Effects of Electrospinning Setup and Process Parameters on Nanofiber Morphology Intended for the Modification of Quartz Crystal Microbalance Surfaces

To improve the performance of mass sensitive biosensors, the surface of a piezoelectric quartz crystal transducer, is expanded by employing electrospun nanofibers to its surface. This work describes the effect of vertical horizontal electrospinning setups and electrospinning parameters on fiber morphology. The research objective was to obtain finer and non-beaded fiber morphologies, via controllable and repeatable process parameters, for further applications of QCM surfaces in high performance DNA-, Aptamer-, Immunosensor applications. INTRODUCTION Quartz crystal microbalances (QCMs) are one of a broad class of acoustic wave (AW) techniques. QCM is highly sensitive to mass changes in the presence of a coating that interacts with the target when used as mass sensitive biosensors [1-3]. Biosensor performance such as sensitivity, selectivity, and response time is largely influenced by the properties of the sensing films [4,5]. Electrospun nanofibers which have controllable membrane thickness, fine structure and large surface area to volume ratio, are expected to be an ideal candidate as the structure of sensing materials [6]. Polyvinyl alcohol (PVA) which is an important polymer that is widely used in electrospun coatings due to its excellent chemical and physical properties such as non toxicity, process ability, good chemical resistance, good film formation capacity, complete biodegradability and high crystal modulus, is used to modify QCM surfaces [7,8]. Even though electrospinning is a novel method for sensor surface modification, it’s an old technique that has been the basis for theoretical studies and new applications for more than a hundred years. The Rayleigh limit, Taylor cone, perturbations, and instabilities are the theoretical backgrounds of the electrospinning process [9,10,12]. Many researchers are investigating novel apparatus to overcome instabilities and chaotic behavior of nanofibers for the purpose of obtaining aligned and reproducible nanofibers [11,12]. Considering polymer solution parameters such as molecular weight, solution viscosity, dielectric effect of the solvent; processing conditions such as voltage, flow rate, temperature, effect of collector, distance between tip and collector; and ambient parameters such as temperature, humidity, and pressure; many experiments have been done to determine the effects of these parameters on fiber morphology [8,11,12]. Following the modification of QCM surfaces by the electrospinning method, it is predicted that the low pressure plasma polymerization technique, which is an elegant method for generating functional polymer surfaces, will be used for creating specific groups on those surfaces for the purpose of novel biosensor applications [2,3]. In this paper, for the modifications on QCM surfaces, vertical and horizontal electrospinning setups are observed and effects of the process parameters on polyvinyl alcohol nanofiber morphology are reported. The appropriate parameters for QCM surface modifications are chosen by the interpretations of SEM images. EXPERIMENTAL DETAILS Materials For the electrospinning process, aqueous solutions of polyvinyl alcohol (10 15 wt %) (Mw=70000– 100000 (LALLS), SIGMA, Germany) were prepared at 80C in an ultrasonic water bath (Ultrasons Medi II J.P. SELECTA). As a mass sensitive transducer, quartz crystals (5MHz, with Ti/Au electrode) were supplied from