AVS 71 Session UN-ThP: Undergraduate Poster Session

Polylactic acid (PLA) is a promising biodegradable polymer that degrades at a faster rate than conventional fossil fuel polymers and can combat the growing issue of plastic pollution. Moreover, it is an excellent alternative to the growing issue of microplastics because it can be readily degraded through hydrolysis. Although PLA is biodegradable, it induces environmental change when degrading. Specifically, the degradation of PLA in soil via hydrolysis has been shown to lower the soil’s pH, adversely affecting plant growth. Previous research demonstrates that certain plants containing nitrogen-processing bacteria use nitrogen moieties to raise the pH of soil. Furthermore, PLA has been shown to degrade at an accelerated rate in alkaline conditions. We hypothesize PLA degradation can be induced by introducing nitrogen functional groups on the surface via nitrogen plasma treatment (NPT), which can then act as Lewis bases upon degradation. The impact of NPT on PLA degradation has not been previously investigated at large.

This study examined the change in pH as NPT PLA degraded in room temperature DI (deionized) water. PLA films were fabricated and plasma treated in an inductively-coupled plasma reactor using nitrogen gas as the precursor. Plasma treatment parameters including 30 W, 328 mTorr, and two minutes of treatment time were selected based on previous literature and optimized to maximize nitrogen incorporation. NPT PLA films and untreated control films were then submerged in 10 mL of DI water at room temperature to initiate degradation. Changes in pH of NPT and control PLA films were compared after degradation. Previous results showed no significant difference in pH change associated with one week of degradation of PLA between control and NPT films, necessitating longer-term degradation studies of NPT PLA film degradation with a specialized pH probe. Collectively, NPT shows potential to alter the chemical degradation of PLA when compared to native PLA degradation.

Polyurethane (PU) is well-suited for indwelling catheters due to its durability and flexibility. However, its inherent hydrophobicity promotes thrombosis and biofouling, leading to complications such as catheter-related bloodstream infections and venous occlusions. Plasma surface modification can improve PU’s hydrophilicity by incorporating polar functional groups. PU, however, exhibits significant hydrophobic recovery within one day after treatment with air, N2, O2, and Ar plasma precursors, meaning the polymer reverts to its original hydrophobic state after treatment. Studies on polydimethylsiloxane demonstrate that while individual feedgases (Ar and O2) enhance hydrophilicity, their combination in an argon/oxygen (Ar/O2) plasma mixture more effectively reduces hydrophobic recovery. This effect has not, however, been examined for PU. Extending this approach to PU has the potential to slow down aging after plasma modification.

This study investigates the influence of varying Ar/O2 plasma precursor concentration on PU’s hydrophobic recovery, incorporating an optimized 7% Ar / 93% O2 composition by pressure— previously shown to mitigate hydrophobic recovery on polydimethylsiloxane. PU samples were plasma-treated using a radio-frequency low-pressure reactor (25 W, 2 min, 300 mTorr), with systematically varied argon composition in the feedgas. Samples were aged for 12 days, with water contact angle (WCA) measurements taken at 1, 2, 3, and 4 hours post-treatment, followed by measurements at 1, 4, 7, and 12 days.. Contact angle goniometry was used to assess wettability as a function of aging. Preliminary results indicate that 100% Ar plasma achieves the greatest hydrophilicity and the greatest reduction in hydrophobic recovery compared to other feedgas compositions, with water contact angles increasing from 39.24±0.74° to 55.24±0.97° over 12 days. By enhancing the longevity and effectiveness of plasma treatment, this work aims to improve the performance and efficacy of PU in antibacterial catheters.

Most high performance optical components, like lenses and windows are designed for sterile, low-contaminate environments, however, optical systems used by the Navy often operate in harsh marine and sandy environments. Improving the lifespan of optical elements in these conditions is essential. Optical elements with anti-reflective (AR) coatings or structured surfaces, which feature nano-textured elements, are particularly vulnerable to degradation. This study aims to evaluate the impact of submerged environments on these components. Long term testing was conducted on five 1-inch-diameter fused silica windows with different surface treatments: a polished blank, a hydrophilic "web-like" AR, a hydrophobic "moth-eye" AR structured surface (ARSS), a commercially available ARSS and a thin-film AR coating. Samples produced in-lab are done through high-vacuum mask deposition and plasma etching to produce the AR structured surface desired. Prior to submersion, the contact angles and optical transmission spectra of each window was measured. The samples were placed in a flotation housing unit and submerged in a semi-controlled biological freshwater environment for 30 days. Once removed, the windows were analyzed for biofouling accumulation and changes to optical performance. This experiment aims to identify how surface coatings and nano-structures influence the biofouling resistance of optical elements, providing insights into improving optical components durability in challenging environments.

Endoscope lenses easily fog within closed body cavities, disrupting the visual field during surgery within minutes. Lens opacification is due to water vapor condensation, which forces surgeons to remove the scopes, wipe their lenses, and reinsert them. Repeated scope wiping and reinsertion increases infection risks, length of surgery and OR use, and tissue scarring due to prolonged air exposure.

Current strategies to inhibit fogging, such as alcohol-based coatings and heating, introduce complications. For example, alcohol solutions evaporate quickly and irritate damaged tissue due to their acidity. Another strategy is to pre-heat endoscope lenses; this requires reheating due to the cooling of small diameter lenses (2- 12 mm) connected to 30-200 mm endoscopes. Textured lens surfaces rapidly wear and are very difficult to clean and sterilize.

This work has developed a phenomenological model for fogging on smooth surfaces: the SEE (or Surface Energy Engineering) model with direct surface energy measurements. SEE has guided development and testing of new hyper-hydrophilic sol-gel coatings, KnoxFog¹, using two key properties to inhibit fogging. First, coating’ surfaces are super-hydrophilic, meaning molecules condense in 2D sheets (Frank-Vander Merwe Growth Mode) instead of 3D droplets (Volmer-Weber Growth Mode). Second, nanopores in the Sol-Gel absorb water as the condensate thickens. This combination yields a lasting anti-fog coating, where water condenses for 2+ hours into a continuous, flat film, free of optical distortion and droplets, even when exposed to blood and tissue debris.

Using four pairs of endoscopes in vitro, at T= 38±2°C, the time-to-fog (TTF) of a pair of identical endoscopes whose lens is coated with KnoxFog is compared in a closed cavity simultaneously with a pair of bare lenses and two pairs using the current anti-fog strategies. TTFs of KnoxFog coatings exceed 131 min with a variation of < 1 %. TTFs of bare lenses average less than 8 ± 8 min. In these same simultaneous conditions of water evaporation, a variation of 100% can occur in surgery due to a lack of controlled surface conditions on bare lenses. KnoxFog™ improves TTF by 1625 ± 1% over bare lenses, reduces by two orders of magnitude the TTFs unpredictability of bare lenses, and improves over lens tip heating, whose TTF averaged less than 1 min in the same conditions, and on alcohol-based coatings, whose TTF averages 47.5 min with a variability of 56%.

In vivo animal studies show that KnoxFog performance significantly increases TTFs and optical clarity while reducing the need for frequent lens cleaning from blood and tissues.

¹ Trademark owned by SiO2 Innovates

Vanadium disulfide (VS₂), which belongs to the family of transition metal dichalcogenides (TMDs), has garnered significant interest from researchers due to its fascinating properties. These include metal-insulator transition behavior, room-temperature ferromagnetism, a unique layered structure, and metallic conductivity. Additionally, VS₂ can form highly crystalline materials. With advances in achieving a more precise structure of this semiconducting material, VS₂ nanomaterials have the potential to be the most efficient TMDs for various photonic and optoelectronic applications. Chemical vapor deposition (CVD) has proven to be a valuable technique for synthesizing 2D materials. Its straightforward approach, alignment with industry standards, and capability to generate high-quality crystalline samples make it an excellent choice for both researchers and manufacturers. This study examines the optoelectronic properties of VS₂ grown on various substrates using the chemical vapor deposition (CVD) technique, going beyond traditional methods. It identifies optimal growth parameters, including growth temperature and carrier gas flow rate. The characterization tools utilized in this research include photoluminescence, Raman spectroscopy, and confocal laser optical microscopy. These tools are employed to analyze the surface morphology, structural quality, phonon modes, and bandgap of the samples.

Two-dimensional transition metal dichalcogenide (TMD) materials offer exciting opportunities for various applications, particularly due to their unique layer-sensitive band structures, valley-selective optical coupling, and remarkable catalytic activities. Their notably large exciton binding energies and strong nonlinear optical responses underscore their potential. Moreover, by strategically stacking different monolayer TMD materials, we can create heterostructures that allow tuning band gaps across visible to infrared spectrum. This approach enhances their optoelectronic properties and opens new avenues for advancements in fields such as optoelectronics and photonics.

This research investigates the optoelectronic properties of MoSe₂-MoS₂ heterostructures grown on various substrates, including gallium nitride (GaN) and sapphire, using the chemical vapor deposition (CVD) technique. The study also examines how the choice of substrate affects the growth of layered versus vertically aligned heterostructures. We utilize CVD techniques because they have proven more effective for producing samples with extensive monolayer growth than the commonly used exfoliation method. By analyzing the differences in bandgap, the Raman and infrared (IR) vibrational modes, we aim to reveal the unique properties of these heterostructures.

Atomic Layer Deposition (ALD) enables precise, conformal thin-film coatings on high-surface-area nanoparticle powders through sequential, self-limiting reactions. However, coating nanoparticle beds presents unique challenges, including precursor diffusion limitations, particle agglomeration, and extremely high surface areas (reaching ~10s of m²/g). These factors complicate the ALD process, making it essential to monitor reaction progress and identify saturation ("end-pointing") within the powder bed.

In this work, we employ quadrupole mass spectrometry (QMS) as an in situ diagnostic tool to study Al₂O₃ ALD on ZnO nanoparticle powder beds. Using trimethylaluminum (TMA) and ozone (O₃) as precursors at a deposition temperature of 120 °C, we track methane (CH₄) evolution—a key reaction byproduct—to gain insights into surface reaction kinetics and saturation behavior. Furthermore, we develop multivariate analysis tools to interpret ALD reaction dynamics in powder bed reactors with the hope of enabling better process control and optimization.

Polylactic acid (PLA) and chitosan (CS) are popular biopolymers that display tremendous potential for scaffolding applications in the biomedical field. Both polymers are renewable: PLA is produced from renewable feedstock, while CS is obtained through the deacetylation of chitin. The use of these polymers in biomedical-related applications such as scaffolding is promising due to their non-toxicity in vivo and biodegradability. Additionally, they each contain distinct mechanical and degradation properties suitable for different applications. However, both polymers have a hydrophobic surface, which restricts their biomedical implementations where cell adhesion is critical (e.g., in applications related to tissue and bone engineering). There is some evidence that cell adhesion and growth are facilitated by hydrophilic surfaces. Radio-frequency nitrogen plasma treatment displays promise in increasing the polymers’ hydrophilicity, but also displays potential aging instability with hydrophobic recovery. This poses a significant problem for applications of the treatment especially when considering storage-induced aging. Approaches to prevent this phenomenon in PLA and CS are widely unexplored.

This work investigated the impact of various aging conditions (storage in vacuum, cold temperature, and air) on the surface hydrophilicity of PLA and CS after exposure to nitrogen plasma. Films were prepared as model substrates using the solvent-casting method, and treated in a RF plasma reactor under optimized parameters (power, pressure, and treatment time). After treatment, the films were aged in the different aging environments for two weeks. Throughout the aging period, multiple surface analyses were conducted on samples exposed to the various preservation environments, including untreated samples as controls. Surface wettability analysis utilizing water contact angle goniometry displayed that vacuum aged PLA films and cold temperature aged CS samples possess the least hydrophobic recovery in comparison to other aging conditions. Surface chemical composition of PLA and CS samples was examined using x-ray photoelectron spectroscopy. These treatment preservation methods to PLA and CS have potential to positively impact their future use in the biomedical field as scaffolds.

Calcium Lanthanum Sulfide (CLS) is being studied as a potentially strong material in the field of Long Wave Infrared (LWIR) optics. Derived from the γ-La₂S₃ structure and doped with CaS, we can achieve a stable CLS structure¹. However, via X-ray photoelectron spectroscopy, we can see substitutional oxygen impurities within the CLS structure.² Subjecting multiple iterations of CLS powders and ceramics to metrology testing – XPS, and FTIR for example – we can gather a database on the properties of the compound. This database consists of 60+ powders and ceramic CLS samples, each with different compositions aimed at optimizing fitting to an ideal composition that provides the highest optical transmission.

This study focuses on the correlation between points of this database, focusing on correlations made between XPS and transmission gathered via FTIR. Machine learning is a useful process in determining these correlations with such a large database, as the algorithm can be trained to search for specific connections and properties.³ If successful, we hope to see a direct correlation between the transmission of the CLS and the substitutional oxygen content.

References

1. Brian Butkus, Matthew Havel, Alexandros Kostogiannes, Andrew Howe, Myungkoo Kang, Romain Gaume, Kathleen A. Richardson, Parag Banerjee. 31 Jan. 2023. “Lanthanum Sulfide powder analyzed by XPS.” Surface Science Spectra 30, 01400. https://doi.org/10.1116/6.0002252
2. Alexandros Kostogiannes, Nicholas G. Rugawski, Brianna Ellsworth, Andrew Howe, Brian Butkus, Andrew Cooper, Kathleen A. Richardson, Romain Gaume, Parag Banerjee. Apr. 2025. “High temperature annealing of calcium lanthanum sulfide.” Journal of the European Ceramic Society 45, 117062. https://doi.org/10.1016/j.jeurceramsoc.2024.117062
3. Ayush Arunachalam, S. Novia Berriel, Corbin Feit, Udit Kumar, Sudipta Seal, Kanad Basu, Parag Banerjee. 22 Dec. 2021. “Machine Learning approach to thickness prediction from in situ spectroscopic ellipsometry data for atomic layer deposition processes.” Journal of Vacuum Science & Technology A 40, 012405. https://doi.org/10.1116/6.0001482

In 2025, the gold standard for bacterial infection diagnosis, developed in the 70s, is plate culturing. State-of-the art infection diagnostics use the universally accepted Colony Forming Units (CFUs) counting on cultured plates, which requires 10-30 mL of blood, urine, sputum, etc... and 2-3 days for results.

However, about 40% of all positive cultures are false positives due to contamination from skin pathogens and handling in blood, urine, sputum, etc... during collection or environmental contaminations.

Per the NIH, false positives are “independently associated with increased subsequent laboratory charges (+20%) and IV antibiotic charges (+39%)”. The excess of diagnosed infections costs US hospitals about $20+Billions/year in 2025. False positives lead to administration of antibiotics in healthy patients, leading to antibiotic resistance, and to more than 48,000 US deaths/ year.

New, reliable methods are needed for bacterial detection, loads, infection diagnosis.

The present research investigates whether Macroscopic DNA Epi-Fluorescence (MaDRE) can be used for bacterial detection, and whether macroscopic epi-fluorescence intensity scales quantitatively with bacterial load in small volume drops using fluorophores developed for fluorescence microscopy. To sort detected microbes by class, 3 fluorophore combinations are designed to detect DNA/RNA in live bacteria and protozoa, RNA in viruses, and fungi-specific proteins.

A quantitative study was thus conducted to establish whether a MaDRE-based device is viable in accuracy and reproducibility. An initial stock solution in Luria Broth is diluted logarithmically into 10 bacterial serial loads from 1.0 to 10^-9 for calibration. Next, MaDRE’s sensitivity is tested on these 2 x ten bacterial loads, to establish whether 520 nm fluorescence intensity of safe green DNA fluorophores I_G scales reproducibly with bacterial concentration. The two sequential experiments were conducted by applying four 0.1 mL identical drops from each of the 20 solutions on 2 hyper-hydrophilic prototype strips.

I_G is normalized to the 497 nm excitation intensity, I_B, before and after 0.1 mL dye drops are applied, as RG/B. The difference between post-dye R_Raw and pre-dye R_Bgd yields the net R_Net

R_Net averages of 8.5 ± 2.1 for 300k E.Coli CFU/mL, and 3.6 ± 0.34 for 100 k E.Coli CFU/mL. Thus, R_Net decreases 250% with a decrease of one order of magnitude in bacterial load.Pre-dye R_Bgd averages = 1.8 ± 0.25, thus lower by a factor 2 to 4 than post-dye R_Net.