Universal Microfluidic Automaton for Autonomous Sample Processing: Application to the Mars Organic Analyzer

Controlling Biomedical Devices Using Pneumatic Logic

Many biomedical devices are powered and controlled by electrical components. These electronics add to the cost of a device (possibly making the device too expensive for use in resource-limited or point-of-care settings) and can also render the device unsuitable for use in some environments (for example, high-humidity areas such as incubators where condensation could cause electrical short circuits, ovens where electronic components may overheat, or explosive or flammable environments where electric sparks could cause serious accidents). In this work, we show that pneumatic logic can be used to power and control biomedical devices without the need for electricity or electric components. Originally developed for controlling microfluidic "lab-on-a-chip" devices, these circuits use microfluidic valves like transistors in air-powered logic "circuits." We show that a modification to the basic valve design-adding additional air channels in parallel through the valve-creates a "high-flow" valve that is suitable for controlling a broad range of bioinstruments, not just microfluidics. As a proof-of-concept, we developed a high-flow pneumatic oscillator that uses five high-flow Boolean NOT gates arranged in a loop. Powered by a single constant vacuum source, the oscillator provides five out-of-phase pneumatic outputs that switch between vacuum and atmospheric pressure every 1.3 s. Additionally, a user can adjust the frequency of the oscillator by squeezing a bellows attached to one of the pneumatic outputs. We then used the pneumatic oscillator to power a low-cost 3D-printed laboratory rocker/shaker commonly used to keep blood products, cell cultures, and other heterogeneous samples in suspension. Our air-powered rocker costs around $12 USD to build and performs as well as conventional electronic rockers that cost $1000 USD or more. This is the first of many biomedical devices that can be made cheaper and safer using pneumatic logic.

Microfluidic Nanoparticle Separation for Precision Medicine

A deeper understanding of disease heterogeneity highlights the urgent need for precision medicine. Microfluidics, with its unique advantages, such as high adjustability, diverse material selection, low cost, high processing efficiency, and minimal sample requirements, presents an ideal platform for precision medicine applications. As nanoparticles, both of biological origin and for therapeutic purposes, become increasingly important in precision medicine, microfluidic nanoparticle separation proves particularly advantageous for handling valuable samples in personalized medicine. This technology not only enhances detection, diagnosis, monitoring, and treatment accuracy, but also reduces invasiveness in medical procedures. This review summarizes the fundamentals of microfluidic nanoparticle separation techniques for precision medicine, starting with an examination of nanoparticle properties essential for separation and the core principles that guide various microfluidic methods. It then explores passive, active, and hybrid separation techniques, detailing their principles, structures, and applications. Furthermore, the review highlights their contributions to advancements in liquid biopsy and nanomedicine. Finally, it addresses existing challenges and envisions future development spurred by emerging technologies such as advanced materials science, 3D printing, and artificial intelligence. These interdisciplinary collaborations are anticipated to propel the platformization of microfluidic separation techniques, significantly expanding their potential in precision medicine.

Integrated high performance microfluidic organic analysis instrument for planetary and space exploration

The exploration of our solar system to characterize the molecular organic inventory will enable the identification of potentially habitable regions and initiate the search for biosignatures of extraterrestrial life. However, it is challenging to perform the required high-resolution, high-sensitivity chemical analyses in space and in planetary environments. To address this challenge, we have developed a microfluidic organic analyzer (MOA) instrument that consists of a multilayer programmable microfluidic analyzer (PMA) for fluidic processing at the microliter scale coupled with a microfabricated glass capillary electrophoresis (CE) wafer for separation and analysis of the sample components. Organic analytes are labeled with a functional group-specific (e.g. amine, organic acid, aldehyde) fluorescent dye, separated according to charge and hydrodynamic size by capillary electrophoresis (CE), and detected with picomolar limit of detection (LOD) using laser-induced fluorescence (LIF). Our goal is a sensitive automated instrument and autonomous process that enables sample-in to data-out performance in a flight capable format. We present here the design, fabrication, and operation of a technology development unit (TDU) that meets these design goals with a core mass of 3 kg and a volume of <5 L. MOA has a demonstrated resolution of 2 × 105 theoretical plates for relevant amino acids using a 15 cm long CE channel and 467 V cm-1. The LOD of LIF surpasses 100 pM (0.01 ppb), enabling biosignature detection in harsh environments on Earth. MOA is ideally suited for probing biosignatures in potentially habitable destinations on icy moons such as Europa and Enceladus, and on Mars.

Operation of a programmable microfluidic organic analyzer under microgravity conditions simulating space flight environments

A programmable microfluidic organic analyzer was developed for detecting life signatures beyond Earth and clinical monitoring of astronaut health. Extensive environmental tests, including various gravitational environments, are required to confirm the functionality of this analyzer and advance its overall Technology Readiness Level. This work examines how the programmable microfluidic analyzer performed under simulated Lunar, Martian, zero, and hypergravity conditions during a parabolic flight. We confirmed that the functionality of the programmable microfluidic analyzer was minimally affected by the significant changes in the gravitational field, thus paving the way for its use in a variety of space mission opportunities.

A simple and reliable microfabrication process for a programmable microvalve array

We describe our reliable methodology for fabricating a complex programmable microvalve array (PMA) and its integration with a glass microcapillary electrophoresis chip. This methodology is applicable to any device that requires multilayered PDMS, multiple alignment processes, selective PDMS bonding, and multilayered integration with downstream sensing systems. Along with the detailed step-by-step process, we discuss essential quality assurance checks that can be performed throughout fabrication to assist in troubleshooting and maximizing chip yield.•Comprehensive instructions for designing and fabricating a programmable microvalve array.•Selective bonding of PDMS and glass by microcontact printing.•Numerous quality control procedures to boost chip yield.

Microfluidic Chromatography for Enhanced Amino Acid Detection at Ocean Worlds

Increasing interest in the detection of biogenic signatures, such as amino acids, on icy moons and bodies within our solar system has led to the development of compact in situ instruments. Given the expected dilute biosignatures and high salinities of these extreme environments, purification of icy samples before analysis enables increased detection sensitivity. Herein, we outline a novel compact cation exchange method to desalinate proteinogenic amino acids in solution, independent of the type and concentration of salts in the sample. Using a modular microfluidic device, initial experiments explored operational limits of binding capacity with phenylalanine and three model cations, Na⁺, Mg²⁺, and Ca²⁺. Phenylalanine recovery (94-17%) with reduced conductivity (30-200 times) was seen at high salt-to-amino-acid ratios between 25:1 and 500:1. Later experiments tested competition between mixtures of 17 amino acids and other chemistries present in a terrestrial ocean sample. Recoveries ranged from 11% to 85% depending on side chain chemistry and cation competition, with concentration shown for select high affinity amino acids. This work outlines a nondestructive amino acid purification device capable of coupling to multiple downstream analytical techniques for improved characterization of icy samples at remote ocean worlds.

Microvalve array fabrication using selective PDMS (polydimethylsiloxane) bonding through Perfluorooctyl-trichlorosilane passivation for long-term space exploration

To improve the versatility and robustness of microfluidic analytical devices for space exploration, a programmable microfluidic array (PMA) has been implemented to support a variety of missions. When designing a PMA, normally closed valves are advantageous to avoid cross contamination and leaking. However, a stable fabrication method is required to prevent these valves from sticking and bonding over time. This work presents how polydimethylsiloxane (PDMS) can be bonded selectively using chemical passivation to overcome PDMS sticking issue during long-term space exploration. First, on a PDMS stamp, the vaporized perfluorooctyl-trichlorosilane (PFTCS) are deposited under − 80 kPa and 150 °C conditions. The PFTCS was then transferred onto PDMS or glass substrates by controlling temperature and time and 15 min at 150 °C provides the optimal PFTCS transfer for selective bonding. With these characterized parameters, we successfully demonstrated the fabrication of PMA to support long-term space missions. To estimate the stability of the stamped PFTCS, a PMA has been tested regularly for three years and no stiction or performance alteration was observed. A flight test has been done with a Cessaroni L1395 rocket for high g-force and vibration test and there is no difference on PMA performance after exposure of launch and landing conditions. This work shows promise as a simple and robust technique that will expand the stability and capability of PMA for space exploration.

A comprehensive review on advancements in tissue engineering and microfluidics toward kidney-on-chip

This review provides a detailed literature survey on microfluidics and its road map toward kidney-on-chip technology. The whole review has been tailored with a clear description of crucial milestones in regenerative medicine, such as bioengineering, tissue engineering, microfluidics, microfluidic applications in biomedical engineering, capabilities of microfluidics in biomimetics, organ-on-chip, kidney-on-chip for disease modeling, drug toxicity, and implantable devices. This paper also presents future scope for research in the bio-microfluidics domain and biomimetics domain.

Detection and separation of proteins using micro/nanofluidics devices

Microfluidics is the technology or system wherein the behavior of fluids' is studied onto a miniaturized device composed of chambers and tunnels. In biological and biomedical sciences, microfluidic technology/system or device serves as an ultra-high-output approach capable of detecting and separating the biomolecules present even in trace quantities. Given the essential role of protein, the identification and quantification of proteins help understand the various living systems' biological function regulation. Microfluidics has enormous potential to enable biological investigation at the cellular and molecular level and maybe a fair substitution of the sophisticated instruments/equipment used for proteomics, genomics, and metabolomics analysis. The current advancement in microfluidic systems' development is achieving momentum and opening new avenues in developing innovative and hybrid methodologies/technologies. This chapter attempts to expound the micro/nanofluidic systems/devices for their wide-ranging application to detect and separate protein. It covers microfluidic chip electrophoresis, microchip gel electrophoresis, and nanofluidic systems as protein separation systems, while methods such as spectrophotometric, mass spectrometry, electrochemical detection, magneto-resistive sensors and dynamic light scattering (DLS) are discussed as proteins' detection system.

Sensing Techniques for Organochlorides through Intermolecular Interaction with Bicyclic Amidines

Toxic organochloride molecules are widely used in industry for various purposes. With their high volatility, the direct detection of organochlorides in environmental samples is challenging. Here, a new organochloride detection mechanism using 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) is introduced to simplify a sensing method with higher detection sensitivity. Three types of organochloride compounds-trichloroethylene (TCE), dichloromethane (DCM), and dichlorodiphenyltrichloroethane (DDT)—were targeted to understand DCM conjugation chemistry by using nuclear magnetic resonance (NMR) and liquid chromatography with a mass spectrometer (LC-MS). ¹³C-NMR spectra and LC-MS data indicated that DBN can be labeled on these organochloride compounds by chlorine–nitrogen interaction. Furthermore, to demonstrate the organochloride sensing capability, the labeling yield and limit of detection were determined by a colorimetric assay as well as micellar electrokinetic chromatography (MEKC). The interaction with DBN was most appreciable for TCE, among other organochlorides. TCE was detected at picomolar levels, which is two orders of magnitude lower than the maximum contaminant level set by the United States Environmental Protection Agency. MEKC, in conjunction with this DBN-labeling method, enables us to develop a field-deployable sensing platform for detecting toxic organochlorides with high sensitivity.

A pneumatic random-access memory for controlling soft robots

Pneumatically-actuated soft robots have advantages over traditional rigid robots in many applications. In particular, their flexible bodies and gentle air-powered movements make them more suitable for use around humans and other objects that could be injured or damaged by traditional robots. However, existing systems for controlling soft robots currently require dedicated electromechanical hardware (usually solenoid valves) to maintain the actuation state (expanded or contracted) of each independent actuator. When combined with power, computation, and sensing components, this control hardware adds considerable cost, size, and power demands to the robot, thereby limiting the feasibility of soft robots in many important application areas. In this work, we introduce a pneumatic memory that uses air (not electricity) to set and maintain the states of large numbers of soft robotic actuators without dedicated electromechanical hardware. These pneumatic logic circuits use normally-closed microfluidic valves as transistor-like elements; this enables our circuits to support more complex computational functions than those built from normally-open valves. We demonstrate an eight-bit nonvolatile random-access pneumatic memory (RAM) that can maintain the states of multiple actuators, control both individual actuators and multiple actuators simultaneously using a pneumatic version of time division multiplexing (TDM), and set actuators to any intermediate position using a pneumatic version of analog-to-digital conversion. We perform proof-of-concept experimental testing of our pneumatic RAM by using it to control soft robotic hands playing individual notes, chords, and songs on a piano keyboard. By dramatically reducing the amount of hardware required to control multiple independent actuators in pneumatic soft robots, our pneumatic RAM can accelerate the spread of soft robotic technologies to a wide range of important application areas.

A fully integrated isotachophoresis with a programmable microfluidic platform

Conventional isotachophoresis (ITP) can be used for pre-concentration of a single analyte, but preconcentration of multiple analytes is time consuming due to handling and washing steps required for the extensive buffer optimization procedure. In this work, we present a programmable microfluidic platform (PMP) to demonstrate fully automated optimization of ITP of multiple analytes. By interfacing a PMP with ITP, buffer selection and repetitive ITP procedures were automated. Using lifting-gate microvalve technology, a PMP consisting of a two-dimensional microvalve array was designed and fabricated for seamless integration with an ITP chip. The microvalve array was used for basic liquid manipulation such as metering, mixing, selecting, delivering, and washing procedures to prime and run ITP. Initially, the performances of the PMP and ITP channel were validated individually by estimating volume per pumping cycle and preconcentrating Alexa Fluor 594 with appropriate trailing (TE) and leading (LE) buffers, respectively. After confirming basic functions, autonomous ITP was demonstrated using multiple analytes (Pacific blue, Alexa Fluor 594, and Alexa Fluor 488). The optimal buffer combination was was determined by performing multiple ITP runs with three different TEs (borate, HEPES, and phosphate buffers) and three different concentrations of Tris-HCl for the LE. We found that 40 mM borate and 100 mM Tris-HCl successfully preconcentrated all analytes during a single ITP run. The integrated PMP-ITP system can simplify overall buffer selection and validation procedures for various biological and chemical target samples. Furthermore, by incorporating analytical tools that interconnect with the PMP, it can provide high sample concentrations to aid in downstream analysis.

Lab-on-a-chip technology for in situ combined observations in oceanography

The oceans sustain the global environment and diverse ecosystems through a variety of biogeochemical processes and their complex interactions. In order to understand the dynamism of the local or global marine environments, multimodal combined observations must be carried out in situ. On the other hand, instrumentation of in situ measurement techniques enabling biological and/or biochemical combined observations is challenging in aquatic environments, including the ocean, because biochemical flow analyses require a more complex configuration than physicochemical electrode sensors. Despite this technical hurdle, in situ analyzers have been developed to measure the concentrations of seawater contents such as nutrients, trace metals, and biological components. These technologies have been used for cutting-edge ocean observations to elucidate the biogeochemical properties of water mass with a high spatiotemporal resolution. In this context, the contribution of lab-on-a-chip (LoC) technology toward the miniaturization and functional integration of in situ analyzers has been gaining momentum. Due to their mountability, in situ LoC technologies provide ideal instrumentation for underwater analyzers, especially for miniaturized underwater observation platforms. Consequently, the appropriate combination of reliable LoC and underwater technologies is essential to realize practical in situ LoC analyzers suitable for underwater environments, including the deep sea. Moreover, the development of fundamental LoC technologies for underwater analyzers, which operate stably in extreme environments, should also contribute to in situ measurements for public or industrial purposes in harsh environments as well as the exploration of the extraterrestrial frontier.

Characterization and Optimization of Isotachophoresis Parameters for Pacific Blue Succinimidyl Ester Dye on a PDMS Microfluidic Chip

Isotachophoresis (ITP) for Pacific Blue (PB) dye using a polydimethylsiloxane (PDMS) microfluidic chip is developed and characterized by determining the types and concentrations of electrolytes, the ITP duration, and the electric field density. Among candidate buffers for the trailing electrolyte (TE) and leading electrolyte (LE), 40 mM borate buffer (pH 9) and 200 mM trisaminomethane hydrochloride (Tris-HCl) (pH 8) were selected to obtain the maximum preconcentration and resolution of the PB bands, respectively. With the selected TE and LE buffers, further optimization was performed to determine the electric field (EF) density and the ITP duration. These ITP parameters showed a 20–170,000 preconcentration ratio from initial PB concentrations of 10 nM–100 fM. Further demonstration was implemented to preconcentrate PB-conjugated lactate dehydrogenase (LDH) using the PDMS microfluidic chip. By utilizing the quenching nature of PB-LDH conjugation, we were able to identify concentrations of LDH as low as 10 ng/mL. This simple PDMS microfluidic chip-based ITP for PB preconcentration enables highly sensitive biological and chemical analyses by coupling with various downstream detection systems.

3× multiplexed detection of antibiotic resistant plasmids with single molecule sensitivity

Bacterial pathogens resistant to antibiotics have become a serious health threat. Those species which have developed resistance against multiple drugs such as the carbapenems, are more lethal as these are last line therapy antibiotics. Current diagnostic tests for these resistance traits are based on singleplex target amplification techniques which can be time consuming and prone to errors. Here, we demonstrate a chip based optofluidic system with single molecule sensitivity for amplification-free, multiplexed detection of plasmids with genes corresponding to antibiotic resistance, within one hour. Rotating disks and microfluidic chips with functionalized polymer monoliths provided the upstream sample preparation steps to selectively extract these plasmids from blood spiked with E. coli DH5α cells. Waveguide-based spatial multiplexing using a multi-mode interference waveguide on an optofluidic chip was used for parallel detection of three different carbapenem resistance genes. These results point the way towards rapid, amplification-free, multiplex analysis of antibiotic-resistant pathogens.

A modular, easy-to-use microcapillary electrophoresis system with laser-induced fluorescence for quantitative compositional analysis of trace organic molecules

Microcapillary electrophoresis (μCE) enables high-resolution separations in miniaturized, automated microfluidic devices. Pairing this powerful separation technique with laser-induced fluorescence (LIF) enables a highly sensitive, quantitative, and compositional analysis of organic molecule monomers and short polymers, which are essential, ubiquitous components of life on Earth. Improving methods for their detection has applications to multiple scientific fields, particularly those related to medicine, industry, and space science. Here, a modular benchtop system using μCE with LIF detection was constructed and tested by analyzing standard amino acid samples of valine, serine, alanine, glycine, glutamic acid, and aspartic acid in multiple borate buffered solutions of increasing concentrations from 10 mM to 50 mM, all pH 9.5. The 35 mM borate buffer solution generated the highest resolution before Joule heating dominated. The limits of detection of alanine and glycine using 35 mM borate buffer were found to be 2.12 nM and 2.91 nM, respectively, comparable to other state-of-the-art μCE-LIF instruments. This benchtop system is amenable to a variety of detectors, including a photomultiplier tube, a silicon photomultiplier, or a spectrometer, and currently employs a spectrometer for facile multi-wavelength detection. Furthermore, the microdevice is easily exchanged to fit the desired application of the system, and optical components within the central filter cube can be easily replaced to target alternative fluorescent dyes. This work represents a significant step forward for the analysis of small organic molecules and biopolymers using μCE-LIF systems.

A practical guide to rapid-prototyping of PDMS-based microfluidic devices: A tutorial

Micro total analytical systems (μTAS) are attractive to multiple fields that include chemistry, medicine and engineering due to their portability, low power usage, potential for automation, and low sample and reagent consumption, which in turn results in low waste generation. The development of fully-functional μTAS is an iterative process, based on the design, fabrication and testing of multiple prototype microdevices. Typically, microfabrication protocols require a week or more of highly-skilled personnel time in high-maintenance cleanroom facilities, which makes this iterative process cost-prohibitive in many locations worldwide. Rapid-prototyping tools, in conjunction with the use of polydimethylsiloxane (PDMS), enable rapid development of microfluidic structures at lower costs, circumventing these issues in conventional microfabrication techniques. Multiple rapid-prototyping methods to fabricate PDMS-based microfluidic devices have been demonstrated in literature since the advent of soft-lithography in 1998; each method has its unique advantages and drawbacks. Here, we present a tutorial discussing current rapid-prototyping techniques to fabricate PDMS-based microdevices, including soft-lithography, print-and-peel and scaffolding techniques, among other methods, specifically comparing resolution of the features, fabrication processes and associated costs for each technique. We also present thoughts and insights towards each step of the iterative microfabrication process, from design to testing, to improve the development of fully-functional PDMS-based microfluidic devices at faster rates and lower costs.

Fabrication of high-quality glass microfluidic devices for bioanalytical and space flight applications

Microfabricated glass microfluidic and Capillary Electrophoresis (CE) devices have been utilized in a wide variety of applications over the past thirty years. At the Berkeley Space Sciences Laboratory, we are working to further expand this technology by developing analytical instruments to chemically explore our solar system. This effort requires improving the quality and reliability of glass microfabrication through quality control procedures at every stage of design and manufacture. This manuscript provides detailed information on microfabrication technology for the production of high-quality glass microfluidic chips in compliance with industrial standards and space flight instrumentation quality control.•

The methodological protocol provided in this paper includes the scope of each step of the manufacturing process, materials and technologies recommended and the specific challenges that often confront the process developer.

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Types and sources of fabrication error at every stage have been identified and their solutions have been proposed and verified.

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We present robust and rigorous manufacturing and quality control procedures that will assist other researchers in achieving the highest possible quality glass microdevices using the latest apparatus in a routine and reliable fashion.

Recent progress, challenges, and prospects of fully integrated mobile and wearable point-of-care testing systems for self-testing

The rapid growth of research in the areas of chemical and biochemical sensors, lab-on-a-chip, mobile technology, and wearable electronics offers an unprecedented opportunity in the development of mobile and wearable point-of-care testing (POCT) systems for self-testing. Successful implementation of such POCT technologies leads to minimal user intervention during operation to reduce user errors; user-friendly, easy-to-use and simple detection platforms; high diagnostic sensitivity and specificity; immediate clinical assessment; and low manufacturing and consumables costs. In this review, we discuss recent developments in the field of highly integrated mobile and wearable POCT systems. In particular, aspects of sample handling platforms, recognition elements and sensing methods, and new materials for signal transducers and powering devices for integration into mobile or wearable POCT systems will be highlighted. We also summarize current challenges and future prospects for providing personal healthcare with sample-in result-out mobile and wearable POCT.

Primary Step Towards In Situ Detection of Chemical Biomarkers in the UNIVERSE via Liquid-Based Analytical System: Development of an Automated Online Trapping/Liquid Chromatography System

The search for biomarkers in our solar system is a fundamental challenge for the space research community. It encompasses major difficulties linked to their very low concentration levels, their ambiguous origins (biotic or abiotic), as well as their diversity and complexity. Even if, in 40 years’ time, great improvements in sample pre-treatment, chromatographic separation and mass spectrometry detection have been achieved, there is still a need for new in situ scientific instrumentation. This work presents an original liquid chromatographic system with a trapping unit dedicated to the one-pot detection of a large set of non-volatile extra-terrestrial compounds. It is composed of two units, monitored by a single pump. The first unit is an online trapping unit able to trap polar, apolar, monomeric and polymeric organics. The second unit is an online analytical unit with a high-resolution Q-Orbitrap mass spectrometer. The designed single pump system was as efficient as a laboratory dual-trap LC system for the analysis of amino acids, nucleobases and oligopeptides. The overall setup significantly improves sensitivity, providing limits of detection ranging from ppb to ppt levels, thus meeting with in situ enquiries.

Integration of sample preparation and analysis into an optofluidic chip for multi-target disease detection

Detection of molecular biomarkers with high specificity and sensitivity from biological samples requires both sophisticated sample preparation and subsequent analysis. These tasks are often carried out on separate platforms which increases required sample volumes and the risk of errors, sample loss, and contamination. Here, we present an optofluidic platform which combines an optical detection section with single nucleic acid strand sensitivity, and a sample processing unit capable of on-chip, specific extraction and labeling of nucleic acid and protein targets in complex biological matrices. First, on-chip labeling and detection of individual lambda DNA molecules down to concentrations of 8 fM is demonstrated. Subsequently, we demonstrate the simultaneous capture, fluorescence tagging and detection of both Zika specific nucleic acid and NS-1 protein targets in both buffer and human serum. We show that the dual DNA and protein assay allows for successful differentiation and diagnosis of Zika against cross-reacting species like dengue.

A microfluidic cardiac flow profile generator for studying the effect of shear stress on valvular endothelial cells

To precisely investigate the mechanobiological responses of valvular endothelial cells, we developed a microfluidic flow profile generator using a pneumatically-actuated micropump consisting of microvalves of various sizes. By controlling the closing pressures and the actuation times of these microvalves, we modulated the magnitude and frequency of the shear stress to mimic mitral and aortic inflow profiles with frequencies in the range of 0.8-2 Hz and shear stresses up to 20 dyn cm-2. To demonstrate this flow profile generator, aortic inflow with an average of 5.9 dyn cm-2 shear stress at a frequency of 1.2 Hz with a Reynolds number of 2.75, a Womersley number of 0.27, and an oscillatory shear index (OSI) value of 0.2 was applied to porcine aortic valvular endothelial cells (PAVECs) for mechanobiological studies. The cell alignment, cell elongation, and alpha-smooth muscle actin (αSMA) expression of PAVECs under perfusion, steady flow, and aortic inflow conditions were analyzed to determine their shear-induced cell migration and trans-differentiation. In this morphological and immunocytochemical study, we found that the PAVECs elongated and aligned themselves perpendicular to the directions of the steady flow and the aortic inflow. In contrast, under perfusion with a fluidic shear stress of 0.47 dyn cm-2, the PAVECs elongated and aligned themselves parallel to the direction of flow. The PAVECs exposed to the aortic inflow upregulated their αSMA-protein expression to a greater degree than those exposed to perfusion and steady flow. By comparing these results to those of previous studies of pulsatile flow, we also found that the ratio of positive to negative shear stress plays an important role in determining PAVECs' trans-differentiation and adaptation to flow. This microfluidic cardiac flow profile generator will enable future valvular mechanobiological studies to determine the roles of magnitude and frequency of shear stresses.

A microengineered human corneal epithelium-on-a-chip for eye drops mass transport evaluation

Animals are commonly used for pharmacokinetic studies which are the most frequent events tested during ocular drug development and preclinical evaluation. Inaccuracy, cost, and ethical criticism in these tests have created a need to construct an in vitro model for studying corneal constraints. In this work, a porous membrane embedded microfluidic platform is fabricated that separates a chip into an apical and basal side. After functionalizing the membrane surface with fibronectin, the membrane's mechanical and surface properties are measured to ensure correct modeling of in vivo characteristics. Immortalized human corneal epithelial cells are cultured on the membrane to create a microengineered corneal epithelium-on-a-chip (cornea chip) that is validated with experiments designed to test the barrier properties of the human corneal epithelium construct using model drugs. A pulsatile flow model is used that closely mimics the ocular precorneal constraints and is reasonable for permeability analysis that models in vivo conditions. This model can be used for preclinical evaluations of potential therapeutic drugs and to mimic the environment of the human cornea.

An automated optofluidic biosensor platform combining interferometric sensors and injection moulded microfluidics

A primary limitation preventing practical implementation of photonic biosensors within point-of-care platforms is their integration with fluidic automation subsystems. For most diagnostic applications, photonic biosensors require complex fluid handling protocols; this is especially prominent in the case of competitive immunoassays, commonly used for detection of low-concentration, low-molecular weight biomarkers. For this reason, complex automated microfluidic systems are needed to realise the full point-of-care potential of photonic biosensors. To fulfil this requirement, we propose an on-chip valve-based microfluidic automation module, capable of automating such complex fluid handling. This module is realised through application of a PDMS injection moulding fabrication technique, recently described in our previous work, which enables practical fabrication of normally closed pneumatically actuated elastomeric valves. In this work, these valves are configured to achieve multiplexed reagent addressing for an on-chip diaphragm pump, providing the sample and reagent processing capabilities required for automation of cyclic competitive immunoassays. Application of this technique simplifies fabrication and introduces the potential for mass production, bringing point-of-care integration of complex automated microfluidics into the realm of practicality. This module is integrated with a highly sensitive, label-free bimodal waveguide photonic biosensor, and is demonstrated in the context of a proof-of-concept biosensing assay, detecting the low-molecular weight antibiotic tetracycline.

Microengineered biomimetic ocular models for ophthalmological drug development

Current ophthalmological drug discovery and testing methods have limitations and concerns regarding reliability, ethicality, and applicability. These drawbacks can be mitigated by developing biomimetic eye models through mathematical and experimental methods which are often referred to as "eye-on-a-chip" or "eye chip". These eye chip technologies emulate ocular physiology, anatomy, and microenvironmental conditions. Such models enable understanding of the fundamental biology, pharmacology, and toxicology mechanisms by investigating the pharmacokinetics and pharmacodynamics of various candidate drugs under ocular anatomical and physiological conditions without animal models. This review provides a comprehensive overview of the latest advances in theoretical and in vitro experimental models of the anterior segment of the eye and its microenvironment, including eye motions and tear film dynamics. The current state of ocular modeling and simulation from predictive models to experimental models is discussed in detail with their advantages and limitations. The potential for future eye chip models to expedite new ophthalmic drug discoveries is also discussed.

Multiplexed efficient on-chip sample preparation and sensitive amplification-free detection of Ebola virus

An automated microfluidic sample preparation multiplexer (SPM) has been developed and evaluated for Ebola virus detection. Metered air bubbles controlled by microvalves are used to improve bead-solution mixing thereby enhancing the hybridization of the target Ebola virus RNA with capture probes bound to the beads. The method uses thermally stable 4-formyl benzamide functionalized (4FB) magnetic beads rather than streptavidin coated beads with a high density of capture probes to improve the target capture efficiency. Exploiting an on-chip concentration protocol in the SPM and the single molecule detection capability of the antiresonant reflecting optical waveguide (ARROW) biosensor chip, a detection limit of 0.021pfu/mL for clinical samples is achieved without target amplification. This RNA target capture efficiency is two orders of magnitude higher than previous results using streptavidin beads and the limit of detection (LOD) improves 10×. The wide dynamic range of this technique covers the whole clinically applicable concentration range. In addition, the current sample preparation time is ~1h which is eight times faster than previous work. This multiplexed, miniaturized sample preparation microdevice establishes a key technology that intended to develop next generation point-of-care (POC) detection system.

A fully automated microfluidic micellar electrokinetic chromatography analyzer for organic compound detection

An integrated microfluidic chemical analyzer utilizing micellar electrokinetic chromatography (MEKC) is developed using a pneumatically actuated Lifting-Gate microvalve array and a capillary zone electrophoresis (CZE) chip. Each of the necessary liquid handling processes such as metering, mixing, transferring, and washing steps are performed autonomously by the microvalve array. In addition, a method is presented for automated washing of the high resistance CZE channel for device reuse and periodic automated in situ analyses. To demonstrate the functionality of this MEKC platform, amino acids and thiols are labeled and efficiently separated via a fully automated program. Reproducibility of the automated programs for sample labeling and periodic in situ MEKC analysis was tested and found to be equivalent to conventional sample processing techniques for capillary electrophoresis analysis. This platform enables simple, portable, and automated chemical compound analysis which can be used in challenging environments.

Pneumatically actuated microvalve circuits for programmable automation of chemical and biochemical analysis

Programmable microfluidic platforms (PMPs) are enabling significant advances in the utility of microfluidics for chemical and biochemical analysis. Traditional microfluidic devices are analogous to application-specific devices--a new device is needed to implement each new chemical or biochemical assay. PMPs are analogous to digital electronic processors--all that is needed to implement a new assay is a change in the order of operations conducted by the device. In this review, we introduce PMPs based on normally-closed microvalves. We discuss recent applications of PMPs in diverse fields including genetic analysis, antibody-based biomarker analysis, and chemical analysis in planetary exploration. Prospects, challenges, and future concepts for this emerging technology will also be presented.

End-to-end automated microfluidic platform for synthetic biology: from design to functional analysis

Background

Synthetic biology aims to engineer biological systems for desired behaviors. The construction of these systems can be complex, often requiring genetic reprogramming, extensive de novo DNA synthesis, and functional screening.

Results

Herein, we present a programmable, multipurpose microfluidic platform and associated software and apply the platform to major steps of the synthetic biology research cycle: design, construction, testing, and analysis. We show the platform’s capabilities for multiple automated DNA assembly methods, including a new method for Isothermal Hierarchical DNA Construction, and for Escherichia coli and Saccharomyces cerevisiae transformation. The platform enables the automated control of cellular growth, gene expression induction, and proteogenic and metabolic output analysis.

Conclusions

Taken together, we demonstrate the microfluidic platform’s potential to provide end-to-end solutions for synthetic biology research, from design to functional analysis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13036-016-0024-5) contains supplementary material, which is available to authorized users.

Fabrication of complex PDMS microfluidic structures and embedded functional substrates by one-step injection moulding

We report a novel injection moulding technique for fabrication of complex multi-layer microfluidic structures, allowing one-step robust integration of functional components with microfluidic channels and fabrication of elastomeric valves.

Implementation of microchip electrophoresis instrumentation for future spaceflight missions

We present a comprehensive discussion of the role that microchip electrophoresis (ME) instrumentation could play in future NASA missions of exploration, as well as the current barriers that must be overcome to make this type of chemical investigation possible. We describe how ME would be able to fill fundamental gaps in our knowledge of the potential for past, present, or future life beyond Earth. Despite the great promise of ME for ultrasensitive portable chemical analysis, to date, it has never been used on a robotic mission of exploration to another world. We provide a current snapshot of the technology readiness level (TRL) of ME instrumentation, where the TRL is the NASA systems engineering metric used to evaluate the maturity of technology, and its fitness for implementation on missions. We explain how the NASA flight implementation process would apply specifically to ME instrumentation, and outline the scientific and technology development issues that must be addressed for ME analyses to be performed successfully on another world. We also outline research demonstrations that could be accomplished by independent researchers to help advance the TRL of ME instrumentation for future exploration missions. The overall approach described here for system development could be readily applied to a wide range of other instrumentation development efforts having broad societal and commercial impact.

3D printed microfluidic devices with integrated valves

We report the successful fabrication and testing of 3D printed microfluidic devices with integrated membrane-based valves. Fabrication is performed with a low-cost commercially available stereolithographic 3D printer. Horizontal microfluidic channels with designed rectangular cross sectional dimensions as small as 350 μm wide and 250 μm tall are printed with 100% yield, as are cylindrical vertical microfluidic channels with 350 μm designed (210 μm actual) diameters. Based on our previous work [Rogers et al., Anal. Chem. 83, 6418 (2011)], we use a custom resin formulation tailored for low non-specific protein adsorption. Valves are fabricated with a membrane consisting of a single build layer. The fluid pressure required to open a closed valve is the same as the control pressure holding the valve closed. 3D printed valves are successfully demonstrated for up to 800 actuations.

Biomimetic cardiac microsystems for pathophysiological studies and drug screens

Microfabricated organs-on-chips consist of tissue-engineered 3D in vitro models, which rely on engineering design and provide the physiological context of human organs. Recently, significant effort has been devoted to the creation of a biomimetic cardiac system by using microfabrication techniques. By applying allometric scaling laws, microengineered cardiac systems simulating arterial flow, pulse properties, and architectural environments have been implemented, allowing high-throughput pathophysiological experiments and drug screens. In this review, we illustrate the recent trends in cardiac microsystems with emphasis on cardiac pumping and valving functions. We report problems and solutions brought to light by existing organs-on-chip models and discuss future directions of the field. We also describe the needs and desired design features that will enable the control of mechanical, electrical, and chemical environments to generate functional in vitro cardiac disease models.

Present state of microchip electrophoresis: state of the art and routine applications

Microchip electrophoresis (MCE) was one of the earliest applications of the micro-total analysis system (μ-TAS) concept, whose aim is to reduce analysis time and reagent and sample consumption while increasing throughput and portability by miniaturizing analytical laboratory procedures onto a microfluidic chip. More than two decades on, electrophoresis remains the most common separation technique used in microfluidic applications. MCE-based instruments have had some commercial success and have found application in many disciplines. This review will consider the present state of MCE including recent advances in technology and both novel and routine applications in the laboratory. We will also attempt to assess the impact of MCE in the scientific community and its prospects for the future.

Integration of programmable microfluidics and on-chip fluorescence detection for biosensing applications

We describe the integration of an actively controlled programmable microfluidic sample processor with on-chip optical fluorescence detection to create a single, hybrid sensor system. An array of lifting gate microvalves (automaton) is fabricated with soft lithography, which is reconfigurably joined to a liquid-core, anti-resonant reflecting optical waveguide (ARROW) silicon chip fabricated with conventional microfabrication. In the automaton, various sample handling steps such as mixing, transporting, splitting, isolating, and storing are achieved rapidly and precisely to detect viral nucleic acid targets, while the optofluidic chip provides single particle detection sensitivity using integrated optics. Specifically, an assay for detection of viral nucleic acid targets is implemented. Labeled target nucleic acids are first captured and isolated on magnetic microbeads in the automaton, followed by optical detection of single beads on the ARROW chip. The combination of automated microfluidic sample preparation and highly sensitive optical detection opens possibilities for portable instruments for point-of-use analysis of minute, low concentration biological samples.

Microfluidic Valves Made From Polymerized Polyethylene Glycol Diacrylate

Pneumatically actuated, non-elastomeric membrane valves fabricated from polymerized polyethylene glycol diacrylate (poly-PEGDA) have been characterized for temporal response, valve closure, and long-term durability. A ~100 ms valve opening time and a ~20 ms closure time offer valve operation as fast as 8 Hz with potential for further improvement. Comparison of circular and rectangular valve geometries indicates that the surface area for membrane interaction in the valve region is important for valve performance. After initial fabrication, the fluid pressure required to open a closed circular valve is ~50 kPa higher than the control pressure holding the valve closed. However, after ~1000 actuations to reconfigure polymer chains and increase elasticity in the membrane, the fluid pressure required to open a valve becomes the same as the control pressure holding the valve closed. After these initial conditioning actuations, poly-PEGDA valves show considerable robustness with no change in effective operation after 115,000 actuations. Such valves constructed from non-adsorptive poly-PEGDA could also find use as pumps, for application in small volume assays interfaced with biosensors or impedance detection, for example.

Microfluidics-assisted in vitro drug screening and carrier production

Microfluidic platforms provide several unique advantages for drug development. In the production of drug carriers, physical properties such as size and shape, and chemical properties such as drug composition and pharmacokinetic parameters, can be modified simply and effectively by tuning the flow rate and geometries. Large numbers of carriers can then be fabricated with minimal effort and with little to no batch-to-batch variation. Additionally, cell or tissue culture models in microfluidic systems can be used as in vitro drug screening tools. Compared to in vivo animal models, microfluidic drug screening platforms allow for high-throughput and reproducible screening at a significantly lower cost, and when combined with current advances in tissue engineering, are also capable of mimicking native tissues. In this review, various microfluidic platforms for drug and gene carrier fabrication are reviewed to provide guidelines for designing appropriate carriers. In vitro microfluidic drug screening platforms designed for high-throughput analysis and replication of in vivo conditions are also reviewed to highlight future directions for drug research and development.

Metal sulfide-functionalized DNA concatamer for ultrasensitive electronic monitoring of ATP using a programmable capillary-based aptasensor

A new flow-through electrochemical aptasensor was designed for ultrasensitive monitoring of adenosine triphosphate (ATP) by coupling microvalve-programmable capillary column with CdS-functionalized DNA concatamer for signal amplification. Initially, a layer of primary DNA-conjugated polyacrylamide hydrogel was covalently linked onto the internal surface of capillary column, and then an automated sequenctial injection format with a syringe pump was employed for development of the programmable capillary-based aptasensor. In the presence of target DNA aptamer, the immobilized primary DNA hybridized with partial bases of the aptamer. The excess aptamer fregment could trigger the formation of DNA concatamer between auxiliary DNA1 and CdS-labeled auxiliary DNA2. Upon target ATP introduction, a specific ATP-aptamer reaction was excuated, thereby resulting in the release of CdS-functionalized DNA concatamer from the capillary. Subsenquent anodic stripping voltammetric detection of cadmium released under acidic conditions from the released CdS nanoparticles could be conducted in a homemade detection cell. Under optimal conditions, the dynamic concentration range spanned from 0.1 pM to 10nM ATP with a detection limit of 0.06 pM ATP. The electrochemical aptasensor showed good reproducibility, selectivity, and stability. In addition, the methodology was evaluated for the analysis of ATP spiked serum samples, and the recoveries was 81-140%.