Nanofabrication and Characterization of Nanoelectronic Biosensors Based on Emerging Layered Semiconductors.

Abstract

Many important biomedical and clinical applications, such as early-stage cancer diagnosis, autoimmune disease treatment, and real-time monitoring of patients’ immune status, demand new integrated multiplexing nanoelectronic/microfluidic biosensors. These biosensors are anticipated to enable fast (minute-scale) quantification of illness-related biomarkers, unprecedented detection sensitivity, fM-level limit-of-detection (LOD), and point-of-care capability. However, these new highly desirable biosensing capabilities have not been realized yet. Atomically layered transition metal dichalcogenides (TMDCs) have gained a lot of attention because of their excellent electronic and structural properties. Especially, semiconducting TMDCs can serve as an essential complement to zero-band-gap graphene and enable novel semiconductor-related applications, such as thin-film transistors, phototransistors, and various types of sensors. More importantly, such TMDCs hold significant potential to be exploited for making new electronic biosensors and realize the highly desirable biosensing capabilities mentioned above. The research presented in this thesis sought to advance the scientific and technical knowledge for fabricating and operating new TMDC-based electronic/microfluidic-integrated biosensors and realizing rapid fM-level quantification of biomarkers. The first part (i.e., the second chapter) is mainly focused on developing a top-down nanofabrication approach for producing orderly arranged, pristine few-layer MoS2 flakes, which holds significant potential to be developed into a upscalable nanomanufacturing technology. The second part (i.e., the third-to-fifth chapters) presents a systematic study on the biosensing characteristics of the TMDC-based transistor sensors fabricated using our nanoprinting techniques. First, multiple sets of MoS2-based transistor biosensors were fabricated using our plasma-assisted nanoprinting method. Second, we studied the underlying device physics governing the response characteristics of TDMC transistor biosensors. Third, we further studied a cycle-wise method for operating MoS2/WSe2-based transistor biosensors to enable rapid, low-noise, highly specific biomolecule quantification at femtomolar levels. The presented research has leveraged the superior electronic properties of emerging layered semiconductors for biosensing applications and advances label-free biosensing techniques toward realizing fast real-time immunoassay for low-abundance biomolecule detection. Moreover, the nanofabrication approaches developed in this research can be generally utilized for making other nanoelectronic devices based on emerging 2D layered materials, and the obtained device physics knowledge is anticipated to greatly leverage the excellent electronic and structural properties of TMDCs for other relevant sensing applications.