Patterning of polymer-encapsulated optical oxygen sensors by electron beam lithography

In this paper we show a novel fabrication process capable of yielding arbitrarily-shaped optical oxygen sensor patterns at sub-micron resolution. The wafer-level process uses a thin-film sacrificial metal layer as intermediate mask, protecting the sensor material and enabling the use of electron beam lithography for sensor patterning. Feature sizes down to 500 nm are demonstrated and currently only limited by the optical system used for sensor readout. Gaseous oxygen detection using the patterned sensors shows Stern-Volmer behavior with a measured intensity ratio I₁₀₀/I₀ of 4.1. The process enables the integration of sensor patch arrays underneath single cells for laterally registered oxygen sensing in cell-culture applications.