Bonding of SU-8 films onto KMPR structures for microfluidic, air-suspended photonic and optofluidic applications

We present a method to bond unstructured and structured SU-8 films down to sub-micron thicknesses onto microchannels fabricated in KMPR using a flexible polydimethylsiloxane (PDMS) stamp. By exploiting differently casted PDMS stamps, 3D microfluidic channel networks, air-suspended photonic devices and optofluidic structures have been fabricated. First, microchannels of KMPR are patterned by photolithography and an SU-8 film is spin coated onto a prepared PDMS stamp. The stamp is then placed on top of the KMPR microchannels and the SU-8 layer is cross-linked by applying sufficient heat and pressure. After peeling off the PDMS stamp, the SU-8 layer remains bonded on the KMPR. In our experiments, we demonstrate the bonding of approximately 0.5 mu m thick structured SU-8 films onto KMPR microchannels of about 500 mu m width and 25 mu m height. Bond strength tests demonstrated that such thin layers can withstand pressures up to 1100 hPa. The laminated SU-8 layers can enable various functionalities, e.g. sealing of microfluidic channels, realization of air-suspended photonic structures or optofluidic devices. Most importantly, the combination of fluid handling in the microchannels and air-suspended photonic structures realized in the laminated SU-8 layer enables research towards a large range of applications, such as optofluidics, biosensors, chemical and biomedical analysis, environmental investigations, and renewable energy.