Papers by Matiar Howlader

A Deep-learning Approach for Modeling Phase-change Metasurface in the Mid-infrared
2021 International Applied Computational Electromagnetics Society Symposium (ACES), 2021
Reconfigurable metasurface constitutes an important block for future adaptive and smart nanophoto... more Reconfigurable metasurface constitutes an important block for future adaptive and smart nanophotonic applications. In this work we introduce a new modeling approach for the fast design of tunable and reconfigurable metasurface structures using convolutional deep learning network. The metasurface structure is modeled as a multilayer image tensor to model the material properties as image maps. The dimensionality mismatch problem is avoided by using the operating wavelength as an input to the network, so the model is used as single-point solver. As a case study, we model the response of a reconfigurable absorber employing phase transition of vanadium dioxide in the mid-infrared. The results show that our model provides accurate prediction of the metasurface response using small training dataset.

Low-Loss Switchable Metasurface-Based Waveplate using Phase Change of Antimony Triselenide for Telecom Applications
2021 International Applied Computational Electromagnetics Society Symposium (ACES), 2021
In this paper we introduce the design of a switchable metasurface waveplate using low-loss phase-... more In this paper we introduce the design of a switchable metasurface waveplate using low-loss phase-change material. The structure includes Antimony Triselenide grating deposited over a glass substrate, which can be easily fabricated using standard silicon fabrication technology. By employing the different birefringent effect induced, the grating operates as a quarter-wave plate when Antimony Triselenide is in the amorphous state, and operates as a half-wave plate when it is in the crystalline state. The grating parameters (thickness, height, and period) are optimized using global genetic algorithm. The design provides above 80% transmission for amorphous and crystalline states over the telecom band between 1.3 and 1.65 µm. The proposed design constitutes an important device for integrated silicon nanophotonics and flat optics applications.
A Dual Band Plasmonic Metasurface Absorber for Energy Harvesting Applications
2019 International Applied Computational Electromagnetics Society Symposium (ACES), 2019
A plasmonic dual-band polarization-insensitive metasurface absorber is proposed. The design provi... more A plasmonic dual-band polarization-insensitive metasurface absorber is proposed. The design provides subwavelength and confined collection of the absorbed energy in the gaps of the structure. In this paper, we study the absorption behavior of the metasurface operating in a dual-band mode targeting the mid-infrared range suitable for energy harvesting applications such as thermophotovoltaics. The design is optimized using a global optimization technique.

Thermoelectric generation via tellurene for wearable applications: recent advances, research challenges, and future perspectives
Materials Today Energy, 2021
Abstract Wearable real-time, non-invasive personalized health monitoring sensors and low-power el... more Abstract Wearable real-time, non-invasive personalized health monitoring sensors and low-power electronics critically necessitate alternative power supplies because batteries have proven insufficient due to their demerits of charging cycles and periodic degradation and replacement. Thermoelectric energy harnessing from human body heat via the Seebeck effect is an effective route to develop flexible thermoelectric generators that enables continuous power supply for the wearable devices. This review focuses on critically assessing the theory, the performance, fabrication, and future steps of thermoelectric generation using two-dimensional (2D) tellurene and aims to provide insights as to how to integrate 2D tellurene into practical, durable wearable generators. The literature survey shows that 2D Tellurene nanomaterial has exceptional thermoelectric properties including high thermoelectric figure of merit (ZT) as high as 2.9, and it possesses fabrication process-dependent thermoelectric properties and forms desirable electrical contacts. The flexible nature of 2D tellurene with high environmental stability and high strain resistance of up to 36% and Young's modulus of 27 GPa under bending conditions makes it an excellent material for especially wearable applications. Future research should focus on developing thermoelectric theory with computational methods for tellurene and its manufacturing methods to develop proof-of-concepts for thermoelectric devices. We hope this review would be a seminal work in the growing frontier of 2D tellurene wearable thermoelectrics for sensors for real-time monitoring of personalized health status.

ACS Sensors, 2020
Cannabinoid sensing in biofluids provides great insight into the effects of medicinal cannabis on... more Cannabinoid sensing in biofluids provides great insight into the effects of medicinal cannabis on the body. The prevalence of cannabis for pain management and illicit drug use necessitates knowledge translation in cannabinoids. In this review, we provide an overview of the current detection methods of cannabinoids in bodily fluids emphasizing electrochemical sensing. First, we introduce cannabinoids and discuss the structure and metabolism of Δ 9-THC and its metabolites in relation to blood, urine, saliva, sweat and breath. Next, we briefly discuss lab-based techniques for cannabinoids in biofluids. While these techniques are highly sensitive and specific, roadside safety requires a quick, portable and cost-effective sensing method. These needs motivated a comprehensive review of advantages, disadvantages and future directions for electrochemical sensing of cannabinoids. The literature shows the lowest limit of detection to be 3.3 pg of Δ 9-THC/mL using electrochemical immunosensors, while electrodes fabricated with low cost methods such as screen printing and carbon paste can detect as little as 25 and 1.26 ng of Δ 9-THC/mL respectively. Future research will include nanomaterial modified working electrodes, for simultaneous sensing of multiple cannabinoids. Additionally, there should be an emphasis on selectivity for cannabinoids in the presence of interfering compounds. Sensors should be fully integrated on biocompatible substrates with control electronics and intelligent components for wearable diagnostics. We hope this review will prove to be the seminal work in the electrochemical sensing of cannabinoids.
Analyzing chronic disease biomarkers using electrochemical sensors and artificial neural networks
TrAC Trends in Analytical Chemistry

Biosensors
Chronic pain is now included in the designation of chronic diseases, such as cancer, diabetes, an... more Chronic pain is now included in the designation of chronic diseases, such as cancer, diabetes, and cardiovascular disease, which can impair quality of life and are major causes of death and disability worldwide. Pain can be treated using cannabinoids such as Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD) due to their wide range of therapeutic benefits, particularly as sedatives, analgesics, neuroprotective agents, or anti-cancer medicines. While little is known about the pharmacokinetics of these compounds, there is increasing interest in the scientific understanding of the benefits and clinical applications of cannabinoids. In this review, we study the use of nanomaterial-based electrochemical sensing for detecting Δ9-THC and CBD. We investigate how nanomaterials can be functionalized to obtain highly sensitive and selective electrochemical sensors for detecting Δ9-THC and CBD. Additionally, we discuss the impacts of sensor pretreatment at fixed potentials and physiochemica...

Biosensors
Glutamate is an important neurotransmitter due to its critical role in physiological and patholog... more Glutamate is an important neurotransmitter due to its critical role in physiological and pathological processes. While enzymatic electrochemical sensors can selectively detect glutamate, enzymes cause instability of the sensors, thus necessitating the development of enzyme-free glutamate sensors. In this paper, we developed an ultrahigh sensitive nonenzymatic electrochemical glutamate sensor by synthesizing copper oxide (CuO) nanostructures and physically mixing them with multiwall carbon nanotubes (MWCNTs) onto a screen-printed carbon electrode. We comprehensively investigated the sensing mechanism of glutamate; the optimized sensor showed irreversible oxidation of glutamate involving one electron and one proton, and a linear response from 20 μM to 200 μM at pH 7. The limit of detection and sensitivity of the sensor were about 17.5 μM and 8500 μA·mM−1·cm−2, respectively. The enhanced sensing performance is attributed to the synergetic electrochemical activities of CuO nanostructure...

Materials
With the growing need for portable, compact, low-cost, and efficient biosensors, plasmonic materi... more With the growing need for portable, compact, low-cost, and efficient biosensors, plasmonic materials hold the promise to meet this need owing to their label-free sensitivity and deep light–matter interaction that can go beyond the diffraction limit of light. In this review, we shed light on the main physical aspects of plasmonic interactions, highlight mainstream and future plasmonic materials including their merits and shortcomings, describe the backbone substrates for building plasmonic biosensors, and conclude with a brief discussion of the factors affecting plasmonic biosensing mechanisms. To do so, we first observe that 2D materials such as graphene and transition metal dichalcogenides play a major role in enhancing the sensitivity of nanoparticle-based plasmonic biosensors. Then, we identify that titanium nitride is a promising candidate for integrated applications with performance comparable to that of gold. Our study highlights the emerging role of polymer substrates in the ...

Talanta, 2016
Highly sensitive, easy-to-fabricate, and low-cost pH sensors with small dimensions are required t... more Highly sensitive, easy-to-fabricate, and low-cost pH sensors with small dimensions are required to monitor human bodily fluids, drinking water quality and chemical/biological processes. In this study, a low-temperature, solution-based process is developed to prepare palladium/palladium oxide (Pd/PdO) thin films for pH sensing. A precursor solution for Pd is spin coated onto pre-cleaned glass substrates and annealed at low temperature to generate Pd and PdO. The percentages of PdO at the surface and in the bulk of the electrodes are correlated to their sensing performance, which was studied by using the X-ray photoelectron spectroscope. Large amounts of PdO introduced by prolonged annealing improve the electrode's sensitivity and long-term stability. Atomic force microscopy study showed that the lowtemperature annealing results in a smooth electrode surface, which contributes to a fast response. Nanovoids at the electrode surfaces were observed by scanning electron microscope, indicating a reason for the long-term degradation of the pH sensitivity. Using the optimized annealing parameters of 200°C for 48 h, a linear pH response with sensitivity of 64.71 7 0.56 mV/pH is obtained for pH between 2 and 12. These electrodes show a response time shorter than 18 s, hysteresis less than 8 mV and stability over 60 days. High reproducibility in the sensing performance is achieved. This low-temperature solution-processed sensing electrode shows the potential for the development of pH sensing systems on flexible substrates over a large area at low cost without using vacuum equipment.
MEMS/microfluidics packaging without heating
SPIE Proceedings, 2010

Journal of Nuclear Materials, 2000
The current±voltage (I±V) characteristics of single-and poly-crystal alumina and aluminum nitride... more The current±voltage (I±V) characteristics of single-and poly-crystal alumina and aluminum nitride (AlN) were measured at temperatures ranging from room temperature to 723 K with or without 1 MeV electron irradiation in a high voltage electron microscope (HVEM). Both alumina and AlN specimens exhibit non-ohmic I±V characteristics without irradiation. The I±V characteristics in alumina, however, change from non-ohmic to almost ohmic under electron irradiation. But the I±V characteristics in AlN is still non-ohmic under irradiation. There are remarkable dierences in I±V characteristics between the alumina and AlN specimens. The non-ohmic behavior is due to the electronic barrier formed near the interface between the titanium electrode and the alumina or AlN specimen. No bulk and surface radiation induced electrical degradation (RIED) was found in AlN up to 1X5 Â 10 À5 dpa.
The effects of oxygen plasma and humidity on surface roughness, water contact angle and hardness of silicon, silicon dioxide and glass
Journal of Micromechanics and Microengineering, 2014

Wafer-scale surface activated bonding of Cu-Cu, Cu-Si, and Cu-SiO2 at low temperature
Wafer scale direct bonding of Cu-Cu, Cu-Si, and Cu-SiO 2 was performed at low temperature using s... more Wafer scale direct bonding of Cu-Cu, Cu-Si, and Cu-SiO 2 was performed at low temperature using surface activated bonding (SAB) method. Successful direct bonding of Cu-Cu and Cu-Si was achieved at room temperature. However, bonding of Cu-SiO 2 using SAB process at low temperature failed. In order to integrate Cu to SiO 2 , two-step surface activation process was adopted. The copper was exposed to Ar ion beam and SiO 2 was exposed to oxygen plasma, respectively. In addition, the oxygen plasma-treated SiO 2 were subsequently bombarded by Ar ion beam for 10 s prior to bonding. The two heterogeneously treated Cu and SiO 2 surfaces were bonded at low temperatures. The bonding interface of Cu-Cu, Cu-Si, and Cu-SiO 2 was evaluated by tensile pulling tests and transmission electron microscopy (TEM) observations.
Bonding mechanism and electrochemical impedance of directly bonded liquid crystal polymer and copper
2017 5th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D), 2017
We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing fo... more We report direct bonding of liquid crystal polymer and copper film for electrochemical sensing for the first time. A peel strength of 683 g/cm was observed indicating strong adhesion. X-ray photoelectron and electrochemical impedance spectroscopies were used to characterize the sensing electrodes.
Combined process for wafer direct bonding by means of the surface activation method
2004 Proceedings. 54th Electronic Components and Technology Conference (IEEE Cat. No.04CH37546)
A sequential plasma activation process consisting of oxygen reactive ion etching (RIE) plasma and... more A sequential plasma activation process consisting of oxygen reactive ion etching (RIE) plasma and nitrogen radical activation is proposed for wafer direct bonding at room temperature. The Si wafer surface is activated by oxygen RIE plasma and subsequently exposed to nitrogen radicals. The activated wafers by the two-step process were brought into contact in air followed by keeping them in

Surface preparation and its exposure to different processing conditions is a key step in heteroge... more Surface preparation and its exposure to different processing conditions is a key step in heterogeneous integration of electronics, photonics, fluidics and/or mechanical components for More-than-Moore applications. Therefore, it is critical to understand how various processing and environmental conditions affect the surface properties of bonding substrates. In this thesis, the effects of oxygen reactive-ion etching (O 2 RIE) plasma followed by storage in ambient and 98% relative humidity on some key surface properties such as roughness, water contact angle, hardness, and the elemental and compositional states of three materialssilicon (Si), silicon dioxide (SiO 2) and glassare investigated to analyze their influence on bondability. Lower O 2 RIE plasma activation times cause low surface roughness, high surface reactivity and high hydrophilicity of Si, SiO 2 and glass. Although, the surface reactivity iv of plasma-and ambient-humidity-treated Si and SiO 2 is considerably reduced, their reduction of roughness and increase of hydrophilicity may enable good bonding at low temperature heating due to augmented hydroxyl groups. The decrease of hardness of Si and SiO 2 with increased activation time is attributed to higher surface roughness and formation of amorphous layers of Si. While contact angle and surface roughness results show correlation with bondability, the role of hardness on bondability requires further investigation. The high-resolution X-ray Photoelectron Spectroscopy (XPS) spectra of O 2 RIE treated Si, SiO 2 and glass showed the presence of Si(-O) 2 resulting in highly reactive surfaces. A considerable shift in the binding energy of Si(-O) 2 was observed only in Si. The ambient and 98% relative humidity storage of plasma-activated Si and SiO 2 increased Si(-OH) x due to enhanced sorption of hydroxyls. The variation in the amounts of Si(-O) 2 and Si(-OH) x in the ambient-and 98% relative humidity-stored Si were attributed to the crystalorientation dependent surface roughness and oxidation of Si. The surface roughness, contact angle and hardness measurement results and their correlation with the XPS results give useful insights into the direct wafer bonding of Si, SiO 2 and glass. Based on the analysis, the bondability of Si, SiO 2 and glass can be summarized. The high surface reactivity of Si, SiO 2 and glass obtained from oxygen plasma activation at lower activation times can result in better bondability. Also, the ambient humidity-induced Si(-OH) x plays an important role in the hydrophilic wafer bonding of Si and SiO 2 which may require a low temperature heating. v ACKNOWLEDGEMENTS This thesis would not have been possible without the cooperation, encouragement and support of many people. First of all, I would like to express my sincere gratitude to my supervisor Dr. Matiar R. Howlader, who has introduced me to the field of nanotechnology and provided me with thorough training and guidance in research, and helped me with learning the equipment in Micro-and Nano-Systems Laboratory (MNSL). His excellent supervision, utmost cooperation and incessant encouragement contributed greatly to this thesis. I also greatly appreciate my co-supervisor Dr. Thomas E. Doyle for his guidance. I acknowledge Dr. M. Jamal Deen for his encouragements and suggestions. I would like to extend my appreciation to Fangfang Zhang for her assistance in the experiments. Without her help, the experiments presented in this thesis would have been very difficult vi for me. I am indebted to Dr. Moon J. Kim, University of Texas at Dallas for his contribution to review and comment on my experimental results. I am especially grateful to Dr. Peter Cruse, Department of Chemistry at McMaster University for his critical comments and suggestions on X-ray Photoelectron Spectroscopy (XPS) results. I would like to acknowledge Mubeen Mashroor, Engineer, JEOL Canada for his special training in XPS instrument and his continuous support throughout my experimental works.

Switching plasmonic resonance in multi-gap infrared metasurface absorber using vanadium dioxide patches
Smart Materials and Structures, 2021
Reconfigurable metasurface absorbers enable collecting or emitting radiation within selected freq... more Reconfigurable metasurface absorbers enable collecting or emitting radiation within selected frequency bands. It is thus necessary to decipher such behavior for many applications, including plasmonic energy harvesting, radiative cooling and thermal emitters. In this article, we propose a compact reconfigurable vanadium dioxide (VO2)-based metasurface absorber/emitter to demonstrate switching between dual and single-band absorption modes in the mid-infrared regime. The unit cell of the design employs a four-split gold circular ring resonator with gaps filled with VO2 patches. The phase-transition property of VO2 between semiconductor and metallic states is used to control the mode of operation of the metasurface absorber. When VO2 is in the semiconductor state, a dual-band absorption at 6 μm and 10.6 μm is obtained. When it attains a metallic state, the metasurface exhibits a single-band absorption at 8.25 μm. To achieve the maximum absorption efficiency in both single and dual-band ...
Applied Computational Electromagnetics Society, 2021
A plasmonic switchable polarization-insensitive metasurface absorber is proposed. The design prov... more A plasmonic switchable polarization-insensitive metasurface absorber is proposed. The design provides two modes of operation by employing phase-change material in semiconductor and metallic phases. In this paper, we study the switchable absorption behavior of the metasurface operating in a dual-band and single-band modes targeting the mid-infrared range suitable for energy harvesting applications such as thermophotovoltaics. The design is optimized using a global optimization technique.
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Papers by Matiar Howlader