Frontiers in Engineering Science: Diethelm Johannsmann
- Date: Wednesday 7 December 2016, 13:00 – 14:00
- Location: Baines Wing
- Cost: Free event
Frontiers in Engineering Science is the flagship monthly seminar program hosted by the School of Chemical and Process Engineering.
The latest research to influence the evolution of Chemical and Process Engineering is explored by eminent academics and industrialists invited from the global research community.
The Quartz Crystal Microbalance as Versatile Tool in Soft-Matter Research
Diethelm Johannsmann - Institute of Physical Chemistry
Clausthal University of Technology, Clausthal-Zellerfeld, Germany
In the last two decades, the quartz crystal microbalance (QCM) has seen an impressive evolution from a film thickness monitor to a surface -analytical tool with capabilities much beyond gravimetry. Two developments were crucial to this change: Firstly, the second-generation QCMs measure the resonance frequency and the resonance bandwidth on a number of different overtones. This added information opens applications “beyond gravimetry”. Secondly, a frame of modeling has emerged (a frame has been rediscovered), which puts all effects beyond gravimetry onto a common ground. This frame is the small-load approximation.
Current developments continue along these lines. Firstly, the depth of information gained from the QCM is enhanced by adding the amplitude of motion as a new sensing dimension, by exploiting piezoelectric stiffening, and by bringing the time-resolution down into the ms range. Also, the QCM is combined in-situ with electrochemistry, electrical impedance spectroscopy, optical reflectometry, and other surface-analytical techniques. On the side of modeling, the field waits for software, which would realistically predict shifts of frequency and bandwidth induced by viscoelastic samples of arbitrary geometry. Currently, approximations are needed. Given these advances, novel applications are reported regularly. Among these is high-frequency contact mechanics. QCM experiments have provided for new insights on the role of partial slip.
Biography: Prof. Diethelm Johannsmann is head of the Institute of Physical Chemistry at Clausthal University of Technology, where he directs a research group on soft matter at interfaces (pc.tu-clausthal.de). Of specific interest are responsive, functional polymers. The group has made numerous contribution to the development and the understanding of the second-generation quartz crystal microbalance (QCM). Diethelm Johannsmann obtained a degree in physics from Heidelberg in 1986. His PhD thesis at the Max-Planck-Institute of Polymer Research at Mainz was concerned with early uses of the QCM to determine the shear modulus of thin films. After a post-doc at the University of California at Berkeley, he returned to a staff position at Mainz, where we was concerned with soft polymers at interfaces. Among other topics, the group pursued instrumental developments connected to the QCM, explored novel applications, and broadened the conceptual base of the underlying models. In 2002, Diethelm moved to Clausthal University of Technology, where has been since then.