International Institute for Nanotechnology
Through technologies like the integrated circuit, nanotechnology has revolutionized our lives. Furthermore, fields such as semiconductor physics have been built on a foundation provided by the patterning tools used to make these circuits. Unfortunately, our ability to make small structures composed of diverse materials, particularly the soft materials that are important in biology, is very limited. This limitation has left open important questions in fields spanning catalysis, bioengineering, and medicine. Scanning probe instruments, such as the atomic force microscope (AFM), have great promise because they enable the direct study of physical and chemical phenomena on the nanoscale. Here, we describe how fundamental studies of the ways in which scanning probes interact with materials have led to the ability to make scientifically interesting nanostructures. First, we describe how discrete objects can be trapped and positioned without contact using an AFM probe. This technique allows for ultra-high resolution manipulation of nanomaterials and presents opportunities for force spectroscopy. Rather than manipulating discrete particles, molecular inks can also be patterned using a scanning probe through a technique known as dip-pen nanolithography (DPN). Building on this approach, we study the physical process of transfer from the tip to a sample and find that in many cases DPN can be considered a fluid flow rather than a diffusive process. This insight affords new lithographic capabilities and opportunities to study nanoscale soft matter. As a final example, we ask if the cantilever commonly used in scanning probe is necessary and find that a new architecture in which an elastomeric film on a glass slide is used in lieu of cantilevers confers enabling advantages in terms of scaling and versatility. Importantly, we demonstrate that each probe in these arrays can be individually addressed both physically and by directing light in such that a way that more than ten thousand probes can write arbitrary high resolution patterns across centimeter-scale regions. Finally, we consider the implications of these lessons and explore the scientific questions that can be answered using the capabilities conferred by these advances.
Dr. Keith A. Brown is an International Institute for Nanotechnology postdoctoral fellow with Chad A. Mirkin at Northwestern University. Prior to this, he earned a Ph.D. in Applied Physics at Harvard University under the guidance of Robert M. Westervelt and an S.B. in physics from MIT. Throughout Dr. Brown’s research career, he has explored new ways of imaging and manipulating nanoscale materials using scanning probes. Keith has co-authored 37 peer-reviewed publications, nine patent applications, and his work has been recognized through the reception of awards including the Omar Farha Award for Research Leadership from Northwestern University, the American Vacuum Society Nanometer-Scale Science and Technology Division Postdoctoral Award, and the National Defense Science and Engineering Graduate (NDSEG) Fellowship.