The breath figure (BF) approach offers the opportunity of realizing microporous polymer films where the cavities are arranged in a close packed manner. By adjusting the key parameters of the deposition (polymer concentration, kind of solvent, evaporation rate, relative humidity) one can make this arrangement highly ordered, resembling the hexagonal geometry, or even obtain more disordered and polydisperse patterns.1-3 We take advantage of this matter manipulation tool, for preparing structures which are intrinsically auto-organized. At the same time, the morphology of these films is tuned according to the application we thought for them. In the first example, honeycomb films having different size of pores are employed as micro-compartmented recipients for liquid crystals. A double layer of chemically vapour polymerized parylene allows for the encapsulation of liquid crystals without dissolving the honeycomb film. Such structures are expected to aid the realization of flexible bistable displays, avoiding the usual drawback of liquid crystal state transition when the device is tilted or squeezed.4 In a second example, micro or submicrometric structures are covered with a thin metal layer and employed as plasmonic patterns, which are built directly on top of an optical fiber. The optical and spectroscopic properties of these prototypes are then studied for the developing high-sensitivity sensing devices, such as pH sensors and organic vapour sensors. The use of self-assembled patterns in this field promises to be a facile fabrication option for lab-on-fiber devices.5 In the last example, different microporous films have been replicated by PDMS, so that elastomeric microlens arrays with different morphological features are obtained. These films have been applied on the external face of an OLED, with the aim of increasing the fraction of light outcoupled from the device.6 Following this approach, a neat efficiency enhancement up to 32% has been measured.
ARRANGING MICROPORES IN A POLYMER FILM: BREATH FIGURE APPROACH TOWARDS DIFFERENT APPLICATIONS
FRANCESCO GALEOTTI;CHIARA BOTTA
2012
Abstract
The breath figure (BF) approach offers the opportunity of realizing microporous polymer films where the cavities are arranged in a close packed manner. By adjusting the key parameters of the deposition (polymer concentration, kind of solvent, evaporation rate, relative humidity) one can make this arrangement highly ordered, resembling the hexagonal geometry, or even obtain more disordered and polydisperse patterns.1-3 We take advantage of this matter manipulation tool, for preparing structures which are intrinsically auto-organized. At the same time, the morphology of these films is tuned according to the application we thought for them. In the first example, honeycomb films having different size of pores are employed as micro-compartmented recipients for liquid crystals. A double layer of chemically vapour polymerized parylene allows for the encapsulation of liquid crystals without dissolving the honeycomb film. Such structures are expected to aid the realization of flexible bistable displays, avoiding the usual drawback of liquid crystal state transition when the device is tilted or squeezed.4 In a second example, micro or submicrometric structures are covered with a thin metal layer and employed as plasmonic patterns, which are built directly on top of an optical fiber. The optical and spectroscopic properties of these prototypes are then studied for the developing high-sensitivity sensing devices, such as pH sensors and organic vapour sensors. The use of self-assembled patterns in this field promises to be a facile fabrication option for lab-on-fiber devices.5 In the last example, different microporous films have been replicated by PDMS, so that elastomeric microlens arrays with different morphological features are obtained. These films have been applied on the external face of an OLED, with the aim of increasing the fraction of light outcoupled from the device.6 Following this approach, a neat efficiency enhancement up to 32% has been measured.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
