obituary OBITUARY Jacob Israelachvili (1944–2018) rofessor Jacob Israelachvili was a He was also one of the pioneers of the field paragon of colloid and interface science. now called nanotribology. His work on PHe devised world-leading experimental friction and lubrication informed modelling methods to measure the physical forces studies by others and led to insights on the acting between surfaces in close proximity. stick–slip phenomenon and the relationships These surface forces determine the between adhesion and friction. behaviour of a collection of particles or Jacob (as everyone knew him) was an objects, and they are important in many outstanding adviser to his research group areas of nanotechnology, colloid science, and to many others who sought out his tribology, biophysics and materials science. company and insights. He took the time Israelachvili’s key achievement was to to provide the individualized advice and design and build a device, the surface forces support each person needed, an approach apparatus (SFA), capable of measuring these that was viewed with some envy by members forces in a variety of systems. A kind, witty of other research groups (and occasional and charismatic person, he won the respect scepticism by their advisers). All data were and the affection of his many students, examined with kind interest, possible sources postdocs and colleagues over a career of mistakes were patiently discussed, new and spanning almost five decades. improved experiments were suggested, and any While his many successes with the SFA frustration he may have felt was concealed well. can be attributed to a rare combination Having designed the instruments himself, he of physical insight and great skill as an was also the expert on their use. On occasions experimentalist, Israelachvili also liked when he was called in to troubleshoot some to develop theoretical models, and one of particularly problematic experiment, he would his most important contributions was in Credit: UCSB Photo Services/Tony J. Masters quietly inspect the set-up for some time, and the area of membrane biophysics when then provide a diagnosis, often prefaced with in 1976 he conceived the idea of a simple a smile and “You know, I saw that problem parameter based on the geometry of surface research in membrane biophysics, he was once before… ” With his gentle approach, he active molecules, later called the ‘surfactant brought back to surface force measurements inspired and motivated more than 70 graduate packing parameter’. This allows prediction by Professor Barry Ninham of the Australian students and postdocs, about 30 of whom have of the type of surfactant aggregate (micelle, National University in Canberra. Ninham, a become faculty, and more than one-third of the vesicle, bilayer membrane and so on) that mathematical physicist, wanted to conduct latter are women. molecules can form. In 1985, the first edition experimental work to measure the forces that Always interested in the history and of his book Intermolecular and Surface he and his colleagues studied theoretically. development of scientific thought, Jacob had Forces was published. With its succinct and Advised that Israelachvili was the best person anecdotes about scientists from every era. accessible style, this text (now in its third for the job, he duly recruited him in 1974. His scintillating wit made him an entertaining edition) has become a standard reference for Within two years, Israelachvili had built an speaker, and a wonderful companion at any students and researchers in many areas of SFA that could be filled with liquids, greatly social gathering. Those who worked with him materials science and engineering. extending the suite of forces that could be will remember his eternally optimistic mantra, Born on 19 August 1944 in Israel, measured. His first experiments confirmed “If it can possibly go right, it will” — the Israelachvili died on 20 September 2018 the foundations of the classical DLVO theory very antithesis of Murphy’s Law — and how in Santa Barbara, California. He studied of colloid stability, and later ones explored its surprisingly often the experiments that he tried physics at the University of Cambridge, limitations when other forces come into play. did go right. Many people around the world first as an undergraduate and then for his Over the next decade, he and his colleagues have happy memories of their interactions PhD with Professor David Tabor (whose produced a series of landmark papers showing with him. He will be deeply missed. ❐ gentle, inclusive and egalitarian style of how surface chemistry and the properties of supervision he inherited). Tabor’s lab had a liquid or vapour medium determine inter- Marina Ruths1* and Roger Horn* been developing methods to measure surface and particle interactions. 1Department of Chemistry, University of forces acting between molecularly smooth In 1986, he moved to the University Massachusetts Lowell, Lowell, MA, USA. Marina mica surfaces. A finely developed form of California at Santa Barbara. His group Ruths was a PhD student in Israelachvili’s group at of optical interferometry was adapted to was at the forefront of research on the the University of California at Santa Barbara from measure the separation between two mica interactions of biological and biomimetic 1992 to 1996, and a regular visitor thereafer. Roger surfaces with an accuracy of 0.1–0.2 nm. model surfaces across aqueous solutions, Horn, now retired, was one of Israelachvili’s frst Israelachvili made further refinements of underwater adhesives derived from or two postdoctoral fellows at the Australian National the experimental methods, leading to a inspired by mussel foot proteins, and the University, working with him from 1978 until 1986. landmark paper in 1972 on the measurement adhesion mechanism of gecko toes to *e-mail: [email protected]; [email protected] of van der Waals forces in air and vacuum. different types of surfaces. Another area of After a period at the Karolinska Institute research, sustained throughout his career, Published online: 5 November 2018 in Stockholm, where he embarked on was the elusive origin of hydrophobic forces. https://doi.org/10.1038/s41565-018-0300-2 NATURE NANOTECHNOLOGY | VOL 13 | NOVEMBER 2018 | 977 | www.nature.com/naturenanotechnology 977.