of the thrombus may now be in the canister, and further that some adjustment to the aspiration procedure (e.g. a distal advancement, or a full withdrawal) is now appropriate. [0068] In some examples, all or just parts of flow oscillator 20 through which fluid flow may be coated with at least one of an anti-thrombogenic material or a lubricious material. For example, fluid received from catheter 12 may include tissues, such as pieces of a thrombus, suspended in the fluid. These tissues may bind to walls of channels or chambers within fluid oscillator 20, such that flow through fluid oscillator 20 may be changed. By including an anti-thrombogenic material or a lubricious material in flow oscillator 20, tissues suspended in the fluid may be less likely to bind to flow oscillator 20 . [0069] In some examples, fluid oscillator 20 may be free of moving parts. For example, fluid oscillator 20 may comprise a plurality of channels and/or chambers configured to oscillate flow of fluid through fluid oscillator 20. The plurality of channels may be more resistant to clogging or breaking that flow sensors that include moving parts. As such, fluid flow sensor 16 may reliably operate with fewer parts that may malfunction, stick, or change in operation. In some examples, fluid flow sensor 16 may be free of electronics. For example, a housing of fluid oscillator 20 may receive kinetic energy from oscillating jets of fluid flow, thereby generating vibrations. As such, fluid flow sensor 16 may operate without an external power source, such as a power supply or battery. [0070] FIG. 2A is conceptual block diagram illustrating aspiration system 10 of FIG. 1 at an infusion state. For example, aspiration system 10 may operate in an infusion state when flushing components of aspiration system 10 and/or delivering fluid (e.g., a therapeutic agent or a fluid configured to aid aspiration) to a treatment site in vasculature of a patient. In the infusion state, fluid pump 18 pumps a fluid through fluid flow sensor 16 and fluid switch 14 to catheter 12 in the second flow direction. For example, a clinician may operate fluid pump 18 to generate a positive pressure and may operate fluid switch 14 to be in an “open” position. In some examples, fluid flow sensor 16 may be configured pass the aspiration fluid through fluid flow sensor 16 without generating vibrations capable of detection by the clinician operating aspiration system 10. [0071] FIG. 2B is a conceptual block diagram illustrating aspiration system 10 of FIG. 1 at an unblocked aspiration state. For example, aspiration system 10 may operate in an unblocked aspiration state when drawing fluid from a treatment site within vasculature of a patient during positioning of catheter 12 and/or in an attempt to withdraw