Abstract
This research introduces a novel approach to control light transmittance based on flexible polydimethylsiloxane (PDMS) films that have been plasma-treated such that micro-scale surface features have a visual effect as the film responds to applied strain. The effect is continuously tunable from optically clear (71.5% Transmittance over a 400–900 nm wavelength) to completely diffuse (18.1% T). Changes in the film's optical properties are triggered by bi-axial strains applied using a pneumatic system to form pressurized envelopes. This paper reports on a series of experimental studies and provides system integration research using prototypes, simulations and geometric models to correlate measured optical properties, strain, and global surface curvatures. In conclusion, a design is proposed to integrate PDMS light control within existing building envelopes.Two alternatives are investigated and compared: System A uses positive pressure featuring an exterior grid to restrain and shape the inflated film during expansion; System B uses negative pressure where the films are shaped according to the geometry of an interstitial grid that serves as a spacer between two film surfaces. Both systems can provide effective control of opacity levels using pneumatic pressure and may be suitable for use with existing glazing systems or ethylene tetrafluoroethylene (ETFE) pneumatic envelopes.
Highlights
This research introduces a novel approach to control light transmittance based on flexible polydimethylsiloxane (PDMS) films that have been plasma-treated such that micro-scale surface features have a visual effect as the film responds to applied strain
The research presents new experimental insight on the optical properties of doubly-curved PDMS film, correlating light transmittance with simulated bi-axial strains using non-linear finite element analysis
The heat effectively expands the PDMS film and keeps it in a pre-stretched state thereby increasing the area of surface exposed to oxidization
Summary
An alternative to glazed envelopes are pneumatically pressurized ethylene tetrafluoroethylene (ETFE) film ’pillow’ facades; these systems have few options to control light and privacy. Static glazing systems such as textured glass, cast glass panes, colored glass and more recently, fritted or etched glass panes, allow for privacy while maintaining light transmittance. Activated dynamic light control systems exist but are slow to react to environmental conditions [1] [2] Solutions such as blinds, shades, and curtains can reduce light levels and provide privacy, but mechanically actuated dynamic shading and privacy systems are not very robust, require regular maintenance, and are difficult to deploy at a large scale. The paper presents various prototypes and proposes an initial design solution for integrating a Pneumatically Adaptive Light Modulation System (PALMS) into existing roof systems and building facades, with a focus on pneumatic ETFE systems
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