Lubricants play an integral role in the operation of several technologies and in biology, ranging from moving parts in machinery to the biolubrication of articular joints. The main purposes of a lubricant are to reduce friction and surface wear. We propose a collaborative project involving 3 faculty members fromTulane University and a faculty member from the University of Maryland, each bearing unique expertise required for the success of the project. The PI (N. Pesika) is a junior faculty in his 2nd year and was a postdoctoral associate in the Interface laboratory at UCSB working under the guidance of Dr. Israelachvili. In recent years, N. Pesika has done theoretical and experimental work to understand the adhesion mechanism of the gecko and has become proficient in tribology and the characterization of lubricants. V. John is a senior faculty member with experience in the field of surface and colloidal science, specifically in the synthesis and modification of colloids. H. Ashbaugh's research focuses on the multiscale simulation and the theory of self assembly processes of molecules including surfactants, polymer melts, and biopolymer gels. S. Raghavan heads the complex fluid and nanomaterials group at the University of Maryland, and is an authority on self-assembling soft materials. We have found that an easily synthesized system of monodisperse hard carbon submicron spherical particles (HCS) has frictional coefficients that start approaching those of synovial fluids. When these observations are coupled with a novel discovery in S. Raghavan's laboratory that a modified biopolymer (chitosan) is able to gel vesicles, we are able to realize a unique gel system containing the carbon microspheres serving as nodes in a network of this biopolymer. This forms the basis of our proposed work to develop novel gel based lubricants containing monodisperse particles or cushioning vesicles. Our hypothesis is that these composite materials will be able to reduce friction and minimize surface wear synergistically through the boundary lubrication of biomolecules/biopolymers and the rolling mechanism (similar to ball bearings) employed by HCS particles. We therefore propose to develop biomimetic lubricants with ultralow coefficients of friction that are robust and easy to synthesize. Several formulations composed of phospholipid based liposomes, biopolymers and carbon microspheres will be systematically explored to optimize the lubrication properties, including a low coefficient of friction and minimal surface wear, through molecular and particulate design.
Broader Impacts of research: While several types of lubricants have been formulated water-based lubricants that mimic synovial fluid remain elusive. A biomimetic lubricant exhibiting ultralow coefficient of friction has several applications including potential substitutes for synovial fluid in diseased or damaged articular joints or in applications to microfluidics or microelectromechanical devices. The potential scientific impact is extremely broad, affecting all industries utilizing lubricants.
Broader Educational and Outreach efforts: N. Pesika and H. Ashbaugh are committed to improving local K-12 education and have established a service learning course at the New Orleans Charter Science and Mathematics (NOCSM) High School. The demography of the school closely parallels that of the community, with 85% being from households classified as economically disadvantaged, and 86% of the student population belonging to a minority (82% African American). The outreach program was designed to present every day uses of the scientific method through presentation made by Tulane students followed up with experiments to illuminate the nature of the demonstrated phenomenon, like the rheological properties of biopolymers and the operation of heat engines. V. John has been a consistent participant of the LAMP (Louisiana Alliance for Minority Participation in Research) program for the last 8 years supervising one or two students every summer while N. Pesika will begin participation in the LAMP program over the summer. These minority students are typically from the minority institutions in the state (Xavier, Southern, Grambling State) or from non-minority New Orleans institutions including Tulane. We plan to apply for REU supplements which will be leveraged through the LAMP program.
The goal of this project was to develop a new type of lubricant which relied on using highly uniform spherical micron-sized carbon particles as ball-bearings in a water-based medium to lower friction and reduce surface damage. The advantages of such a formulation are that it no longer relies of oils and has the potential to be used as a lubricant within the body, e.g., as a synovial fluid replacement in articular joints. Based on our studies, we have found that carbon microparticles dispersed in water do lower friction significantly and also minimize surface damage. We are currently developing a different formulation, based on similar concepts, which is biocompatible and may serve as a biolubricant in joints or joint replacement devices. The project has had a significant impact in the field of lubrication and has provided valuable insights into the mechanisms by which particles lower friction between shearing surfaces. The project has also spurred a wide range of other formulations of particle-based lubricants. Futhermore, as a result of outreach efforts originating from this project, several K-12 students have been exposed to ongoing research in the sciences and engineering. In addition, the project supported the education of 2 graduate students and 2 undergraduate students, providing them with a unique skill set in the workforce.
