Current Readout Research Articles

Rapid‐Response and Portable Lead Ion Sensor Using Co/Pt/Si Schottky Heterojunction Without Reference Electrode

AbstractLead ions (Pb2+) are classified as highly toxic heavy metals that pose substantial threats to both human health and environmental integrity. Consequently, the sensitive detection of Pb2+, particularly at low concentrations, is imperative for the purposes of environmental surveillance and safeguarding public health. Here, we introduce a Co/Pt/Si Schottky heterostructure for a rapid, portable Pb2+ detection sensor. One electrode of the heterojunction serves as a Pb2+ probe, and sensor processing circuits are integrated. The Co/Pt thin films were deposited via magnetron sputtering on a Si(100) substrate, followed by heterojunction fabrication using semiconductor process technology. The sensor is functionalized with a glutathione‐modified gold electrode, leveraging the sulfur‐donor properties of cysteine in glutathione and the electron‐acceptor behavior of Pb2+. This interaction modulates the surface potential of the gold electrode, altering the current‐voltage rectification of the Co/Pt/Si heterojunction. A two‐terminal configuration enables current signal readout without reference electrodes. The sensor demonstrates a linear response to Pb2+ concentrations ranging from 1×10−8 to 1×10−3 mol/L, with high selectivity attributed to the affinity of glutathione for Pb2+. The key benefits are the simplicity of its fabrication process and its portability, which are enhanced by the integration of measurement circuitry. This makes the sensor a promising candidate for rapid, on‐site detection of heavy metal ions in applications related to health and environmental monitoring.

Performance of the DAQ system of the PANDA Micro-Vertex Detector

The Micro-Vertex Detector (MVD) is the innermost subdetector of the PANDA (anti-Proton ANnihilations at DArmstadt) detector at FAIR. Its microstrip sensors are read out by custom front-end electronics called ToASt (Torino ASIC for Strip readout) [1]. The ToASt chips are locally managed by an MDC (Module Data Concentrator) [2]. The MDC processes incoming event data and forwards them to the off-detector readout cards based on the AMC (Advanced Mezzanine Card) standard. Both the MDC and the AMC readout card are currently under development at KIT [3].The complete readout chain, including the double-sided microstrip sensor read by the ToASt chips and the FPGA implementation of the MDC, was successfully tested during a 2023 beam test at COSY (Forschungszentrum Jülich). This proof-of-concept validation of the MDC logic paves the way for the forthcoming ASIC version of the MDC, which is planned for submission in February 2025.Extensive performance characterization of the current readout chain has been achieved with the MDC-FPGA optically connected to an AMD-Xilinx ZCU102 evaluation card [4], which emulates the AMC off-detector card, through a Versatile Link+ Demo Board (VLDB+) [5].This contribution presents the MDC-ASIC design, its integration with both the front-end and back-end electronics and the performance results of the complete readout chain.

Electrochemical Aptamer-Based Biosensor for Detecting Pap31, a Biomarker for Carrion's Disease.

Carrion's disease, caused by infection with the bacterium Bartonella bacilliformis (B. bacilliformis), is effectively treated with antibiotics, but reaches fatality rates of ~90% if untreated. Current diagnostic methods are limited, insufficiently sensitive, or require laboratory technology unavailable in endemic areas. Electrochemical aptamer-based (E-AB) biosensors provide a potential solution for this unmet need, as these biosensors are portable, sensitive, and can rapidly report the detection of small molecule targets. Here, we developed an E-AB biosensor to detect Pap31, a biomarker of Carrion's disease and an outer membrane protein in B. bacilliformis. We identified an aptamer with Pap31-specific binding affinity using a magnetic pull-down assay with magnetic bead-bound Pap31 and an aptamer library followed by electrophoretic mobility shift assays. We incorporated the Pap31-binding aptamer into a DNA oligonucleotide that changes conformation upon binding Pap31. The resultant Pap31 E-AB biosensor produced a rapid, significant, and target-specific electrical current readout in the buffer, demonstrating an apparent KD of 0.95 nM with a limit of detection of 0.1 nM, and no significant signal change when challenged with off-target proteins. This proof-of-concept Pap31 biosensor design is a first step toward the development of more rapid, sensitive, and portable diagnostic tools for detecting Carrion's disease.

Precision Basecalling of Single DNA Nucleotide from Overlapped Transmission Readouts with Machine Learning Aided Solid-State Nanogap.

DNA sequencing with the quantum tunneling technique heralds a paradigm shift in genetic analysis, promising rapid and accurate identification for diverging applications ranging from personalized medicine to security issues. However, the widespread distribution of molecular conductance, conduction orbital alignment for resonant transport, and decoding crisscrossing conductance signals of isomorphic nucleotides have been persistent experimental hurdles for swift and precise identification. Herein, we have reported a machine learning (ML)-driven quantum tunneling study with solid-state model nanogap to determine nucleotides at single-base resolution. The optimized ML basecaller has demonstrated a high predictive basecalling accuracy of all four nucleotides from seven distinct data pools, each containing complex transmission readouts of their different dynamic conformations. ML classification of quaternary, ternary, and binary nucleotide combinations is also performed with high precision, sensitivity, and F1 score. ML explainability unravels the evidence of how extracted normalized features within overlapped nucleotide signals contribute to classification improvement. Moreover, electronic fingerprints, conductance sensitivity, and current readout analysis of nucleotides have promised practical applicability with significant sensitivity and distinguishability. Through this ML approach, our study pushes the boundaries of quantum sequencing by highlighting the effectiveness of single nucleotide basecalling with promising implications for advancing genomics and molecular diagnostics.

Sensitive electrochemical biosensor for Ustilaginoidea Virens short-stranded DNA segment via higher-ordered G-quadruplex multimerization induced by LAMP/H+-responsive i-motif folding

By using variable loop-mediated isothermal amplification byproduct H+ ions (vLAMP/H+) as signal transducer, exploring the electrochemical assay of short-stranded DNA segment related to U. virens (uDNA, 21-nt) is intriguing. Herein, we report the first design of a sensitive electrochemical biosensor for uDNA as targeting input promoter of vLAMP, for which a discernible template hairpin and a precursor hairpin are well-designed. The specific recognition and complementary hybridization among them form a double-dumbbell DNA structure tethering two stem-loop motifs that is served as template precursor to operate vLAMP for DNA+1 polymerization via nucleotide incorporation, generating vLAMP/H+ to modulate pH-responsive i-motif folding of a C-rich strand. A ferrocene-tagged G-rich strand is dehybridized and incubated in modified electrode surface including an amino-labeled G-rich strand that adopts compact G-quadruplex (G4) conformation. This G4, as an initiator, guides the ‘head-to-tail’ π-π stacking of electroactive tags for developing higher-ordered wire-like G4 multimers (G4W), which are stably held together via interquadruplex multimerization. No involving additional nucleic acid amplifiers, numerous electroactive mediators are repetitively cascaded, thereby significantly amplifying the current readout signal and achieving sensitive electrochemical detection of U. virens. Benefited from simple and rapid vLAMP/H+-G4W route, our assay strategy would provide a new paradigm to create applicable electrochemical biosensors for diverse short-stranded DNA biomarkers by altering LAMP operation modes readily.

A Multi-bit ECRAM-Based Analog Neuromorphic System with High-Precision Current Readout Achieving 97.3% Inference Accuracy.

This article proposes an analog neuromorphic system that enhances symmetry, linearity, and endurance by using a high-precision current readout circuit for multi-bit nonvolatile electro-chemical random-access memory (ECRAM). For on-chip training and inference, the system uses activation modules and matrix processing units to manage analog update/read paths and perform precise output sensing with feedback-based current scaling on the ECRAM array. The 250nm CMOS neuromorphic chip was tested with a 32 x 32 ECRAM synaptic array, achieving linear and symmetric updates and accurate read operations. The proposed circuit system updates the 32 x 32 ECRAM across 100 levels, maintaining consistent synaptic weights, and operates with an output error rate of up to 2.59% per column. It consumes 5.9 mW of power excluding the ECRAM array and achieves 97.3% inference accuracy on the MNIST dataset, close to the software-confirmed 97.78%, with only the final layer (64 x 10) mapped to the ECRAM.

Dynamics of parafermionic states in transport measurements

Advances in hybrid fractional quantum Hall (FQH)-superconductor platforms pave the way for realisation of parafermionic modes. We analyse signatures of these non-abelian anyons in transport measurements across devices with \mathbb{Z}_6ℤ6 parafermions (PFs) coupled to an external electrode. Simulating the dynamics of these open systems by a stochastic quantum jump method, we show that a current readout over sufficiently long times constitutes a projective measurement of the fractional charge shared by two PFs. Interaction of these topological modes with the FQH environment, however, may cause poisoning events affecting this degree of freedom which we model by jump operators that describe incoherent coupling of PFs with FQH edge modes. We analyse how this gives rise to a characteristic three-level telegraph noise in the current, constituting a very strong signature of PFs. We discuss also other forms of poisoning and noise caused by interaction with fractional quasiparticles in the bulk of the Hall system. We conclude our work with an analysis of four-PF devices, in particular on how the PF fusion algebra can be observed in electrical transport experiments.

Enhancing single-cell biology through advanced AI-powered microfluidics.

Microfluidic technology has largely benefited both fundamental biological research and translational clinical diagnosis with its advantages in high-throughput, single-cell resolution, high integrity, and wide-accessibility. Despite the merits we obtained from microfluidics in the last two decades, the current requirement of intelligence in biomedicine urges the microfluidic technology to process biological big data more efficiently and intelligently. Thus, the current readout technology based on the direct detection of the signals in either optics or electrics was not able to meet the requirement. The implementation of artificial intelligence (AI) in microfluidic technology matches up with the large-scale data usually obtained in the high-throughput assays of microfluidics. At the same time, AI is able to process the multimodal datasets obtained from versatile microfluidic devices, including images, videos, electric signals, and sequences. Moreover, AI provides the microfluidic technology with the capability to understand and decipher the obtained datasets rather than simply obtaining, which eventually facilitates fundamental and translational research in many areas, including cell type discovery, cell signaling, single-cell genetics, and diagnosis. In this Perspective, we will highlight the recent advances in employing AI for single-cell biology and present an outlook on the future direction with more advanced AI algorithms.

Three-Phase Motor Inverter and Current Sensing GaN Power IC.

A three-phase GaN-based motor inverter IC with three integrated phase current mirror sensors (sense-FETs or sense-HEMTs, 1200:1 ratio), a temperature sensor, and an amplifier is presented and experimentally operated. The three low-side currents are read out by virtual grounding transimpedance amplifiers. A modified summed DC current readout circuit using only one amplifier is also discussed. During continuous 24 V motor operation with space-vector pulse width modulation (SVPWM), the sensor signal is measured and a bidirectional measurement capability is verified. The measured risetime of the sensor signal is 51 ns, indicating around 7 MHz bandwidth (without intentional optimization for high bandwidth). The IC is operated up to 32 V on DC-biased semi-floating substrate to limit negative static back-gating of the high-side transistors to around -7% of the DC-link voltage. Analysis of the capacitive coupling from the three switch-nodes to the substrate is calculated for SVPWM based on capacitance measurement, resulting in four discrete semi-floating substrate voltage levels, which is experimentally verified. Integrated advanced power converter topologies with sensors improve the power density of power electronics applications, such as for low-voltage motor drive.

Rapid and Quantitative Detection of Lung Cancer Biomarker ENOX2 Using a Novel Aptamer in an Electrochemical DNA-Based (E-DNA) Biosensor.

To overcome early cancer detection challenges, diagnostic tools enabling more sensitive, rapid, and noninvasive detection are necessary. An attractive cancer target for diagnostic blood tests is human Ecto-NOX disulfide-thiol exchanger 2 (ENOX2), expressed in most human cancer types and regularly shed into blood sera. Here, we developed an electrochemical DNA-based (E-DNA) biosensor that rapidly detects physiologically relevant levels of ENOX2. To identify ENOX2-binding aptamers that could potentially be used in a biosensor, recombinantly expressed ENOX2 was used as a binding target in an oligonucleotide library pull-down that generated a highly enriched ENOX2-binding aptamer. This candidate aptamer sensitively bound ENOX2 via gel mobility shift assays. To enable this aptamer to function in an ENOX2 E-DNA biosensor, the aptamer sequence was modified to adopt two conformations, one capable of ENOX2 binding, and one with disrupted ENOX2 binding. Upon ENOX2 introduction, a conformational shift to the ENOX2 binding state resulted in changed dynamics of a redox reporter molecule, which generated a rapid, significant, and target-specific electrical current readout change. ENOX2 biosensor sensitivity was at or below the diagnostic range. The ENOX2 E-DNA biosensor design presented here may enable the development of more sensitive, rapid, diagnostic tools for early cancer detection.

Deep TL: progress of a machine learning aided personal dose monitoring system.

Personal dosemeters using thermoluminescence detectors can provide information about the irradiation event beyond the pure dose estimation, which is valuable for improving radiation protection measures. In the presented study, the glow curves of the novel TL-DOS dosemeters developed by the Materialprüfungsamt NRW in cooperation with the TU Dortmund University are analysed using deep learning approaches to predict the irradiation date of a single-dose irradiation of 10mGy within a monitoring interval of 41d. In contrast of previous work, the glow curves are measured using the current routine read-out process by pre-heating the detectors before the read-out. The irradiation dates are predicted with an accuracy of 2-5d by the deep learning algorithm. Furthermore, the importance of the input features is evaluated using Shapley values to increase the interpretability of the neural network.

Design and Fabrication of Two-stage SQUID for Transition Edge Sensor

The X-ray transition edge sensor (TES) modeled by calorimeter is extremely sensitive to temperature changes when operating at a voltage bias in the temperature region, and is widely used for the detection of particles and photons from submicron frequency to gamma rays. Superconducting quantum interference device (SQUID) is the key to TES current signal readout, we have designed a two-stage SQUID amplifier circuit. First-stage sensor SQUID uses first-grade gradiometer with high input mutual inductance about 176.2 , it increases the coupling sensitivity with the TES detector and has stronger resistance to external interference. Second-stage SQUID array(SSA) adopts 32 single SQUIDs in series, which has low magnetic flux noise and high magnification. We have verified the characteristics of this two-stage circuit and demonstrated that it has a lower magnetic flux noise.

Towards Enhanced Eddy Current Testing Array Probes Scalability for Powder Bed Fusion Layer-Wise Imaging

This work presents a new eddy current testing array probe and readout electronics that target the layer-wise quality control in powder bed fusion metal additive manufacturing. The proposed design approach brings important benefits to the sensors' number scalability, exploring alternative sensor elements and minimalist signal generation and demodulation. Small-sized, commercially available surface-mounted technology coils were evaluated as an alternative to usually employed magneto-resistive sensors, demonstrating low cost, design flexibility, and easy integration with the readout electronics. Strategies to minimize the readout electronics were proposed, considering the specific characteristics of the sensors' signals. An adjustable single phase coherent demodulation scheme is proposed as an alternative to traditional in-phase and quadrature demodulation provided that the signals under measurement showed minimal phase variations. A simplified amplification and demodulation frontend using discrete components was employed together with offset removal, vector amplification, and digitalization implemented within the microcontrollers' advanced mixed signal peripherals. An array probe with 16 sensor coils and a 5 mm pitch was materialized together with non-multiplexed digital readout electronics, allowing for a sensor frequency of up to 1.5 MHz and digitalization with 12 bits resolution, as well as a 10 kHz sampling rate.

A Compact Reconfigurable Resonator-Based Direct Current Sensing System

A compact and reconfigurable current readout system is presented that is based on microelectromechanical system (MEMS) resonators. The proposed system generates analog and digital outputs by electrothermally tuning the microbeam resonant frequency according to variations in the input current signal. A single resonator is utilized to generate the analog output, while a resonator array operating at different frequencies is utilized to generate a digital one-hot output. Experiments showed that the frequency shift is linearly proportional to the square of the current. The single resonator has a detection limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.16 ~\mu \text{A}$ </tex-math></inline-formula> , and the resonator array offers good static linearity with a maximum differential/integral non-linearity of 0.55/0.23 least significant bits. The single resonator is suitable for applications requiring high-resolution measurements. The proposed resonator sensing system has a small footprint, is compatible with large-scale integration, and provides considerable flexibility for reconfiguration.

A highly sensitive electrochemical biosensor via short-stranded DNA activating LAMP(H+) to regulate i-motif folds for signal transduction

Exploring loop-mediated isothermal amplification (LAMP)-based electrochemical assay for short-stranded DNA biomarkers is intriguing. Herein, a HIV-specific DNA segment (tDNA) was introduced to implement a variant LAMP reaction, where the generated by-products H+, vLAMP(H+), acted as signal transducers for developing a sensitive electrochemical biosensor. As proof-of-concept, the tDNA-recognizable complement was programmed in a template hairpin (TH) that was ended with a 3′-terminus phosphate group to avoid non-specific elongation. Upon TH simultaneously hybridizing with tDNA and a precursor hairpin (PH), the PH underwent a loop-mediated extension with Bst polymerase and dNTPs, forming a new stem-loop hairpin in another terminus. Then the elongated product containing a double stem-loop dumbbell-like DNA structure (dDDS) was displaced and released. Using dDDS as an initiator, the vLAMP reaction occurred via consecutively cycled strand displacement for self-primed DNA incorporation. The resulting tDNA-dependent vLAMP(H+) was introduced in the modified electrode surface to guide the pH-sensitive i-motif (iM) folding. Thus, a signaling hairpin labeled with electroactive ferrocene (Fc) was dehybridized and closed, thereby bringing Fc close to the electrode interface for increased current signal readout that was highly sensitive to tDNA down to 0.034 fM. Our electrochemical biosensor would be applicable for detecting various short-stranded DNA or miRNA.

Development of a new high-speed data acquisition system prototype for SOI pixel detector using SiTCP-XG, a 10-gigabit Ethernet network processor

We are developing a new readout board with a newer generation field-programmable gate array (FPGA) and the 10-gigabit ethernet to improve the performance and usability of the current readout board based on the 1-gigabit ethernet. In this new readout board, the SiTCP-XG network processor supporting 10 Gigabit Ethernet was implemented. SiTCP is a network processor circuit running on FPGA, and SiTCP-XG is the newly developed version of the SiTCP that supports 10-gigabit ethernet. Before developing the new board, we constructed a prototype system using the Xilinx FPGA evaluation board KC705 to evaluate the SiTCP-XG. This prototype system was tested with the SOI pixel detector, which has 425,984 (column 832 × row 512 matrix) pixels and a pixel size of 17 × 17 μm2 at the synchrotron beamlines of the PhotonFactory (KEK). This was the first test of the X-ray imaging for this system. The results showed that this system worked stably with a transfer rate of 682 Mbps (equivalent to a frame rate of 100 fps, limited by detector operation parameters), and also worked stably with a transfer rate of 2.4 Gbps (equivalent to 350 fps, the maximum rate limited by the detector performance). These results suggest that the SiTCP-XG system has sufficient transfer performance to cover the SOIPIX detector performance.

The Phase-2 upgrade of the CMS Drift Tube detectors for High Luminosity LHC

The Large Hadron Collider (LHC) will undergo a major upgrade in the mid-2020s referred to as the High Luminosity LHC (HL-LHC) to extend its operability by another decade and, in addition, to increase its luminosity with the aim of increasing the potential for new discoveries. In order to meet the experimental challenges of unprecedented proton–proton luminosity that will cause an expected increase of both radiation and rates, the experiments have to upgrade its electronics and detector performance. To withstand the high rate environment of the HL-LHC, an upgrade is planned for the current readout and trigger electronics that comprises of new On-Board electronics (OBDT) for the Drift Tube (DT) detectors in the CMS muon barrel region, which serve as both offline tracking and triggering devices. During Long Shutdown 2 (LS2), prototypes of the new electronics were installed in four DT chambers with the same azimuthal acceptance. This demonstrator of the HL-LHC DT upgrade (DT slice-test) was integrated into the central CMS data acquisition and trigger systems. This report summaries the present status of the slice-test, as well as its performance assessed with cosmic-ray events.

A slice-test demonstrator for the upgrade of the CMS drift tubes at High-Luminosity LHC

Drift Tubes (DT) detectors equip the CMS muon system barrel region serving both as offline tracking and triggering devices. Existing DT chambers will operate throughout High-Luminosity LHC, but, in order to withstand event rates and integrated doses far beyond the initial design specification, an upgrade of the current readout and trigger electronics is planned. In the upgraded system, time-to-digital converters will stream hits to new back-end boards that, beyond event matching, will perform online tracking of trigger segments exploiting the ultimate DT cell resolution. During the second LHC long shutdown, prototypes of the aforementioned electronics were installed in four DT chambers with the same azimuthal acceptance, instrumenting a demonstrator of the HL-LHC DT upgrade (DT slice-test). In this report, the motivation for such an upgrade will be highlighted, and the status of the DT slice-test operation, as well as its performance measured with cosmic muons, will be presented. Plans towards future developments of the demonstrator throughout the LHC Run-3 will also be discussed.

Enhancement of Sensitivity in AlGaN/GaN HEMT Based Sensor Using Back-Barrier Technique

In the state of the art, most of the Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) based sensors provide current readout rather than voltage readout. Further, to improve the sensitivity, surface side optimization has been done rather than epi-layer optimization. In this paper, a back-barrier (epi-layer) technique is proposed to improve the sensitivity of the GaN based sensor. To measure the sensitivity, voltage readout is used as it provides better sensitivity than that of a current readout. SILVACO ATLAS Technology Computer Aided Design (TCAD) is used to analyze the performance of the proposed technique. In order to perform a realistic simulation, the TCAD simulation is validated with measured data. The proposed back-barrier technique in the GaN HEMT is shown to improve the sensitivity by 14% as compared to the state of the art. Therefore, the use of the proposed back-barrier technique is considered promising for the GaN HEMT based sensors.

A Design of Real-Time Data Acquisition and Processing System for Nanosecond Ultraviolet-Visible Absorption Spectrum Detection

Ultraviolet-visible absorption spectroscopy is widely used to monitor water quality, and rapid optical signal detection is a key technology in the process of spectrum measurement. In this paper, an ultrafast spectrophotometer system that can achieve spectrum data acquisition in a single flash of the xenon lamp (within 200 ns) is introduced, and a real-time denoising method for the spectrum is implemented on a field programmable gate array (FPGA) to work cooperatively with the nanosecond spectrum acquisition system, in order to guarantee the quality of the spectrum signals without losing running speed. The hardware of the data acquisition and processing system are constructed on a Xilinx Spartan 6 FPGA chip and its peripheral circuit, including an analog to digital converter and a complementary metal-oxide-semiconductor transistor (CMOS) sensor’s diver circuit. An oversampling method that is suitable for the CMOS sensor’s output is proposed, which works on the CMOS sensor’s dark current noise and readout noise. Another moving-average filter method is designed adaptively, which works on the low-frequency component to filter out the residual spectrum noise of the spectrum signal. The implementation of the filter on the FPGA has been optimized by using a pipelined structure and dual high-speed random-access memory (RAM). As a result, the CMOS linear image sensor successfully captured the spectrum of xenon flash light at the readout clock frequency of 500 kHz and the processing manipulation to the full UV-Vis spectrum data was accomplished at a sub-microsecond speed performance. After the digital filter and oversampling technology were implemented, the coefficient of variation of the measurements reduced from 9.57% to 1.74%, while the signal noise ratio (SNR) of the absorption spectrum increased nine times, compared to the raw data of the CMOS sensor’s output. The tests towards different analyte samples were conducted, and the system shows good performance on distinguishing different concentrations of different analyte solutions on both ultra-violet and visible spectrum bands. The present work showcases the potential of the CMOS sensor’s technique for the fast detection of contaminated water containing nitrate and organic compounds.