Keynote: MATERIALS, MEDICINE, HEALTH: SENSING THE WORLD AROUND US AT ALL SCALES
Director, Institute for Medical Engineering and Science, MIT
Democratizing Single Molecule Nanoarrays
Assistant Professor, Mechanical Engineering
Interferometric Imaging for Studying Sickle Cell Disease and Cancer Metastasis
Professor, Mechanical Engineering and Biological Engineering
Dynamic Lens Systems for Biosensing
John D. MacArthur Professor of Chemistry
This lecture will detail the creation of ultrasensitive sensors based on electronically active conjugated polymers (CPs) and carbon nanotubes (CNTs). Conceptually a single nano- or molecular-wire spanning between two electrodes would create an exceptional sensor if binding of a molecule of interest to it would block all electronic transport. Nanowire networks of CNTs modified chemically or in composites with polymers provide for a practical approximation to the single nanowire scheme. Creating chemiresistive and FET based sensors that have selectivity and accuracy requires the development of new methods. I will discuss covalent and non-covalent medication of CNTs with groups that impart selectivity for target analytes. This can involve reactions at the CNT sidewalls and rapping of the CNTs with CPs. Highly specific chemical processes orthogonal responses can be produced for mixtures of analytes through careful integration of chemical functionality. A prevailing problem in all chemiresistive schemes, which is seldom highlighted by researchers, is drift. This is intrinsic for systems that need to interface with their surroundings and changes in the position of ions of small changes in the organization of the CNTs relative to each other, the electrodes, or their surroundings can change the base resistance. I will detail different methods designed to lock the CNT networks in place. These novel compositions are also designed to accommodate functionality and I will demonstrate how we can use a diversity of transition metals to create selective responses to gases. We will also show that this scheme creates CNT networks that are robust enough for solution sensing and demonstrate chemiresistive based glucose sensing. I will also briefly discuss the successful use of CNT based gas sensors for the detection of ethylene and other gases relevant to agricultural and food production/storage/transportation and integrated systems that increase production, manage inventories, and minimize losses.
The utility of carbon nanomaterials is highly dependent upon the precision upon which they can be assembled and functionalized. New methods enable high impact applications in sensing, mechanical, membrane, and energy storage/conversion. Approaches to the formation of functional assemblies of carbon nanotubes will be described that involved the non-covalent immobilization of the materials into functional assemblies. In a non-covalent method, no direct chemical bonds are made to the carbon nanotubes, thereby leaving their electronic properties intact. New covalent connections to the graphene surfaces (sidewalls) of the carbon nanotubes will also be discussed and how these materials can serve to modify their electronic properties for devices as well as hard wire functional assemblies to the carbon nanotubes to provide interactions with chemicals (sensors) or electrocatalysis (energy conversion). Many of these methods are also applicable to the functionalization of graphite to create new forms of graphene. We will also show how high purity graphene can be produced in using new scalable electrochemical methods.
This lecture will detail the creation of ultrasensitive sensors based on electronically active conjugated polymers (CPs) and carbon nanotubes (CNTs). A central concept that a single nano- or molecular-wire spanning between two electrodes would create an exceptional sensor if binding of a molecule of interest to it would block all electronic transport. The use of molecular electronic circuits to give signal gain is not limited to electrical transport and CP-based fluorescent sensors can provide ultratrace detection of chemical vapors via amplification resulting from exciton migration. Nanowire networks of CNTs provide for a practical approximation to the single nanowire scheme. These methods include abrasion deposition and selectivity is generated by covalent and/or non-covalent binding selectors/receptors to the carbon nanotubes. Sensors for a variety of materials and cross-reactive sensor arrays will be described. The use of carbon nanotube based gas sensors for the detection of ethylene and other gases relevant to agricultural and food production/storage/transportation are being specifically targeted and can be used to create systems that increase production, manage inventories, and minimize losses.