The innovation engine for new materials

Sam Halliday


University of Oxford


Materials Science


Andrew Dittmore
Dustin McIntosh

Faculty Sponsor(s): 

Professor Omar Saleh

Faculty Sponsor's Department: 

Materials Research Laboratory

Project Title: 

Static Properties Of Single Polyethylene Oxide (PEO) Molecules As Measured By Magnetic Tweezers

Project Description: 

Conventionally, single molecule experiments have been performed on long biological polymers (notably double-stranded DNA) in which their mechanical properties have been revealed with great success. While a plethora of non-biological polymers are used in a variety of scientific and industrial applications, their short length has precluded study of their properties at the single-molecule level. Here, we use magnetic tweezers to probe the mechanical properties of single molecules of bifunctional polyethylene oxide (PEO), a common polymer used in everything from gene therapy, to surfactants, to toothpaste. We tether the molecule to a silanated glass surface on one end using a maleimide/thiol reaction and to a paramagnetic bead on the other using a biotin/streptavidin reaction. By comparison to the typically-studied biological macromolecules, our PEO is short with a total contour length of 695 nm. Methods for accurately determining force-extension curves at the low forces accessible to magnetic tweezers have not been fully formulated due to issues of mis-tethering and bead tracking. The more serious of the issues, mis-tethering, is where the attachment of the PEO chain to the magnetic bead is misaligned with respect to the bead’s magnetic moment, causing serious length measurement problems. We investigate corrections to these issues and show the first low-force force-extension data on PEO known to date.