UCSB Materials Research Laboratory scientists recently developed magnetic tweezers tailored to provide a more efficient and precise method of measuring plastic polymers.
Biomolecular Science and Engineering professor Omar Saleh and graduate student Andrew Dittmore worked together to invent the first device capable of grabbing onto polymers — large molecules of natural and synthetic materials such as rubber and nylon — and stretching them to determine their various volumes, structures and levels of elasticity with precision.
Chemist Paul Flory was the first person to examine polymer structure and elasticity in his 1974 Nobel Prize-winning research and concluded that understanding a polymer’s composition and energy requires the evaluation of its volume extension — commonly referred to as “springiness.”
According to Saleh, the research provides a means of quantifying the latter component.
“With the magnetic tweezers, we have found a signature volume of how springy the polymer is,” Saleh said.
Saleh said the new technology provides a simplified and more economically viable means for measuring the polymeric molecules found in the formulas for many household liquids such as shampoos and medicines.
“Many materials we use everyday … contain polymer, a long string-like molecule,” Saleh said. “The magnetic tweezers are good at grabbing onto a single polymer and stretching it out, which allows us to figure out its shape and structure.”
The breakthrough in research is also the product of UCSB Biomolecular Science & Engineering Program Director Philip Pincus’s studies conducted 30 years ago, Dittmore said.
“In general, we had an opportunity to test out a theory that was developed by another professor, Professor Pincus,” Dittmore said. “He had made a prediction about the particular elasticity of a polymer due to a physical effect — the excluded volume.”
Pincus’s prediction that the excluded volume determines the size and shape of a polymer set the foundation for Saleh’s team’s discoveries.
The tools they developed have given scientists the ability to reveal polymers’ unique properties with ease, Pincus said.
“By just pulling on these polymers, [the tweezers] can effectively reproduce the information of polymers that had only been available through very expensive experiments,” Pincus said. “A simply beautiful experiment … the magnetic tweezers invented a new tool to short circuit a lot of very expensive experiments.”
The study also possesses implications for polyethylene glycol. PEG helps deliver drugs into the body and prevent bodily fluids from sticking to implantable medical devices.
Saleh said the magnetic tweezers provide significant improvements in PEG measurement accuracy and allow researchers to take a closer look at their mechanisms and reactions.
“Rather than randomly testing out different codings to understand the structure of the PEG and why this polymer is a good nonstick coding in medical procedures, with these magnetic tweezers — by stretching out the PEG as well as other polymers — scientists and researchers can measure the extension of the polymer with nanometer accuracy and say something about the structure,” Saleh said. “We can understand the physics of the polymer to make these materials work better and understand how these structures react to solutions and different solvents, such as water.”
