P2.9.2 Small and Simple Devices for Increase Mixing on Detector Surfaces

Abstract

Due to transport phenomena, analyte adsorption on the detector surface can be hindered, which increases the detection limit. Therefore, this work aims the simulation, production and tests of a simple miniaturized structure that favors mixing on detector surfaces. The conception of the manufactured device is based on passive mixers. Mixing is improved by changing the surfaces properties of plasma deposited thin films. Hexamethyldisilazane (HMDS) and nonafluoro(iso)butyl ether (HFE) and codeposited HMDS/HFE plasma films were modified by ultraviolet (UVC) or beta radiation exposure (electron beam, 2 MeV, from 10 nA to 100 nA). Silicon, acrylics and piezoelectric quartz crystal (PQC) were used as substrates. Film characterization used profilemeter for thickness and ellipsometer for refractive index determinations; Raman, infrared (FTIR) and x-ray photoelectron (XPS) spectroscopies determined chemical composition. Optical, scanning electron (SEM) and atomic force (AFM) microscopies evaluated the film resistance toward ultraviolet light or beta radiation and cluster formation; cluster size were estimated using ImageJ software. Contact angle measurements tested hydrophobicity and the adsorption of volatile organic compounds (VOCs). Simulations of detector surfaces (based on PQC detection) and respective package used FEMLAB 3.2 software. All films are hydrophobic and adsorbent, even after exposition to ultraviolet radiation. HMDS films exposed to ultraviolet form a silicone-like structure whereas beta radiation exposure leads to carbon nodules formation. HFE films act as passive layer, even for beta radiation. Best design for surface modification has approximately a sinoidal shape.