High sensitivity and selectivity vertically-oriented silicon nanowire array-based bioelectronic sensor platform

Silicon nanowires are next-generation high performance biosensor materials compatible with multiple types of biomolecules. Bioelectronic sensors, which outputs electrical signals for biological detection, have unique advantages in miniaturization, fast response, and portability. Despite that these nanomaterials have demonstrated high performance, complex fabrication methods that are not compatible with industrial production are usually implemented. This work deals with the development, fabrication, and testing of a rapid and cost-effective silicon nanowire biosensor that is less than one inch in width and suited for industrial mass production. The silicon nanowires are fabricated using a silver-assisted chemical etching which mass-producible and CMOS-compatible, tunable etch rate, and high consistency. The nanowire sensor is then fabricated using a series of nanofabrication instruments that are commonly used for semiconductor processing. The fabrication process is developed and modified to be suited for biosensing applications.

The fabricated vertically-oriented silicon nanowire array-based sensor consists of a p-n diode. Since the diode type nanowire biosensors have not been thoroughly implemented and studied, in this work, in order to simulate and validate the operation mechanisms of the proposed biosensor, a characterization approach is proposed, the mathematical and physical models of the device are studied, and a water-gate experiment is conducted to justify the models. In the case when the unexpected disturbance occurs, the model also provides with a method to eliminate the noise in the effective resistance of the sensor.

The fabricated biosensors are then functionalized for the testing of three types of analytes including two cancer cell antibodies and the spike protein of the severe acute respiratory syndrome coronavirus 2. The results show that the developed sensors have high sensitivity and specificity against bovine serum albumin. Although still with a preliminary design, the proposed sensor has already been demonstrated to be able to detect clinically relevant concentrations of the target for the diagnosis of the disease. This technology offers the potential to complement conventional biosensor systems in applications of portable and rapid responding biosensing.