This proposed research will significantly enhance the body of knowledge for water remediation, environmental sustainability, nano porous filtration membranes, and sensing and delivery platforms using non-toxic natural materials, supporting the basis for the next generation of economically sustainable devices. Strategies to assess structure, properties and performance, resulting from this research, will include determining how precursor type and viscosity, composition, temperature, catalyst, substrate surface energy constrain fabrication of nanofiber membrane systems. The scientific goal is to enable the cost-effective production of nontoxic sustainable biodegradable cactus membranes for two specific applications: (i) filtering and (ii) sensing. Preliminary investigations by the PIs have led to a successful experimental fabrication of novel cactus nanofiber membranes with varied geometry, providing promise for scalability for future commercialization. The research activities in this proposal will contribute to scientific breakthroughs for understanding and implementing natural materials as membrane systems.
The proposed research will provide fundamental understanding of how current and future natural material membrane systems can affect water, wastewater, overall environmental quality, and public health issues. With the knowledge gained from this novel research we will be able to make a global impact, addressing environmental, social/health care, economical, and engineering design needs. This research can impact worldwide water filtration and ultimately lead to further investigations for air and gas filtration, oil absorption, sensors, tissue scaffolding, drug delivery, enzyme transporting, food additive, and textiles. In addition, through workshops and student mentoring with the Florida-Georgia Louis Stokes Alliance for Minority Participation (NSF AMP), Society of Women Engineers (SWE), the Alfred P. Sloan Foundation, National Society of Black Engineers (NSBE), and Society of Hispanic Professional Engineers (SHPE), we will broaden the research impact for underrepresented minority students and faculty. Overall, this novel research will increase the body of knowledge in the field of electrospun natural fibers through comprehensive optimization and characterization of this novel nanofiber and transform how natural products can be utilized by engineers and scientists for future technology to help sustain separation technology on a global level.
Fresh water, one of the most essential needs for human life, is only available to 1 out of every 12 people in the world, and only 1 percent of this fresh water is safe for drinking. The World Health Organization has mandated that research be conducted to reduce this 1:12 ratio of people currently living without clean drinking water and experiencing the burden of disease. This project capitalizes on the natural ability of the Opuntia ficus-indica-Ofi (Nopal or Prickly pear) cactus to purify water. A cactus plant has a gooey liquid material inside, often referred to as cactus mucilage, giving the plant the ability to clean water, including removing arsenic, bacteria, and cloudiness from rural drinking water. This natural material has the potential to enhance developing technologies for cleansing drinking water of bacteria, cleanups following oil spills, and purifying groundwater in regions that see significant heavy metal contamination. This work addresses the engineering challenge of how researchers can utilize this ability of the cactus plant to naturally clean water and develop a usable water filtration system. Can you imagine engineers creating a form of natural cactus mucilage that can be used in homes and businesses? Can this natural material change the number of children and families we can save from dehydration, starvation, and disease, just by making the water we use and consume cleaner? At the University of South Florida, the Advanced Materials Bio and Integration Research (AMBIR) Group is electrospinning naturally occurring cactus mucilage into nanofiber membranes. These spider web-like nanofibers are then layered to produce membranes to be used for filtration. These polymeric cactus membranes are made of nontoxic, biodegradable, and inexpensive materials. Cactus mucilage is mixed with different types of polymers, such as polystyrene, to form nanofiber membranes using an electrospinning process. Electrospinning is a process in which the surface tension of the polymeric cactus mucilage solution is influenced by an electric field and then undergoes plastic stretching to form fibers. The polymeric cactus mucilage solution forms a cone at the tip of a syringe needle, and a jet of fibers collects on a plate as a non-woven web. The nanofibers are gathered in a spiral manner with fiber diameters ranging from nanometers to a few micrometers. We have characterized a cost effective electrospinning process to fabricate novel non-toxic, biodegradable cactus membranes that could revolutionize current technology that utilizes plastic or ceramic materials that are unsustainable and non-environmentally benign. Electrospun cactus membrane characteristics are influenced by various process parameters (operating voltage, pressure, flow rate, distance of syringe tip to collector plate, molecular weights, blend ratios, temperature, and viscosity). Using a voltage range of 20~22kV, 18 ½" ~ 22" gauge needles, an infusion rate of 2.5 μL/min at atmospheric pressure, we have fabricated Ofi nanofibers with diameters ranging from 70 ~ 180 nm. Characteristics, which make these nanofiber membranes prevalent for water treatment, are the high surface area and nano-scale pore size of the nanostructures. This work demonstrates the versatility of opuntia ficus-indica [cactus mucilage] nanofiber membranes to form hydro surfaces that can be effective for water filtration devices. Utilizing Atomic Fluorescence Spectrometry (AFS), relative tests have been performed using different filtration layers: 1) coated and non-coated GVWP 0.22 μm and 0.45 μm filters from Millipore and 2) 1 g of pre-washed sand from Fisher Scientific and a layer of mucilage nanofibers. The final results show that mucilage nanofiber membranes are capable of removing arsenic from sample solutions. We anticipate the research outcomes of this work will contribute to scientific breakthroughs for understanding and implementing natural materials as biological systems. These results have the potential to broaden global knowledge for using natural materials, such as carbohydrates and sugar-type technologies, in separation techniques that integrate biomimicry (learning from nature protocols) and sustainable engineering principles for the manufacturing of membranes and fibrils. This is just the beginning. Further investigations are under way to use these cactus nanofiber membranes for toxic sensing, wound healing, and tissue scaffolding to further explore the natural capability of the cactus.
