Current Research

Within biological physics,
we are at present working in three areas: the study of the linear and non-linear electrical properties of cardiac tissue during stimulation, propagation, and recovery for threshold- and defibrillation-strength shocks; the electrical behavior of intestinal smooth muscle, as can be observed using SQUID magnetometry; and the development and application of micro- and nano-scale devices for instrumenting and controlling the single biological cell and small populations of interconnected cells.

Specific questions that we are trying to answer include: What are the spatio-temporal dynamics of phase singularities that occur in functional reentry and fibrillation? How can strong electric fields and properly timed stimuli be used to modify singularity dynamics? How do strong electric fields defibrillate the heart? What are the relative roles of the differences in intracellular and extracellular electrical conductivity and tissue architecture on the interaction between strong electric fields and cardiac tissue? Why does the endocardial surface activate more rapidly during field stimulation than the epicardial surface? Can a SQUID magnetometer be used to detect noninvasively life-threatening disorders of the human small intestine such as regional ischemia, and infarct as well as other clinically significant problems such as gastric and intestinal disarrhythmias. Can scanning SQUID magnetometers be used to study the time course of injury currents during cardiac ischemia and wound currents following damage to other tissues?

We are also addressing a number of interesting questions in nonbiological systems: What factors govern the production of magnetic fields by electrochemical corrosion activity, and how can these magnetic fields be used to quantify the distribution array and response to environmental variables for hidden corrosion such as occurs in aluminum lap joints for aircraft? Can SQUID magnetometers be used to map the stress distribution in composite materials loaded with magneto-strictive materials? What are the optimum design, data acquisition, and analysis techniques that would allow the SQUID magnetometers to detect crack and corrosion damage deep within aluminum aircraft structures? What does SQUID mapping of magnetic inclusions in geological specimens, including the Allan Hills Martian meteorite, reveal about the thermal history of the sample?

In response to the great strides achieved by genomics and proteomics and in micro- and nano-technology, we have decided to launch a new initiative at Vanderbilt to "Instrument and Control the Single Cell." A group of investigators, at Vanderbilt and elsewhere, are working to develop three technologies suitable for biosensors and biocontrols: picocalorimetry to measure the metabolic energy dissipation of one to 100 cells, patch-clamp-to-silicon for measurement of single ion channel currents and other transmembrane and intracellular properties of cells, and nanoliter bioreactors to exploit the reduction in thermal and chemical diffusion times achieved by microminiaturization. If successful, these technologies and the ones that follow will open a new window into the physics of living systems.

John P.Wikswo