Impedimetric Microfluidic Sensor-in-a-Tube for Label-Free Immune Cell Analysis

Modular Design of Functional Glucose Monomer and Block Co-Polymer toward Stable Zn Anodes

Aqueous Zn batteries employing mildly acidic electrolytes have emerged as promising contenders for safe and cost-effective energy storage solutions. Nevertheless, the intrinsic reversibility of the Zn anode becomes a focal concern due to the involvement of acidic electrolyte, which triggers Zn corrosion and facilitates the deposition of insulating byproducts. Moreover, the unregulated growth of Zn over cycling amplifies the risk of internal short-circuiting, primarily induced by the formation of Zn dendrites. In this study, a class of glucose-derived monomers and a block copolymer are synthesized through a building-block assembly strategy, ultimately leading to uncover the optimal polymer structure that suppresses the Zn corrosion while allowing efficient ion conduction with a substantial contribution from cation transport. Leveraging these advancements, remarkable enhancements are achieved in the realm of Zn reversibility, exemplified by a spectrum of performance metrics, including robust cycling stability without voltage overshoot and short-circuiting during 3000 h of cycling, stable operation at a high depth of charge/discharge of 75% and a high current density, >95% Coulombic efficiency over 2000 cycles, successful translation of the anode improvement to full cell performance. These polymer designs offer a transformative path based on the modular synthesis of polymeric coatings toward highly reversible Zn anode.

3D and 4D assembly of functional structures using shape-morphing materials for biological applications

3D structures are crucial to biological function in the human body, driving interest in their in vitro fabrication. Advances in shape-morphing materials allow the assembly of 3D functional materials with the ability to modulate the architecture, flexibility, functionality, and other properties of the final product that suit the desired application. The principles of these techniques correspond to the principles of origami and kirigami, which enable the transformation of planar materials into 3D structures by folding, cutting, and twisting the 2D structure. In these approaches, materials responding to a certain stimulus will be used to manufacture a preliminary structure. Upon applying the stimuli, the architecture changes, which could be considered the fourth dimension in the manufacturing process. Here, we briefly summarize manufacturing techniques, such as lithography and 3D printing, that can be used in fabricating complex structures based on the aforementioned principles. We then discuss the common architectures that have been developed using these methods, which include but are not limited to gripping, rolling, and folding structures. Then, we describe the biomedical applications of these structures, such as sensors, scaffolds, and minimally invasive medical devices. Finally, we discuss challenges and future directions in using shape-morphing materials to develop biomimetic and bioinspired designs.

Self-assembly of Co/Pt stripes with current-induced domain wall motion towards 3D racetrack devices

Modification of the magnetic properties under the induced strain and curvature is a promising avenue to build three-dimensional magnetic devices, based on the domain wall motion. So far, most of the studies with 3D magnetic structures were performed in the helixes and nanowires, mainly with stationary domain walls. In this study, we demonstrate the impact of 3D geometry, strain and curvature on the current-induced domain wall motion and spin-orbital torque efficiency in the heterostructure, realized via a self-assembly rolling technique on a polymeric platform. We introduce a complete 3D memory unit with write, read and store functionality, all based on the field-free domain wall motion. Additionally, we conducted a comparative analysis between 2D and 3D structures, particularly addressing the influence of heat during the electric current pulse sequences. Finally, we demonstrated a remarkable increase of 30% in spin-torque efficiency in 3D configuration.

Nanosensor Chemical Cytometry: Advances and Opportunities in Cellular Therapy and Precision Medicine

With the definition of therapeutics now encompassing transplanted or engineered cells and their molecular products, there is a growing scientific necessity for analytics to understand this new category of drugs. This Perspective highlights the recent development of new measurement science on label-free single cell analysis, nanosensor chemical cytometry (NCC), and their potential for cellular therapeutics and precision medicine. NCC is based on microfluidics integrated with fluorescent nanosensor arrays utilizing the optical lensing effect of a single cell to real-time extract molecular properties and correlate them with physical attributes of single cells. This new class of cytometry can quantify the heterogeneity of the multivariate physicochemical attributes of the cell populations in a completely label-free and nondestructive way and, thus, suggest the vein-to-vein conditions for the safe therapeutic applications. After the introduction of the NCC technology, we suggest the technological development roadmap for the maturation of the new field: from the sensor/chip design perspective to the system/software development level based on hardware automation and deep learning data analytics. The advancement of this new single cell sensing technology is anticipated to aid rich and multivariate single cell data setting and support safe and reliable cellular therapeutics. This new measurement science can lead to data-driven personalized precision medicine.

Label-Free, Impedance-Based Biosensor for Kidney Disease Biomarker Uromodulin

We demonstrate the development of a label-free, impedance-based biosensor by using a passivation layer of 50-nm tantalum pentoxide (Ta2O5) on interdigitated electrodes (IDE). This layer was fabricated by atomic layer deposition (ALD) and has a high dielectric constant (high-κ), which improves the capacitive property of the IDE. We validate the biosensor's performance by measuring uromodulin, a urine biomarker for kidney tubular damage, from artificial urine samples. The passivation layer is functionalized with uromodulin antibodies for selective binding. The passivated IDE enables the non-faradaic impedance measurement of uromodulin concentrations with a measurement range from 0.5 ng/mL to 8 ng/mL and with a relative change in impedance of 15 % per ng/mL at a frequency of 150 Hz (log scale). This work presents a concept for point-of-care biosensing applications for disease biomarkers.

Sensor integration into microfluidic systems: trends and challenges

The combination of sensors and microfluidics has become a promising approach for detecting a wide variety of targets relevant in biotechnology. Thanks to recent advances in the manufacturing of microfluidic systems, microfluidics can be manufactured faster, cheaper, and more accurately than ever before. These advances make microfluidic systems very appealing as a basis for constructing sensor systems, and microfluidic devices have been adapted to house (bio)sensors for various applications (e.g. protein biomarker detection, cell culture oxygen control, and pathogen detection). This review article highlights several successfully integrated microfluidic sensor systems, with a focus on work that has been published within the last two years. Different sensor integration methods are discussed, and the latest trends in wearable- and smartphone-based sensors are described.

Mechanically-Guided 3D Assembly for Architected Flexible Electronics

Architected flexible electronic devices with rationally designed 3D geometries have found essential applications in biology, medicine, therapeutics, sensing/imaging, energy, robotics, and daily healthcare. Mechanically-guided 3D assembly methods, exploiting mechanics principles of materials and structures to transform planar electronic devices fabricated using mature semiconductor techniques into 3D architected ones, are promising routes to such architected flexible electronic devices. Here, we comprehensively review mechanically-guided 3D assembly methods for architected flexible electronics. Mainstream methods of mechanically-guided 3D assembly are classified and discussed on the basis of their fundamental deformation modes (i.e., rolling, folding, curving, and buckling). Diverse 3D interconnects and device forms are then summarized, which correspond to the two key components of an architected flexible electronic device. Afterward, structure-induced functionalities are highlighted to provide guidelines for function-driven structural designs of flexible electronics, followed by a collective summary of their resulting applications. Finally, conclusions and outlooks are given, covering routes to achieve extreme deformations and dimensions, inverse design methods, and encapsulation strategies of architected 3D flexible electronics, as well as perspectives on future applications.

Advances in TEER measurements of biological barriers in microphysiological systems

Biological barriers are multicellular structures that precisely regulate the transport of ions, biomolecules, drugs, cells, and other organisms. Transendothelial/epithelial electrical resistance (TEER) is a label-free method for predicting the properties of biological barriers. Understanding the mechanisms that control TEER significantly enhances our knowledge of the physiopathology of different diseases and aids in the development of new drugs. Measuring TEER values within microphysiological systems called organ-on-a-chip devices that simulate the microenvironment, architecture, and physiology of biological barriers in the body provides valuable insight into the behavior of barriers in response to different drugs and pathogens. These integrated systems should increase the accuracy, reproducibility, sensitivity, resolution, high throughput, speed, cost-effectiveness, and reliable predictability of TEER measurements. Implementing advanced micro and nanoscale manufacturing techniques, surface modification methods, biomaterials, biosensors, electronics, and stem cell biology is necessary for integrating TEER measuring systems with organ-on-chip technology. This review focuses on the applications, advantages, and future perspectives of integrating organ-on-a-chip technology with TEER measurement methods for studying biological barriers. After briefly reviewing the role of TEER in the physiology and pathology of barriers, standard techniques for measuring TEER, including Ohm's law and impedance spectroscopy, and commercially available devices are described. Furthermore, advances in TEER measurement are discussed in multiple barrier-on-a-chip system models representing different organs. Finally, we outline future trends in implementing advanced technologies to design and fabricate nanostructured electrodes, complicated microfluidic chips, and membranes for more advanced and accurate TEER measurements.

Non-contact microfluidic analysis of the stiffness of single large extracellular vesicles from IDH1-mutated glioblastoma cells

In preparation for leveraging extracellular vesicles (EVs) for disease diagnostics and therapeutics, fundamental research is being done to understand EV biological, chemical, and physical properties. Most published studies have investigated nanoscale EVs and focused on EV biochemical content. There is much less understanding of large microscale EV characteristics and EV mechanical properties. We recently introduced a non-contact microfluidic technique that measures the stiffness of large EVs (>1 μm diameter). This pilot study probes the robustness of the microfluidic technique to distinguish between EV populations by comparing stiffness distributions of large EVs derived from glioblastoma cell lines. EVs derived from cells expressing the IDH1 mutation, a common glioblastoma mutation known to disrupt lipid metabolism, were stiffer than those expressed from wild-type cells in a statistical comparison of sample medians. A supporting lipidomics analysis showed that the IDH1 mutation increased the amount of saturated lipids in EVs. Taken together, these data encourage further investigation into the potential of high-throughput microfluidics to distinguish between large EV populations that differ in biomolecular composition. These findings contribute to the understanding of EV biomechanics, in particular for the less studied microscale EVs.

Assembly of complex 3D structures and electronics on curved surfaces

Electronic devices with engineered three-dimensional (3D) architectures are indispensable for frictional-force sensing, wide-field optical imaging, and flow velocity measurement. Recent advances in mechanically guided assembly established deterministic routes to 3D structures in high-performance materials, through controlled rolling/folding/buckling deformations. The resulting 3D structures are, however, mostly formed on planar substrates and cannot be transferred directly onto another curved substrate. Here, we introduce an ordered assembly strategy to allow transformation of 2D thin films into sophisticated 3D structures on diverse curved surfaces. The strategy leverages predefined mechanical loadings that deform curved elastomer substrates into flat/cylindrical configurations, followed by an additional uniaxial/biaxial prestretch to drive buckling-guided assembly. Release of predefined loadings results in an ordered assembly that can be accurately captured by mechanics modeling, as illustrated by dozens of complex 3D structures assembled on curved substrates. Demonstrated applications include tunable dipole antennas, flow sensors inside a tube, and integrated electronic systems capable of conformal integration with the heart.

Electrochemical Cell-based Biosensors for Biomedical Applications

Abstract:

Electrochemical cell-based biosensors have been showing increasing interest within the last 15 years, with a large number of reports generally dealing with the sensors’ sensitivity, selectivity, stability, signal-to-noise ratio, spatiotemporal resolution, etc. However, only a few of them are now available as commercial products on the market. In this review, technological advances, current challenges and opportunities of electrochemical cell-based biosensors are presented. The article encompasses emerging studies, mainly focusing on the last five years (from 2016 to mid 2021), towards cell-based biological field-effect devices, cell-based impedimetric sensors and cell-based microelectrode arrays. In addition, special attention lies on recent progress in recording at the single-cellular level, including intracellular monitoring with high spatiotemporal resolution as well as integration into microfluidics for lab-on-a-chip applications. Moreover, a comprehensive discussion on challenges and future perspectives will address the future potential of electrochemical cell-based biosensors.

Continuous monitoring of molecular biomarkers in microfluidic devices

The ability to monitor molecular targets is crucial in fields ranging from healthcare to industrial processing to environmental protection. Devices employing biomolecules to achieve this goal are called biosensors. Over the last half century researchers have developed dozens of different biosensor approaches. In this chapter we analyze recent advances in the biosensing field aiming at adapting these to the problem of continuous molecular monitoring in complex sample streams, and how the merging of these sensors with lab-on-a-chip technologies would be beneficial to both. To do so we discuss (1) the components that comprise a biosensor, (2) the challenges associated with continuous molecular monitoring in complex sample streams, (3) how different sensing strategies deal with (or fail to deal with) these challenges, and (4) the implementation of these technologies into lab-on-a-chip architectures.

Identifying the grade of bladder cancer cells using microfluidic chips based on impedance

Bladder cancer diagnosis is made by microfluidic chip based-on impedance analysis.

Electronically integrated microcatheters based on self-assembling polymer films

Existing electronically integrated catheters rely on the manual assembly of separate components to integrate sensing and actuation capabilities. This strongly impedes their miniaturization and further integration. Here, we report an electronically integrated self-assembled microcatheter. Electronic components for sensing and actuation are embedded into the catheter wall through the self-assembly of photolithographically processed polymer thin films. With a diameter of only about 0.1 mm, the catheter integrates actuated digits for manipulation and a magnetic sensor for navigation and is capable of targeted delivery of liquids. Fundamental functionalities are demonstrated and evaluated with artificial model environments and ex vivo tissue. Using the integrated magnetic sensor, we develop a strategy for the magnetic tracking of medical tools that facilitates basic navigation with a high resolution below 0.1 mm. These highly flexible and microsized integrated catheters might expand the boundary of minimally invasive surgery and lead to new biomedical applications.

Materials Chemistry of Neural Interface Technologies and Recent Advances in Three-Dimensional Systems

Advances in materials chemistry and engineering serve as the basis for multifunctional neural interfaces that span length scales from individual neurons to neural networks, neural tissues, and complete neural systems. Such technologies exploit electrical, electrochemical, optical, and/or pharmacological modalities in sensing and neuromodulation for fundamental studies in neuroscience research, with additional potential to serve as routes for monitoring and treating neurodegenerative diseases and for rehabilitating patients. This review summarizes the essential role of chemistry in this field of research, with an emphasis on recently published results and developing trends. The focus is on enabling materials in diverse device constructs, including their latest utilization in 3D bioelectronic frameworks formed by 3D printing, self-folding, and mechanically guided assembly. A concluding section highlights key challenges and future directions.

Self-sufficient self-oscillating microsystem driven by low power at low Reynolds numbers

Oscillations at several hertz are a key feature of dynamic behavior of various biological entities, such as the pulsating heart, firing neurons, or the sperm-beating flagellum. Inspired by nature’s fundamental self-oscillations, we use electroactive polymer microactuators and three-dimensional microswitches to create a synthetic electromechanical parametric relaxation oscillator (EMPRO) that relies on the shape change of micropatterned polypyrrole and generates a rhythmic motion at biologically relevant stroke frequencies of up to ~95 Hz. We incorporate an Ag-Mg electrochemical battery into the EMPRO for autonomous operation in a nontoxic environment. Such a self-sufficient self-oscillating microsystem offers new opportunities for artificial life at low Reynolds numbers by, for instance, mimicking and replacing nature’s propulsion and pumping units.

A microfluidic field-effect transistor biosensor with rolled-up indium nitride microtubes

Field-effect-transistor (FET) biosensors capable of rapidly detecting disease-relevant biomarkers have long been considered as a promising tool for point-of-care (POC) diagnosis. Rolled-up nanotechnology, as a batch fabrication strategy for generating three-dimensional (3D) microtubes, has been demonstrated to possess unique advantages for constructing FET biosensors. In this paper, we report a new approach combining the two fascinating technologies, the FET biosensor and the rolled-up microtube, to develop a microfluidic diagnostic biosensor. We integrated an excellent biosensing III-nitride material-indium nitride (InN)-into a rolled-up microtube and used it as the FET channel. The InN possesses strong, intrinsic, and stable electron accumulation (~10¹³ cm^-2) on its surface, thereby providing a high device sensitivity. Multiple rolled-up InN microtube FET biosensors fabricated on the same substrate were integrated with a microfluidic channel for convenient fluids handling, and shared the same external electrode (inserted into the microchannel outlet) for gating voltage modulation. Using human immunodeficiency virus (HIV) antibody as a model disease marker, we characterized the analytical performance of the developed biosensor and achieved a limit of detection (LOD) of 2.5 pM for serum samples spiked with HIV gp41 antibodies. The rolled-up InN microtube FET biosensor represents a new type of III-nitride-based FET biosensor and holds significant potential for practical POC diagnosis.