Based Microfluidics Prepared in Nitrocellulose Membrane By Wax Printing

Anisotropic, Mesoporous Microfluidic Frameworks with Scalable, Aligned Cellulose Nanofibers

Cellulose paper has been extensively used in microfluidic analytical devices because of its hydrophilic nature. However, cellulose is randomly packed in paper without any particular orientation or channels within the bulk of the material, necessitating a complicated design of hydrophilic microchannels to guide the liquid flow. Herein, we develop an anisotropic mesoporous microfluidic framework (named as white wood) with aligned cellulose nanofibers and inherent microchannels via a facile one-step delignification process from natural wood. The hydrophilic nature of the innate microchannels in white wood makes it ideal for application as a pump-free microfluidic chip, exhibiting a fast and anisotropic liquid and large solid particle (as demonstrated with carbon nanotubes) mass transport, with a high transport speed along the channel direction approximately five times faster than that perpendicular to the channel direction. The anisotropic mass transport is further exemplified in the fabrication of chitosan films with aligned microstructures and birefringence, formed by virtue of unidirectional capillary forces exerted by the microchannels. We envision that our anisotropic mesoporous framework can have great applications to pump-free microfluidics, and the simple preparation process will pave a new way for the development of microfluidic devices based on chemically modified wood.

Laminated Copper Nanocluster Incorporated Antioxidative Paper Device with RGB System-Assisted Signal Improvement

Paper-based analytical devices are an emerging class of lightweight and simple-to-use analytical platform. However, challenges such as instrumental requirements and chemical reagents durability, represent a barrier for less-developed countries and markets. Herein, we report an advanced laminated device using red emitting copper nanocluster and RGB digital analysis for signal improvement. Upon RGB system assistance, the device signal-to-background ratio and the calibration sensitivity are highly enhanced under a filter-free setup. In addition, the calibration sensitivity, limit of detection, and coefficient of determination are on par with those determined by instrumental fluorescence analysis. Moreover, the limitation of using oxidation-susceptible fluorescent nanomaterials is overcome by the introduction of protecting tape barriers, antioxidative sheets, and lamination enclosing. The robustness of device is highly advanced, and the durability is prolonged to more than tenfold.

Signal Amplified Gold Nanoparticles for Cancer Diagnosis on Paper-Based Analytical Devices

In this work, we report a highly sensitive colorimetric sensing strategy for cancer biomarker diagnosis using gold nanoparticles (AuNPs) labeled with biotinylated poly(adenine) ssDNA sequences and streptavidin-horseradish peroxidase for enzymatic signal enhancement. By adopting this DNA-AuNP nanoconjugate sensing strategy, we were able to eliminate the complicated and costly thiol-binding process typically used to modify AuNP surfaces with ssDNA. In addition, different antibodies can be introduced to the AuNP surfaced via electrostatic interactions to provide highly specific recognition sites for biomolecular sensing. Moreover, multiple, simultaneous tests can be rapidly performed with low sample consumption by incorporating these surface-modified AuNPs into a paper-based analytical device that can be read using just a smartphone. As a result of these innovations, we were able to achieve a detection limit of 10 pg/mL for a prostate specific antigen in a test that could be completed in as little as 15 min. These results suggest that the proposed paper platform possesses the capability for sensitive, high-throughput, and on-site prognosis in resource-limited settings.

Design of a simple paper-based colorimetric biosensor using polydiacetylene liposomes for neomycin detection

A paper-based analytical device (μPAD) combined with self-signaling polydiacetylene liposomes was developed for convenient visual neomycin detection.

Low-cost Paper Analytical Devices for Environmental and Biomedical Sensing Applications

Over the last decade, the fabrication of analytical devices utilizing microfluidic structures and lab-on-a-chip platforms has shown breakthrough advancements, both for environmental and biological applications. The ASSURED criteria (affordable, sensitive, specific, user-friendly, robust, equipment-free, delivered), developed by the WHO for diagnostics devices, point towards the need of paper-based analytical devices (PAD) for diagnostics. On the other hand, cost-effective PADs owing the great advantage of affordable applicability in both resource-rich and -limited settings are recently employed for on-site environmental monitoring. In this book chapter, we will discuss about the brief history of paper analytical devices, fabrications, need, and its environmental and biomedical applications.

Simple Screening of Listeria monocytogenes Based on a Fluorescence Assay via a Laminated Lab-On-Paper Chip

Monitoring food safety is essential for protecting the health and safety of consumers. Conventional methods used are time consuming and laborious, requiring anywhere from three to seven days to obtain results. Thus, better monitoring methods are required. In this study, a laminated lab-on-paper chip was developed, and its use for the screening of ready-to-eat seafood was demonstrated. The assay on a chip was based on loop-mediated isothermal DNA amplification (LAMP) of the hly gene of Listeria monocytogenes and fluorescence signal detection via SYBR Gold^TM. Overall assay processes were completed in 4.5 h., (including 3.5 h. incubation for the bacteria enrichment, direct DNA amplification with no DNA extraction, and signal detection), without relying on standard laboratory facilities. Only positive samples induced fluorescence signals on chip upon illumination with UV light (λ = 460). The method has a limit of detection of 100 copies of L. monocytogenes DNA per 50 g of sample. No cross-reactivity was observed in samples contaminated with other bacteria. On-site monitoring of the seafood products using this chip revealed that one of 30 products from low sanitation vendors (3.33%) were contaminated, and these agreed with the results of PCR. The results demonstrated a benefit of this chip assay for practical on-site monitoring.

The recent development and applications of fluidic channels by 3D printing

The technology of “Lab-on-a-Chip” allows the synthesis and analysis of chemicals and biological substance within a portable or handheld device. The 3D printed structures enable precise control of various geometries. The combination of these two technologies in recent years makes a significant progress. The current approaches of 3D printing, such as stereolithography, polyjet, and fused deposition modeling, are introduced. Their manufacture specifications, such as surface roughness, resolution, replication fidelity, cost, and fabrication time, are compared with each other. Finally, novel application of 3D printed channel in biology are reviewed, including pathogenic bacteria detection using magnetic nanoparticle clusters in a helical microchannel, cell stimulation by 3D chemical gradients, perfused functional vascular channels, 3D tissue construct, organ-on-a-chip, and miniaturized fluidic “reactionware” devices for chemical syntheses. Overall, the 3D printed fluidic chip is becoming a powerful tool in the both medical and chemical industries.

Paper-based assays for urine analysis

A transformation of the healthcare industry is necessary and imminent: hospital-centered, reactive care will soon give way to proactive, person-centered care which focuses on individuals' well-being. However, this transition will only be made possible through scientific innovation. Next-generation technologies will be the key to developing affordable and accessible care, while also lowering the costs of healthcare. A promising solution to this challenge is low-cost continuous health monitoring; this approach allows for effective screening, analysis, and diagnosis and facilitates proactive medical intervention. Urine has great promise for being a key resource for health monitoring; unlike blood, it can be collected effortlessly on a daily basis without pain or the need for special equipment. Unfortunately, the commercial rapid urine analysis tests that exist today can only go so far-this is where the promise of microfluidic devices lies. Microfluidic devices have a proven record of being effective analytical devices, capable of controlling the flow of fluid samples, containing reaction and detection zones, and displaying results, all within a compact footprint. Moving past traditional glass- and polymer-based microfluidics, paper-based microfluidic devices possess the same diagnostic ability, with the added benefits of facile manufacturing, low-cost implementation, and disposability. Hence, we review the recent progress in the application of paper-based microfluidics to urine analysis as a solution to providing continuous health monitoring for proactive care. First, we present important considerations for point-of-care diagnostic devices. We then discuss what urine is and how paper functions as the substrate for urine analysis. Next, we cover the current commercial rapid tests that exist and thereby demonstrate where paper-based microfluidic urine analysis devices may fit into the commercial market in the future. Afterward, we discuss various fabrication techniques that have been recently developed for paper-based microfluidic devices. Transitioning from fabrication to implementation, we present some of the clinically implemented urine assays and their importance in healthcare and clinical diagnosis, with a focus on paper-based microfluidic assays. We then conclude by providing an overview of select biomarker research tailored towards urine diagnostics. This review will demonstrate the applicability of paper-based assays for urine analysis and where they may fit into the commercial healthcare market.

Paper microfluidics for nucleic acid amplification testing (NAAT) of infectious diseases

The diagnosis of infectious diseases is entering a new and interesting phase. Technologies based on paper microfluidics, coupled to developments in isothermal amplification of Nucleic Acids (NAs) raise opportunities for bringing the methods of molecular biology in the field, in a low setting environment. A lot of work has been performed in the domain over the last few years and the landscape of contributions is rich and diverse. Most often, the level of sample preparation differs, along with the sample nature, the amplification and detection methods, and the design of the device, among other features. In this review, we attempt to offer a structured description of the state of the art. The domain is not mature and there exist bottlenecks that hamper the realization of Nucleic Acid Amplification Tests (NAATs) complying with the constraints of the field in low and middle income countries. In this domain however, the pace of progress is impressively fast. This review is written for a broad Lab on a Chip audience.

Polydiacetylene/Anti-HBs Complexes for Visible and Fluorescent Detection of Hepatitis B Surface Antigen on a Nitrocellulose Membrane

The immunochromatographic assay (ICA) using a nitrocellulose (NC) membrane offers several advantages. This technique is a rapid and straightforward method in contrast to other immunoassays. Polydiacetylene (PDA) vesicles have unique optical properties, displaying red color and red fluorescence at the same time. In this system, red-phase PDA vesicles are used as a fluorescent dye as well as a surface for immobilized hepatitis B surface antibody (HBsAb). PDA has a remarkable stability compared with other fluorescent dyes. In this study, the most suitable PDA/HBsAb complexes are introduced for detecting hepatitis B surface antigen (HBsAg). Then, the PDA/HBsAb complexes affixed antibody is attached to NC membrane, which has two lines to confirm detection of HBsAg. The main advantage of this system is that the detection of HBsAg can be observed in both visible and fluorescent images due to the optical properties of polydiacetylene. Detection of HBsAg is observed up to 0.1 ng mL^-1 by fluorescent analysis and confirmed by red line on the NC membrane up to 1 ng mL^-1 (HBsAg) using the naked eye. Consequently, these results show that PDA/HBsAb complexes were successfully applied to ICA for the diagnosis of hepatitis B.

A review on wax printed microfluidic paper-based devices for international health

Paper-based microfluidics has attracted attention for the last ten years due to its advantages such as low sample volume requirement, ease of use, portability, high sensitivity, and no necessity to well-equipped laboratory equipment and well-trained manpower. These characteristics have made paper platforms a promising alternative for a variety of applications such as clinical diagnosis and quantitative analysis of chemical and biological substances. Among the wide range of fabrication methods for microfluidic paper-based analytical devices (μPADs), the wax printing method is suitable for high throughput production and requires only a commercial printer and a heating source to fabricate complex two or three-dimensional structures for multipurpose systems. μPADs can be used by anyone for in situ diagnosis and analysis; therefore, wax printed μPADs are promising especially in resource limited environments where people cannot get sensitive and fast diagnosis of their serious health problems and where food, water, and related products are not able to be screened for toxic elements. This review paper is focused on the applications of paper-based microfluidic devices fabricated by the wax printing technique and used for international health. Besides presenting the current limitations and advantages, the future directions of this technology including the commercial aspects are discussed. As a conclusion, the wax printing technology continues to overcome the current limitations and to be one of the promising fabrication techniques. In the near future, with the increase of the current interest of the industrial companies on the paper-based technology, the wax-printed paper-based platforms are expected to take place especially in the healthcare industry.

Microfluidic paper-based analytical devices for potential use in quantitative and direct detection of disease biomarkers in clinical analysis

Clinicians, working in the health-care diagnostic systems of developing countries, currently face the challenges of rising costs, increased number of patient visits, and limited resources. A significant trend is using low-cost substrates to develop microfluidic devices for diagnostic purposes. Various fabrication techniques, materials, and detection methods have been explored to develop these devices. Microfluidic paper-based analytical devices (μPADs) have gained attention for sensing multiplex analytes, confirming diagnostic test results, rapid sample analysis, and reducing the volume of samples and analytical reagents. μPADs, which can provide accurate and reliable direct measurement without sample pretreatment, can reduce patient medical burden and yield rapid test results, aiding physicians in choosing appropriate treatment. The objectives of this review are to provide an overview of the strategies used for developing paper-based sensors with enhanced analytical performances and to discuss the current challenges, limitations, advantages, disadvantages, and future prospects of paper-based microfluidic platforms in clinical diagnostics. μPADs, with validated and justified analytical performances, can potentially improve the quality of life by providing inexpensive, rapid, portable, biodegradable, and reliable diagnostics.

Turning the Page: Advancing Paper-Based Microfluidics for Broad Diagnostic Application

Infectious diseases are a major global health issue. Diagnosis is a critical first step in effectively managing their spread. Paper-based microfluidic diagnostics first emerged in 2007 as a low-cost alternative to conventional laboratory testing, with the goal of improving accessibility to medical diagnostics in developing countries. In this review, we examine the advances in paper-based microfluidic diagnostics for medical diagnosis in the context of global health from 2007 to 2016. The theory of fluid transport in paper is first presented. The next section examines the strategies that have been employed to control fluid and analyte transport in paper-based assays. Tasks such as mixing, timing, and sequential fluid delivery have been achieved in paper and have enabled analytical capabilities comparable to those of conventional laboratory methods. The following section examines paper-based sample processing and analysis. The most impactful advancement here has been the translation of nucleic acid analysis to a paper-based format. Smartphone-based analysis is another exciting development with potential for wide dissemination. The last core section of the review highlights emerging health applications, such as male fertility testing and wearable diagnostics. We conclude the review with the future outlook, remaining challenges, and emerging opportunities.

High-throughput rapid-prototyping of low-cost paper-based microfluidics

Paper-based micro analytical devices offer significant advantages compared to the conventional microfluidic chips including cost-effectiveness, ease of fabrication, and ease of use while preserving critical features including strong capillary action and biological compatibility. In this work, we demonstrate an inexpensive, rapid method for high-throughput fabrication of paper-based microfluidics by patterning hydrophobic barriers using a desktop pen plotter integrated with a custom-made, low-cost paper feeder. We tested various types of commercial permanent markers and compared their water-resistant capabilities for creating hydrophobic barriers. Additionally, we studied the performance of markers with different types of paper, plotting speeds, and pattern dimensions. To verify the effectiveness of the presented fabrication method, colorimetric analysis was performed on the results of a glucose assay.

Controlling Capillary-Driven Fluid Transport in Paper-Based Microfluidic Devices Using a Movable Valve

This paper describes a novel strategy for fabricating the movable valve on paper-based microfluidic devices to manipulate capillary-driven fluids. The movable valve fabrication is first realized using hollow rivets as the holding center to control the paper channel in different layer movement that results in the channel's connection or disconnection. The relatively simple valve fabrication procedure is robust, versatile, and compatible with microfluidic paper-based analytical devices (μPADs) with differing levels of complexity. It is remarkable that the movable valve can be convenient and free to control fluid without the timing setting, advantages that make it user-friendly for untrained users to carry out the complex multistep operations. For the performance of the movable valve to be verified, several different designs of μPADs were tested and obtained with satisfactory results. In addition, in the proof-of-concept enzyme-linked immunosorbent assay experiments, we demonstrate the use of these valves in μPADs for the successful analysis of samples of carcino-embryonic antigen, showing good sensitivity and reproducibility. We hope this technique will open new avenues for the fabrication of paper-based valves in an easily adoptable and widely available way on μPADs and provide potential point-of-care applications in the future.

Applications of Microfluidic Devices for Urology

Microfluidics is considered an important technology that is suitable for numerous biomedical applications, including cancer diagnosis, metastasis, drug delivery, and tissue engineering. Although microfluidics is still considered to be a new approach in urological research, several pioneering studies have been reported in recent years. In this paper, we reviewed urological research works using microfluidic devices. Microfluidic devices were used for the detection of prostate and bladder cancer and the characterization of cancer microenvironments. The potential applications of microfluidics in urinary analysis and sperm sorting were demonstrated. The use of microfluidic devices in urology research can provide high-throughput, high-precision, and low-cost analyzing platforms.

Paper-based analytical devices for clinical diagnosis: recent advances in the fabrication techniques and sensing mechanisms

INTRODUCTION

There is a significant interest in developing inexpensive portable biosensing platforms for various applications including disease diagnostics, environmental monitoring, food safety, and water testing at the point-of-care (POC) settings. Current diagnostic assays available in the developed world require sophisticated laboratory infrastructure and expensive reagents. Hence, they are not suitable for resource-constrained settings with limited financial resources, basic health infrastructure, and few trained technicians. Cellulose and flexible transparency paper-based analytical devices have demonstrated enormous potential for developing robust, inexpensive and portable devices for disease diagnostics. These devices offer promising solutions to disease management in resource-constrained settings where the vast majority of the population cannot afford expensive and highly sophisticated treatment options. Areas covered: In this review, the authors describe currently developed cellulose and flexible transparency paper-based microfluidic devices, device fabrication techniques, and sensing technologies that are integrated with these devices. The authors also discuss the limitations and challenges associated with these devices and their potential in clinical settings. Expert commentary: In recent years, cellulose and flexible transparency paper-based microfluidic devices have demonstrated the potential to become future healthcare options despite a few limitations such as low sensitivity and reproducibility.

Toward practical application of paper-based microfluidics for medical diagnostics: state-of-the-art and challenges

Microfluidic paper-based analytical devices (μPADs) have emerged as a promising diagnostic platform a decade ago. In contrast to highly active academic developments, their entry into real-life applications is still very limited. This discrepancy is attributed to the gap between research developments and their practical utility, particularly in the aspects of operational simplicity, long-term stability of devices, and associated equipment. On the basis of these backgrounds, this review attempts to: 1) identify the reasons for success of paper-based devices already in the market, 2) describe the current status and remaining issues of μPADs in terms of operational complexity, signal interpretation approaches, and storage stability, and 3) discuss the possibility of mass production based on established manufacturing technologies. Finally, the state-of-the-art in commercialisation of μPADs is discussed, and the "upgrades" required from a laboratory-based prototype to an end user device are demonstrated on a specific example.

Time-Dependent Model for Fluid Flow in Porous Materials with Multiple Pore Sizes

An understanding of fluid transport through porous materials is critical for the development of lateral flow assays and analytical devices based on paper microfluidics. Models of fluid transport within porous materials often assume a single capillary pressure and permeability value for the material, implying that the material comprises a single pore size and that the porous material is fully saturated behind the visible wetted front. As a result, current models can lead to inaccuracies when modeling transport over long distances and/or times. A new transport model is presented that incorporates a range of pore sizes to more accurately predict the capillary transport of fluid in porous materials. The model effectively predicts the time-dependent saturation of rectangular strips of Whatman filter no. 1 paper using the manufacturer's data, published pore-size distribution measurements, and the fluid's properties.

Improving FoRe: A New Inlet Design for Filtering Samples through Individual Microarray Spots

In this publication we present an improvement to our previously introduced vertical flow microarray, the FoRe array, which capitalizes on the fusion of immunofiltration and densely packed micron test sites. Filtering samples through individual microarray spots allows us to rapidly analyze dilute samples with high-throughput and high signal-to-noise. Unlike other flowthrough microarrays, in the FoRe design samples are injected into micron channels and sequentially exposed to different targets. This arrangement makes it possible to increase the sensitivity of the microarray by simply increasing the sample volume or to rapidly reconcentrate samples after preprocessing steps dilute the analyte. Here we present a new inlet system which allows us to increase the analyzed sample volume without compromising the micron spot size and dense layout. We combined this with a model assay to demonstrate that the device is sensitive to the amount of antigen, and as a result, sample volume directly correlates to sensitivity. We introduced a simple technique for analysis of blood, which previously clogged the nanometer-sized pores, requiring only microliter volumes expected from an infant heel prick. A drop of blood is mixed with buffer to separate the plasma before reconcentrating the sample on the microarray spot. We demonstrated the success of this procedure by spiking TNF-α into blood and achieved a limit of detection of 18 pM. Compared to traditional protein microarrays, the FoRe array is still inexpensive, customizable, and simple to use, and thanks to these improvements has a broad range of applications from small animal studies to environmental monitoring.

Anti-microbial surfaces: An approach for deposition of ZnO nanoparticles on PVA-Gelatin composite film by screen printing technique

Initially micro-organisms get exposed to the surfaces, this demands development of anti-microbial surfaces to inhibit their proliferation. Therefore, herein, we attempt screen printing technique for development of PVA-GE/ZnO nanocomposite (PG/ZnO) films. The synthesis of PG/ZnO nanocomposite includes two steps as: (i) Coating of Zinc Oxide nanoparticles (ZnO NPs) by poly ethylene glycol in order to be compatible with organic counterparts. (ii) Deposition of coated nanoparticles on the PG film surface. The results suggest the enhancement in anti-microbial activity of PG/ZnO nanocomposite over pure ZnO NPs against both Gram positive Bacillus subtilis and Gram negative Escherichia coli from zone of inhibition. The uniformity in deposition is further confirmed by scanning electron microscopy (SEM) images. The phase identification of ZnO NPs and formation of PG/ZnO nanocomposite has been confirmed by X-ray diffraction (XRD) analysis and UV-vis spectroscopy (UV-vis). The Attenuated total reflection Spectroscopy (ATR) analysis indicates the ester bond between PVA and gelatin molecules. The thermal stability of nanocomposite is studied by thermogravimetric analysis (TGA) revealing increase in crystallinity due to ZnO NPs which could be utilized to inhibit the growth of micro-organisms. The tensile strength is found to be higher and percent elongation is double of PG/ZnO nanocomposite than PG composite film.

A novel method for blood-typing using nitrocellulose

Blood wicking in its steady-state form, i.e. the uniform distribution of blood cells in plasma, is completely different from that in its coagulated form on a porous surface like paper. The hydrophilic property of the cellulose leads to a significant wicking of the blood cells on paper fibers after rinsing with isotonic solution. The difference in the wicking length of the blood cells in steady state and that in the coagulated form could be considered as a criterion to recognize the blood type in a paper-based kit. However, owing to the molecular structure of the nitrocellulose, a better process occurs while separating the coagulated blood from the steady-state form of cells. Therefore, it is possible to use the nitrocellulose for the blood-typing kit which leads to a simpler way to diagnose a blood type. Two series of experiments were performed on nitrocellulose membrane. First, antibody solutions and blood samples were sequentially absorbed on nitrocellulose strips, allowed to interact, rinsed with an isotonic solution and distilled water, and image processing performed on a digital picture of the remaining blood cells. The efficiency of the agglutinated blood cell fixation was quantified by red color intensity. Then, it was demonstrated that there is no considerable difference in fixation of agglutinated blood cells with rinsing using isotonic and nonisotonic solutions. This fact can be a considerable advantage over paper since it can eliminate the probable mistake from using unisotonic solution for rinsing. Second, owing to the nonwicking property of the blood cells on the hydrophobic nitrocellulose fibers, we employed another diagnostic criterion and investigated nitrocellulose blood-typing prototypes. The nitrocellulose blood-typing kit provides more simple, sensitive and trustworthy assay for rapid blood typing in situations with no access to laboratory facilities.

Electrochemical paper-based peptide nucleic acid biosensor for detecting human papillomavirus

A novel paper-based electrochemical biosensor was developed using an anthraquinone-labeled pyrrolidinyl peptide nucleic acid (acpcPNA) probe (AQ-PNA) and graphene-polyaniline (G-PANI) modified electrode to detect human papillomavirus (HPV). An inkjet printing technique was employed to prepare the paper-based G-PANI-modified working electrode. The AQ-PNA probe baring a negatively charged amino acid at the N-terminus was immobilized onto the electrode surface through electrostatic attraction. Electrochemical impedance spectroscopy (EIS) was used to verify the AQ-PNA immobilization. The paper-based electrochemical DNA biosensor was used to detect a synthetic 14-base oligonucleotide target with a sequence corresponding to human papillomavirus (HPV) type 16 DNA by measuring the electrochemical signal response of the AQ label using square-wave voltammetry before and after hybridization. It was determined that the current signal significantly decreased after the addition of target DNA. This phenomenon is explained by the rigidity of PNA-DNA duplexes, which obstructs the accessibility of electron transfer from the AQ label to the electrode surface. Under optimal conditions, the detection limit of HPV type 16 DNA was found to be 2.3 nM with a linear range of 10-200 nM. The performance of this biosensor on real DNA samples was tested with the detection of PCR-amplified DNA samples from the SiHa cell line. The new method employs an inexpensive and disposable device, which easily incinerated after use and is promising for the screening and monitoring of the amount of HPV-DNA type 16 to identify the primary stages of cervical cancer.

A centrifugal microfluidic device with integrated gold leaf electrodes for the electrophoretic separation of DNA

Current conventional methods utilized for forensic DNA analysis are time consuming and labor-intensive requiring large and expensive equipment and instrumentation. While more portable Rapid DNA systems have been developed, introducing them to a working laboratory still necessitates a high cost of initiation followed by the recurrent cost of the devices. This has highlighted the need for an inexpensive, rapid and portable DNA analysis tool for human identification in a forensic setting. In order for an integrated DNA analysis system such as this to be realized, device operations must always be concluded by a rapid separation of short-tandem repeat (STR) DNA fragments. Contributing to this, we report the development of a unique, multi-level, centrifugal microdevice that can perform both reagent loading and DNA separation. The fabrication protocol was inspired by the print, cut and laminate (PCL) technique described previously by our group, and in accordance, offers a rapid and inexpensive option compared with existing approaches. The device comprises multiple polyester-toner fluidic layers, a cyclic olefin copolymer separation domain and integrated gold leaf electrodes. All materials are commercially-available and complement the PCL process in a way that permits fabrication of increasingly sought after single-use devices. All reagents, including a viscous sieving matrix, are loaded centrifugally, eliminating external pneumatic pumping, and the sample is separated in <5 minutes using an effective separation length of only 4 cm (reagent loading to completed separation, is <37 minutes). The protocol for gold leaf electrode manufacture yielded up to 30 electrodes for less than $3 (cost of a 79 mm × 79 mm gold leaf sheet) and when using a device combining these electrodes and centrifugal reagent/polymer loading, the electrophoretic separation of STR fragments with two base resolution was demonstrated. This exemplary performance makes the device an ideal candidate for further integration and development of an inexpensive, portable and rapid forensic human identification system.

Note: Professional grade microfluidics fabricated simply

Microfluidics has found increasingly wide usage in the research and teaching laboratory, but setting up a facility for its production has typically required either significant capital expense or sacrifice of quality. We present an approach to produce devices, without a clean room, using LEDs and spin-coaters, and plasma bonded using a commercial microwave oven. Submicron features can be readily reproduced with good fidelity.

Paper-based sensors and assays: a success of the engineering design and the convergence of knowledge areas

This review shows the recent advances and state of the art in paper-based analytical devices (PADs) through the analysis of their integration with microfluidics and LOC micro- and nanotechnologies, electrochemical/optical detection and electronic devices as the convergence of various knowledge areas. The important role of the paper design/architecture in the improvement of the performance of sensor devices is discussed. The discussion is fundamentally based on μPADs as the new generation of paper-based (bio)sensors. Data about the scientific publication ranking of PADs, illustrating their increase as an experimental research topic in the past years, are supplied. In addition, an analysis of the simultaneous evolution of PADs in academic lab research and industrial commercialization highlighting the parallelism of the technological transfer from academia to industry is displayed. A general overview of the market behaviour, the leading industries in the sector and their commercialized devices is given. Finally, personal opinions of the authors about future perspectives and tendencies in the design and fabrication technology of PADs are disclosed.

3D Printed Paper-Based Microfluidic Analytical Devices

As a pump-free and lightweight analytical tool, paper-based microfluidic analytical devices (μPADs) attract more and more interest. If the flow speed of μPAD can be programmed, the analytical sequences could be designed and they will be more popular. This reports presents a novel μPAD, driven by the capillary force of cellulose powder, printed by a desktop three-dimensional (3D) printer, which has some promising features, such as easy fabrication and programmable flow speed. First, a suitable size-scale substrate with open microchannels on its surface is printed. Next, the surface of the substrate is covered with a thin layer of polydimethylsiloxane (PDMS) to seal the micro gap caused by 3D printing. Then, the microchannels are filled with a mixture of cellulose powder and deionized water in an appropriate proportion. After drying in an oven at 60 °C for 30 min, it is ready for use. As the different channel depths can be easily printed, which can be used to achieve the programmable capillary flow speed of cellulose powder in the microchannels. A series of microfluidic analytical experiments, including quantitative analysis of nitrite ion and fabrication of T-sensor were used to demonstrate its capability. As the desktop 3D printer (D3DP) is very cheap and accessible, this device can be rapidly printed at the test field with a low cost and has a promising potential in the point-of-care (POC) system or as a lightweight platform for analytical chemistry.

Rapid detection of aflatoxigenic Aspergillus sp. in herbal specimens by a simple, bendable, paper-based lab-on-a-chip

Postharvest herbal product contamination with mycotoxins and mycotoxin-producing fungi represents a potentially carcinogenic hazard. Aspergillus flavus is a major cause of this issue. Available mold detection methods are PCR-based and rely heavily on laboratories; thus, they are unsuitable for on-site monitoring. In this study, a bendable, paper-based lab-on-a-chip platform was developed to rapidly detect toxigenic Aspergillus spp. DNA. The 3.0-4.0 cm(2) chip is fabricated using Whatman™ filter paper, fishing line and a simple plastic lamination process and has nucleic acid amplification and signal detection components. The Aspergillus assay specifically amplifies the aflatoxin biosynthesis gene, aflR, using loop-mediated isothermal amplification (LAMP); hybridization between target DNA and probes on blue silvernanoplates (AgNPls) yields colorimetric results. Positive results are indicated by the detection pad appearing blue due to dispersed blue AgNPls; negative results are indicated by the detection pad appearing colorless or pale yellow due to probe/target DNA hybridization and AgNPls aggregation. Assay completion requires less than 40 min, has a limit of detection (LOD) of 100 aflR copies, and has high specificity (94.47%)and sensitivity (100%). Contamination was identified in 14 of 32 herbal samples tested (43.75%). This work demonstrates the fabrication of a simple, low-cost, paper-based lab-on-a-chip platform suitable for rapid-detection applications.

Water Activated Graphene Oxide Transfer Using Wax Printed Membranes for Fast Patterning of a Touch Sensitive Device

We demonstrate a graphene oxide printing technology using wax printed membranes for the fast patterning and water activation transfer using pressure based mechanisms. The wax printed membranes have 50 μm resolution, longtime stability and infinite shaping capability. The use of these membranes complemented with the vacuum filtration of graphene oxide provides the control over the thickness. Our demonstration provides a solvent free methodology for printing graphene oxide devices in all shapes and all substrates using the roll-to-roll automatized mechanism present in the wax printing machine. Graphene oxide was transferred over a wide variety of substrates as textile or PET in between others. Finally, we developed a touch switch sensing device integrated in a LED electronic circuit.

Aspartate Aminotransferase and Alanine Aminotransferase Detection on Paper-Based Analytical Devices with Inkjet Printer-Sprayed Reagents

General biochemistry detection on paper-based microanalytical devices (PADs) uses pipette titration. However, such an approach is extremely time-consuming for large-scale detection processes. Furthermore, while automated methods are available for increasing the efficiency of large-scale PAD production, the related equipment is very expensive. Accordingly, this study proposes a low-cost method for PAD manufacture, in which the reagent is applied using a modified inkjet printer. The optimal reaction times for the detection of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are shown to be 6 and 7 min, respectively, given AST and ALT concentrations in the range of 5.4 to 91.2 U/L (R² = 0.9932) and 5.38 to 86.1 U/L (R² = 0.9944). The experimental results obtained using the proposed PADs for the concentration detection of AST and ALT in real human blood serum samples are found to be in good agreement with those obtained using a traditional spectrophotometric detection method by National Cheng Kung University hospital.

Fast and Efficient Fabrication of Intrinsically Stretchable Multilayer Circuit Boards by Wax Pattern Assisted Filtration

Intrinsically stretchable multilayer circuit boards are fabricated with a fast and material efficient method based on filtration. Silver nanowire conductor patterns of outstanding performance are defined by filtration through wax printed membranes and the circuit board is assembled by subsequent transfers of the nanowires onto the elastomer substrate. The method is used to fabricate a bright stretchable light emitting diode matrix display.

A simple method for fabrication of microfluidic paper-based analytical devices and on-device fluid control with a portable corona generator

A simple method for fabrication of microfluidic paper-based analytical devices and on-device fluid control with a portable corona generator was developed.

Surface Modification Chemistries of Materials Used in Diagnostic Platforms with Biomolecules

Biomolecules including DNA, protein, and enzymes are of prime importance in biomedical field. There are several reports on the technologies for the detection of these biomolecules on various diagnostic platforms. It is important to note that the performance of the biosensor is highly dependent on the substrate material used and its meticulous modification for particular applications. Therefore, it is critical to understand the principles of a biosensor to identify the correct substrate material and its surface modification chemistry. The imperative surface modification for the attachment of biomolecules without losing their bioactivity is a key to sensitive detection. Therefore, finding of a modification method which gives minimum damage to the surface as well as biomolecule is highly inevitable. Different surface modification technologies are invented according to the type of a substrate used. Surface modification techniques of the materials used as platforms in the fabrication of biosensors are reviewed in this paper.