Field-Structured Chemiresistors

We have developed a significantly improved chemiresistor for sensing volatile organic compounds that consists of Au-coated Ni particles organized into electrically conducting pathways in a polymer matrix by a magnetic field [1]. This sensor overcomes the problems inherent to conventional carbon-black chemiresistors, while achieving an unprecedented magnitude of response. When exposed to chemical vapors, the polymer swells only slightly, yet this is amplified into large, reversible resistance changes, as much as 100,000,000,000% at a swelling ratio of only 1.5%. These conductor-insulator transitions occur over such a narrow range of analyte vapor concentration that these devices can be described as chemical switches. We have demonstrated that the sensitivity and response range of these sensors can be tailored over a wide range by controlling the stress field within the polymer phase. Such tailorable sensors can be used to create sensor arrays that can accurately determine analyte concentration over a broad concentration range, or can be used to create logic circuits that signal a particular chemical environment.