Protein patterning using germanium as a sacrificial layer

With the rise of microfluidic diagnostics, there is a need for more efficient methods of patterning surface-attached moieties, including proteins like antibodies, onto microchannel surfaces. This arises because almost all of the solvents and processes used for surface-attachment chemistries (or their payloads) are incompatible with sacrificial layers usually photoresist during microfabrication, rendering it difficult to easily pattern active chemistry onto a surface in manufacture scale. We present a simple method, based on thin film germanium dissolution, which is compatible with both modern nanolithographic techniques and surface chemistries. Simply, because germanium thin films dissolve readily, controllably and rapidly in water (but not organic solvents), these films can be used to mask and protect areas of the substrate during the attachment of surface chemistries. We demonstrate the process and results using microscale patterns. The resolution and alignment of this method depends on the photolithography tool used; nanoscale patterning is not difficult to achieve. In addition, we show that with non-conformal germanium deposition (e.g. e-beam evaporation), the conjugation of surface chemistry on vertical side walls can be manipulated by controlling the thickness of the deposited germanium layer, opening another dimension for microfluidic devices and cell manipulation research.