This research addresses the topic of functionalized soils whose wettability behavior is switchable and fully reversible, controlled by thermal energy to extend the mono-functionality of natural soils. The thermo-responsive polymer serves as a coating material to impose the tunable wettability on the soil surface. The surface wettability of natural soils and granular media strongly influences the contaminant flow in subsurface, the fate and transport of organic matters in pore space, and the separation technology. The investigation of remediation technologies and natural manifestations require the fundamental understanding of interfacial interaction between particles and participating fluids.
The research focuses on the discovery of the innovative engineering implications relevant to tunable engineered soils. The primary emphasis of the research is to investigate the particle-level mechanism that induces the macro-scale response, followed by the synthesis of thermo-responsive polymer coated soils using a state-of-the-art polymerization method. The nano-structure of coated surface will be characterized using the spectroscopic and microscopic observation. The interfacial behavior of particle-fluid interaction in turn will elucidate the selective affinity of tunable soil particles to fluids triggered by temperature change via optical inspection. The measurement of contact angle and wettability correlates the interfacial behavior with quantitative values. The mechanical and physical characterization of functionalized soils responding to the temperature variation will be evaluated using controlled experiments. Then, the immiscible fluids will be separated to validate the performance of the tunable soils. The potential impact and extendibility of this geo-material include the intelligent hydrologic barrier and the granular filter to separate the immiscible fluids and to control the microorganisms in soils.
The educational activities directly tie to the research, and are intended to benefit K-12 and undergraduate students. The PI will actively participate to the university wide efforts of outreach programs and involve an undergraduate student in support of the research activities. The development of a short course nodule based on the outcome from the research will be adapted to the undergraduate and graduate courses currently offered in the department.
Intellectual Merit: This research extends the use of intelligent materials to improve the functionality of natural soils by cross-disciplinary approaches. The surface modification of soil surface at nano-scale will be up-scaled to the macro-scale manifestation via particle-level interpretation. The novel concept and approach in the research enables us to evaluate the multi-scale symptom, to unveil the emergent phenomena prevailing in geo-engineering, and to organically integrate knowledge about surface and material science and geo-engineering. The Lehigh University has a well-renowned surface chemistry programs geared with the top-rated facilities and knowledgeable faculty. This research brings them to produce a synergetic impact in the field of engineering soils.
Broader Impact: The development of functionalized soils offers an alternative way to produce environmentally sustainable geo-materials beneficial to society. The participating undergraduate will be extensively exposed to the advanced experiments and analyses tool to be a prospective engineer. To promote education related to this research, a short course module will be developed and the produced samples will be distributed to local high schools to stimulate the creativity of K-12 students. The research team will disseminate the research and educational results regionally, nationally, and internationally through conferences and journal publications.
The idea of being able to separate oil and other contaminants from water has been around for some time and there are a number of methods used on the market currently. This technology falls within this category, but is an enhanced method using state of the art polymerization technique to bind polymer on to natural substrates such as sand. These synthesized sand packs show distinct change in surface wettability. The process was demonstrated to be completely reversible. The end result once fully developed will be modular packs embedded in the subsurface as a modifier to civil infrastructure (i.e. pipelines, geo-thermal columns, environmental barrier, separator or filter system). The temperature stimulated synthesized sand can perform on demand as oil-water separator, contaminant plume filter, flow retardant or flow enhancer. The sand surface can be synthesized in a similar manner with other types of smart polymers that change functionality with external stimulant such as UV or solvent exposure, or change in pH or ionic concentration of the surrounding to create specific tasks for an engineered sand pack. A mixture of smart polymers synthesized sands can be packed in the same modular unit to broaden the functionality of these units as needed. To demonstrate the proof of concept, a thermal sensitive smart polymer (Poly-NIPAAm PNIPAAm) was synthesized on to silica sand using a state-of-the-art Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) technique that resulted in permanent grafting of the polymer onto the sand particle surface. The synthesized sand packs showed distinct change in surface wettability, from water wetting to water non-wetting, when the temperature was increased to 32?C and above. The functionality of the surface modified sands was demonstrated successfully through immediate and reversible response of the sand pack that prevented water infiltration when the surrounding temperature was raised above 32?C. Other characterization measurements of the funtionalized sand showed distinct property changes between its hydrophilic and hydrophobic state, including electrical and thermal conductivity, low strain stiffness and water infiltration and drainage rates at unsturated and saturated conditions. Synthesis and performance of stimuli-responsive "smart" polymers has been explored in a wide range of applications, including liquid chromatography, controlled drug release, adhesion and release of cultured cell from the substrate, and membrane filters to control fluid flow, but never on a natural, geological material, such as silica sand. The new functionalized smart sand which possesses switchable and fully reversible surface wettability triggered by external stimuli can be deployed as an integral part of civil infrastructure for environmental mitigation and fluid separation purposes as well as other functions such as electrical and thermal insulation on demand.
