CAREER: Fundamental Studies to Advance the Science and Engineering of Water at Negative Pressures

Cornell University, Ithaca NY

Investigators

Abstract

ABSTRACT CAREER: Fundamental Studies to Advance the Science and Engineering of Water at Negative Pressures CBET- 0747993 Cornell University Intellectual merit: The objectives of this proposal are to provide knowledge and potential practical use of liquid water into a physical regime that has been only sparsely explored experimentally and nearly entirely unexploited technologically: the mechanically stable and thermodynamically metastable state of liquid water at negative pressures. Liquid water is known to be very strong: plants have been shown to move water during transpiration at pressures down to -10 MPa; in the laboratory, it has been placed at pressures < -102 MPa. Nonetheless, no human technology has ever exploited water at significant negative pressures (i.e., < -1.5 MPa). The negative pressure regime also harbors important information about the outstanding mysteries of water's properties throughout the liquid state: molecular models indicate that the thermodynamic and dynamic anomalies not only persist in this regime but also become more dramatic and tightly coupled to the unusual molecular properties of the fluid. Despite significant interest from the scientific community, the thermodynamic, dynamic, and structural properties of water at negative pressures have been virtually uncharted by experiment. This experimental effort is ripe for undertaking due to the emergence of advanced fabrication tools and recent developments in our laboratory of a new method to drive liquid water deep into the negative pressure regime based on thermodynamic coupling of liquid water to a sub-saturated vapor through molecular membranes. The investigator will exploit these tools to build a microfluidic platform with which to manipulate and study water under tension with unprecedented precision. Their studies will map thermodynamic, dynamic, and structural properties of the stretched state of water with an emphasis on elucidating the molecular origins of macroscopic properties. These measurements will allow them to address some of the deepest outstanding questions about the nature of the liquid water and to fill a major gap in the foundation of knowledge for the science and engineering of this unusual state of matter. This effort is also timely, as it will create a dynamic interface with the rapidly progressing developments in computational modeling of water (see letters of collaboration). Broader Impact: This research has the potential to open a new regime of operation for water management technologies: heat pipes, soil wicks environmental remediation, microfluidic lab-on-a-chip systems for separations and purifications, and breathing electrodes for low temperature fuel cells. In all of these technologies, wicks or membranes have been used mediate the flow of water at positive or very slightly negative pressures (>-0.1 MPa), and function is severely limited by the inability to control water under substantial tension. Based on the developments proposed here, these rates of mass transfer could be increased by orders of magnitude and ranges of operational parameters (size, temperature, relative humidity) could be dramatically broadened. Exciting changes in the applications of today's engineers create an obligation to update the curriculum and the modes by which it is taught. The investigator describes plans to modify existing components of the curriculum and add new ones at both the undergraduate and graduate levels. Plans are proposed that address critical challenges in modern engineering curricula: 1) the maintenance of effective teaching of fundamental concepts while updating the context to include more material relevant to new contexts such as microchemical technology and bioengineering, 2) the encouragement of innovative use of skills, such that future engineers are poised to invent as well as operate the next generation of technology, and 3) the encouragement of research as a vital component of both undergraduate and graduate education and as a career option. As new technologies emerge, it is also important to educate the public, and, in particular, children on both the timeless (e.g., thermodynamics) and the timely (e.g., micro and nanotechnology) aspects of their function. In Section VII, I propose the development of a set of presentations, demonstrations, and teaching materials that exploit the extraordinary properties of water to motivate experiential science learning. These materials will be developed and presented in collaboration with the outreach program of the Cornell Center for Material Science (see letter), the Franklin Institute of Philadelphia, and the Ithaca Sciencenter. These collaborations will enable interaction with people from a broad range of socio economic scales and underrepresented groups.