Applications in water flow monitoring. (a) Schematics of biological fish sensing weak water pressure changes, acoustic waves, and underwater electric fields with the help of the FLN system, and an underwater robot recognizing water waves, water sounds, and underwater electric fields with the help of different responses of the AFLN system [93]. (b) The AFLN system structure and sensing method. The inset shows its potential application in underwater robotics. Scale bar: 2 mm [93]. (c) Illustration of the AUV’s obstacle avoidance application. The inset showcases the real-time signal acquired from the system [93]. (d) Schematic of a target perceived through the effect of the vortex on the whiskers [94]. (e) Structural diagram of UBWS [94]. (f) Three states during the movement of the robotic fish, with corresponding voltage signal of the UBWS [94]. (g) Schematic of an individual microfabricated, out-of-plane HWA sensor used to build artificial neuromasts. The hot wire is elevated above the substrate surface by a prescribed distance [99]. (h) Analytical model of pressure contours (blue lines) and a linear array of lateral line canal neuromasts (in orange) [99]. (i) Time-elapsed spatial profiles of displacement amplitude with step-by-step translation of the dipole source along the artificial lateral line following path 1 [99]. (j) Displacement profiles under step-by-step translation following path 2 [99]. (k) Schematic showing experimental set-up [99]. (l) The pattern of RMS water velocity in the wake of a cylinder [99]. (m) The pattern of peak water velocity at vortex shedding frequency in the wake of a cylinder. Both RMS and peak water velocities were normalized by free-stream inflow velocity [99].