AC/DC differential bridge based solution-electrode interfacial capacitance biosensor, for field-deployable real-time and low-cost detection of MCLR in drinking water.

Microcystin-LR (MCLR, one of the most toxic and commonly found products of cyanobacteria in freshwater resources, threatens human health and the livestock. WHO has set a standard limit of 1 μg⁄l for the concentration of MCLR in drinking water. The lab-based, specialized water quality monitoring tests for this purpose are not only expensive but also slow and require sample preparation and transportation from distant sites. Therefore, there is a need for a handheld, field-deployable and low-cost biosensor to make frequent water quality monitoring easier. Many field-deployable biosensors with applications in environmental monitoring and healthcare where concentrations of interest are on the order of μg/l and fewer face challenges in achieving high dynamic range and lower detection resolution due to the resultant small fractional change in the transducer characteristics. Additionally, non-faradaic label-free biosensors for MCLR type applications face difficulty in real-time data analysis due to signal drift, non-specific binding of non-target particles and last but not least noise coming from both transducer and readout electronics. This dissertation is mainly focused on utilizing electronic circuit methods to fill the gap of reading small responses from the bio-transducer with sufficient accuracy and sensitivity. Differential bridge based transduction as sensitivity booster and careful design of amplification unit and real-time signal processing capable of extracting signal information buried in noise are part of the presented work that achieves 8-bit resolution within a 1% full-scale transducer fractional capacitive change

AC/DC differential bridge based solution-electrode interfacial capacitance biosensor, for field-deployable real-time and low-cost detection of MCLR in drinking water.

Microcystin-LR (MCLR, one of the most toxic and commonly found products of cyanobacteria in freshwater resources, threatens human health and the livestock. WHO has set a standard limit of 1 μg⁄l for the concentration of MCLR in drinking water. The lab-based, specialized water quality monitoring tests for this purpose are not only expensive but also slow and require sample preparation and transportation from distant sites. Therefore, there is a need for a handheld, field-deployable and low-cost biosensor to make frequent water quality monitoring easier. Many field-deployable biosensors with applications in environmental monitoring and healthcare where concentrations of interest are on the order of μg/l and fewer face challenges in achieving high dynamic range and lower detection resolution due to the resultant small fractional change in the transducer characteristics. Additionally, non-faradaic label-free biosensors for MCLR type applications face difficulty in real-time data analysis due to signal drift, non-specific binding of non-target particles and last but not least noise coming from both transducer and readout electronics. This dissertation is mainly focused on utilizing electronic circuit methods to fill the gap of reading small responses from the bio-transducer with sufficient accuracy and sensitivity. Differential bridge based transduction as sensitivity booster and careful design of amplification unit and real-time signal processing capable of extracting signal information buried in noise are part of the presented work that achieves 8-bit resolution within a 1% full-scale transducer fractional capacitive change.</p

Highly Sensitive Readout Interface for Real-Time Differential Precision Measurements with Impedance Biosensors

Field deployment is critical to developing numerous sensitive impedance transducers. Precise, cost-effective, and real-time readout units are being sought to interface these sensitive impedance transducers for various clinical or environmental applications. This paper presents a general readout method with a detailed design procedure for interfacing impedance transducers that generate small fractional changes in the impedance characteristics after detection. The emphasis of the design is obtaining a target response resolution considering the accuracy in real-time. An entire readout unit with amplification/filtering and real-time data acquisition and processing using a single microcontroller is proposed. Most important design parameters, such as the signal-to-noise ratio (SNR), common-mode-to-differential conversion, digitization configuration/speed, and the data processing method are discussed here. The studied process can be used as a general guideline to design custom readout units to interface with various developed transducers in the laboratory and verify the performance for field deployment and commercialization. A single frequency readout unit with a target 8-bit resolution to interface differentially placed transducers (e.g., bridge configuration) is designed and implemented. A single MCU is programmed for real-time data acquisition and sine fitting. The 8-bit resolution is achieved even at low SNR levels of roughly 7 dB by setting the component values and fitting algorithm parameters with the given methods.This article is published as Neshani, Sara, Kasra Momeni, Degang J. Chen, and Nathan M. Neihart. "Highly Sensitive Readout Interface for Real-Time Differential Precision Measurements with Impedance Biosensors." Biosensors 13, no. 1 (2023): 77. DOI: 10.3390/bios13010077. Copyright 2023 by the authors. Attribution 4.0 International (CC BY 4.0). Posted with permission

Highly Sensitive Readout Interface for Real-Time Differential Precision Measurements with Impedance Biosensors

Field deployment is critical to developing numerous sensitive impedance transducers. Precise, cost-effective, and real-time readout units are being sought to interface these sensitive impedance transducers for various clinical or environmental applications. This paper presents a general readout method with a detailed design procedure for interfacing impedance transducers that generate small fractional changes in the impedance characteristics after detection. The emphasis of the design is obtaining a target response resolution considering the accuracy in real-time. An entire readout unit with amplification/filtering and real-time data acquisition and processing using a single microcontroller is proposed. Most important design parameters, such as the signal-to-noise ratio (SNR), common-mode-to-differential conversion, digitization configuration/speed, and the data processing method are discussed here. The studied process can be used as a general guideline to design custom readout units to interface with various developed transducers in the laboratory and verify the performance for field deployment and commercialization. A single frequency readout unit with a target 8-bit resolution to interface differentially placed transducers (e.g., bridge configuration) is designed and implemented. A single MCU is programmed for real-time data acquisition and sine fitting. The 8-bit resolution is achieved even at low SNR levels of roughly 7 dB by setting the component values and fitting algorithm parameters with the given methods

Role of tilt grain boundaries on the structural integrity of WSe2 monolayers

Transition metal dichalcogenides (TMDCs) are potential materials for future optoelectronic devices. Grain boundaries (GBs) can significantly influence the optoelectronic properties of TMDC materials. Here, we have investigated the mechanical characteristics of tungsten diselenide (WSe2) monolayers and failure process with symmetric tilt GBs using ReaxFF molecular dynamics simulations. In particular, the effects of topological defects, loading rates, and temperatures are investigated. We considered nine different grain boundary structures of monolayer WSe2, of which six are armchair (AC) tilt structures, and the remaining three are zigzag (ZZ) tilt structures. Our results indicate that both tensile strength and fracture strain of WSe2 with symmetric tilt GBs decrease as the temperature increases. We revealed an interfacial phase transition for high-angle GBs reduces the elastic strain energy within the interface at finite temperatures. Furthermore, brittle cracking is the dominant failure mode in the WSe2 monolayer with tilted GBs. WSe2 GB structures showed more strain rate sensitivity at high temperatures than at low temperatures

AC and DC Differential Bridge Structure Suitable for Electrochemical Interfacial Capacitance Biosensing Applications

This paper presents a capacitive differential bridge structure with both AC and DC excitation and balancing capability for low cost electrode-solution interfacial capacitance biosensing applications. The proposed series RC balancing structure offers higher sensitivity, lower susceptibility to common-mode interferences, and drift control. To evaluate the bridge performance in practice, possible effects of initial bridge imbalance due to component mismatches are investigated considering the required resolution of the balancing networks, sensitivity, and linearity. This evaluation is also a guideline to designing the balancing networks, balancing algorithm and the proceeding readout interface circuitry. The proposed series RC bridge structure is implemented along with a custom single frequency real-time amplification/filtering readout board with real-time data acquisition and sine fitting. The main specifications for the implemented structure are 8-bit detection resolution if the total expected fractional capacitance change at the interface is roughly 1%. The characterization and measurement results show the effectiveness of the proposed structure in achieving the design target. The implemented structure successfully achieves distinct detection levels for tiny total capacitance change at the electrode-solution interface, utilizing Microcystin-(Leucine-Arginine) toxin dilutions as a proof of concept

AC and DC Differential Bridge Structure Suitable for Electrochemical Interfacial Capacitance Biosensing Applications

This paper presents a capacitive differential bridge structure with both AC and DC excitation and balancing capability for low cost electrode-solution interfacial capacitance biosensing applications. The proposed series RC balancing structure offers higher sensitivity, lower susceptibility to common-mode interferences, and drift control. To evaluate the bridge performance in practice, possible effects of initial bridge imbalance due to component mismatches are investigated considering the required resolution of the balancing networks, sensitivity, and linearity. This evaluation is also a guideline to designing the balancing networks, balancing algorithm and the proceeding readout interface circuitry. The proposed series RC bridge structure is implemented along with a custom single frequency real-time amplification/filtering readout board with real-time data acquisition and sine fitting. The main specifications for the implemented structure are 8-bit detection resolution if the total expected fractional capacitance change at the interface is roughly 1%. The characterization and measurement results show the effectiveness of the proposed structure in achieving the design target. The implemented structure successfully achieves distinct detection levels for tiny total capacitance change at the electrode-solution interface, utilizing Microcystin-(Leucine-Arginine) toxin dilutions as a proof of concept.This article is published as Neshani, Sara, Charles KA Nyamekye, Scott Melvin, Emily A. Smith, Degang J. Chen, and Nathan M. Neihart. "AC and DC Differential Bridge Structure Suitable for Electrochemical Interfacial Capacitance Biosensing Applications." Biosensors 10, no. 3 (2020): 28. DOI: 10.3390/bios10030028. Posted with permission.</p