Fabrication of superhydrophobic gold film on polymer substrates

Abstract

Superhydrophobic surface was fabricated by a reduction reaction between chloroauric acid (HAuCl4) and sodium formate (HCOONa) on polydimethylsiloxane (PDMS) substrate without any further surface modification. This generated gold films with superhydrophobic properties examined by water contact angle (WCA) and contact angle hysteresis measurement. Wettability of the fabricated gold film on PDMS substrate can be controlled by the deposition time which provides the WCA > 160o and it could be up to 164.41o with a contact angle hysteresis of 1.93o when the deposition time was prolonged at least 2 hours. To propose the deposition mechanism, the morphological structure and chemical characters of the gold films at different deposition time was deeply investigated using scanning electron microscope (SEM), Energy Dispersed X-ray spectrometer (EDS), X-ray diffractometer (XRD) and infrared spectrophotometer (IR). The gold films contain two different layers including uniformly spherical particles and the secondary structure. The secondary structure is the key factor to control roughness and hydrophobicity of the gold films. The stability of the gold films was inspected by using water-drop testing. The gold films can be tolerated for 7,200 drops without any loss of hydrophobic properties. The potential applications of using the gold films as magneto-wetting surface and a powerful SERS substrate were demonstrated.