Electrical Detection of Self-Assembled Polyelectrolyte Multilayers by a Thin Film Resistor

TL;DR

This paper demonstrates the electrical detection of polyelectrolyte multilayers using a silicon-on-insulator thin film resistor, revealing potential shifts due to layer buildup and modeling electrostatic screening effects within the multilayers.

Contribution

It introduces a novel electrical sensing method for PEMs using a thin film resistor and models the electrostatic response considering ion screening and dielectric properties.

Findings

Potential shifts decrease with more layers

Debye screening length is increased inside PEMs

Mobile ion partitioning allows dielectric constant estimation

Abstract

The build up of polyelectrolyte multilayers (PEMs) was observed by a silicon-on-insulator (SOI) based thin film resistor. Differently charged polyelectrolytes adsorbing to the sensor surface result in defined potential shifts, which decrease with the number of layers deposited. We model the response of the device assuming electrostatic screening of polyelectrolyte charges by mobile ions within the PEMs. The Debye screening length inside the PEMs was found to be increased compared to the value corresponding to the bulk solution. Furthermore the partitioning of mobile ions between the bulk phase and the polyelectrolyte film was employed to calculate the dielectric constant of the PEMs and the concentration of mobile charges.