A Stimulus-Responsive Polymer Composite Surface with Magnetic Field-Governed Wetting and Photocatalytic Properties

Abstract

With the increasing demand for liquid manipulation and microfluidic techniques, surfaces with real-time tunable wetting properties are becoming the focus of materials science researches. In this study, we present a simple preparation method for a 0.5–4 µm carbonyl iron (carbonyl Fe) loaded polydimethylsiloxane (PDMS)-based magnetic composite coating with magnetic field-tailored wetting properties. Moreover, the embedded 6.3–16.7 wt.% Ag-TiO2 plasmonic photocatalyst (d~50 nm) content provides additional visible light photoreactivity to the external stimuli-responsive composite grass surfaces, while the efficiency of this photocatalytic behavior also turned out to be dependent on the external magnetic field. The inclusion of the photocatalyst introduced hierarchical surface roughness to the micro-grass, resulting in the broadening of the achievable contact and sliding angle ranges. The photocatalyst-infused coatings are also capable of catching and releasing water droplets, which alongside their multifunctional (photocatalytic activity and tunable wetting characteristics) nature makes surfaces of this kind the novel sophisticated tools of liquid manipulation.

Visible light-photoreactive composite surfaces with thermoresponsive wetting and photocatalytic properties

“…Ag-TiO 2 /PDMS-co-INI samples As an elastic and hydrophobic base polymer material, two-component Elastosil C1200 PDMS elastomer (Wacker; Burghausen, Germany) was used: component A contains the silicone-hydride prepolymer and the vinyl-terminated crosslinker, while component B contains the prepolymer alongside the Pt-complex catalyst for the curing reaction [11]. In each of our formulations, we kept the recommended 1:1 massto-mass ratio of A and B.…”

“…As Figure 1a shows, the INI is covalently bound to the PDMS-network by the Pt-complex catalyst content of the applied two-component Elastosil C1200 PDMS: besides keeping the optimal (1:1 = m:m) ratio between the two PDMS-component [11], the increasing amount of added INI can result in a drastic decline of cross-linking density and therefore, elasticity. According to a previous study, the optimal m:m ratio between the PDMS and the INI is 11:0.13 (1.2 wt% INI), and the recommended upper limit is 11:0.5 (4.3 wt% INI) when Sylgard 184 PDMS is applied: if the INI-content is increased above this level, the resulting copolymer might have viscous characteristics [26].…”

“…The stimulus-responsivity of such composites can influence many properties, like shape, size [7], density, swelling degree, and the real-time regulation of surface wetting properties. Latter attracted specific attention in recent years due to the increasing popularity of microfluidic and liquid manipulation devices.The wetting characteristics of a surface may be manipulated by altering surface charge excess, functionality, roughness, or topology [8,9]: all of these can be subjected to external stimuli, ranging, for example, from the applications of electrowetting [5], to roughness-changing magnetorheological elastomers [10] and liquid manipulator magnetic pillar systems [11,12]. In a widely known approach, the wetting properties of a solid surface become tunable through its functionalization with poly(N-isopropylacrylamide) (PNIPAAm).…”

“…The wetting characteristics of a surface may be manipulated by altering surface charge excess, functionality, roughness, or topology [8,9]: all of these can be subjected to external stimuli, ranging, for example, from the applications of electrowetting [5], to roughness-changing magnetorheological elastomers [10] and liquid manipulator magnetic pillar systems [11,12]. In a widely known approach, the wetting properties of a solid surface become tunable through its functionalization with poly(N-isopropylacrylamide) (PNIPAAm).…”

Intelligent Polymers, Fibers and Applications

“…For those composites, adding magnetic nanoparticles leads to added magnetic features, so that materials can interact with magnetic fields [ 101 ]. As a result, the magnetic field easily deforms the polymer matrix without noise, heat or fatigue, making it suitable for the preparation of sensors, micromachines, energy transducers, controlled distribution systems and environmental and biomedical applications [ 102 , 103 , 104 ]. Although the uncontrollable manner of the way magnetic nanoparticles scattered in the gel hindered the promotion of its applications, this issue has been solved by forming cross-linking hydrogel nodes [ 98 , 105 ].…”