The Physical Limits of Self-Healing Materials

Self-healing materials demonstrate the ability to automatically repair damage similar to the healing process found in nearly all biological materials [1]. While most reported self-healing materials rely on slow diffusion-driven mass transport to achieve healing, stabilized liquid materials represent a class of materials which can self-heal at unprecedented speeds (~1 m/s), nearly three orders of magnitude faster than conventional diffusion-driven self-healing materials [2]. Such an ultrafast self-healing response has enabled engineering applications that were previously unachievable such as reverse filtration where large particles can pass through the material while retaining smaller ones [3]. In order to engineer self-healing materials capable of ultrafast self-healing, it is essential to understand the physical limits of the self-healing mechanisms involved. Here we show that inertial-capillary self-healing is the fastest mode of self-healing in functional materials. Our results suggest that the inertial-capillary self-healing rate of a liquid film scales with its Taylor-Culick rupture speed, an intrinsic material property of the system. We also provide a relationship for the critical impact speed of an impinging object, beyond which the film will rupture instead of self-heal, defining the functional regime of self-healing liquid films. Our findings offer the first physical design principles for engineering ultrafast self-healing materials that surpass the current state-of-the-art self-healing materials.<br/><br/>References:<br/>[1] S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, M.R. Kessler, S.R. Sriram, E.N. Brown, S. Viswanathan, <i>Nature</i> <b>409</b>, 794 – 797 (2001).<br/>[2] B.J. Blaiszik, S.L.B. Kramer, S.C. Olugebefola, J.S. Moore, N.R. Sottos, S.R. White, <i>Annu. Rev. Mater. Res.</i> <b>40</b>, 179 – 211 (2010).<br/>[3] B.B. Stogin, L. Gockowski, H. Feldstein, H. Claure, J. Wang, T.-S. Wong. <i>Sci. Adv. </i><b>4</b>, eaat3276 (2018).