Energy invariance in capillary systems

Elfego Ruiz-Gutierrez, Jian H. Guan, Ben Xu, Glen McHale, Gary G. Wells, Rodrigo Ledesma-Aguilar

Research output: Contribution to journalArticlepeer-review


We demonstrate the continuous translational invariance of the energy of a capillary surface in contact with reconfigurable solid boundaries. We present a theoretical approach to find the energy-invariant equilibria of spherical capillary surfaces in contact with solid boundaries of arbitrary shape and examine the implications of dynamic frictional forces upon of a reconfiguration of the boundaries. Experimentally, we realise our ideas by manipulating the position of a droplet in a wedge geometry using lubricant-impregnated solid surfaces, which eliminate the contact-angle hysteresis and provide a test bed for quantifying dissipative losses out of equilibrium. Our experiments show that dissipative energy losses for an otherwise energy-invariant reconfiguration are relatively small, provided that the actuation timescale is longer than the typical relaxation timescale of the capillary surface. We discuss the wider applicability of our ideas as a pathway for liquid manipulation at no potential energy cost in low-pinning, low-friction situations.
Original languageEnglish
Pages (from-to)218003
Number of pages1
JournalPhysical Review Letters
Issue number21
Publication statusPublished - 26 May 2017


  • applications of soft matter
  • capillarity
  • gas-liquid interfaces
  • Metamaterials


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