ABSTRACT
The ability to heal wounds is one of the truly remarkable properties of biological systems. A grand challenge in materials science is to design “smart” synthetic systems that can mimic this behavior by not only “sensing” the presence of a “wound” or defect, but also actively reestablishing the continuity and integrity of the damaged area. Such materials would signi˜cantly extend the lifetime and utility of a vast array of manufactured items. Nanotechnology is particularly relevant to both the utility and fabrication of self-healing materials. For example, as devices reach nanoscale dimensions, it becomes critical to establish means of promoting repair at these length scales. Operating and directing minute tools to carry out this operation is still far from trivial. An optimal solution would be to design a system that could recognize the appearance of a nanoscopic crack or ˜ssure and then could direct agents of repair speci˜cally to that site. Even in the manufacture of various macroscopic components, nanoscale damage is a critical issue. For instance, nanoscopic
13.1 Introduction .................................................................................................. 313 13.2 Methodology ................................................................................................. 315 13.3 Results and Discussion: Site-Speci˜c Healing of Damaged Substrates ....... 318
13.3.1 Effect of Imposing a Steady Shear Flow .......................................... 320 13.3.2 Utility of Applying a Pulsatile Flow ................................................. 325 13.3.3 Microcapsule Motion on a Nanoparticle-Filled Domain ................. 327
13.4 Conclusions ................................................................................................... 328 Acknowledgments .................................................................................................. 329 References .............................................................................................................. 329
notches and scratches can appear on the surface of materials during the manufacturing process. Due to the small size of these defects, they are dif˜cult to detect and consequently, dif˜cult to repair. Such defects, however, can have a substantial effect on the mechanical properties of the system. For example, signi˜cant stress concentrations can occur at the tip of notches in the surface; such regions of high stress can ultimately lead to the propagation of cracks through the system and the degradation of mechanical behavior.
