Studying Electrical Conductivity Using a 3D Printed Four-Point Probe Station

Abstract

The design and fabrication of functional scientific instrumentation allows students to forge a link between commonly reported numbers and physical material properties. Here, a two-point and four-point probe station for measuring electrical properties of solid materials is fabricated via 3D printing utilizing an inexpensive benchtop fused-deposition modeling system and designed by standard computer-aided design software. Stainless steel tapestry needles serve as probes for contacting a sample; these are also electroplated in order to study their electrical performance, and provide a framework for discussion of electrical charge transport, contact resistance, and conductivity in materials. A microcontroller board is integrated into the probe and controlled using open-source software. Our robust and simple design provides an instrument that is easily fabricated by students and readily applied to a wide range of classroom settings focused on materials science, mechanical and electrical engineering, as well as solid-state physics and chemistry. This 3D printed probe station costs less than $100 US in materials per unit excluding source meter. We demonstrate that two- and four-point resistance measurements carried out on a solid-state semiconductor differ only by less than 5% in magnitude when compared to data collected using a standard and expensive commercial probe station. Two- and four-point resistance measurements carried out on gold deposited on silicon and on the soft nanostructured organic semiconductor poly(3,4-ethylenedioxythiophene) result in reproducible and accurate current versus voltage (I-V) curves.