Nanoelectromechanical systems (NEMS) such as a nano-resonator have promising applications in small mass sensing and signal processing. However, existing manufacturing methods for NEMS are either too expensive or limited in design flexibility. Here, we present progress on fabricating silicon NEMS devices using Tip Based Nanofabrication (TBN), which offers both low cost and design flexibility. A heated Atomic Force Microscope (AFM) probe deposits dense molten polymer on substrate to form nanopatterned polymer masks, which are transferred to silicon by etching processes. In our first approach, the TBN-created polymer mask is used along with conventional wet etching and dry etching. In our second approach, we use Metal Assisted Chemical Etching (MacEtch) to transfer the polymer nanopatterns into silicon. We compare the NEMS structures resulting from the two different approaches.
Nanopore based DNA sensing methods use electrophoresis to drive negatively charged molecules through nanometer sized pores and monitor the change in ionic current to examine the length or sequence of DNA molecules. It is an inexpensive and attractive alternative to traditional sequencing and analysis technologies as it is a label-free, amplification-free, single-molecule approach that can be scaled for high-throughput DNA analysis.
We demonstrate a stacked graphene-Al2O3 dielectric nanopore architecture to investigate electrochemical activity at graphene edges. It has proven to be difficult to isolate electrochemical activity at the graphene edges from those at the basal planes. We use 24 nm of Al2O3 to isolate the graphene basal planes from an ionic fluid environment. Nanopores ranging from 5 to 20 nm are formed by an electron beam sculpting process to expose graphene edges. Electrochemical measurements at isolated graphene edges show current densities as high as 1.2 x 104 A/cm2, 300 times greater than those reported for carbon nanotubes. Additionally, we modulate nanopore conductance by tuning the graphene edge electrochemical current as a function of the applied bias on the embedded graphene electrode. Our results indicate that electrochemical devices based on graphene nanopores have promising applications as sensitive chemical and biological sensors, energy storage devices, and DNA sequencing.