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Papers by Lanju Mei

2022 IEEE Frontiers in Education Conference (FIE)

2022 IEEE Frontiers in Education Conference (FIE)

The 9th International Electronic Conference on Sensors and Applications

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Proceedings of the 16th International Multi-Conference on Society, Cybernetics and Informatics: IMSCI 2022

Our world has been permanently changed by the pandemic outbreak of COVID-19 starts around the end... more Our world has been permanently changed by the pandemic outbreak of COVID-19 starts around the end of 2019. In the first few months of 2020, the whole world was in urgent need of an effective, easy, and quick method for the identification of the infection of the new virus. Polymerase Chain Reaction (PCR) machine, which can test DNA samples by rapidly making millions of copies of a specific DNA sample through the PCR process, including the COVID-19 virus, can perfectly fit this demand. In this study, a design project on PCR is introduced for undergraduate education in electrical and mechanical engineering. The objective of this project is to develop a low-cost, ease-of-use, wallet-size, portable real-time PCR (RT-PCR) machine for accurate testing of various bacteria or viruses. The key function of the PT-PCR system is to precisely control and maintain the temperature of the biosample solution within a range between 55°C and 95°C. This project provides students opportunities in studying and practicing a wide range of engineering technics and skills, including mechanical design, electronics design, microcomputer programming, data acquisition and processing, etc. Students can gain comprehensive understanding of the design of multiphysics system after they overcome various challenges emerging in the project. From the view of engineering education, the process of this project development has demonstrated the importance and benefits of adopting complex interdisciplinary engineering problems for student teams to solve, especially those involve contemporary issues.

2021 IEEE Frontiers in Education Conference (FIE)

This is a work in progress on the research-to-practice to advance engineering development using l... more This is a work in progress on the research-to-practice to advance engineering development using logistic regression design methods in engineering education through project-based learning (PBL) activities. The aviation community has witnessed a growing concern with safety and security issues due to system vulnerability of manned and unmanned aircrafts. The implementation PBL in engineering education with major airports identified the benefits of this investigation as a multidisciplinary approach to address system vulnerabilities and analysis design approaches. This investigation includes defined methods and the factors to assess undergoing efforts of environment threats associated with complex networked systems in aviation through analysis design activities with machine learning. The ability to examine the analysis design allows learners in engineering education to deploy methods that will assess the combination of techniques and security consideration through machine learning. This project comprised of a collected dataset of network traces and malicious traffic that requires a solution and strategic model based on various scenarios to improve the software architecture design. Aviation safety and security standards are critical to the degree in which threats are constituted as each node within the network determined specific case studies for evaluation. This approach will feature a dataset that assess the spam detection categorization from a human behavior perspective and the factors to formulate data mining techniques and models in R programming language. The framework adopts the use of logistic regression and proposed techniques of the performance baseline to explore a systematic approach in the engineering design process. PBL in engineering education revealed a viewpoint from interdisciplinary approach as this study will have a wide range of features in the design analysis (e.g., revealing unwanted electronic information spread causing concerns and environmental threats to the aviation community). This study is developed to examine a common framework for processing and structuring a model using logistic regression analysis to classify key elements in the engineering process and PBL activities.

Micromachines, 2021

This paper investigates the electroosmotic micromixing of non-Newtonian fluid in a microchannel w... more This paper investigates the electroosmotic micromixing of non-Newtonian fluid in a microchannel with wall-mounted obstacles and surface potential heterogeneity on the obstacle surface. In the numerical simulation, the full model consisting of the Navier–Stokes equations and the Poisson–Nernst–Plank equations are solved for the electroosmotic fluid field, ion transport, and electric field, and the power law model is used to characterize the rheological behavior of the aqueous solution. The mixing performance is investigated under different parameters, such as electric double layer thickness, flow behavior index, obstacle surface zeta potential, obstacle dimension. Due to the zeta potential heterogeneity at the obstacle surface, vortical flow is formed near the obstacle surface, which can significantly improve the mixing efficiency. The results show that, the mixing efficiency can be improved by increasing the obstacle surface zeta potential, the flow behavior index, the obstacle heig...

Physical Chemistry Chemical Physics, 2016

Gate modulation of proton transport in a pH-regulated nanopore is investigated by considering the... more Gate modulation of proton transport in a pH-regulated nanopore is investigated by considering the electric double layer overlap effect.

IEEE Sensors Journal, 2017

This paper presents a performance investigation of a wearable distributed-deflection sensor in ar... more This paper presents a performance investigation of a wearable distributed-deflection sensor in arterial pulse waveform measurement. Built on a flexible substrate, the sensor entails a polymer microstructure embedded with an electrolyte-enabled resistive transducer array. By pressing the sensor against an artery with hold-down pressure exerted by two fingers, the pulse signal from the artery deflects the microstructure and registers as a resistance change by the transducer at the artery site. The radial and carotid pulse signals of five subjects are recorded via the sensor. Related signal-processing algorithms are written in Matlab to remove motion artifacts from a recorded pulse signal, extract its key tonometric parameters, and calculate the Pulse Wave Velocity (PWV) and radial and carotid Augmentation Index (AI). Whereas the tonometric parameters of the measured radial and carotid pulse waveforms on each subject are consistent with the related findings in the literature, the difference in tonometric parameters among the subjects also reveals physiological significance. The measured PWV and radial and carotid AI of the subjects show good agreement with how they should vary with age, gender and hypertension. Finally, the effect of the hold-down pressure on a measured pulse signal and the repeatability of the sensor are examined.

Nano Energy, 2017

Electrokinetic energy, where the pressure-driven transport of ions through nanofluidics yields st... more Electrokinetic energy, where the pressure-driven transport of ions through nanofluidics yields streaming potential/current, is one of the next generation, sustainable, clean energies by converting hydraulic to electrical power. In this study, we develop an analytical model taking into account many practical effects, such as the Stern layer, buffer anions (e.g., HEPES, ACES, and lactic acid), electric double layers (EDLs) overlap, and surface equilibrium reactions, to investigate the buffer effect on the electrokinetic energy conversion in a long, pH-regulated nanochannel. Taking the nanochannel made of silica as an example, we for the first time show that introducing buffer anions into the working fluid can significantly enhance not only the maximum electrokinetic power output but also the corresponding conversion efficiency in a nanochannel under the condition of highly overlapped EDLs (e.g., low background salt concentration and/or small channel height). With buffer anions, the performance of electrokinetic energy, depending on the salt concentration, pH, and nanoscale channel height, can be enhanced at a degree as high as 1.5-26 times, as compared to the case without buffer anions. This work provides a useful receipt for estimating the electrokinetic energy in the nanochannel in the presence of buffer anions and the finding is of crucial importance for renewable energy applications.

Journal of Biomechanical Engineering, 2017

Epithelial cells form quasi-two-dimensional sheets that function as contractile media to effect t... more Epithelial cells form quasi-two-dimensional sheets that function as contractile media to effect tissue shape changes during development and homeostasis. Endogenously generated intrasheet tension is a driver of such changes, but has predominantly been measured in the presence of directional migration. The nature of epithelial cell-generated forces transmitted over supracellular distances, in the absence of directional migration, is thus largely unclear. In this report, we consider large epithelial cell colonies which are archetypical multicell collectives with extensive cell–cell contacts but with a symmetric (circular) boundary. Using the traction force imbalance method (TFIM) (traction force microscopy combined with physical force balance), we first show that one can determine the colony-level endogenous sheet forces exerted at the midline by one half of the colony on the other half with no prior assumptions on the uniformity of the mechanical properties of the cell sheet. Importan...

IEEE Sensors Journal, 2016

A typical microfluidic load sensor consists of an electrolyte-filled microfluidic channel capped ... more A typical microfluidic load sensor consists of an electrolyte-filled microfluidic channel capped by a flexible plate. Under a load applied on the top flexible plate, the fluid within the microchannel is squeezed by the deflected plate, resulting in an opposite hydrodynamic pressure force on the plate. Thus, the electrolyte within the microchannel can induce a significant viscous damping effect on the dynamic response of such a microfluidic load sensor, whose output signal is proportional to the deformation of the flexible plate. Considering the coupling between the deformation of the flexible plate and the hydrodynamic fluid pressure, a mathematical model for analyzing the dynamics and viscous damping of the sensor is developed. Dynamic characteristics of the plate and the equivalent viscous damping coefficient as the functions of the load amplitude and the frequency as well as the sensor's geometric parameters are investigated. The obtained results qualitatively agree with the experimental observations in the literature. The results show that the load sensor is overdamped, and the viscous damping has significant influences on the dynamic response of the flexible plate in the microfluidic load sensor. The microfluidic channel depth has more significant effects on the plate deformation than the plate's width and thickness.

Sensors and Actuators B: Chemical, 2016

Functionalized nanofluidics has recently emerged as a powerful platform for applications of energ... more Functionalized nanofluidics has recently emerged as a powerful platform for applications of energy conversion as well as ionic diodes. Inspired by biological cells, we theoretically investigate for the first time the gate modulation of ion transport and selectivity in the soft nanochannel functionalized with biomimetic, pH-tunable, zwitterionic polyelectrolyte (PE) brush layers. The gate effect on the modulation of Donnan potential, ionic conductance, and ion selectivity in the biomimetic soft nanochannel is remarkable when the background salt concentration is low, pH is close to the isoelectric point of PE brush layers (slightly acidic), and the grafting density of PE brushes on the channel wall is small. Under those conditions, the biomimetic gated soft nanochannel is capable of being highly cation-selective when a negative gate voltage is applied. The findings provide a novel way for designing nanofluidic devices used in osmotic energy conversion and ion current rectification.

Electrochemistry Communications, 2015

An electrical four layer model taking into account surface chemical reactions and adsorption of t... more An electrical four layer model taking into account surface chemical reactions and adsorption of the metal and Tris buffer cations is developed for the first time to investigate the buffer effect on the ionic conductance in a pH-regulated nanochannel. Predictions from the analytical model agree well with experimental data of the conductance in silica nanochannels. The buffer effect is significant at low salt concentration, and the behaviors of zeta potential, surface charge density, and conductance in a nanochannel with buffer are distinctly different from those without buffer.

Electrochemistry Communications, 2015

There has been a significant growth of interest in single nanopore ionic devices that could contr... more There has been a significant growth of interest in single nanopore ionic devices that could control the transport of ions and rectify ionic current. To improve the advance of relevant nanofluidic devices, a model is derived for the first time to investigate the zeta potential and ionic conductance of a cylindrical nanopore with overlapped electric double layer as functions of pH, salt concentration as well as the Stern layer capacitance. The developed model is validated by the experimental data of the nanopore conductance. Results show that in addition to the magnitudes, the relevant behaviors of zeta potential and conductance of the nanopore might be significantly influenced by the Stern layer.

Physical Chemistry Chemical Physics, 2016

The Stern layer effect on the surface charge property and electrophoretic motion of pH-regulated ... more The Stern layer effect on the surface charge property and electrophoretic motion of pH-regulated silica nanoparticles is investigated theoretically.

Analytical chemistry, Jan 3, 2015

Accurately and rapidly analyzing the ionic current/conductance in a nanochannel, especially under... more Accurately and rapidly analyzing the ionic current/conductance in a nanochannel, especially under the condition of overlapped electric double layers (EDLs), is of fundamental significance for the design and development of novel nanofluidic devices. To achieve this, an analytical model for the surface charge properties and ionic current/conductance in a pH-regulated nanochannel is developed for the first time. The developed model takes into account the effects of the EDL overlap, electroosmotic flow, Stern layer, multiple ionic species, and the site dissociation/association reactions on the channel walls. In addition to good agreement with the existing experimental data of nanochannel conductance available from the literature, our analytical model is also validated by the full model with the Poisson-Nernst-Planck and Navier-Stokes equations. The EDL overlap effect is significant at small nanochannel height, low salt concentration, and medium low pH. Neglecting the EDL overlap effect ...

Micromachines

Microfluidics has seen a remarkable growth over the past few decades, with its extensive applicat... more Microfluidics has seen a remarkable growth over the past few decades, with its extensive applications in engineering, medicine, biology, chemistry, etc [...]

2022 IEEE Frontiers in Education Conference (FIE)

2022 IEEE Frontiers in Education Conference (FIE)

The 9th International Electronic Conference on Sensors and Applications

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Proceedings of the 16th International Multi-Conference on Society, Cybernetics and Informatics: IMSCI 2022

Our world has been permanently changed by the pandemic outbreak of COVID-19 starts around the end... more Our world has been permanently changed by the pandemic outbreak of COVID-19 starts around the end of 2019. In the first few months of 2020, the whole world was in urgent need of an effective, easy, and quick method for the identification of the infection of the new virus. Polymerase Chain Reaction (PCR) machine, which can test DNA samples by rapidly making millions of copies of a specific DNA sample through the PCR process, including the COVID-19 virus, can perfectly fit this demand. In this study, a design project on PCR is introduced for undergraduate education in electrical and mechanical engineering. The objective of this project is to develop a low-cost, ease-of-use, wallet-size, portable real-time PCR (RT-PCR) machine for accurate testing of various bacteria or viruses. The key function of the PT-PCR system is to precisely control and maintain the temperature of the biosample solution within a range between 55°C and 95°C. This project provides students opportunities in studying and practicing a wide range of engineering technics and skills, including mechanical design, electronics design, microcomputer programming, data acquisition and processing, etc. Students can gain comprehensive understanding of the design of multiphysics system after they overcome various challenges emerging in the project. From the view of engineering education, the process of this project development has demonstrated the importance and benefits of adopting complex interdisciplinary engineering problems for student teams to solve, especially those involve contemporary issues.

2021 IEEE Frontiers in Education Conference (FIE)

This is a work in progress on the research-to-practice to advance engineering development using l... more This is a work in progress on the research-to-practice to advance engineering development using logistic regression design methods in engineering education through project-based learning (PBL) activities. The aviation community has witnessed a growing concern with safety and security issues due to system vulnerability of manned and unmanned aircrafts. The implementation PBL in engineering education with major airports identified the benefits of this investigation as a multidisciplinary approach to address system vulnerabilities and analysis design approaches. This investigation includes defined methods and the factors to assess undergoing efforts of environment threats associated with complex networked systems in aviation through analysis design activities with machine learning. The ability to examine the analysis design allows learners in engineering education to deploy methods that will assess the combination of techniques and security consideration through machine learning. This project comprised of a collected dataset of network traces and malicious traffic that requires a solution and strategic model based on various scenarios to improve the software architecture design. Aviation safety and security standards are critical to the degree in which threats are constituted as each node within the network determined specific case studies for evaluation. This approach will feature a dataset that assess the spam detection categorization from a human behavior perspective and the factors to formulate data mining techniques and models in R programming language. The framework adopts the use of logistic regression and proposed techniques of the performance baseline to explore a systematic approach in the engineering design process. PBL in engineering education revealed a viewpoint from interdisciplinary approach as this study will have a wide range of features in the design analysis (e.g., revealing unwanted electronic information spread causing concerns and environmental threats to the aviation community). This study is developed to examine a common framework for processing and structuring a model using logistic regression analysis to classify key elements in the engineering process and PBL activities.

Micromachines, 2021

This paper investigates the electroosmotic micromixing of non-Newtonian fluid in a microchannel w... more This paper investigates the electroosmotic micromixing of non-Newtonian fluid in a microchannel with wall-mounted obstacles and surface potential heterogeneity on the obstacle surface. In the numerical simulation, the full model consisting of the Navier–Stokes equations and the Poisson–Nernst–Plank equations are solved for the electroosmotic fluid field, ion transport, and electric field, and the power law model is used to characterize the rheological behavior of the aqueous solution. The mixing performance is investigated under different parameters, such as electric double layer thickness, flow behavior index, obstacle surface zeta potential, obstacle dimension. Due to the zeta potential heterogeneity at the obstacle surface, vortical flow is formed near the obstacle surface, which can significantly improve the mixing efficiency. The results show that, the mixing efficiency can be improved by increasing the obstacle surface zeta potential, the flow behavior index, the obstacle heig...

Physical Chemistry Chemical Physics, 2016

Gate modulation of proton transport in a pH-regulated nanopore is investigated by considering the... more Gate modulation of proton transport in a pH-regulated nanopore is investigated by considering the electric double layer overlap effect.

IEEE Sensors Journal, 2017

This paper presents a performance investigation of a wearable distributed-deflection sensor in ar... more This paper presents a performance investigation of a wearable distributed-deflection sensor in arterial pulse waveform measurement. Built on a flexible substrate, the sensor entails a polymer microstructure embedded with an electrolyte-enabled resistive transducer array. By pressing the sensor against an artery with hold-down pressure exerted by two fingers, the pulse signal from the artery deflects the microstructure and registers as a resistance change by the transducer at the artery site. The radial and carotid pulse signals of five subjects are recorded via the sensor. Related signal-processing algorithms are written in Matlab to remove motion artifacts from a recorded pulse signal, extract its key tonometric parameters, and calculate the Pulse Wave Velocity (PWV) and radial and carotid Augmentation Index (AI). Whereas the tonometric parameters of the measured radial and carotid pulse waveforms on each subject are consistent with the related findings in the literature, the difference in tonometric parameters among the subjects also reveals physiological significance. The measured PWV and radial and carotid AI of the subjects show good agreement with how they should vary with age, gender and hypertension. Finally, the effect of the hold-down pressure on a measured pulse signal and the repeatability of the sensor are examined.

Nano Energy, 2017

Electrokinetic energy, where the pressure-driven transport of ions through nanofluidics yields st... more Electrokinetic energy, where the pressure-driven transport of ions through nanofluidics yields streaming potential/current, is one of the next generation, sustainable, clean energies by converting hydraulic to electrical power. In this study, we develop an analytical model taking into account many practical effects, such as the Stern layer, buffer anions (e.g., HEPES, ACES, and lactic acid), electric double layers (EDLs) overlap, and surface equilibrium reactions, to investigate the buffer effect on the electrokinetic energy conversion in a long, pH-regulated nanochannel. Taking the nanochannel made of silica as an example, we for the first time show that introducing buffer anions into the working fluid can significantly enhance not only the maximum electrokinetic power output but also the corresponding conversion efficiency in a nanochannel under the condition of highly overlapped EDLs (e.g., low background salt concentration and/or small channel height). With buffer anions, the performance of electrokinetic energy, depending on the salt concentration, pH, and nanoscale channel height, can be enhanced at a degree as high as 1.5-26 times, as compared to the case without buffer anions. This work provides a useful receipt for estimating the electrokinetic energy in the nanochannel in the presence of buffer anions and the finding is of crucial importance for renewable energy applications.

Journal of Biomechanical Engineering, 2017

Epithelial cells form quasi-two-dimensional sheets that function as contractile media to effect t... more Epithelial cells form quasi-two-dimensional sheets that function as contractile media to effect tissue shape changes during development and homeostasis. Endogenously generated intrasheet tension is a driver of such changes, but has predominantly been measured in the presence of directional migration. The nature of epithelial cell-generated forces transmitted over supracellular distances, in the absence of directional migration, is thus largely unclear. In this report, we consider large epithelial cell colonies which are archetypical multicell collectives with extensive cell–cell contacts but with a symmetric (circular) boundary. Using the traction force imbalance method (TFIM) (traction force microscopy combined with physical force balance), we first show that one can determine the colony-level endogenous sheet forces exerted at the midline by one half of the colony on the other half with no prior assumptions on the uniformity of the mechanical properties of the cell sheet. Importan...

IEEE Sensors Journal, 2016

A typical microfluidic load sensor consists of an electrolyte-filled microfluidic channel capped ... more A typical microfluidic load sensor consists of an electrolyte-filled microfluidic channel capped by a flexible plate. Under a load applied on the top flexible plate, the fluid within the microchannel is squeezed by the deflected plate, resulting in an opposite hydrodynamic pressure force on the plate. Thus, the electrolyte within the microchannel can induce a significant viscous damping effect on the dynamic response of such a microfluidic load sensor, whose output signal is proportional to the deformation of the flexible plate. Considering the coupling between the deformation of the flexible plate and the hydrodynamic fluid pressure, a mathematical model for analyzing the dynamics and viscous damping of the sensor is developed. Dynamic characteristics of the plate and the equivalent viscous damping coefficient as the functions of the load amplitude and the frequency as well as the sensor's geometric parameters are investigated. The obtained results qualitatively agree with the experimental observations in the literature. The results show that the load sensor is overdamped, and the viscous damping has significant influences on the dynamic response of the flexible plate in the microfluidic load sensor. The microfluidic channel depth has more significant effects on the plate deformation than the plate's width and thickness.

Sensors and Actuators B: Chemical, 2016

Functionalized nanofluidics has recently emerged as a powerful platform for applications of energ... more Functionalized nanofluidics has recently emerged as a powerful platform for applications of energy conversion as well as ionic diodes. Inspired by biological cells, we theoretically investigate for the first time the gate modulation of ion transport and selectivity in the soft nanochannel functionalized with biomimetic, pH-tunable, zwitterionic polyelectrolyte (PE) brush layers. The gate effect on the modulation of Donnan potential, ionic conductance, and ion selectivity in the biomimetic soft nanochannel is remarkable when the background salt concentration is low, pH is close to the isoelectric point of PE brush layers (slightly acidic), and the grafting density of PE brushes on the channel wall is small. Under those conditions, the biomimetic gated soft nanochannel is capable of being highly cation-selective when a negative gate voltage is applied. The findings provide a novel way for designing nanofluidic devices used in osmotic energy conversion and ion current rectification.

Electrochemistry Communications, 2015

An electrical four layer model taking into account surface chemical reactions and adsorption of t... more An electrical four layer model taking into account surface chemical reactions and adsorption of the metal and Tris buffer cations is developed for the first time to investigate the buffer effect on the ionic conductance in a pH-regulated nanochannel. Predictions from the analytical model agree well with experimental data of the conductance in silica nanochannels. The buffer effect is significant at low salt concentration, and the behaviors of zeta potential, surface charge density, and conductance in a nanochannel with buffer are distinctly different from those without buffer.

Electrochemistry Communications, 2015

There has been a significant growth of interest in single nanopore ionic devices that could contr... more There has been a significant growth of interest in single nanopore ionic devices that could control the transport of ions and rectify ionic current. To improve the advance of relevant nanofluidic devices, a model is derived for the first time to investigate the zeta potential and ionic conductance of a cylindrical nanopore with overlapped electric double layer as functions of pH, salt concentration as well as the Stern layer capacitance. The developed model is validated by the experimental data of the nanopore conductance. Results show that in addition to the magnitudes, the relevant behaviors of zeta potential and conductance of the nanopore might be significantly influenced by the Stern layer.

Physical Chemistry Chemical Physics, 2016

The Stern layer effect on the surface charge property and electrophoretic motion of pH-regulated ... more The Stern layer effect on the surface charge property and electrophoretic motion of pH-regulated silica nanoparticles is investigated theoretically.

Analytical chemistry, Jan 3, 2015

Accurately and rapidly analyzing the ionic current/conductance in a nanochannel, especially under... more Accurately and rapidly analyzing the ionic current/conductance in a nanochannel, especially under the condition of overlapped electric double layers (EDLs), is of fundamental significance for the design and development of novel nanofluidic devices. To achieve this, an analytical model for the surface charge properties and ionic current/conductance in a pH-regulated nanochannel is developed for the first time. The developed model takes into account the effects of the EDL overlap, electroosmotic flow, Stern layer, multiple ionic species, and the site dissociation/association reactions on the channel walls. In addition to good agreement with the existing experimental data of nanochannel conductance available from the literature, our analytical model is also validated by the full model with the Poisson-Nernst-Planck and Navier-Stokes equations. The EDL overlap effect is significant at small nanochannel height, low salt concentration, and medium low pH. Neglecting the EDL overlap effect ...

Micromachines

Microfluidics has seen a remarkable growth over the past few decades, with its extensive applicat... more Microfluidics has seen a remarkable growth over the past few decades, with its extensive applications in engineering, medicine, biology, chemistry, etc [...]