SST: Patchy Sensor Surfaces for Selective Dynamic Adhesion of Micron and SubMicron Objects

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AbstractProposal Number: CTS-0428455Principal Investigator: Maria M. SantoreInstitution: University of Massachusetts AmherstTitle: Patchy Sensor Surfaces for Selective Dynamic Adhesion of Micron and Submicron Objects Merit: This program will develop the science for robust field-ready sensors for particles with sizes from 50 nm to 5 um, applicable to the detection of bacteria, spores, viruses, inorganic fines, and chemically-sensitive scavenging particles from aqueous and airborne environments. Focusing on reversible dynamic adhesion as these objects flow over detector surfaces that spontaneously recover after a .detection event., the program targets a new sensing concept that will screen and discriminate classes of biological cells or inorganic particles based on their surfaces. This class-level selectivity will not require steps that lyze cells, extract proteins or genetic material, or conduct molecular recognition. Multiple applications are therefore targeted. At the heart of this new sensing technology lies a heterogeneous or patterned surface which is robust to pH, temperature, and other environmental factors, and which selectively adheres target particles while rejecting those outside target ranges in size or surface character (mean density or nanoscale distribution of surface charge, nano-meter scale patches of hydrophobic and hydrophilic chemistries, scale of roughness and other aspects of surface topography, and even specific peptide sequences). The sensor surfaces present nanometer-scale patches of different sizes and chemistries, and micron-scale hydrodynamic features that generate a landscape of competing colloidal and hydrodynamic forces to discriminate approaching colloidal particles based on their dynamic signature, including reversible adhesion, rolling, skipping, and arrest. The proposed collaboration between Santore, Coughlin, and Davis spans the disciplines of polymer interfaces, synthetic chemistry, and fluid mechanics. Through combined experiment and modeling, the team will develop design rules for collector surface patterns, robust detector chemistry, and operating strategies that manipulate concentration, ionic strength, and flow rates. With model particles capturing the essential features of spores, bacteria, viruses, resins, and minerals, the program will probe adhesion and detachment rates on patterned collector surfaces with systematic variations in the scale and chemistry of surface features. Surface features will be designed with particular colloidal forces (electrostatic, Van der Waals, hydrophobic, and polymer mechanical) and hydrodynamic fields in mind, exploiting the versatility of block copolymer architectures, and flow fields engineered to manipulate particle-surface encounters. Broader impacts. The new sensing technology will benefit society not only in terms of homeland security, but also in terms of public welfare: The sensing principles employ active surfaces which could be produced at modest cost, and designs which can operate unattended and automatically, in chemical processes and public buildings such as hospitals and schools, and ultimately the home. The program, while rooted in the interdisciplinary fields of nanochemistry and colloid science, impacts the fields of polymer surface chemistry, biophysics, and pattern recognition, and will initiate a surface fingerprinting database of single cell organisms. Graduate students will carry forward the bulk of the fundamental science while a liaison program will benefit engineering, chemistry, and physics undergraduates via a hybrid industrial / university research experience. Undergraduates will spend a summer in industry on a project with science parallel to that in the Santore / Davis/ and Coughlin labs, returning to UMass to conduct a related research project during the academic year. Integrated teaching and research will be accomplished with a special topics course on smart interfaces, and with guest lectures in key courses in the undergraduate curriculum of two UMass colleges. The program will target underrepresented groups by recruiting students from local colleges who take courses at UMass.