The distorted impedance diagram, shown on this page, was intended to resemble an elephant, and, in doing so, evoke the lessons of the Buddhist tradition of the blind men and the elephant. The multiple loops resemble the Nyquist plots obtained in some cases for the impedance of corroding systems influenced by the formation of surface films. The low-frequency inductive loop was deformed to evoke the image of the elephant’s trunk, and the capacitive loops resemble the head and body of the elephant.
The elephant has become a symbol for our group. I chose the elephant logo while organizing the 2004 International Symposium on Impedance Spectroscopy. Members of our group have even defined a constant-phase elephant (a bad pun), which is deployed in the second edition of our book on electrochemical impedance spectroscopy. My student, Ming Gao, drew the elephant on the video room page on our lab blackboard as a welcome to prospective graduate students.
Impedance spectroscopy is an application of a frequency-domain measurement to a complex system that cannot be easily visualized. The quantities measured, e.g., current and potential for electrochemical or electronic systems and stress and strain for mechanical systems, are macroscopic values that represent the spatial average of individual events. These quantities are influenced by the desired physical properties, such as diffusivity, rate constants, and viscosity, but do not provide a direct measure.
The point is that every experimental measurement we use gives us one view of a system. We can develop a model of the system under investigation from the results of this measurement. Our confidence in the validity of the model can be improved by performing new observations of the system, often guided by the model we developed. Impedance spectroscopy is a powerful tool, but the elephant reminds us that impedance spectroscopy is not a stand-alone technique.
As a grade-school student, I learned the poem by John Godfrey Saxe (1816-1887) based on the Buddhist parable of the blind men and the elephant.
The Blind Men and the Elephant It was six men of Indostan The First approached the Elephant, The Second, feeling of the tusk, | The Sixth no sooner had begun About the beast to grope, Then, seizing on the swinging tail That fell within his scope, “I see,” quoth he, “the Elephant Is very like a rope!”And so these men of Indostan Disputed loud and long, Each in his own opinion Exceeding stiff and strong, Though each was partly in the right, And all were in the wrong! Moral: | The Sixth no sooner had begun About the beast to grope, Then, seizing on the swinging tail That fell within his scope, “I see,” quoth he, “the Elephant Is very like a rope!”And so these men of Indostan Disputed loud and long, Each in his own opinion Exceeding stiff and strong, Though each was partly in the right, And all were in the wrong! Moral: |