Sanjay Kumar | University of Nebraska Lincoln (original) (raw)

Papers by Sanjay Kumar

Biosensors, 2024

This manuscript offers a concise overview of paper microfluidics, emphasizing its sustainable sen... more This manuscript offers a concise overview of paper microfluidics, emphasizing its sustainable sensing applications in healthcare, environmental monitoring, and food safety. Researchers have developed innovative sensing platforms for detecting pathogens, pollutants, and contaminants by leveraging the paper’s unique properties, such as biodegradability and affordability. These portable, low-cost sensors facilitate rapid diagnostics and on-site analysis, making them invaluable tools for resource-limited settings. This review discusses the fabrication techniques, principles, and applications of paper microfluidics, showcasing its potential to address pressing challenges and enhance human health and environmental sustainability.

Biosensors, 2023

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

arxiv, 2023

The burgeoning field of organic electronics has ushered in a new era of biosensing technology, of... more The burgeoning field of organic electronics has ushered in a new era of biosensing technology, offering a promising frontier for applications in both medical diagnostics and environmental monitoring. This review paper provides a comprehensive overview of the remarkable progress and potential of organic electronics in biosensing applications. It explores the multifaceted aspects of organic materials and devices, highlighting their unique advantages, such as flexibility, biocompatibility, and low-cost fabrication. The paper delves into the diverse range of biosensors enabled by organic electronics, including electrochemical, optical, piezoelectric, and thermo sensors, showcasing their versatility in detecting biomolecules, pathogens, and environmental pollutants. Furthermore, integrating organic biosensors into wearable devices and the Internet of Things (IoT) ecosystem is discussed, offering real-time, remote, and personalized monitoring solutions. The review also addresses the current challenges and future prospects of organic biosensing, emphasizing the potential for breakthroughs in personalized medicine, environmental sustainability, and the advancement of human health and well-being.

Applied Acoustics, 2023

Exploring the potential of sound absorption is foremost for improving room acoustics and unleashi... more Exploring the potential of sound absorption is foremost for improving room acoustics and unleashing the power of noise remediation. Acoustic metamaterials are considered promising candidates for tunable broadband sound absorption in the low-to-high frequency range. In this work, an acoustic meta-absorber with multi-order Helmholtz resonator cavities is proposed. The meta-absorber unit cell comprises multiple disks, spacers, and a bottom cavity arranged in a series configuration. Therefore, the assembled acoustic meta-absorber is reconfigurable to have different absorption characteristics. Experimental results demonstrate that the proposed meta-absorber unit cell exhibits high sound absorption, with multiple absorption peaks observed within the 80-1600 Hz frequency range. Additionally, tunable broadband and quasi-perfect absorption (≥0.9) can be achieved at low frequencies (≤600 Hz) by adjusting the positions of individual disks and other structural parameters. Furthermore, a feedforward network-design approach based on machine learning models is proposed and experimentally demonstrated for the meta-absorber. Two types of metaabsorber features and different machine learning algorithms, including artificial neural network (ANN), k-Nearest Neighbor (kNN), and radial basis function neural network (RBFN), are utilized to compare their predictive abilities. The implementation of machine learning models allows for efficient design optimization of the meta-absorber’s geometrical parameters to achieve specific functionalities without relying on physical models. The geometrical parameters are adaptively tuned during the design process to enhance sound absorption performance, particularly at low frequencies. The predicted sound absorption values are compared with the experimental results, and among the machine learning algorithms employed, ANN demonstrates the best performance, followed by the kNN method.

Building and Environment, 2023

Global aging strains health infrastructure • Experts identify facets of smart, healthy built envi... more Global aging strains health infrastructure • Experts identify facets of smart, healthy built environments for older adults • IEQ and smart building technologies are contextualized for older adults and caregivers • Challenges for implementation and gaps in knowledge are identified

Journal of Applied Physics, 2023

This study presents a compact, lightweight, and reconfigurable acoustic metatile for sound mitiga... more This study presents a compact, lightweight, and reconfigurable acoustic metatile for sound mitigation applications. The metatile prototype is designed based on a circular maze-like acoustic metastructure, which utilizes a space-coiling technique for enhanced acoustic performance
in low-to-mid frequencies. The proposed labyrinthine acoustic metadisk structure comprises a central hollow front face sheet and two coiling-up backing cavities. Experimental results show that the metadisk has high absorption peaks of 0.81 and 0.75 at 574 and 1436 Hz, respectively, and exhibits high sound transmission loss (STL) values (25 dB) in separate wide frequency bands between 100–580 Hz and 820–1600 Hz. Based on the metadisk samples, metatiles are constructed, which are 30.5* 30.5 cm2 in size. The acoustic performance of these metatiles is investigated in two distinct scenarios. Two prototypes of the acoustic metatile are presented: the metacage and the metapanel. The metacage is a cubical box-shaped structure constructed using five metatiles, which showed a wideband insertion loss of 10 dB in 200–16000 Hz and 20 dB over 400–5000 Hz. On the other hand, the metapanel is constructed using nine metatiles, which exhibited STL values of >20 dB over 125–5000 Hz and had a sound transmission class rating of 34. The study highlights the potential of circular maze-like space-coiling-based acoustic disk metastructures to be reconfigured into metatiles and assembled into a metacage or metapanel for practical sound mitigation applications.

Applied Acoustics, 2022

The quest for a quiet environment has led to numerous efforts to shield noise at the source or de... more The quest for a quiet environment has led to numerous efforts to shield noise at the source or develop an efficient acoustic proof system. We present a threedimensional sonic crystal acoustic metacage structure for hybrid purposes of noise shielding and natural ventilation. The metacage prototype comprises six

Applied Acoustics, 2022

This study demonstrates a modular, compact, and lightweight sonic cage for sound mitigation appli... more This study demonstrates a modular, compact, and lightweight sonic cage for sound mitigation applications. The design prototype utilized the principle of sonic crystals and has been composed of periodically arranged readily available aluminum extrusion T-slot columns. The preliminary design has demonstrated a sound insertion loss peak of 2.94 dB at 2000 Hz, while a broad insertion loss spectrum has been obtained in 630-1000 Hz. Additionally, to improve the low-frequency performance, two additional design strategies utilizing the characteristics of T-slots have been proposed. The experimental results have revealed the significant improvement of sound insertion loss peak values in low-to-mid frequency. With design strategy I, an insertion loss peak value of 10.2 dB was observed at 500 Hz, while with design strategy II, two significant insertion loss peaks of 7.26 dB and 10.33 dB were observed at 800 Hz and 2000 Hz. Moreover, the proposed designs have revealed the tunable insertion loss peaks frequency. The designed insertion loss peaks demonstrated the feasibility of the sonic cage concept for mitigating the noise sources.

Acoustics, 2021

In this paper, the cabin noise of four airport express rail systems, namely the Taiwan Taoyuan In... more In this paper, the cabin noise of four airport express rail systems, namely the Taiwan Taoyuan International Airport MRT, the Hong Kong Airport Express, RER B service from Paris Gare du Nord to Paris Charles de Gaulle Airport, and the Shanghai Maglev, have been measured. These four airport express rail systems have different specifications and maximum speeds, ranging from 100 to 300 km/h. The results show a significant low-frequency noise content below 100 Hz, which would not be captured if the measurements were conducted in dB(A). The difference between Leq in terms of dB(C) and dB(A) ranges from 11.3 to 17.0 dB. The maximum speed of the Taoyuan Airport MRT was found to be the lowest at 100 km/h and with the lowest Leq in terms of 66.4 dB(A) and 81.4 dB(C). The Shanghai Maglev has a maximum speed of 300 km/h but a relatively low Leq of 69.7 dB(A), although its top speed is almost three times the maximum of the other airport rail systems. It also has the lowest Lmax of 73.1 dB(A) am...

arXiv: Applied Physics, 2020

The continuous increase of hospital noise levels has become a vital challenge for society. The co... more The continuous increase of hospital noise levels has become a vital challenge for society. The complex soundscapes in the hospital produce unpleasant noise, which may exceed the prescribed noise level for the patients and healthcare professionals. Previous studies have reported that extended exposure to loud noise may cause auditory and nonauditory disorders in healthcare professionals, medical staff, and patients. Therefore, there is an increased interest for the design and fabrication of effective noise barriers for the hospital premises. Herein, we have performed the thorough experimental investigations on the acoustical performances for PVC coated polyester fabrics and 100 % pure PVC sheets. The performances of these potential acoustic curtains have found to be superior to that of existing acoustic curtains for hospitals. Also, the results showed that the sound transmission class rating of PVC curtains are much higher than the existing commercial acoustic curtains.

Designs, 2021

A micro-perforated plate or panel (MPP) is a device used to absorb sound. It consists of a thin f... more A micro-perforated plate or panel (MPP) is a device used to absorb sound. It consists of a thin flat plate made from several different materials with small holes and a back cavity. Several reported modifications and enhancements to the original design of the MPP acoustic absorber were modified by the holes or the back-cavity shape and sizes following the original idea. The present study attempts to artistically beautify the MPP acoustic absorbers by incorporating dotted arts into the design of MPP. The perforation for micro-perforated panels could be dotted arts with a perforation size smaller than 1 mm for enhanced acoustic absorption performance in the form of various artistic designs. Small LED lights could be placed inside the acoustic chamber to create the color lights emanating from the perforations instead of dots with different colors. Several MPP incorporated artistic designs of dotted patterns were presented and their acoustic absorption performance was analyzed using impe...

Acoustics, 2021

The pandemic has impacted every facet of our life, society, and environment. It has also affected... more The pandemic has impacted every facet of our life, society, and environment. It has also affected both the requirement and challenges for acoustic research and applications. The present article attempts to present a summary of the impact of COVID-19 on several aspects of acoustics, from the changes in the sonic environment due to reduced human and industrial activities to natural ventilation requirements for mitigating the transmission of coronavirus while mitigating noise, and, more importantly, discusses the potential impacts and challenges for acoustics in the post-COVID-19 era. The present study specifically examines the effects of COVID-19 on the sonic environment, the acoustic treatment by considering the need for constant disinfection, the noise control on construction and neighborhood activities in response to an increased number of people working from home, and the need for having natural ventilation while mitigating noise at home and offices.

Applied Acoustics, 2022

There is an increased concern about aircraft flypast noise, especially for residents living near ... more There is an increased concern about aircraft flypast noise, especially for residents living near an airport. Airlines typically fly at lower heights near the airports for taking off and landing. In this study, we measured the aircraft flypast noise near the Singapore Changi Airport, and the measurement locations were about 1.5 km away from the tip of the nearest runway. For the incoming flights, the average continuous sound pressure levels for the 12 aircraft recorded were 69.6 dB(A) and 77.8 dB(C), with an average difference of 8.3 dB between dB(A) and dB(C) scales. The plane flypast noise for the taking-off aircraft was significantly higher than that of incoming aircraft. The average continuous sound pressure levels for the 17 aircraft were equal to 75 dB(A) and 84 dB(C). The present study has shown a significant difference in the noise level between taking off and landing and between A-weighting and C-weighting measurements.

Physics of Fluids, 2020

Paper published as part of the special topic on Flow and the Virus This paper was selected as Fea... more Paper published as part of the special topic on Flow and the Virus This paper was selected as Featured ARTICLES YOU MAY BE INTERESTED IN Numerical investigation of aerosol transport in a classroom with relevance to COVID-19

Applied Physics Letters, 2020

There is growing interest in the development of path coiling-based labyrinthine acoustic metamate... more There is growing interest in the development of path coiling-based labyrinthine acoustic metamaterials for realizing extraordinary acoustical properties such as low-to-mid frequency sound absorption. We present a subwavelength labyrinthine acoustic metastructure (3 cm) exhibiting a superior sound absorption with a high bandwidth (more than one octave in the range of 400-1400 Hz). The metastructure is orchestrated of multiple labyrinthine unit cells of different configurations in a hexagonal array, and broadband absorption has been achieved by the dissipation of incident propagating sound waves inside the labyrinthine zigzag channels. Furthermore, the unique design of the metastructure allows for simultaneous air circulation for facilitating natural ventilation and sound absorption. The proposed unique designs may find potential applications in architectural acoustics and noise shielding where simultaneous natural ventilation and noise mitigation are required.

Journal of Applied Physics, 2019

The unique characteristics like periodic and locally resonant behaviors of acoustic metamaterials... more The unique characteristics like periodic and locally resonant behaviors of acoustic metamaterials result in an anomalous response to the wave propagation and exhibit complete elastic wave bandgaps. However, these unusual properties arise from the geometry of the artificially designed metastructure and can be significantly affected under the exposure of the thermal environment. In this paper, we present a thermally tunable two-dimensional acoustic metamaterial with a hexagonal lattice. The numerical results demonstrated that by adjusting the externally applied temperature to the structure and imposing several different load conditions like thermal deformation and thermal stress, a tunable effective mass density of the metamaterial could be obtained. The proposed concept further extends the ongoing research in the field of tunable acoustic metamaterials.

Acoustics, 2019

Owing to a steep rise in urban population, there has been a continuous growth in construction of ... more Owing to a steep rise in urban population, there has been a continuous growth in construction of buildings, public or private transport like cars, motorbikes, trains, and planes at a global level. Hence, urban noise has become a major issue affecting the health and quality of human life. In the current environmental scenario, architectural acoustics has been directed towards controlling and manipulating sound waves at a desired level. Structural engineers and designers are moving towards green technologies, which may help improve the overall comfort level of residents. A variety of conventional sound absorbing materials are being used to reduce noise, but attenuation of low-frequency noise still remains a challenge. Recently, acoustic metamaterials that enable low-frequency sound manipulation, mitigation, and control have been widely used for architectural acoustics and traffic noise mitigation. This review article provides an overview of the role of acoustic metamaterials for archi...

ArXiv, 2020

Vacuum cleaners are one of the most widely used household appliances associated with unpleasant n... more Vacuum cleaners are one of the most widely used household appliances associated with unpleasant noises. Previous studies have indicated the severity of vacuum cleaner noise and its impact on the users nearby. The quantified measurements of the generated noise standalone are not sufficient for the selection or designing of vacuum cleaners. The human perception must also be included for a better assessment of the quality of sound. A hybrid approach known as psychoacoustics, which comprises subjective and objective evaluations of sounds, is widely used in recent times. This paper focuses on the experimental assessment of psychoacoustical matrices for household vacuum cleaners. Three vacuum cleaners with different specifications have been selected as test candidates, and their sound qualities have been analyzed. Besides, the annoyance index has been assessed for these vacuum cleaners.

Applied Acoustics, 2022

The aviation industry has seen dramatic growth over the decades till the recent disruption due to... more The aviation industry has seen dramatic growth over the decades till the recent disruption due to the COVID-19 pandemic. Moreover, long-haul routes with a distance of more than 4000 km are common for major airlines worldwide. Therefore, aircraft cabin noise assessment is essential, especially in long-haul flights, for passenger and flight crew health wellness. In this paper, the cabin noise of five wide-body aircraft, namely Airbus A330-300ER, A350-900, A380-800, and Boeing B777-200ER and B787-900, was recorded using a calibrated inhouse developed smartphone application. The sound pressure levels of in-cabin noise have been measured on two different decibel scales, namely, A-weighted [dB(A)] and C-weighted scales [dB(C)]. The sound pressure levels of Airbus A380-800 were lowest among selected models, while the in-cabin pressure level values of Airbus A350-900 were maximum. However, the difference in decibel levels between the aircraft is minimal as it is within 3 dB.

Biosensors, 2024

Biosensors, 2023

arxiv, 2023

Applied Acoustics, 2023

Building and Environment, 2023

Journal of Applied Physics, 2023

Applied Acoustics, 2022

Acoustics, 2021

arXiv: Applied Physics, 2020

Designs, 2021

Acoustics, 2021

Applied Acoustics, 2022

Physics of Fluids, 2020

Applied Physics Letters, 2020

Journal of Applied Physics, 2019

Acoustics, 2019

ArXiv, 2020

Applied Acoustics, 2022

Springer, Singapore, 2019

Paper microfluidics is one of the rapidly growing technology and shown a tremendous caliber in fi... more Paper microfluidics is one of the rapidly growing technology and shown a tremendous caliber in field of healthcare, biochemistry, environmental monitoring, analytical chemistry, etc. Owing to their distinct advantages such as rapid, easy-to-use, compatible with biological, organic and inorganic entities, chemical inertness, robustness, economical, environment-friendly and easy disposal, paper microfluidic-based devices have become a prominent alternative for existing technologies POC technologies. The challenge remains, however, in the designing of an efficient paper-based device for specific applications. A great deal of work has been done in this field to address the challenges in its two key enabling parameters namely ‘materials properties’ and ‘fluid-transport mechanism’ to achieve the functional paper device in an efficient and predictive way. Keeping in mind the previously published articles, the focus here is primarily on showcasing the fluid transport mechanisms through paper-based microfluidic devices. This chapter intends to provide an understanding towards theoretical modelling from a device perspective. The commonly used paper substrates and critical factors involved with any fluid transport phenomena is also covered.

Springer, Singapore, 2019

Paper-based microfluidic systems have emerged as one of the most favorable technologies used in m... more Paper-based microfluidic systems have emerged as one of the most favorable technologies used in many potential applications such as point-of-care diagnostics, flexible electronics, energy storage, etc. From the past several decades, paper-based technology has readily accepted in the academic research lab and industries as well. The paper-based devices have changed the life of humankind. The distinguishing characteristics of paper substrate like low cost, biodegradability, biocompatibility, and ease of fabrication helped their adaptability in biosensing applications. This chapter gives a concise overview of the historical perspective of paper-based devices, classification of paper types, and their recent applications.

Nanofabrication has been a critical area of research in the last two decades and has found wide-r... more Nanofabrication has been a critical area of research in the last two decades and has found wide-ranging application in improvising material properties, sensitive clinical diagnostics, and detection, improving the efficiency of electron transport processes within materials, generating high energy densities leading to pulse power, novel therapeutic mechanisms, environmental remediation and control. The continued improvements in the various fabrication technologies have led to realization of highly sensitive nanostructure-based devices. The fabrication of nanostructures is in principle carried out primarily using top-down or bottom-up approaches. This chapter summarizes the important bottom-up nanofabrication processes for realizing nanostructures and also highlights the recent research conducted in the domain of therapeutics and diagnostics.

Sensory systems are available today at all length scales and formulate an important mandate in su... more Sensory systems are available today at all length scales and formulate an important mandate in sustainability of environment and health. They use a wide spectrum of transduction mechanisms and signal conversion approaches with different levels of accuracy and rapidity. Sensors as deployed in various ranges of applications span from relatively simple temperature measurement bimetallic thermocouple structures to the detection of specific entities using advanced physical principles. The best example of sensors emanates from nature itself. Almost all living beings are blessed with sensory systems to sense and act to various environmental stimuli. There is a lot of inferential learning from such systems which can be translated to modern day sensor research. Within the environmental, chemical, and medical domains sensing can be carried out across a variety of length scales like the macroscale, microscale, or nanoscale. In a very organized manner a sensory system can be simplified into an analyte of interest (external to the sensor), a detection element (which is fixated to the sensory surface), a single transduction mechanism (to record measurable signal coming out from the change of analyte concentration), an analyzer and a decision tool. Further, the sensory systems can be using mechanical, microelectronic, micromechanical or electromechanical, optical, electrochemical, colorimetric, and other means to perform rapid sensing in the physical, chemical, and biological types of analytes. This book describes the basic mechanisms, fabrication techniques, and recent advancements in developments related to environmental, chemical, and medical sensors.

The Journal of the Acoustical Society of America, 2023

Autism is a set of complex neurobehavioral conditions that involve, among other characteristics, ... more Autism is a set of complex neurobehavioral conditions that involve, among other characteristics, hypo/hypersensitive responses to any sensory input, usually referred to as sensory processing disorder. The most common sensory difference associated with autistic individuals is an over or under response to visuals, touch, smells, tastes, balance, and sounds when compared to neurotypical individuals. Among these, auditory sensitivity has a significant influence. Research studies to date have revealed that autistic individuals are highly susceptible to surrounding sounds, and show that certain noises, such as loud sounds, classroom bells, sirens, the radio or the TV, and traffic noise, may induce uncomfortable and distracting behavior. In this study, we investigated the acoustic environment of classrooms/facilities designed for a more inclusive education. A number of room acoustic descriptors, such as reverberation time (RT), speech clarity (C50), speech transmission index (STI), sound levels, and auditory strength (S/N ratio) were measured in this regard. The experimental measurements were performed in several rooms and facilities focusing on autistic individuals in Campinas, São Paulo, in Brazil and in Omaha, Nebraska, in the United States.

Acoustics, 2022

Dear Colleagues, This Special Issue focuses on the broad topic of “Classroom Acoustics”. Acousti... more Dear Colleagues,

This Special Issue focuses on the broad topic of “Classroom Acoustics”. Acoustic comfort is one of the significant factors that affect occupants’ comfort, health, and performance. The poor acoustic design of spaces in buildings can affect occupants’ learning and work efficiency. The aim is to create efficient learning environments with desirable listening conditions.

We invite contributions on topics related to classroom acoustics, including but not limited to innovative solutions for the development of quiet spaces, acoustic comfort, speech intelligibility, listening effort, acoustic materials, acoustic metamaterials, sound absorbers, etc., for this particular Special Issue. Research articles that cover theoretical and/or experimental studies, as well as comprehensive review or survey papers, are welcome.

We hope that you will contribute a paper to this Special Issue. If you have any questions, please do not hesitate to contact us. Thank you for your consideration!

Prof. Dr. Lily Wang
Dr. Sanjay Kumar
Guest Editors

Lightweight materials have often been used in transportation vehicles, giving rise to faster and ... more Lightweight materials have often been used in transportation vehicles, giving rise to faster and more energy efficient vehicles. Apart from making the materials lighter and stronger, one consideration would be the improvement of the acoustic rating of the material. Effective use of sandwich panels can significantly increase the load bearing capacity and also reduce unwanted noise. This work aims at evaluating the acoustical performance of 3D printed skeletal sandwich panels. A finite element based simulation is performed to understand the acoustical properties of the structure, and the results obtained from simulation is in good agreement with the experimental results. The work reported here shows a great promise for the future applications.

A novel paper-based colorimetric sensor has been developed for ultrasensitive detection of hepari... more A novel paper-based colorimetric sensor has been developed for ultrasensitive detection of heparin based on aggregation of positively charged silver nanoparticles. The electrostatic interaction between negatively charged heparin and positively charged silver nanoparticles (AgNPs) resulted in a shift in the surface plasmon resonance (SPR) wavelength leading to a color change from yellow to colorless. The proposed assay can selectively detect heparin with an ultra-low detection limit of 1.898 ng mL−1 in solution and 8.68 µg mL−1 on paper. In future, the assay can be further employed for detection of heparin in human blood serum samples.

Springer Singapore, 2019

This volume provides an overview of the recent advances in the field of paper microfluidics, whos... more This volume provides an overview of the recent advances in the field of paper microfluidics, whose innumerable research domains have stimulated considerable efforts to the development of rapid, cost-effective and simplified point-of-care diagnostic systems. The book is divided into three parts viz. theoretical background of paper microfluidics, fabrication techniques for paper-based devices, and broad applications. Each chapter of the book is self-explanatory and focuses on a specific topic and its relation to paper microfluidics and starts with a brief description of the topic’s physical background, essential definitions, and a short story of the recent progress in the relevant field. The book also covers the future outlook, remaining challenges, and emerging opportunities. This book shall be a tremendous up-to-date resource for researchers working in the area globally.