Nanostructured PMMA-coated Love wave device as a platform for protein adsorption studies

Abstract

The development of nanostructured surfaces can enhance molecular interaction with sensors by increasing the available surface area. The associated potential for increased sensitivity towards analytes is of significance to the analytical and biophysical sector. In this work we explore the effect of nanostructures created on the surface of an acoustic wave device based on a Love wave geometry. Nanopillars with a diameter of 35nm and a height range of 60–280nm were created on top of a PMMA waveguide film by oxygen plasma etching. The effect of the pillar height on the acoustic response was tested by measuring the adsorption of BSA; increasing the pillar height up to 155nm led to an increase in the acoustic phase response associated with wave velocity. At higher surface roughness, wave-scattering effects dominated: at nanopillar heights larger than 200nm these effects were so severe that the sensors could not be used for protein sensing. In addition to phase, amplitude measurements were used to derive information on the structure of the adsorbed protein film and its dependency on the nanopillar height. This work demonstrates the importance of controlling the roughness of the waveguiding layer of a Love wave device, since the nanostructure-dependent response has considerable effects on designing sensitive biochip platforms for clinical and diagnostic applications.