Cleaning by Surfactant Gradients: Particulate Removal from Porous Materials and the Significance of Rinsing in Laundry Detergency

After thousands of years of practice, we may not n00exe00exe00exd to know physics to wash our clothes, but (as usual) it might really help. In the cleaning of fabric, a hierarchical porous material, it is understood that soil particles are first detached by detergent, then washed away by fluid flow during rinsing. A common belief is that dirt in the fabric's pores is removed by flow advection, but small pores do not admit significant flow, leaving the role of advection dubious. The authors show that the detergent concentration gradient arising during rinsing with fresh water, though an unintended consequence, can be an effective route to enhancing soil removal from deep pores in fabric.