Hot embossing of microstructures on addition curing polydimethylsiloxane films

Abstract

To our knowledge no known technologies or processes are commercially available for embossing microstructures and sub-micron structures on elastomers like silicones in large scale production of films. The predominantly used technologies to make micro-scale components for micro-fluidic devices and microstructures on PDMS elastomer are 1) reaction injection molding 2) UV lithography and 3) photolithography, which all are time-consuming and not suitable for large scale productions. A hot-embossing process to impart micro-scale corrugations on an addition curing vinyl terminated PDMS (polydimethyl siloxane) film, which is thermosetting elastomer, was established based on the existing and widely applied technology for thermoplasts. We focus on hot-embossing as it is one of the simplest, most costeffective and time saving methods for replicating structures for thermoplasts. Addition curing silicones are shown to possess the ability to capture and retain an imprint made on it 10-15 minutes after the gel-point at room temperature. This property is exploited in the hot-embossing technology.

Techniques for hot embossing microstructures on liquid silicone rubbers with fillers

“…Furthermore, the common carrier webs that stick too well to the films are not stable at high temperatures for extended periods of time and have seam lines breaking the corrugation pattern. 6 Processing techniques should be easy, economic, fast, and should not induce any defects in the thin films. The performance of the film as transducer material depends on the excellence and precision of the production-processing techniques.…”

“…7 An alternative method called the hot embossing for producing thin corrugated films was formulated by Vudayagiri et al (Figure 3). 6 In this method, a thin coating of the addition curing PDMS mixture is applied on a flat polyethylene terephthalate (PETE) substrate, which is 0.2 mm thick. The thin elastomer coating is preheated on a hot steel roller at 110 C for 10-15 s until the mixture approaches gel point (GP).…”

“…The thin elastomer coating is preheated on a hot steel roller at 110 C for 10-15 s until the mixture approaches gel point (GP). 6 The film that is precured to the GP is now run through the embossing roll that is running at a speed of 1.4 r min À1 with a pressure of 25 psi between the rolls (Figure 3). The surface of embossing roll has the corrugations and the rolls are at a temperature of 100 C. The film runs through the rolls and comes out embossed.…”

Methods to ease the release of thin polydimethylsiloxane films from difficult substrates

“…Non‐ionic surfactants are chosen in this case, in order to avoid ionization of the surfactant under electric field because the application of films as actuators requires use of high voltage. Another option for improving the process is of course to reinvent the process such as applying embossing where the elastomer is not cured on the corrugated web and thus avoiding release problem. One of possible solution can be the addition of highly cross‐linked silicone resins (ex: Belsil® TMS 803), which can be compounded with PDMS.…”

“…Another option for improving the process is of course to reinvent the process such as applying embossing where the elastomer is not cured on the corrugated web [4,5] and thus avoiding release problem. One of possible solution can be the addition of highly cross-linked silicone resins (ex: Belsil W TMS 803), which can be compounded with PDMS.…”