Research Programs

• Response and evolution of molecules and microstructures
  

  We have investigated how molecules and microstructures -- from the vital to the virulent -- respond to excitation:  hemoglobin to carbon dioxide and oxygen, carbon nanotubes to shear, bacteriorhodopsin to light, liquid crystals and bacterial exopolymers to strain, microstructures in asphalt binders to temperature and time, and grains within perovskite solar cells to pressure.
  [Ref. 42, 43, 46, 51, 52, 53, 58, 61, 63 in journal list.]

• Adhesive and visco-elastic properties of nanomaterials
  

  Not only the chemical environment, but also the topographic and mechanical environments of cells influence their growth into tissues. We have characterized the mechanical properties of polyacrylimide gels on which cells are grown. Similarly, the adhesive asphalt binder that holds roads together is visco-elastic, and we have monitored the evolution of its microstructures -- no wonder there are so many potholes in roads!  Source rocks for oil and gas production are likewise nanomaterials with intriguing properties, which, if better known, could improve the efficiency and safety with which these non-renewables can be extracted.
  [Refs. 39, 50, 54, 56, 59, 60, 62, 64  in journal list.]
  

• Topography and device performance
  

  Silicon-based microsensors can be fabricated with moving devices that can make contact with the substrate upon which they are grown. Their surfaces are coated with a molecular layer that lowers the likelihood of sticking and thus prevents failure of the device.  We investigated the contribution of surface roughness to the "stiction" using the tip of an AFM to replace one side of the silicon-oxide interface.  Likewise, topography changes the capacitance of self-assembled monolayer devices.
  [Refs. 38, 40, 41, 45 in journal and Refs. 12, 13 in proceedings list.]

• Instrumentation and metrology for nanomechanics
  

  Early versions of atomic-force microscopes (AFMs) measured forces precisely, yet without good accuracy. We developed a method that quickly calibrates the normal spring constant of the cantilevers used to measure forces in AFM to an accuracy of 10%. We also developed a method to quantitatively measure lateral forces.  Other progress lies in tip-radius calibration, the use of optical excitation at the tip-sample interface, and the influence of higher modes of the cantilever on its response.  Here are links for programs for tip-radius and lateral-force calibration.
  [Refs. 32-37, 40, 44, 47, 48 in journal list.]   
  

• Excel workbook for calibrating the radii of spheres attached to AFM cantilevers

• Test data file for above
  
  
• Lateral force calibration package

• Physics and nanoscience education
  

  Introductory physics is challenging to teach, particularly when there are large numbers of students.  Concerning nanoscience, the creation of in-person and online content for AFM education has been a labor of love.
  [Refs. 49, 55, 57 in journal, Ref. 8 in book, Ref. 14 in proceedings, and Refs.43, 46 in project list.  YouTube AFM lectures.]

• Nanoscience and society

There are technologies that have not universally accepted by the public, for example, vaccines, nuclear power, and genetically modified foods. The public is currently generally content with nanoscience, although people balk at the thought of injecting "nanobots" into their bodies. The level of precautions taken in nanoscience research labs has been inconsistent thus far.
[Refs. 11, 13, 19, 22, 26, 41, and 42 in project list.]