Glancing angle deposition for biosensing applications

The properties of sculptured thin films (STFs) grown by glancing angle deposition (GLAD) make them attractive for biosensing applications. Such biosensors, based on the enhancement of optical response signals of certain molecules, can be applied for detection of DNA, glucose, endocrine disruption compounds and bacteria. In this work, a short overview about the preparation of STFs by oblique angle deposition and GLAD is given. These techniques are capable to fabricate nanostructures with a wide variety of morphology by utilization of the atomic shadowing and the surface diffusion effects at highly oblique deposition angles. With the aim of the lateral separation of nanostructures, prepatterned template substrates can be introduced, which are characterized by uniformly separated seed elements that act as nucleation points for the nanostructure growth. The electromagnetic field enhancement in the vicinity of STF nanostructures is a highly attractive effect that is used by surface-enhanced Raman spectroscopy and surface-enhanced fluorescence spectroscopy to reduce the detection limits. The STF nanostructures are further functionalized to come as close as possible to this scientific intent. The details are discussed, and the subsequent chemical surface functionalization of the used sensors is shown. Specific and sensible detections of the endocrine disruptor biomarker protein vitellogenin, of glycated hemoglobin, and of E. coli bacteria are demonstrated.