In this second part of the webinar series on rheometric applications, we explore advanced applications of Optimally Windowed Chirps (or OWCh) to characterize complex material systems, including aging thixotropic systems such as clay dispersions. We describe how user control of the initial phase and the frequency slew rate of the chirp, which is a new approach to rapidly obtain frequency dependent material behavior, can be leveraged to improve data quality for very short chirps or highly viscoelastic samples.

We also introduce a recent Thermally Optimized Ramped Chirp (TORCh) protocol, which applies a user‑controlled heating rate to the sample while repeatedly applying windowed chirp pulses. This approach enables rapid construction of time–temperature master curves for polymer samples over a wide range of reduced frequencies.

With these tools, rheologists can design chirp‑based testing techniques and quality control protocols that significantly improve sample throughput. Compared with other approaches, the chirp-based ones increase data quality and density—supporting future data‑driven scientific machine learning (SciML) applications.

What you’ll learn:

• Discover how optimally‑windowed exponential chirps (OWCh) deliver rapid, broadband viscoelastic spectra for mutating materials in seconds.
• Learn how to minimize spectral leakage, tune chirp parameters, and implement protocols in MATLAB or instrument firmware for high‑quality, time‑resolved data.
• Learn how to use Thermally Optimized Ramped Chirp (TORCh) protocols to produce time-temperature superposition master curves in significantly less time.

Gareth H. McKinley is a renowned mechanical engineer and professor at the Massachusetts Institute of Technology (MIT), where he serves as the School of Engineering Professor of Teaching Innovation and Professor of Mechanical Engineering.

McKinley is internationally recognized for his expertise in fluid dynamics and rheology—the study of how complex materials flow and deform. His research explores non-Newtonian fluids, microfluidics, hydrogels, and advanced materials, with applications ranging from industrial processes to biotechnology. His work has led to important advances in understanding phenomena such as bubble formation in liquids and the behavior of viscoelastic materials, as well as practical innovations like techniques for harvesting drinking water from fog in arid environments.

He earned his Ph.D. from MIT in 1991 after completing a B.A. and M.Eng. at the University of Cambridge. Over his career, McKinley has published more than 275 scientific papers and has played a significant role in shaping the field of rheology.

His achievements have been widely honored. He is a Fellow of the Royal Society and the American Physical Society and a member of the U.S. National Academy of Engineering. He has also received major awards such as the Bingham Medal and the Gold Medal of the British Society of Rheology.

In addition to his research, McKinley has held several leadership roles at MIT and is known for his dedication to teaching and mentoring, influencing the next generation of engineers and scientists.