Room-temperature direct heterogeneous bonding of glass and polystyrene substrates

Organic-inorganic hybrid structures enable new opportunities for ubiquitous sensors. Bonding of organic and inorganic materials is highly desirable but challenging. Polystyrene and glass are two of typical substrate materials for micro/nanofluidic devices. However, they are very difficult to be combined due to their extremely large thermal expansion mismatches. To avoid thermal stress generated at elevated temperatures, we developed a room-temperature direct bonding process between polystyrene and glass substrates using vacuum ultraviolet-ozone (VUV/O3) surface irradiation without employing heat. After storage at room temperature (∼25^◦C) for 24 h, the bonding strengths were measured to be >2 MPa, representing a robust interfacial bonding. The bonded polystyrene-glass pair exhibited excellent optical transparency due to nearly no deterioration at the bonding interface. The details of VUV/O₃ treated surfaces and bonding interfaces were characterized and a bonding model was demonstrated to elucidate the glass-polystyrene bonding mechanism.