Functionalization and microfluidic integration of silicon nanowire biologically gated field effect transistors

摘要

This thesis deals with the development of a novel biosensor for the detection of biomolecules based on a silicon nanowire biologically gated field-effect transistor and its integration into a point-of-care device. The sensor and electrical on-chip integration was developed in a different project. The presented research is based on this sensor structure and investigates its potential as a versatile biomarker detection platform by evaluating different functionalization approaches. The functionalization of the silicon sensor surface with organic molecules was investigated in detail to determine the suitability of different methods for the preparation of organic interfaces for protein attachment. Oxide-free silicon surfaces offer unique possibilities to create highly sensitive sensor surfaces for charge detection due to the lack of an insulating oxide layer, but the highly reactive surface presents a challenge for modification under ambient conditions. Self-assembled monolayer formation by hydrosilylation with alkenes and alkynes was thus investigated under different conditions, both ambient and controlled, and quantified using x-ray photoelectron spectroscopy.With the aim to create a platform for subsequent immobilization of receptor molecules, amine-and carboxylic acid- as well as alkyne-terminated surfaces were prepared that allow for the conjugation of biomolecules using established cross-linking schemes. Using a receptor-ligand model system protein detection experiments were performed with nanowire sensors functionalized using different modification schemes. To facilitate functionalization and measurement and as a first step towards integration into a point-of-care device, several microfluidic tools were developed for sample delivery to the sensor surface and as a modular platform for the further development of automated functionalization and sample preparation schemes.