DESIGN, FABRICATION, AND CHARACTERIZATION OF A NANOSCALE FOUR-POINT PROBE FOR INTRACELLULAR SENSING

Open Access
Author:
Kundrat, James Robert
Graduate Program:
Engineering Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 16, 2011
Committee Members:
  • Stephen Fonash, Thesis Advisor
Keywords:
  • bionems
  • biomems
  • nano sensor
  • biosensor
  • four point probe
  • four terminal sensing
  • intracellular sensing
  • nanosensor
  • NEMS
Abstract:
A novel, sub-micron scale, four-probe sensor was developed and fabricated with an intended use as an intracellular sensor. The sensor design is straightforward, using standard micro- and nano-fabrication methods for much of the process. Additionally, the application of some methods, such as focused ion beam milling, is unique in the processing of a biological sensor. The devices designed and fabricated in this research are also reproducible and adaptable to mass production. Proof of concept testing was conducted to evaluate the mechanical and electrical properties of the device. Mechanical testing showed that the device was capable of surviving insertion through the cell membrane of a test organism and into the cytoplasmic space. Electrical testing involved measuring the resistive properties of a simulated biological environment. While sub-micron scale probes are very advantageous in biomedical applications and the focus of significant activity, the results of this work show that four-probe/four-terminal measurements with submicron-scale probes show significant difference from two-probe/two-terminal measurements. Therefore, probe/liquid interface resistance is concluded to be a significant problem at small scales, and future sensor designs must account for such resistance. The four-probe/four-terminal sensor design presented here is one method for implementing sub-micron-scale probes and yet eliminating probe/liquid interface resistance from biological environment resistance measurements.