A wealth of micro/nanoscale fluidic channels between/in cells maintain essential mass transfer processes, ensuring the proper functioning of living organisms. Nevertheless, the artificial construction and simulation of such all-liquid channels remain, yet, a formidable challenge, due to the inherent Plateau–Rayleigh instability. Here, we present a new “quasi-static stretching” approach applied to a liquid bridge in another immiscible liquid, where the liquid/liquid interfaces were manipulated by interfacial nanoparticle–polymer co-assemblies. These co-assemblies, with characteristic of reconfigurable, tunable jammed networks, enable stepwise stretching the channel in liquid bridge size downward. We establish a selection rule of component inputs that yield ultrafine liquid channels during the stretching process. The superior flexibility and moderate entanglement or crosslinking of polymer chains within the nanoparticle–polymer microstructures endow the liquid bridge with plastic deformability, allowing the channel forward to hundred nanometer size, reducing by two-orders-of-magnitude on state-of-the-art technology and approaching the size range of biomimetic counterparts. Furthermore, biomimetic functions—intercellular mitochondrial rescue and compartmentalized immunotherapy—were proved using the organism tubular analogue—liquid bridge based channels, via controlling the flowrate of the mass transfer in the channels. These simulations may offer a potential framework for biophysically understanding cellular processes mediated by tubular structures.