Experimental electrochemistry offers unique opportunities for interactive instruction at all levels of education; however, widespread adoption in curricula is hindered by high costs associated with ...electrochemical instrumentation. Thus, the development of affordable instruments represents an essential step toward making electrochemistry accessible to everyone. While numerous commercially available three-electrode potentiostats exist, two-electrode potentiostats provide a simple and inexpensive alternative. Herein, we present the two-electrode SweepStat as a low-cost option capable of performing voltammetry and amperometry with comparable data acquisition to commercially available potentiostats valued from $4,000–40,000 USD. Additionally, the SweepStat’s design facilitates current measurements in the nanoampere regime, permitting experiments with ultramicroelectrodes (UMEs; r electrode < 25 μm). The fabrication, programming, and testing of this device constitute a valuable experimental exercise at the intersection of circuit design and construction, computer programing, and electrochemical analysis. A set of simple electrochemical experiments are presented for both macroelectrodes and UMEs, highlighting key electrochemical techniques, equations, and concepts. Furthermore, finite element modeling and commercial potentiostat comparisons are used to verify the efficacy of the SweepStat platform. The open-source nature of the SweepStat coupled with the wealth of electrochemical techniques and experiments that can be implemented with a simple two-electrode circuit offers an unparalleled opportunity for electrochemical instruction with extensive method development driven by student research.
Ratcheting effects play an important role in systems ranging from mechanical socket wrenches to biological motor proteins. The underlying principle is to convert a fluctuating, unbiased force into ...unidirectional motion. Here, we report the ratcheting of electrons at room temperature using a semiconductor nanowire with precisely engineered asymmetry. Modulation of the nanowire diameter creates a cylindrical sawtooth geometry with broken inversion symmetry on a nanometer-length scale. In a two-terminal device, this structure responded as a three-dimensional geometric diode that funnels electrons preferentially in one direction through specular reflection of quasi-ballistic electrons at the nanowire surface. The ratcheting effect causes charge rectification at frequencies exceeding 40 gigahertz, demonstrating the potential for applications such as high-speed data processing and long-wavelength energy harvesting.
Over the last several decades, fast-scan cyclic voltammetry (FSCV) has proved to be a valuable analytical tool for the real-time measurement of neurotransmitter dynamics in vitro and in vivo. Indeed, ...FSCV has found application in a wide variety of disciplines including electrochemistry, neurobiology, and behavioral psychology. The maturation of FSCV as an in vivo technique led users to pose increasingly complex questions that require a more sophisticated experimental design. To accommodate recent and future advances in FSCV application, our lab has developed High Definition Cyclic Voltammetry (HDCV). HDCV is an electrochemical software suite that includes data acquisition and analysis programs. The data collection program delivers greater experimental flexibility and better user feedback through live displays. It supports experiments involving multiple electrodes with customized waveforms. It is compatible with transistor–transistor logic-based systems that are used for monitoring animal behavior, and it enables simultaneous recording of electrochemical and electrophysiological data. HDCV analysis streamlines data processing with superior filtering options, seamlessly manages behavioral events, and integrates chemometric processing. Furthermore, analysis is capable of handling single files collected over extended periods of time, allowing the user to consider biological events on both subsecond and multiminute time scales. Here we describe and demonstrate the utility of HDCV for in vivo experiments.
Nanoscale electrophoresis allows for unique separations of single molecules, such as DNA/RNA nucleobases, and thus has the potential to be used as single molecular sensors for exonuclease sequencing. ...For this to be envisioned, label‐free detection of the nucleotides to determine their electrophoretic mobility (i.e., time‐of‐flight, TOF) for highly accurate identification must be realized. Here, for the first time a novel nanosensor is shown that allows discriminating four 2‐deoxyribonucleoside 5'‐monophosphates, dNMPs, molecules in a label‐free manner by nanoscale electrophoresis. This is made possible by positioning two sub‐10 nm in‐plane pores at both ends of a nanochannel column used for nanoscale electrophoresis and measuring the longitudinal transient current during translocation of the molecules. The dual nanopore TOF sensor with 0.5, 1, and 5 µm long nanochannel column lengths discriminates different dNMPs with a mean accuracy of 55, 66, and 94%, respectively. This nanosensor format can broadly be applicable to label‐free detection and discrimination of other single molecules, vesicles, and particles by changing the dimensions of the nanochannel column and in‐plane nanopores and integrating different pre‐ and postprocessing units to the nanosensor. This is simple to accomplish because the nanosensor is contained within a fluidic network made in plastic via replication.
A dual‐nanopore time‐of‐flight (TOF) sensor, which consists of two in‐plane nanopores formed at both ends of a nanochannel column, is designed and fabricated to determine the mobility of single molecules in nanoscale electrophoresis in a label‐free manner. This novel nanosensor with a 5 µm long nanochannel column demonstrates discrimination of four deoxynucleotide monophosphates (dNMPs) molecules with a mean identification accuracy of 94%.
Identification of Mononucleotides
In article number 2102567, Steven A. Soper, Sunggook Park, and co‐workers develop a novel polymer nanofluidic sensor consisting of a nanochannel column and two ...sub‐10 nm in‐plane pores formed in polymer substrate via nanoimprint lithography. This nanosensor demonstrates label‐free detection and identification of dNMPs, the building block of DNAs, via their time‐of‐flight through the nanochannel column.
Carbon-based electrodes combined with fast-scan cyclic voltammetry (FSCV) enable neurochemical sensing with high spatiotemporal resolution and sensitivity. While their attractive electrochemical and ...conductive properties have established a long history of use in the detection of neurotransmitters both in vitro and in vivo, carbon fiber microelectrodes (CFMEs) also have limitations in their fabrication, flexibility, and chronic stability. Diamond is a form of carbon with a more rigid bonding structure (
-hybridized) which can become conductive when boron-doped. Boron-doped diamond (BDD) is characterized by an extremely wide potential window, low background current, and good biocompatibility. Additionally, methods for processing and patterning diamond allow for high-throughput batch fabrication and customization of electrode arrays with unique architectures. While tradeoffs in sensitivity can undermine the advantages of BDD as a neurochemical sensor, there are numerous untapped opportunities to further improve performance, including anodic pretreatment, or optimization of the FSCV waveform, instrumentation,
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character, doping, surface characteristics, and signal processing. Here, we review the state-of-the-art in diamond electrodes for neurochemical sensing and discuss potential opportunities for future advancements of the technology. We highlight our team's progress with the development of an all-diamond fiber ultramicroelectrode as a novel approach to advance the performance and applications of diamond-based neurochemical sensors.
Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit ...electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals.
Motivated by the extraordinary physical properties and potential optoelectronic applications of organic–inorganic hybrid perovskites (HPs), a variety of methods to synthesize and design high-quality ...HP structures has been developed. Nevertheless, the soft, organic nature of HP materials such as methylammonium lead iodide (MAPbI3) poses limitations to existing techniques, particularly for patterning the materials. Here, we demonstrate a hybrid top-down/bottom-up approach to patterning single-crystal HP microstructures. First, top-down lithography and chemical surface functionalization are used to prepare patterns with specific surface characteristics. Next, solid MAPbI3 powder is deposited on the patterns and liquefied by amino-deliquescence with methylamine (MA0) vapor, causing liquid MA0(MAPbI3) n to flow into the patterns while dewetting the remaining substrate. Lastly, MAPbI3 recrystallizes in the patterns by amino-efflorescence. By controlling the nucleation and growth conditions during amino-efflorescence, the characteristic grain size during recrystallization is orders of magnitude larger than the feature sizes of the patterns, thus causing the patterned microstructures to be single crystals. Contact angle measurements between liquid MA0(MAPbI3) n and a variety of organic and inorganic surfaces with and without chemical functionalization show that the wettability of surfaces can be tuned over a large range, providing flexibility in the choice of substrate and lithographic resist. The microstructures are free of exogenous solvents and suitable for optoelectronic device integration. As proof of concept, we demonstrate a photodetector that exhibits performance metrics consistent with single-crystal MAPbI3. The results provide a process for photonic and optoelectronic device design that can likely be extended to other potentially amino-deliquescent HP materials.
The purpose of this study was to better understand patients' perspective of asthma self-management by focusing on the sociocultural and medical context shaping patients' illness representations and ...individual decisions.
We conducted a secondary analysis of semi-structured interviews carried out as part of a multicentered collective qualitative case study. In total, 24 patients, aged 2-76 years with a confirmed diagnosis of asthma (or were parents of a child), who renewed the prescription for inhaled corticosteroids in the past year, participated in this study. The thematic analysis focused on asthma-related events and experiences reported by the patients. Consistent with narrative inquiry, similar patterns were grouped together, and three vignettes representing the different realities experienced by the patients were created.
The comparison of experiences and events reported by the patients suggested that patients' perceptions and beliefs regarding asthma and treatment goals influenced their self-management-related behaviors. More specifically, the medical context in which the patients were followed (ie, frame in which the medical encounter takes place, medical recommendations provided) contributed to shape their understanding of the disease and the associated treatment goals. In turn, a patient's perception of the disease and the treatment goals influenced asthma self-management behaviors related to environmental control, lifestyle habits, and medication intake.
Current medical recommendations regarding asthma self-management highlight the importance of the physicians' guidance through the provision of a detailed written action plan and asthma education. These data suggest that while physicians contribute to shaping patients' beliefs and perceptions about the disease and treatment goals, patients tend to listen to their own experience and manage the disease accordingly. Thus, a medical encounter between the patient and the physician, aiming at enhancing a meaningful conversation about the disease, may lead the patient to approach the disease in a more effective manner, which goes beyond taking preventative paths to avoid symptoms.
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