Zhekun Peng

Bio: Zhekun Peng is an academic researcher from Missouri University of Science and Technology. The author has contributed to research in topics: Router. The author has an hindex of 1, co-authored 2 publications receiving 13 citations.

MXene-Graphene Field-Effect Transistor Sensing of Influenza Virus and SARS-CoV-2

Abstract: An MXene-graphene field-effect transistor (FET) sensor for both influenza virus and 2019-nCoV sensing was developed and characterized. The developed sensor combines the high chemical sensitivity of MXene and the continuity of large-area high-quality graphene to form an ultra-sensitive virus-sensing transduction material (VSTM). Through polymer linking, we are able to utilize antibody-antigen binding to achieve electrochemical signal transduction when viruses are deposited onto the VSTM surface. The MXene-graphene VSTM was integrated into a microfluidic channel that can directly receive viruses in solution. The developed sensor was tested with various concentrations of antigens from two viruses: inactivated influenza A (H1N1) HA virus ranging from 125 to 250,000 copies/mL and a recombinant 2019-nCoV spike protein ranging from 1 fg/mL to 10 pg/mL. The average response time was about ∼50 ms, which is significantly faster than the existing real-time reverse transcription-polymerase chain reaction method (>3 h). The low limit of detection (125 copies/mL for the influenza virus and 1 fg/mL for the recombinant 2019-nCoV spike protein) has demonstrated the sensitivity of the MXene-graphene VSTM on the FET platform to virus sensing. Especially, the high signal-to-viral load ratio (∼10% change in source-drain current and gate voltage) also demonstrates the ultra-sensitivity of the developed MXene-graphene FET sensor. In addition, the specificity of the sensor was also demonstrated by depositing the inactivated influenza A (H1N1) HA virus and the recombinant 2019-nCoV spike protein onto microfluidic channels with opposite antibodies, producing signal differences that are about 10 times lower. Thus, we have successfully fabricated a relatively low-cost, ultrasensitive, fast-responding, and specific inactivated influenza A (H1N1) and 2019-nCoV sensor with the MXene-graphene VSTM.

Characterization and Modeling of Commercial ICs for System-Efficient ESD Design

Abstract: Optimizing electrostatic discharge (ESD) protection strategies requires simulation models of both on- and off-die ESD devices, but detailed information about on-die ESD protection is rarely available. Methods are proposed in the following paper to characterize and model the on-chip ESD protection using only measurements, with minimal a priori information about how the protection is implemented. The characterization targets a three-terminal (rather than the traditional two-terminal) protection structure, including the I/O, Vdd, Vss pins, and allows for current to flow between multiple pins simultaneously. A previously-developed behavioral model for TVS devices is used to capture the ESD behavior of the integrated circuit (IC), including its linear, quasi-static, and transient nonlinear response. The approach is used to model the equivalent current that flows through the on-chip ESD protection of two commercial ICs. The model of the on-chip ESD protection is combined with a behavioral model of an off-chip transient voltage suppressor to demonstrate their combined performance in a system-efficient ESD design (SEED) simulation. The model is validated both when the IC is powered-off and powered-on. The SEED model was able to predict quasistatic and peak voltages and currents at the IC with less than a 10% error.

Radiated Emission Tests for High-frequency Router Systems in Class A: Discussion and Improvement

Abstract: The standards for radiated emissions (RE) test in FCC Part 15 and CISPR 32, and the related literature concerning the limit line extrapolation, testing methods and challenges in the RE test are reviewed herein. In particular, factors to be considered during the RE test for the equipment in Class A operating above 10 GHz are discussed including: 1) possibilities to miss the maximal electric field (Emax); 2) specifications of the 2 dB rule; 3) falloff factors in the conversion between the measured electric (E) field at closer distances (1 m or 3 m) to 10 m. Methods that might be considered for improvement are proposed to increase the confidence of the multi-modular systems in passing/failing the RE standard and compliance with other devices in terms of: 1) according to 2 dB rule, 63.1% of the optical modules are proposed to represent the radiation of the fully loaded router system; 2) statistical falloff factors are needed in converting the E field at 1 m/3 m to 10 m at high frequencies (> 10 GHz); and, 3) specific limit lines are preferred at high frequencies for router/multi-modular systems.

Accuracy of novel antigen rapid diagnostics for SARS-CoV-2: A living systematic review and meta-analysis.

Abstract: Background SARS-CoV-2 antigen rapid diagnostic tests (Ag-RDTs) are increasingly being integrated in testing strategies around the world. Studies of the Ag-RDTs have shown variable performance. In this systematic review and meta-analysis, we assessed the clinical accuracy (sensitivity and specificity) of commercially available Ag-RDTs. Methods and findings We registered the review on PROSPERO (registration number: CRD42020225140). We systematically searched multiple databases (PubMed, Web of Science Core Collection, medRvix, bioRvix, and FIND) for publications evaluating the accuracy of Ag-RDTs for SARS-CoV-2 up until 30 April 2021. Descriptive analyses of all studies were performed, and when more than 4 studies were available, a random-effects meta-analysis was used to estimate pooled sensitivity and specificity in comparison to reverse transcription polymerase chain reaction (RT-PCR) testing. We assessed heterogeneity by subgroup analyses, and rated study quality and risk of bias using the QUADAS-2 assessment tool. From a total of 14,254 articles, we included 133 analytical and clinical studies resulting in 214 clinical accuracy datasets with 112,323 samples. Across all meta-analyzed samples, the pooled Ag-RDT sensitivity and specificity were 71.2% (95% CI 68.2% to 74.0%) and 98.9% (95% CI 98.6% to 99.1%), respectively. Sensitivity increased to 76.3% (95% CI 73.1% to 79.2%) if analysis was restricted to studies that followed the Ag-RDT manufacturers’ instructions. LumiraDx showed the highest sensitivity, with 88.2% (95% CI 59.0% to 97.5%). Of instrument-free Ag-RDTs, Standard Q nasal performed best, with 80.2% sensitivity (95% CI 70.3% to 87.4%). Across all Ag-RDTs, sensitivity was markedly better on samples with lower RT-PCR cycle threshold (Ct) values, i.e., <20 (96.5%, 95% CI 92.6% to 98.4%) and <25 (95.8%, 95% CI 92.3% to 97.8%), in comparison to those with Ct ≥ 25 (50.7%, 95% CI 35.6% to 65.8%) and ≥30 (20.9%, 95% CI 12.5% to 32.8%). Testing in the first week from symptom onset resulted in substantially higher sensitivity (83.8%, 95% CI 76.3% to 89.2%) compared to testing after 1 week (61.5%, 95% CI 52.2% to 70.0%). The best Ag-RDT sensitivity was found with anterior nasal sampling (75.5%, 95% CI 70.4% to 79.9%), in comparison to other sample types (e.g., nasopharyngeal, 71.6%, 95% CI 68.1% to 74.9%), although CIs were overlapping. Concerns of bias were raised across all datasets, and financial support from the manufacturer was reported in 24.1% of datasets. Our analysis was limited by the included studies’ heterogeneity in design and reporting. Conclusions In this study we found that Ag-RDTs detect the vast majority of SARS-CoV-2-infected persons within the first week of symptom onset and those with high viral load. Thus, they can have high utility for diagnostic purposes in the early phase of disease, making them a valuable tool to fight the spread of SARS-CoV-2. Standardization in conduct and reporting of clinical accuracy studies would improve comparability and use of data.

The accuracy of novel antigen rapid diagnostics for SARS-CoV-2: a living systematic review and meta-analysis.

Abstract: Background SARS-CoV-2 antigen rapid diagnostic tests (Ag-RDTs) are increasingly being integrated in testing strategies around the world. Studies of the Ag-RDTs have shown variable performance. In this systematic review and meta-analysis, we assessed the clinical accuracy (sensitivity and specificity) of commercially available Ag-RDTs. Methods We registered the review on PROSPERO (Registration number: CRD42020225140). We systematically searched multiple databases (PubMed, Web of Science Core Collection, medRvix and bioRvix, FINDdx) for publications up until December 11th, 2020. Descriptive analyses of all studies were performed and when more than four studies were available, a random-effects meta-analysis was used to estimate pooled sensitivity and specificity in comparison to reverse transcriptase polymerase chain reaction testing. We assessed heterogeneity by subgroup analyses ((1) performed con-form with manufacturer’s instructions for use (IFU) or not, (2) symptomatic vs. asymptomatic, (3) duration of symptoms less than seven days vs. more than seven days, (4) Ct-value Results From a total of 11,715 articles, we extracted 98 analytical and clinical data sets. 74 clinical accuracy data sets were evaluated that included 31,202 samples. Across all meta-analyzed samples, the pooled Ag-RDT sensitivity was 73.8% (CI 68.6 to 78.5). If analysis was restricted to studies that followed the Ag-RDT manufacturers’ instructions using fresh upper respiratory swab samples, the sensitivity increased to 79.1% (95%CI 75.0 to 82.8). The SD Biosensor Standard Q and Abbott Panbio showed the highest sensitivity with 81.7% and 72.7%, respectively. The best Ag-RDT performance was found with nasopharyngeal sampling (77.3%, CI 72.0 to 81.9) in comparison to other sample types (e.g., anterior nasal or mid turbinate 63.5%, CI 49.5 to 75.5). Testing in the first week from symptom onset resulted in higher sensitivity (87.5%, CI 86.0 to 89.1) compared to testing after one week (64.1%, CI 54.4 to 73.8). The tests performed markedly better on samples with lower Ct-values, i.e., Conclusion As Ag-RDTs detect most cases within the first week of symptom onset and those with high viral load, they can have high utility for screening purposes in the early phase of disease, and thus can be a valuable tool to fight the spread of SARS-CoV-2. Standardization of conduct and reporting of clinical accuracy studies would improve comparability and use of data. Summary In this living systematic review we analyzed 98 data sets for performance of SARS-CoV-2 Ag-RDTs compared to RT-PCR. Best-performing tests achieved a sensitivity of 81.7%. Highest sensitivity was found in patients within seven days of symptom onset when NP swabs were utilized.

The development of integrated circuits based on two-dimensional materials

Abstract: Two-dimensional (2D) materials could potentially be used to develop advanced monolithic integrated circuits. However, despite impressive demonstrations of single devices and simple circuits—in some cases with performance superior to those of silicon-based circuits—reports on the fabrication of integrated circuits using 2D materials are limited and the creation of large-scale circuits remains in its infancy. Here we examine the development of integrated circuits based on 2D layered materials. We assess the most advanced circuits fabricated so far and explore the key challenges that need to be addressed to deliver highly scaled circuits. We also propose a roadmap for the future development of integrated circuits based on 2D layered materials. This Perspective examines the development of integrated circuits based on layered two-dimensional materials, exploring where they are likely to first find commercial use and considers the challenges than need to be addressed to create highly scaled circuits.

Molecularly imprinted polymer based electrochemical sensor for quantitative detection of SARS-CoV-2 spike protein

Abstract: The continued spread of the coronavirus disease and prevalence of the global pandemic is exacerbated by the increase in the number of asymptomatic individuals who unknowingly spread the SARS-CoV-2 virus. Although remarkable progress is being achieved at curtailing further rampage of the disease, there is still the demand for simple and rapid diagnostic tools for early detection of the COVID-19 infection and the following isolation. We report the fabrication of an electrochemical sensor based on a molecularly imprinted polymer synthetic receptor for the quantitative detection of SARS-CoV-2 spike protein subunit S1 (ncovS1), by harnessing the covalent interaction between 1,2-diols of the highly glycosylated protein and the boronic acid group of 3-aminophenylboronic acid (APBA). The sensor displays a satisfactory performance with a reaction time of 15 min and is capable of detecting ncovS1 both in phosphate buffered saline and patient’s nasopharyngeal samples with LOD values of 15 fM and 64 fM, respectively. Moreover, the sensor is compatible with portable potentiostats thus allowing on-site measurements thereby holding a great potential as a point-of-care testing platform for rapid and early diagnosis of COVID-19 patients.

Molecularly imprinted polymer based electrochemical sensor for quantitative detection of SARS-CoV-2 spike protein

Abstract: The continued spread of the coronavirus disease and prevalence of the global pandemic is exacerbated by the increase in the number of asymptomatic individuals who unknowingly spread the SARS-CoV-2 virus. Although remarkable progress is being achieved at curtailing further rampage of the disease, there is still the demand for simple and rapid diagnostic tools for early detection of the COVID-19 infection and the following isolation. We report the fabrication of an electrochemical sensor based on a molecularly imprinted polymer synthetic receptor for the quantitative detection of SARS-CoV-2 spike protein subunit S1 (ncovS1), by harnessing the covalent interaction between 1,2-diols of the highly glycosylated protein and the boronic acid group of 3-aminophenylboronic acid (APBA). The sensor displays a satisfactory performance with a reaction time of 15 min and is capable of detecting ncovS1 both in phosphate buffered saline and patient’s nasopharyngeal samples with LOD values of 15 fM and 64 fM, respectively. Moreover, the sensor is compatible with portable potentiostats thus allowing on-site measurements thereby holding a great potential as a point-of-care testing platform for rapid and early diagnosis of COVID-19 patients.