Micro/Nano Integrated Fabrication Technology and Its Applications in Microenergy Harvesting

This chapter mainly reviews the development road map of micro-/nanointegrated fabrication technology as well as the previous research work of micro-/nanohierarchical structures. Consequently, the motivation, purpose, and innovative contributions of this thesis are briefly summarized.

Silicon is one of the most important materials for the development of electronics science and technology, which is the footstone of integrated circuits (IC), electronic communication systems, solar cells, micro-electro-mechanical systems (MEMS), etc. Since the 60s and 70s in the last century, the high-precision fabrication technology based on silicon has been developed rapidly. In the past five decades, Si-based microfabrication technology was developed from two aspects, including bulk processes and surface processes, which has already become a mature technical field. More importantly, bulk processes realize the dream of fabricating 3-D structures at the microscale level. Among all of the bulk processes, deep etching process is one of the most important techniques. Deep reactive-ion etching (DRIE) process is an essential deep etching process, and high-aspect-ratio structures are fabricated by using the alternation of etching steps and passivation steps. DRIE process was also called Bosch process due to the first developer of Bosch company. This chapter presents a micro-/nanointegrated fabrication technique for silicon based on an improved DRIE process, and several Si-based samples with attractive properties are demonstrated.

In Chap. 2, we introduce a mass-production Si-based micro-/nanointegrated fabrication technique, which is simple, cost-efficient, and compatible with CMOS process. The fabricated samples show two important properties of wide-band anti-reflectance and stable super-hydrophobicity; thus, this novel Si-based micro-/nanointegrated fabrication technique has the attractive application potential. However, silicon is fragile and bio-incompatible, which hinds the further application of this technique in biomedical field. Therefore, we extend this micro-/nanointegrated fabrication technique from silicon to flexible materials, especially for biocompatible flexible materials, and then, a universal micro-/nanointegrated fabrication technology suitable for many materials is developed.

This chapter investigates the following five aspects: (I) It utilized the micro-nanointegrated fabrication technology mentioned above to fabricate nanogenerators and realized a novel high-performance sandwich-shaped triboelectric nanogenerator (TENG); (II) it established the theory model for three-layer TENG and obtained the numerical analysis of the device’s electric output based on this model; (III) it thoroughly analyzed the working principle of sandwich-shaped TENG using the finite element method; (IV) it systematically tested its electric output performance and deeply studied the influence of frequency of applied force and the size of the device on device’s output performance; and (V) it explored the performance of this sandwich-shaped TENG under different loads and validated its long-term stability and continuously working ability.

In this chapter, the density functional theory is employed to analyze the triboelectrification effect, which reveals the underlying mechanism of the materials’ abilities of capturing or losing electrons at the molecular level for the first time. Three universal approaches, including single-step plasma treatment, surface texturing-based micro-/nanohierarchical structures, and hybrid mechanisms, are proposed to enhance the output performance of triboelectric nanogenerators. In addition, the applications of triboelectric nanogenerators for self-powered sensors, commercial electronics, and biomedical microsystems are successfully demonstrated.

This chapter summarizes the main contributions and the key innovations of this thesis, and the prospectives are also given. We believe that the proposed micro-/nanointegrated fabrication technology and its applications in microenergy harvesting field is of significance for the development of micro-/nano-science and technology.