Regular Article

Spin-speed independent thickness and molecular adsorption behaviour of polyelectrolyte multilayers

¹ Department of Electronics and Communication Engineering, National Institute of Technology Goa, Farmagudi, Ponda 403401, Goa, India
² Department of Electronics and Telecommunication Engineering, Siddaganga Institute of Technology, Tumkuru 572103, Karnataka, India
³ Department of Applied Sciences, National Institute of Technology Goa, Farmagudi, Ponda 403401, Goa, India
⁴ Centre for Nano Science and Engineering, Indian Institute of Science, Bengaluru 560012, Karnataka, India

^* e-mail: grprashanth@nitgoa.ac.in

Received: 17 September 2020
Received in final form: 29 December 2020
Accepted: 6 January 2021
Published online: 18 February 2021

Abstract

The science behind the build-up mechanism of polyelectrolyte multilayers is important for developing devices for various engineering applications. Here we, study the dependency of thickness of polyelectrolyte multilayer films, fabricated using spin-assisted layer-by-layer self-assembly of polyelectrolytes technique, with respect to varying spin-speed while keeping all other parameters of the fabrication process-window constant. The thickness measurements were performed using variable angle spectroscopic ellipsometry and atomic force microscopy. The experimentally observed results were validated mathematically using a Flory type theory. In addition, the bio-molecular adsorption studies on these polyelectrolyte multilayer films fabricated at various spin-speeds, were also quantitatively analyzed using fluorescence microscopy studies. It was seen that the effect of spin-speed on the thickness of polyelectrolyte multilayers was negligible. In addition, it was also observed that the bio-molecular adsorption modalities onto these substrates were also independent of the spin-speed. This finding prompts to develop low-cost alternative technologies for various biomedical engineering applications, like functionalized substrates for centrifugal assay for fluorescence-based cell adhesion, wherein stability of films against strong mechanical forces generated during spinning can play an important role.