Fig. 1

Types and typical structures of conventional surfactants （anionic （a）, cationic （b）, zwitterionic （c）, and nonionic （d） surfactants; special structural surfactants （e）: Bola type （two hydrophilic groups） and Gemini type （two hydrophilic groups and two hydrophobic groups）; extended types of surfactants （f））"

Tab. 1

Common measurement methods of foam properties"

Fig. 2

Common measurement instruments of foam properties （hand shaking method （a）, agitation method （b）, conductivity method [6]（c）, dumping method [7]（d）, gas flow method [5]（e）, and optical method [20]（f））"

Fig. 3

Mechanism of viscosity change [26]"

Fig. 4

Confocal microscopy images of bubbles in foam: Image of a whole bubble （a）; lamella stabilized with SLES/C10DMA/KCl （b）; lamella stabilized with SLES/KCl （c） [31]"

Fig. 5

Schematic diagram of stabilization mechanism and instability process for the CO2 foam prepared with EAB [41]"

Fig. 6

Sketch map of the roles of elongated wormlike micelles and silica nanoparticles in stabilizing foams （a）[45]; cryo-SEM images of frozen aqueous foams of EAPB with silica nanoparticles （top: foam node blockage by nanoaggregates; bottom: nanoparticle attachment at the gas-water interface）[46]（b）"

Fig. 7

Structural diagram of the network in PINVES fracturing fluids （a） [48]; enhanced mechanism for wormlike micelles by nano-MoS2 （b） [49]"