Microfluidic Biochips Research Articles

A secure fault detection for digital microfluidic biochips

Abstract Among all the modern technological advances, digital microfluidic biochip has been extending a salient solution to healthcare and bio-laboratories with the pledge of high sensitivity and reconfigurability. Such biochip devices fulfill the requirement of a faster testing kit for the detection of different novel diseases, which is indispensable in the market due to the tremendously disrupted scenario of healthcare systems. To eliminate erroneous testing, the current scope of digital microfluidic biochips is widened as a viable testing method using various bioprotocols with a reduced cost in developing countries. This paper addresses the existing security challenges and operational faults in the identification mechanism of proteins such as severe acute respiratory syndrome coronavirus 2 spike protein in state-of-the-art digital microfluidic biochips. We are the first to propose a safety detection solution along with a fault identification algorithm using an inductive transfer learning model. Experimental results of the proposed model register a threshold accuracy of 98% while applying the own dataset. This work will provide a better security-enabled fault-free safety assurance framework against attack and fault identification with better accuracy in digital microfluidic biochips for the detection of different diseases and many other healthcare diagnoses, without any overhead of completion time for bioprotocols.

Fast total cleaning proactive wash droplet routing for digital microfluidics biochip

Fast total cleaning proactive wash droplet routing for digital microfluidics biochip

BioTrojans: viscoelastic microvalve-based attacks in flow-based microfluidic biochips and their countermeasures

Flow-based microfluidic biochips (FMBs) are widely used in biomedical research and diagnostics. However, their security against potential material-level cyber-physical attacks remains inadequately explored, posing a significant future challenge. One of the main components, polydimethylsiloxane (PDMS) microvalves, is pivotal to FMBs' functionality. However, their fabrication, which involves thermal curing, makes them susceptible to chemical tampering-induced material degradation attacks. Here, we demonstrate one such material-based attack termed “BioTrojans,” which are chemically tampered and optically stealthy microvalves that can be ruptured through low-frequency actuations. To chemically tamper with the microvalves, we altered the associated PDMS curing ratio. Attack demonstrations showed that BioTrojan valves with 30:1 and 50:1 curing ratios ruptured quickly under 2 Hz frequency actuations, while authentic microvalves with a 10:1 ratio remained intact even after being actuated at the same frequency for 2 days (345,600 cycles). Dynamic mechanical analyzer (DMA) results and associated finite element analysis revealed that a BioTrojan valve stores three orders of magnitude more mechanical energy than the authentic one, making it highly susceptible to low-frequency-induced ruptures. To counter BioTrojan attacks, we propose a security-by-design approach using smooth peripheral fillets to reduce stress concentration by over 50% and a spectral authentication method using fluorescent microvalves capable of effectively detecting BioTrojans.

Development of conductive carbon-based interdigitated electrode array integrated with microfluidic channel for blood glucose sensing

PurposeThis study aims to provide a microfluidic blood glucose sensing platform based on integrated interdigitated electrode arrays (IDEAs) on a flexible quartz glass substrate, adhering closely to pertinent electrochemical characterizations.Design/methodology/approachSensors are the key elements of the modern electronics era through which all the possible physical quantities can be detected and converted into their equivalent electrical form and processed further. But to make the sensing environment better, various types of innovative architectures are being developed nowadays and among them interdigitated electrodes are quite remarkable in terms of their sensing capability. They are a well-qualified candidate in the field of gas sensing and biosensing, but even their sensitivities are getting saturated due to their physical dimensions. Most of the thin film IDEAs fabricated by conventional optical lithographic techniques do not possess a high surface-to-volume ratio to detect the target specified and that reduces their sensitivity factor. In this context, a classic conductive carbon-based highly sensitive three dimensional (3D) IDEA-enabled biosensing system has been conceived on a transparent and flexible substrate to measure the amount of glucose concentration present in human blood. 3D IDEA possesses a way better capacitive sensing behavior compared to conventional thin film microcapacitive electrodes. To transmit the target biological analyte sample property for the detection purpose to the interdigitated array-based sensing platform, the design of a microfluidic channel is initiated on the same substrate. The complex 3D Inter Digital array structure improves the overall capacitance of the entire sensing platform and the reactive surface area as well. The manufactured integrated device displays a decent value of sensitivity in the order of 5.6 µA mM−1 cm−2.FindingsDevelopment of a low-cost array-based integrated and highly flexible microfluidic biochip to extract the quantity of glucose present in human blood.Originality/valuePotential future research opportunities in the realm of integrated miniaturized, low-cost smart biosensing systems may arise from this study.

Enhanced Watermarking for Paper-Based Digital Microfluidic Biochips

Paper-based digital microfluidic biochip (PB-DMFB) technology provides a promising solution to many biochemical applications. However, the PB-DMFB manufacturing process may suffer from potential security threats. For example, a Trojan insertion attack may affect the functionality of PB-DMFBs. To ensure the correct functionality of PB-DMFBs, we propose a watermarking scheme to hide information in the PB-DMFB layout, which allows users to check design integrity and authenticate the source of the PB-DMFB design. As a result, the proposed method serves as a countermeasure against Trojan insertion attacks in addition to proof of authorship.

Electrochemical and Plasmonic Detection of Myocardial Infarction Using Microfluidic Biochip Incorporated with Mesoporous Nanoscaffolds.

This paper reports a microfluidic device for the electrochemical and plasmonic detection of cardiac myoglobin (cMb) and cardiac troponin I (cTnI) with noticeable limits of detection (LoD) as low as a few picograms per milliliter (pg/mL) ranges, achieved in a short detection time. The device features two working electrodes, each with a mesoporous Ni3V2O8 nanoscaffold grafted with reduced graphene oxide (rGO) that improves the interaction of diffusing analyte molecules with the sensing surface by providing a high surface area and reaction kinetics. Electrochemical studies reveal sensitivities as high as 9.68 μA ng/mL and a LoD of 2.0 pg/mL for cTnI, and 8.98 μA ng/mL and 4.7 pg/mL for cMb. Additionally, the surface plasmon resonance (SPR) studies demonstrate a low-level LoD of 8.8 pg/mL for cMb and 7.3 pg/mL for cTnI. The dual-modality sensor enables dynamic tracking of kinetic antigen-antibody interactions during sensing, self-verification through providing signals of two modes, and reduced false readout. This study demonstrates the complementary nature of the electrochemical and SPR modes in biosensing, with the electrochemical mode being highly sensitive and the SPR mode providing superior tracking of molecular recognition behaviors. The presented sensor represents a significant innovation in cardiovascular disease management and can be applied to monitor other clinically important biomolecules.

Physical design for microfluidic biochips considering actual volume management and channel storage

In recent years, microfluidic biochips have been widely applied in various fields of human society. The optimization design of system-architecture based on continuous-flow microfluidic biochips has been widely studied. However, most previous work was based on the traditional chip architecture with dedicated storage, which not only limits the performance of biochips but also increases their manufacturing costs. In order to improve the execution efficiency and reduce the manufacturing cost, a distributed channel-storage architecture can be used to temporarily cache intermediate fluids in idle flow channels. Under this architecture, careful consideration of the volume management of the fluid to be cached is a prerequisite for ensuring the reliability of bioassay results. However, the existing work has not considered the volume management of the fluid to be cached in detail. This may cause the volume of the fluid to not match the capacity of the storage channel, which can contaminate other fluids and lead to incorrect bioassay results or increase the manufacturing cost of biochips due to long storage channels. In this paper, we propose a physical design method for microfluidic biochips that considers the actual volume of fluid while utilizing distributed channel storage. We address this problem by taking a placement and routing co-design strategy throughout the iterative process of the simulated annealing algorithm. Experimental results under multiple benchmarks show that the proposed method can effectively reduce the completion time of bioassays, minimize the flow path length, and decrease the number of intersections.

GNN-Based Concentration Prediction With Variable Input Flow Rates for Microfluidic Mixers.

Recent years have witnessed significant advances brought by microfluidic biochips in automating biochemical protocols. Accurate preparation of fluid samples is an essential component of these protocols, where concentration prediction and generation are critical. Equipped with the advantages of convenient fabrication and control, microfluidic mixers demonstrate huge potential in sample preparation. Although finite element analysis (FEA) is the most commonly used simulation method for accurate concentration prediction of a given microfluidic mixer, it is time-consuming with poor scalability for large biochip sizes. Recently, machine learning models have been adopted in concentration prediction, with great potential in enhancing the efficiency over traditional FEA methods. However, the state-of-the-art machine learning-based method can only predict the concentration of mixers with fixed input flow rates and fixed sizes. In this paper, we propose a new concentration prediction method based on graph neural networks (GNNs), which can predict output concentrations for microfluidic mixters with variable input flow rates. Moreover, a transfer learning method is proposed to transfer the trained model to mixers of different sizes with reduced training data. Experimental results show that, for microfluidic mixers with fixed input flow rates, the proposed method obtains an average reduction of 88% in terms of prediction errors compared with the state-of-the-art method. For microfluidic mixers with variable input flow rates, the proposed method reduces the prediction error by 85% on average. Besides, the proposed transfer learning method reduces the training data by 84% for extending the pre-trained model for microfluidic mixers of different sizes with acceptable prediction error.

Capacity-Aware Wash Optimization with Dynamic Fluid Scheduling and Channel Storage for Continuous-Flow Microfluidic Biochips

Capacity-Aware Wash Optimization with Dynamic Fluid Scheduling and Channel Storage for Continuous-Flow Microfluidic Biochips

Efficient EVs separation and detection by an alumina-nanochannel-array-membrane integrated microfluidic chip and an antibody barcode biochip

BackgroundSmall endosome-derived lipid nanovesicles (30–200 nm) are actively secreted by living cells and serve as pivotal biomarkers for early cancer diagnosis. However, the study of extracellular vesicles (EVs) requires isolation and purification from various body fluids. Although traditional EVs isolation and detection technologies are mature, they usually require large amount of sample, consumes long-time, and have relatively low-throughput. How to efficiently isolate, purify and detect these structurally specific EVs from body fluids with high-throughput remains a great challenge in in vitro diagnostics and clinical research. ResultsHerein, we suggest a nanosized microfluidic device for efficient and economical EVs filtration based on an alumina nanochannel array membrane. We evaluated the filtration device performance of alumina membranes with different diameters and found that an optimized chamber array with a hydrophilic-treated channel diameter of 90 nm could realize a filtration efficiency of up to 82% without any assistance from chemical or physical separation methods. Importantly, by integrating meticulously designed multichannel microfluidic biochips, EVs can be captured in-situ and monitored by antibody barcode biochip. The proposed filtration chip together with the high-throughput detection chip were capable of filtration of a few tens of μL samples and recognition of different phonotypes. The practical filtration and detection of EVs from clinical samples demonstrated the high performance of the device. SignificantOverall, this work provides a cost-effective, highly efficient and automated EVs filtration chip and detection dual-function integrated chip platform, which can directly separate EVs from serum or cerebrospinal fluid with an efficiency of 82% and conduct in-situ detection. This small fluidic device can provide a powerful tool for highly efficient identifying and analyzing EVs, presenting great application potential in clinical detection.

Abstract 7485: Microfluidic detection of dual positive cells in whole blood of metastatic breast cancer patients

Abstract Background. Dual positive cells (DPCs) that express both epithelial markers and leukocytic markers have been observed in peripheral blood of breast cancer patients. DPCs acquire functional behaviors from both cell types which may drive tumor progression. However, the lack of reliable methods to isolate and identify DPCs has hindered the investigation of their origin and clinical implications in breast cancer patients. While microfluidic devices have been widely used for the detection of circulating tumor cells (CTCs) by liquid biopsy, DPC detection is underexplored in these devices. Herein, we demonstrate rapid onchip isolation and detection of DPCs in whole blood samples from metastatic breast cancer (MBC) patients using an integrated microfluidic device. Methods. Our microfluidic device consists of a unique preconditioning component that concentrates targets in whole blood and a downstream cell immobilization component that captures target cells. We included 7 female patients with MBC, of which 29% are white (2), 57% are African American (4), and 14% are Latina (1). The median age is 50y (34y -75y). All patients were undergoing systemic breast cancer therapy at the time of blood collection. A total of 9 samples (4 mL each) were collected from either an antecubital vein (peripheral vein) or the subcutaneous port catheter (central vein) of these patients. All samples were processed within 5 hours of blood drawn in our novel microfluidic biochip. CTCs (EpCAM+/CK+, CD45-, DAPI+) and DPCs (EpCAM+/CK+, CD45+/CD66b+, DAPI+) were identified by immunofluorescence after cells were fixed. Results. Processing of each sample was completed within 40 minutes using our microfluidic device. Both DPCs and CTCs were detected in all the samples (9/9). The average DPC count was 3 DPCs per 4 mL whole blood with a standard deviation of 1.9 cells. The average CTC count was 9 with a standard deviation of 5 per 4 mL whole blood. 89% of the samples (8/9) had > 5 CTCs after the sample volume is scaled to the standard 7.5 mL. No correlation was found between DPC count and CTC count (Pearson correlation coefficient r=0.08). While the blood collection location (central vs peripheral veins) had a significant impact on the CTC count (12.6 vs 4 on average with p<0.01), there was no statistical difference in DPC counts in the samples collected from central and peripheral veins. Conclusions. Both DPCs and CTCs can be rapidly isolated and detected from MBC patient whole blood in our microfluidic device. Our preliminary results indicate no correlation between DPCs and CTCs, suggesting that DPCs might not originate in blood circulation of MBC patients. More work with a larger patient cohort will be needed to further investigate the clinical implications of DPCs on MBC patients. Citation Format: Jian Zhou, Qiyue Luan, Celine Macaraniag, Arielle B. Guzman, Maria Mantice, Oana Danciu, Kent F. Hoskins, Ian Papautsky. Microfluidic detection of dual positive cells in whole blood of metastatic breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7485.

CRISPR/Cas12a powered air-displacement enhanced evanescent wave fluorescence fiber-embedded microfluidic biochip for nucleic acid amplification-free detection of Escherichia coli O157:H7

Simple yet ultrasensitive and contamination-free quantification of environmental pathogenic bacteria is in high demand. In this study, we present a portable clustered regularly interspaced short palindromic repeats-associated protein 12a (CRISPR/Cas12a) powered Air-displacement enhanced Evanescent wave fluorescence Fiber-embedded microfluidic Biochip (AEFB) for the high-frequency and nucleic acid amplification-free ultrasensitive detection of Escherichia coli O157:H7. The performance of AEFB was dramatically enhanced upon employing a simple air-solution displacement process. Theoretical assays demonstrated that air-solution displacement significantly enhances evanescent wave field intensity on the fiber biosensor surface and increases the V-number in tapered fiber biosensors. Consequently, light-matter interaction is strengthened, and fluorescence coupling and collection efficiency are improved, considerably enhancing sensitivity. By integrating the CRISPR biosensing mechanism, AEFB facilitated rapid, accurate, nucleic acid amplification-free detection of E.coli O157:H7 with polymerase chain reaction (PCR)-level sensitivity (176 cfu/mL). To validate its practicality, AEFB was used to detect E.coli O157:H7 in surface water and wastewater. Comparison with RT-PCR showed a strong linear relationship (R2 = 0.9871), indicating the excellent accuracy and reliability of this technology in real applications. AEFB is highly versatile and can be easily extended to detect other pathogenic bacteria, which will significantly promote the high-frequency assessment and early-warning of bacterial contamination in aquatic environments.

A developmental validation of the Quick TargSeq 1.0 integrated system for automated DNA genotyping in forensic science for reference samples.

Analysis of short tandem repeats (STRs) is a global standard method for human identification. Insertion/Deletion polymorphisms (DIPs) can be used for biogeographical ancestry inference. Current DNA typing involves a trained forensic worker operating several specialized instruments in a controlled laboratory environment, which takes 6-8h. We developed the Quick TargSeq 1.0 integrated system (hereinafter abbreviated to Quick TargSeq) for automated generation of STR and DIP profiles from buccal swab samples and blood stains. The system fully integrates the processes of DNA extraction, polymerase chain reaction (PCR) amplification, and electrophoresis separation using microfluidic biochip technology. Internal validation studies were performed using RTyper 21 or DIP 38 chip cartridges with single-source reference samples according to the Scientific Working Group for DNA Analysis Methods guidelines. These results indicated that the Quick TargSeq system can process reference samples and generate STR or DIP profiles in approximately 2h, and the profiles were concordant with those determined using traditional STR or DIP analysis methods. Thus, reproducible and concordant DNA profiles were obtained from reference samples. Throughout the study, no lane-to-lane or run-to-run contamination was observed. The Quick TargSeq system produced full profiles from buccal swabs with at least eight swipes, dried blood spot cards with two 2-mm disks, or 10ng of purified DNA. Potential PCR inhibitors (i.e., coffee, smoking tobacco, and chewing tobacco) did not appear to affect the amplification reactions of the instrument. The overall success rate and concordance rate of 153 samples were 94.12% and 93.44%, respectively, which is comparable to other commercially available rapid DNA instruments. A blind test initiated by a DNA expert group showed that the system can correctly produce DNA profiles with 97.29% genotype concordance with standard bench-processing methods, and the profiles can be uploaded into the national DNA database. These results demonstrated that the Quick TargSeq system can rapidly generate reliable DNA profiles in an automated manner and has the potential for use in the field and forensic laboratories.

Harnessing the advances of MEDA to optimize multi-PUF for enhancing IP security of biochips

Digital microfluidic biochips (DMFBs) have a significant stride in the applications of medicine and the biochemistry in recent years. DMFBs based on micro-electrode-dot-array (MEDA) architecture, as the next-generation DMFBs, aim to overcome drawbacks of conventional DMFBs, such as droplet size restriction, low accuracy, and poor sensing ability. Since the potential market value of MEDA biochips is vast, it is of paramount importance to explore approaches to protect the intellectual property (IP) of MEDA biochips during the development process. In this paper, an IP authentication strategy based on the multi-PUF applied to MEDA biochips is presented, called bioMPUF, consisting of Delay PUF, Split PUF and Countermeasure. The bioMPUF strategy is designed to enhance the non-linearity between challenges and responses of PUFs, making the challenge–response pairs (CRPs) on the MEDA biochips are difficult to be anticipated, thus thwarting IP piracy attacks. Moreover, based on the easy degradation of MEDA biochip electrodes, a countermeasure is proposed to destroy the availability of piracy chips. Experimental results demonstrate the feasibility of the proposed bioMPUF strategy against the brute force attack and modeling attack.

Competitive Immunoassay in a Microfluidic Biochip for In-Field Detection of Abscisic Acid in Grapes.

Viticulture and associated products are an important part of the economy in many countries. However, biotic and abiotic stresses impact negatively the production of grapes and wine. Climate change is in many aspects increasing both these stresses. Routine sample retrievals and analysis tend to be time-consuming and require expensive equipment and skilled personnel to operate. These challenges could be overcome through the development of a miniaturized analytic device for early detection of grapevine stresses in the field. Abscisic acid is involved in several plant processes, including the onset of fruit ripening and tolerance mechanisms against drought stress. This hormone can be detected through a competitive immunoassay and is found in plants in concentrations up to 10-1 mg/mL. A microfluidic platform is developed in this work which can detect a minimum of 10-11 mg/mL of abscisic acid in buffer. Grape samples were tested using the microfluidic system alongside benchmark techniques such as high-performance liquid chromatography. The microfluidic system could detect the increase to 10-5 mg/mL of abscisic acid present in real berry samples at the veraison stage of ripening.

Dynamic Adaptation Using Deep Reinforcement Learning for Digital Microfluidic Biochips

We describe an exciting new application domain for deep reinforcement learning (RL): droplet routing on digital microfluidic biochips (DMFBs). A DMFB consists of a two-dimensional electrode array, and it manipulates droplets of liquid to automatically execute biochemical protocols for clinical chemistry. However, a major problem with DMFBs is that electrodes can degrade over time. The transportation of droplet transportation over these degraded electrodes can fail, thereby adversely impacting the integrity of the bioassay outcome. We demonstrated that the formulation of droplet transportation as an RL problem enables the training of deep neural network policies that can adapt to the underlying health conditions of electrodes and ensure reliable fluidic operations. We describe an RL-based droplet routing solution that can be used for various sizes of DMFBs. We highlight the reliable execution of an epigenetic bioassay with the RL droplet router on a fabricated DMFB. We show that the use of the RL approach on a simple micro-computer (Raspberry Pi 4) leads to acceptable performance for time-critical bioassays. We present a simulation environment based on the OpenAI Gym Interface for RL-guided droplet routing problems on DMFBs. We present results on our study of electrode degradation using fabricated DMFBs. The study supports the degradation model used in the simulator.

Three-Stage Rapid Physical Design Algorithm for Continuous-Flow Microfluidic Biochips Considering Actual Fluid Manipulations

With the continuous development of microfluidic technology, continuous-flow microfluidic biochips (CFMBs) are being increasingly used in the Internet of Things. The automation design of CFMBs has also received widespread attention. The architecture design of CFMBs is divided into a high-level synthesis stage and a physical design stage. Among them, the problem of the physical design stage is very complex. At this stage, the chip architecture is generated based on the device library and a set of flow paths, taking into account the actual fluid manipulations, while minimizing the cost of the chip, such as the number of ports, total length of flow channels, number of flow channel intersections. As fabrication technology advances, the number of devices integrated into CFMBs is increasing. The existing physical design algorithms can no longer meet the design requirements of CFMBs in terms of time. Therefore, we propose a three-stage rapid physical design algorithm for CFMBs considering the actual fluid manipulations. The proposed algorithm includes a port-driven preprocessing stage, a force-directed quadratic placement stage, and a negotiation-based routing stage. In the port-driven preprocessing stage, a port-driven preprocessing algorithm is proposed to generate connection matrices between ports and devices to reduce the number of ports introduced. In the force-directed quadratic placement stage, we model the placement problem as an extremum problem of a quadratic cost function, which mathematically reduces the search space significantly and shortens the running time of the algorithm significantly. In the negotiation-based routing stage, a heuristic negotiation-based routing algorithm and a flow channel strategy that prioritizes the construction of parallel execution are proposed to reduce the running time of the algorithm while ensuring that the number of crossings in the routing solution is close to the optimal solution. Experimental results confirm that our proposed method is able to generate the high-quality solutions quickly. Under general scale problems, compared to the existing method based on ILP, our proposed method achieves a speedup ratio of 23,171 in terms of CPU time and optimizations in terms of number of ports and port reuse of 3.18% and 6.52%, respectively. These optimizations come at the cost of only a slight increase in the number of intersections, the flow length, and the number of flow valves. In addition, our proposed method can effectively solve large-scale problems that cannot be solved by existing method based on ILP.

Architectural Synthesis of Continuous-Flow Microfluidic Biochips with Connection Pair Optimization

Continuous-flow microfluidic biochips are a type of biochip technology based on microfluidic channels that enable various biological experiments and analyses to be performed on a tiny chip. They have the advantages of a high throughput, high sensitivity, high precision, low cost, and quick response. In the architectural synthesis of continuous-flow microfluidic biochips (CFMBs), prior work has not considered reducing component interconnection requirements, which led to an increase in the number of connection pairs. In this paper, we propose an architectural synthesis flow for continuous-flow microfluidic biochips with connection pair optimization, which includes high-level synthesis, placement, and routing. In the high-level synthesis stage, our method reduces the need for component interconnections, which reduces the number of connection pairs. Our method performs fine-grained binding, ultimately obtaining high-quality binding and scheduling results for flow paths. Based on the high-quality binding results, we propose a port placement strategy based on port correlation and subsequently use a quadratic placer to place the components. During the routing stage, we employ a conflict-aware routing algorithm to generate flow channels to reduce conflicts between liquid transportation tasks. Experimental results on multiple benchmarks demonstrate the effectiveness of our method. Compared with the existing work, the proposed algorithm obtains average reductions of 35.34% in connection pairs, 24.30% in flow channel intersections, 21.71% in total flow channel length, and 18.39% in the execution time of bioassays.

Joule heating and electroosmotic flow in cellular micro/nano electroporation.

Localized micro/nano-electroporation (MEP/NEP) shows tremendous potential in cell transfection with high cell viability, precise dose control, and good transfection efficacy. In MEP/NEP, micro or nanochannels are used to tailor the electric field distribution. Cells are positioned tightly by a micron or nanochannel, and the cargoes are delivered into the cell via the channel by electrophoresis (EP). Such confined geometries with micro and nanochannels are also widely used in sorting, isolation, and condensing of biomolecules and cells. Theoretical studies on the electrokinetic phenomena in these applications have been well established. However, for MEP/NEP applications, electrokinetic phenomena and their impact on the cell transfection efficiency and cell survival rate have not been studied comprehensively. In this work, we reveal the coupling between electric field, Joule heating, electroosmosis (EO), and EP in MEP/NEP at different channel sizes. A microfluidic biochip is used to investigate the electrokinetic phenomena in MEP/NEP on a single cell level. Bubble formation is observed at a threshold voltage due to Joule heating. The bubble is pushed to the cargo side due to EO and grows at the outlet of the nanochannel. As the voltage increases, the cargo transport efficiency decreases due to more intense EO, particularly for plasmid DNAs (3.5 kbp) with a low EP mobility. An 'electroporation zone' is defined for NEP/MEP systems with different channel sizes to avoid bubble formation and excessive EO velocity that may reduce the cargo delivery efficiency.

Multiplexed immunosensing of cancer biomarkers on a split-float-gate graphene transistor microfluidic biochip.

This work reports the development of a novel microfluidic biosensor using a graphene field-effect transistor (GFET) design for the parallel label-free analysis of multiple biomarkers. Overcoming the persistent challenge of constructing μm2-sized FET sensitive interfaces that incorporate multiple receptors, we implement a split-float-gate structure that enables the manipulation of multiplexed biochemical functionalization using microfluidic channels. Immunoaffinity biosensing experiments are conducted using the mixture samples containing three liver cancer biomarkers, carcinoembryonic antigen (CEA), α-fetoprotein (AFP), and parathyroid hormone (PTH). The results demonstrate the capability of our label-free biochip to quantitatively detect multiple target biomarkers simultaneously by observing the kinetics in 10 minutes, with the detection limit levels in the nanomolar range. This microfluidic biosensor provides a valuable analytical tool for rapid multi-target biosensing, which can be potentially utilized for domiciliary tests of cancer screening and prognosis, obviating the need for sophisticated instruments and professional operations in hospitals.