PDMS–PMMA bonding improvement using SiO₂ intermediate layer and its application in fabricating gas micro valves

In this study a modified technique is presented for bonding PDMS membrane to PMMA substrate using thin SiO₂ intermediate layer to enhance PMMA surface’s hydrophilicity, and increase PMMA stickiness to PDMS via O₂ plasma activation. TEOS solution is used to create silica layer on PMMA, and Chloroform is added to sol–gel in order to infuse silica layer to PMMA substrate; this leads to a stronger stickiness of SiO₂ layer to PMMA. It is shown that strong and irreversible bond of PMMA which is covered with SiO₂ nano particles, to PDMS can be reliably achieved. Furthermore, using this technique, two types of polymeric gas micro valves were fabricated that could cease the gas flow hermetically. Additionally, small solenoid actuators were utilized to control valves which lead to switching from a rather high differential pressure. In order to evaluate bonding and banning capability of the valves, several tests such as strength test and Damming test of the valves were performed. Results of the conducted tests indicate an improvement in PDMS/PMMA bonding strength using TEOS/chloroform solution; moreover, damming pressure of the micro valves, at the best condition, was about 2.5 bars.