Electrospun fibers have the potential to play an important role in fields including filtration, tissue engineering and drug delivery. Applications often require precise fiber mechanical properties and orientations. For example, in tissue engineering cells sense and respond to the stiffness, orientation and size of elements in their environment. Researchers can control the orientation of electrospun fibers by altering the electric field in the region of the collector. By placing two collector parallel to one another, aligned fibers are produced in the region between the collectors. Here we hypothesize that electric field alignment of electrospun nanofibers will cause changes in mechanical properties of the fibers.
Fibers were electrospun from 8% polyethylene oxide (PEO) solution under electric field conditions for alignment and nonalignment. Individual fibers were manipulated by AFM in combination with an inverted microscope to determine mechanical properties such as Young’s modulus and extensibility. The force required to stretch the fiber was found using the Sader method to calculate the torsional constant of the cantilever. The diameters of fibers were determined through AFM and SEM imaging.
We found aligned fibers formed under the same working distance, voltage and polymer solution to be significantly smaller in diameters than nonaligned fibers. Fibers aligned using a parallel plate collector had a diameter of 182 +/- 10 nm (average ± standard deviation of the mean) while nonaligned fibers had a diameter of 262 +/- 14 nm. Consistent with previously published data, the smaller aligned fibers had a higher initial modulus on average than nonaligned fibers, 130 ± 10 MPa and 40 ± 10 MPa, respectively. Previous data showed aligned fibers to be less extensible, with an average strain of 1.4 ± 0.2, than nonaligned fibers, with an average strain of 3.2 ± 0.3.
These results indicate a significant effect on electrospun fiber properties due to changes to the electric field and lead to further questions about the effect of the collector and therefore the electric field on electrospun fiber mechanical and physical properties.