Functionalized Solid-State Nanopore: Energy Harvesting and Ionic Circuitry

The study of solid-state nanopores began with the simple concept of separating two reservoirs using a small opening. Over time, the field has expanded to include a wide variety of materials and geometries. Significant progress has been achieved in biosensing applications, where solid-state nanopores provide label-free detection with high precision. Their use has gradually extended to more complex scenarios, further broadening their impact. Insights gained from studying ionic transport through nanopores have also benefited other application areas, such as osmotic energy harvesting and ionic circuitry. These emerging applications impose additional requirements on nanopore devices, demanding specific geometries and surface properties tailored to their respective functions. Many of the initial demonstrations have relied on single devices that exploit only the native properties of the chosen materials. As research transitions from proof-of-concept studies to practical implementations, several challenges have become increasingly apparent. A key limitation is the restricted tunability of the surface properties of solid-state materials. Furthermore, three fundamental factors continue to hinder the practical deployment of nanofluidic technologies: scalability, reproducibility, and integrability. These challenges are especially critical for realizing the potential of solid-state nanopores in advanced applications such as osmotic energy harvesting and ionic circuitry.

In this thesis, we develop scalable fabrication and functionalization technologies based on silicon nitride (SiNx) apertures to address the challenges of scalability and integrability in osmotic energy harvesting and ionic circuitry. First, we present a wafer-scale fabrication method for SiNx apertures using plasma etching techniques. This approach provides a scalable, cost-effective, and adaptable platform for subsequent processes. Second, to overcome the limited surface properties and fixed geometry of native SiNx apertures, we introduce several scalable functionalization strategies. We begin with the anisotropic deposition of hafnium dioxide (HfO2), which enables the formation of stalactite-shaped nanopores with modified geometry. Building on this structure, we further functionalize the nanopores with charged lipid bilayers, a soft-matter coating that enhances interfacial properties. This modification introduces hydration lubrication effects, resulting in improved performance at the membrane scale (108 cm-2 over an area of 314 μm2) in osmotic energy conversion. The effective area significantly exceeds that of conventional single solid-state nanopores, which typically operate in the sub-micrometer square range (hundreds of nm2). Finally, we demonstrate a scalable method for fabricating high asymmetric channel (HAC) devices by depositing discontinuous palladium (Pd) islands on SiNx apertures. The Pd islan