The lateral line system is the flow-sensing organ of fishes, which consists of arrays of flow sensors, known as neuromasts, with hair cells embedded inside a gel-like structure called cupula. There are two types of neuromasts: the superficial ones, which extend from the skin and respond directly to the local velocity, and the canal ones, which are located in recessed canals under the skin and tend to respond to the flow pressure gradient. Inspired by the canal system of fish lateral lines, we propose a pressure gradient sensor integrating an ionic-polymer metal composite (IPMC) sensor with a 3D-printed canal filled with a viscous fluid. Unlike the biological counterpart that has open ends on the surface of the body, the proposed canal has two pores that are covered with a latex membrane, which prevents the canal fluid from mixing with the ambient fluid. Experimental results involving a dipole source show that the proposed sensor is able to capture the pressure difference across the two pores, and the viscosity of the canal fluid has a pronounced effect on the sensitivity of the device. Preliminary finite-element simulation results are also presented to provide insight into the experimental observations.