Poster K8 - Wireless Micromotor Sponges for Environmental and Health Applications

Saturday, October 26, 2024

10:00 AM – 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Anya Tillman

Undergraduate Researcher
National High Magnetic Field Lab, United States

Co-Author(s)

Izabela Kowalik, UG

Undergraduate Researcher
National High Magnetic Field Lab
Land O' Lakes, Florida, United States
Nellymar Santiago-Rivera

Undergraduate Researcher
Florida State University/National High Magnetic Field Lab
Tallahassee, Florida, United States
Vivienne Zacher

Undergraduate Researcher
National High Magnetic Field Lab
Hollywood , Florida, United States
NK

Navneet Kaur

Post-Doctoral Researcher
Florida State University, United States
JK

Jaideep Katuri

Postdoc
Famu-FSU College of Engineering, United States

Primary Investigator(s)

JA

Jamel Ali

Assistant Professor
Department of Chemical and Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Florida, United States

Introduction: Synthetic micromotors represent a new class of active materials with promising environmental applications, enabled by their unique combination of material properties, self-propulsion, and the associated micro-mixing effects. Several pollutant types, including heavy metals, oils, organic pollutants, microplastics, and pathogenic microorganisms have been tackled by researchers using synthetic micromotors. The remediation process employed is dependent on the pollutant type, but physical adsorption of the pollutant on the micromotor surface or chemical degradation by local release of free radicals is most commonly used. Each of these application areas require distinct material combinations and fuel sources to suit the sensitive conditions that the micromotors must operate in, but general challenges include effective location control, achieving sufficient concentration of micromotors, and their safe retrieval after the remediation process. Here we use Hematite (α-Fe2O3) based micromotors that can self-propel under UV actuation and can break down polymer chains through the Photo-Fenton reaction. We plan to design a large porous device that contains these particles for effective location control and to concentrate the particles in a small area. We hypothesize that anisotropic hematite-based micromotors encapsulated in a porous sponge structure can perform in situ organic pollutant degradation more efficiently than previously reported isotropic micromotors freely dispersed in liquid media.

Materials and

Methods: The hematite particles were formed with a gel-sol method, using an Iron (III) Chloride (FeCl3) solution and a Sodium Hydroxide (NaOH) solution. These solutions were mixed and held in an oven for 8 days at 100°C. The morphology of the particles can also be altered by using different additives to produce differently particles. Once made, the particles were mixed with an alginate solution, and crosslinked using a Calcium Chloride (CaCl2) solution to obtain hematite loaded alginate macrostructures. The sponges were created using a two-part polyurethane kit, where each part is mixed separately and then mixed together, stirring quickly to form an expanding foam, which is poured into a cylindrical mold. Once the foam was solidified, the alginate hematite solids were placed onto the sponge, and then another layer of polyurethane was placed on top. Once the whole sponge was made, it was soaked in a Sodium Citrate (C6H9Na3O9) solution to reverse the crosslinking and allow more free movement of the micromotors inside the sponge. The concentration of the organic pollutant we studied, Malachite Green, was determined using a UV-Vis spectrophotometer by comparing results to a calibration curve of known concentrations and their absorbance level at 617nm. A 15µg/mL solution of Malachite Green was created, and various tests were conducted to show the effect of UV light as well as Hydrogen Peroxide (H2O2) on the efficiency of the micromotors and several additional control experiments were performed. Next the micromotors sponges were tested against the results of the micromotors to determine effectiveness.

Results, Conclusions, and Discussions: Our first set of experiments were performed to understand the efficiency of freely suspended hematite micromotors for degradation of organic pollutants. We studied the degradation of malachite green in several different control and experimental conditions over a 90-minute period by obtaining absorbance measurements at 15 minute intervals. We observed that the condition with the highest negative change in absorbance (highest degradation) was hematite particles activated by ultraviolet light and hydrogen peroxide. The second-highest negative change in absorbance was observed for hematite particles activated by only hydrogen peroxide, followed by hematite micromotors activated by UV light only. This is expected as the hematite particles induce the photo-Fenton reaction in the presence of H2O2 and UV light that produce the free OH- radicals responsible for the degradation of organic compounds. The controls without hematite micromotors all changed by less than 0.2 in absorbance, as well as the hematite micromotors by themselves without any H2O2 or UV activation. When testing the sponges, those with hematite micromotors were able to absorb the malachite green from the water more quickly than those without the micromotors.
Since the highest absorbance change comes from hematite microparticles activated by hydrogen peroxide and UV light, with hematite particles activated by each one singularly being a lower change in absorbance, we can reasonably conclude that UV light and hydrogen peroxide together with the hematite particles are the best conditions for hematites particles to break down polymers. Future process of encapsulation in sponges and degradation of pollutants will be studied under these conditions.
Hematite particles in the presence of H2O2 and UV activation were show to be effective at degrading polymer chains, which is promising for work in environmental remediation. It also suggests that their effectiveness can be enhanced by incorporating them in porous structures to increase fluid exchange and micromotor concentration. Future work will be performed to replace the sponge material with a more non-toxic, biodegradable, and biocompatible material.

Acknowledgements (Optional): This work was funded by the National Science Foundation (EES-2000202, EES-2306449, CMMI-2000330 and EES-2219558) and support by the NSF FAMU CREST Center award (EES-1735968). All the work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-1644779 and the State of Florida.