Research Programs

• Instrumentation and metrology for nanomechanics
  

  An important tool in nanotechnology, the atomic force microscope (AFM) measures 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
  

• Topography and device performance
  

  Silicon-based microsensors, "MEMS", 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, but the contribution of surface roughness to the "stiction" remains poorly understood. Using the tip of an AFM to replace one side of the silicon-oxide interface, we are correlating the properties of the interface with stiction. Likewise, topography changes the capacitance of self-assembled monolayer devices.
  [Refs. 38, 40, 41, 45 in journal and Refs. 12, 13 in proceedings list.]

• Visco-elastic properties of tissue-growth substrates and asphalt binders
  

  Not only the chemical environment, but also the topographic and mechanical environments of cells influence their growth into tissues. Using an AFM, which applies displacements on the order of that cells themselves create, we have characterized the topographic properties of implants and are deciphering the mechanical properties of polyacrylimide gels. Similarly, the binder that holds roads together is visco-elastic, and we have started investigating its properties on the nanoscale.
  [Ref. 39 in journal list.]
  

• Mechanical response of molecules
  

  We have investigated how molecules -- from the vital to the virulent -- respond to excitation: hemoglobin to carbon dioxide and oxygen, carbon nanotubes to shear, bacteriorhodopsin to light, and liquid crystals and bacterial exopolymers to strain.
  [Ref. 42, 43, 46 in journal  list.] 

• Nanoscience and society

  There are technologies that have not been well accepted by the public, for example, vaccines, nuclear power, and genetically modified foods. The public is currently generally content with nanotechnology, although people balk at the thought of injecting "nanobots" into their bodies. We found six factors that increase the confidence of WPI students in their acceptance of new medicines. Watching a video on nanotechnology can change its acceptance by the viewers. (For the references used for the 2007-08 video, please read p.31 of the 2007-08 report.) Acceptance of nanotechnology rises as the self-reported knowledge of surveyees rises. There is possible environmental risk when nanosilver particles are released into water, yet it is possible to make guidelines to mitigate the threat.
  Report 2004-05...  Report 2005-06...  Report 2006-07...  Video 07-08...  Report 2007-08...  Report 2008-09...  Report 2009-10...  Poster 2009-10...