Skip to Main Content
Skip Nav Destination

For a couple of millennia, metal-workers have been modifying the properties of metals via creating or manipulating the defects in their atomic organization. The bijel extends this concept into the world of liquids. In a solid metal, the presence of defects significantly changes the mechanical properties and this has been harnessed. The defects are boundaries between ordered crystalline regions, additionally there are localized mistakes in the crystalline packing. The bijel is based on combinations of two liquids that do not mix; here, the defects are the interfaces that separate a domain of one liquid from the domain of the other liquid. In a solid, the difficulty in reorganizing tightly packed atoms makes the defect long-lived. By contrast, for liquids the interfaces will quickly reorganize unless steps are taken to preserve them. In a bijel, the defect pattern can be preserved because it forms a continuous pathway through the sample. By packing the pathway full of tiny particles, it can be solidified and maintained indefinitely. The presence of a pinned defect (the particle-covered interface) turns a mixture of two liquids into a soft solid.

This central concept relies on both the specific defect pattern and a mechanism to stabilize it (introduced in more detail in Chapter 1). Harnessing the tortuous organization of two liquids makes a host of practical applications possible, as described in Chapter 2. Other chapters in this book document how researchers have been able to create the defect pattern, in particular, via changes of temperature (Chapters 1, 3, 4 and 5), composition (Chapters 4 and 6) and via mixing (Chapter 9). They also present the ways in which the mechanism of stabilization has been made more flexible and robust (especially in Chapters 6 and 9). One chapter focuses on the particles in isolation (Chapter 7) and another on idealized mixing in the absence of particles (Chapter 8). Open questions and challenges for the future are pointed out throughout the volume.

I would like to thank everyone who has been part of the bijel team in Edinburgh, including Ronojoy Adhikari, Aidan Brown, Dongyu Cai, Mike Cates, Richard Collins, Katy Dickinson, Stefan Egelhaaf, Joe Forth, David French, Eva Herzig, Niek Hijnen, Grace Kim, Tao Li, Katherine Macmillan (née Rumble), Ignacio Pagonabarraga, Wilson Poon, Matthew Reeves, Eduardo Sanz, Andrew Schofield, Kevin Stratford, Joe Tavacoli, Job Thijssen, Robert Wallace and Kathryn White. I am also immensely grateful to all of the chapter authors for investing their time in making this book possible. They and I would like to thank Connor Sheppard and Michelle Carey at the Royal Society of Chemistry for all their work. Finally, I would like to thank Reena and Annika for continuing support and encouragement.

Paul S. Clegg

Close Modal

or Create an Account

Close Modal
Close Modal