Diatoms are microalgae with unique photonic crystal structures, which can be found in every habitat where water is present. Their abundance and wide distribution make them ideal materials for a wide range of applications as living organisms. We have developed diatom photonic crystals with plasmonic nanoparticles (NPs) as ultra-sensitive, low-cost substrates for surface-enhanced Raman scattering (SERS) sensing and imaging. We also reported the unique micro-fluidic flow, analyte concentration effect, and thin layer chromatography (TLC) on diatom biosilica, which enables selection, separation, detection, and analysis of complex chemical and biological samples. Especially, we developed a lab-on-a-chip technology based on TLC-SERS sensing and successfully applied it to various applications including food safety, illicit drug residue sensing, and biomarker detection. As a relatively new analytical tool, SERS techniques face tremendous challenges in quantitative sensing due to the intrinsic variation of the enhancement factors. In the last topic, we will discuss our efforts of applying data science including support vector regression and convolutional neural network to analyze the data and imaging collected by diatom photonic crystal biosensors, which showed superior performance in quantitative sensing.

We present a cost-affordable capacitive aptasensor specific to Omicron variant of SARS-CoV-2. Laser-induced graphene (LIG) electrodes were used as transducer surfaces due to their performance and facile and low-cost production. Electrochemical impedance spectroscopy (EIS) was applied as signal transduction for biosensing studies of Omicron variant of SARS-CoV-2 and non-target viruses by aptasensor. At lower viral load, the aptasensor showed to be sensitive and specific for Omicron. At higher viral load, aptasensor is not able to differentiate between target and non-target viruses. The proposed biosensor showed promise for detecting Omicron variant of SARS-CoV-2 during early infection stage when concentration of intact virion is low.

Thermally Induced Optical Reflection of Sound (THORS) is a novel technique that allows a user to optically manipulate sound waves in a medium by photothermally exciting that medium with infrared light, thereby creating a transient barrier due to the changes in compressibility of the medium. This phenomenon offers numerous potential applications in fields as varied as acoustic suppression and reflection, photoacoustic spectroscopy and imaging, and ultrasonic waveguiding. Previous results have revealed maximum suppression efficiencies as great as 72 ± 5% using a continuous THORS barrier system with a multi-pulsed carbon monoxide laser operating at 5.5 ± 0.25 μm and 1 ms pulses. To greater understand the spatial variations in medium compressibility between the excited medium and the surrounding environment, we have employed Raman imaging to visualize these barriers.

There has been strong interest in layered materials also known as 2D- materials since several decades for laser development, electro-optic and electronic devices. Although layered structures provide unique properties, but due to the presence of the Vander Waal bonding in certain crystallographic direction, and in many cases asymmetric forces, the growth of single crystals has been great problem. We have been working on ternary and quaternary oxides for variety of applications. There are some reports on bio-medical sensing since biomolecules can stick on the layers. We observed that chalcogenides are extremely low absorption coefficient and have very wide transparency range. In some cases, these have been explored for THZ sensors also. We will summarize example of thallium, gallium and mercury based selenides and present some recent observations. In addition to optical properties, these materials show excellent dielectric and ferroelectric properties and hence have great promise for se

It was demonstrated by Rai et al. in 2014 that artifacts can cause big problems in sensor materials and devices which have smaller than TEM lamella thickness. These artifacts are generated due to incongruency, eutectics and peritectic. In high power, high frequency and high sensitivity optical and electronic devices and systems, binary and ternary materials can be designed with superior properties. For example, halides, selenides and tellurides have wide transparency, high mobility and low absorption and wide transparency. It is extremely difficult to achieve to good quality materials due to multicomponent without knowledge of phase diagram, vapor pressure and other thermodynamic parameters. We will present excess thermodynamic functions of several binary and ternary industrially important materials such as ZnSe, GaSe, Tl3AsSe3 and Tl4HgI6 showing the stability of these materials. These parameters are indications of congruency and stability of melts near the growth temperature.

Public Health (PH) surveillance of disease outbreaks is slowed by delays in reporting and testing, potentially leading to increased morbidity and mortality. We propose a two-tier human sentinel network (HSN) of wearable sensors with algorithms processing physiological data generating alerts in response to infections. Individuals would be prompted to seek testing and alerts/results would be reported to a secure platform. Agent-Based Modeling results comparing detection timelines for traditional PH surveillance and the HSN indicate that an HSN covering ~5% of the population can identify the onset of the influenza season 5 – 14 days earlier than current surveillance approaches.

This conference presentation was prepared for the Defense + Commercial Sensing Conference, 2023.