Electrospun Mats: From White to Transparent with a Drop

• Published in: Macromolecular materials and engineering Vol. 303; no. 10
• Main Authors: Cimadoro, Jonathan, Ribba, Laura, Ledesma, Silvia, Goyanes, Silvia
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01-10-2018
• Subjects: Atomic force microscopy; Composite materials; Cylinders; Drying; Electrospinning; electrospun nanofibers; Mats; Mie scattering; Nanofibers; Refractivity; swelling effects; Transmittance
• ISSN: 1438-7492; 1439-2054
• DOI: 10.1002/mame.201800237

In this article, the transparency of hydrophilic electrospun mats is studied. Results showing how transmittance varies under the action of water are presented. It is observed that swelling plays a crucial role in the transmittance of the material, changing it from opaque to transparent when it is wet. Atomic force microscope measurements show that the diameter distribution of nanofibers is modified during both the wetting and the drying of the mats. Using these distributions and modeling the change in the relative refractive index as a composite material, a qualitative explanation of the mat scattering behavior by using the Mie scattering theory for cylinders has been done. The obtained results indicate that changes on the optical response produced by water contact are different according to the mat thickness: samples with smaller thicknesses can act as a water sensor with a persistent response over time, while samples with thicknesses greater than 7 µm can act as sensors for drying time.
Starting from a transparent polymer it is possible to obtain opaque meshes when generating nanofibers by electrospinning. However, when these meshes come into contact with water they become transparent again due to the swelling of the fibers and the presence of water in the holes between them.