Project 1: Mechanical Characterization of Hot-Pressed Biodegradable Polyester Films
Our NURPH student will be using a heat press to form films from biodegradable polyesters. This heat press is new to our lab, so we would like to collect state-of-the-art data with well-known materials to use as a baseline for comparisons with our more specialized, in-house polymers. The student’s experiments will help us to gauge various processing parameters set by the machine, including temperature, ramping speed, and pressure.
Our goals for the student are to introduce them to a concrete example of the structure-property-processing relationships in materials science through mechanical characterization of the films. They will use dynamic mechanical analysis and IR spectroscopy to uncover a relationship between the chemical composition of the films and their macroscale structural properties. Specifically, we will be varying the degree of aromaticity in the backbone of the polymer, which affects chain rigidity. We will have 5 total compositions to test.
Beyond gaining familiarity with the dynamic mechanical analyzer, we would like them to observe higher-level experimentation in our lab and learn about common polymer characterization techniques. In a broader context, we hope to teach our student how to implement the scientific method to design experiments that answer a research inquiry. We will focus on teaching them the benefits of polymer science, specifically how we can use organic chemistry to achieve applied properties like biodegradability and recyclability.
Project 2: Hydrogen reduction of ferroalloys
Globally, the steel industry contributes about 11% of total CO2 emissions. Decarbonizing the iron and steel industry has significant benefits for reducing the impact of climate change and creating a sustainable future. Hydrogen metallurgy uses hydrogen as a reducing agent for Fe2O3 xiu instead of carbon and produces Fe with water as a by-product. When the utilized hydrogen is produced from a clean energy source (like the electrolysis of water with a renewable source of electricity), it leads to iron with a near-zero carbon footprint. To make alloyed streels such as Fe-18Cr-8Ni (stainless steel), “master alloys” – which are concentrated binary alloys, such as Fe-50Ni or Fe-50Cr – are added to molten iron. The conventional fabrication of master alloys uses an electric arc furnace to reduce mixed oxides (such as Fe2O3 + NiO) at very high temperatures while requiring the use of pure elements (Al and Si) as reductants, each with a high carbon footprint to produce. This research aims to demonstrate and investigate the co-reduction of mixed oxides (e.g., Fe2O3 + NiO) with hydrogen to produce concentrated ferroalloys at near-zero carbon footprint. Using in-situ x-ray diffraction and metallography, we are proceeding with a fundamental material-science investigation of mechanisms of H2-reduction of blends of iron oxide and other element oxides, and their effects on the resultant steel or ferroalloy microstructure and mechanical properties.
Role of the high school student: mixing powder; Sample preparation; Furnace setup; Metallurgy
Project 3: Mechanical Characterization of Custom 3D Printing Resins
Additive manufacturing enables fabrication of complex structures within a single process, while simultaneously minimizing waste material. Commercial light-based 3D printers typically use proprietary material resins that produce consistent, but fixed, mechanical properties. By creating a custom resin, the component ratios can be tuned to produce a range of mechanical properties from softer to stiffer printed parts.
A student on our project would primarily be focused on analyzing changes in mechanical properties that arise from different ratios of key resin components (i.e. acrylates and polyurethanes). The student will learn how to design a photopolymerizable resin for digital light projection 3D printing. They will print several test specimens for impact testing and tensile testing. The project will conclude with mechanical characterization of the student’s custom resin parts compared to identical parts made of a standard commercial resin.
Project 4: Processing supramolecular polymers with ultrasonic atomizers
In 1920, the German chemist Hermann Staudinger proposed an idea that was largely frowned upon by fellow scientists at the time. He suggested that some of the materials used in everyday life may have molecular weights that far exceed the normal molecules, linked by covalent bonds; thus, the name “macromolecules” was born [1]. Fast forward a century, macromolecules, or covalent polymers, shape our lives. We have mastered how to design and synthesize polymers in enormous quantities and process both synthetic and naturally derived polymers in a way that maximizes their materials performance, e.g. Styrofoam vs cutlery.
From the 1980s, some researchers started experimenting with a new type of polymer in which the bonds between the constituent molecules are non-covalent, which vaguely resembles the opposing idea from the 1920’s. This class of materials has now been proven to exist and is called supramolecules. Over the last 30 years, we have learned some of the design criteria for synthesizing such supramolecular polymers: however, due to the weak nature of the non-covalent interaction forces, our understanding on how different processing conditions change the materials properties remains largely unexplored [2]. In this NURPH project, the student will embark on one such aspect of supramolecular materials processing. Can we tailor the materials properties of supramolecules by adopting some of the processing tools from the macromolecular world?
Peptide amphiphiles (PAs) are one such example of molecules that undergo supramolecular polymerization to form filaments ~10 nm in width and micrometer-to-submillimeter in length. They contain a hydrophobic alkyl component covalently linked to a short peptide, containing a β-sheet forming region and a charged amino acid residue. The hydrophobic alkyl tail drives hydrophobic collapse, the β-sheet forming region allows for strong hydrogen bonding along the length of the fiber, and the charged amino acid residue promotes solubility. One of the research directions in the Stupp lab focuses on supramolecular peptide amphiphile materials for biomedical applications such as neural regeneration and drug delivery; processing conditions of these materials play an important role in their bioactive functionality.
The goal of this NURPH summer project is to understand how processing conditions impact the PAs morphology. In this project, the student will use an ultrasonic atomizer as a new way to process PA solutions. Ultrasonic atomization transforms a liquid into a mist of fine particles. It has previously been used in spray coaters, nebulizers and your room humidifiers. Our hypothesis is that ultrasonication disrupts the supramolecular fiber morphology, causing fibers to shorten upon atomization but lengthen after ultrasonication due to the supramolecular nature of these PA materials. We aim to study how parameters such as concentration, pH, and the peptide sequence will influence PA morphology. The student will prepare samples such that structural evolution can be tracked over time, changing parameters such as solvent quality and concentration. They will be working with optical microscopy and other characterization techniques as well as working with mentors on nanoscale characterization techniques.
[1] Cook, A.B. and Bibic, L. (2019) Macromolecules, Actually: From Plastics to DNA. Front. Young Minds. 7:126. doi: 10.3389/frym.2019.00126
[2] Draper, E.R. and Adams, D. (2024) Controlling Supramolecular Gels. Nat. Mater. 23, 13, doi: 10.1038/s41563-023-01765-0
Project 5: Mechanical properties of solid acid electrolytes
Fuel cells and batteries are both electrochemical devices that convert chemical energy into usable electricity. Both technologies will be foundational for storing and utilizing energy for our world’s rapidly expanding clean energy infrastructure. What sets fuel cells and batteries apart is that, in a battery, the energy storage capacity is built into the battery itself. A bigger battery stores more energy, and when it dies it must be recharged or disposed of. With a fuel cell, the energy storage capacity decoupled from the device itself. Rather, as long as a workable fuel is supplied to the fuel cell, it will continue to produce electricity. If a machine running on a fuel cell dies, one just has to refill the fuel tank. Fuel cells can be advantageous over batteries in situations with strict weight limitations or where recharging/reloading time must be kept at a minimum, such as with cargo ships, heavy duty freight vehicles, and possibly even airplanes.
One class of fuel cell devices are solid acid fuel cells (SAFCs). Solid acids are salts which contain easily exchangeable protons. Superprotonic CsH2PO4 (CDP) is the most studied solid acid compound for fuel cell applications, owing to its remarkably high proton conductivity. This high proton conductivity as well as its low electronic conductivity are what makes CDP a great choice for forming the electrolyte membrane in SAFCs.
During SAFC fabrication, the CDP electrolyte membranes have been observed to compress and distort under pressure from the SAFC device holders. These distortions are hazardous and hamper long term SAFC performance due to short circuiting and gas leakage through distorted electrolyte membranes. The goal of this project is to measure the mechanical properties of CDP and other solid acid compounds in order to quantify the degree of electrolyte distortion in SAFC devices. This summer research project will begin with synthesizing and characterizing CsH2PO4 and other solid acid compounds commonly employed in solid acid fuel cells. Once synthesized, the student will help construct the custom hardness testing apparatus that will subsequently be used to measure the hardness and ductility of our synthesized solid acid membranes.
In this project, the NURPH student will gain hands on experience in chemical synthesis, instrumentation, and material characterization.