aspiration system 10 without causing significant leakage of fluid from aspiration system 10 during decoupling. [0060] Within fluid flow sensor 16, flow oscillator 20 is configured to oscillate flow of the fluid through fluid flow sensor 16 to generate flow-induced vibrations. For example, structural characteristics or components of flow oscillator 20 may be configured to produce two or more states of alternating stability for one or more jets of a fluid within flow oscillator 20. Fluid flow may oscillate between the two or more states to producing sweeping or pulsating motions of the jets through one or more channels or chambers of flow oscillator 20. These sweeping or pulsating motions may produce vibrations in a housing of the fluid flow sensor that may be felt by holding or contacting the housing. For example, oscillatingjets of fluid may impact walls or structures of the housing of the fluid flow sensor at a frequency proportional to a frequency of the oscillations. In this way, kinetic energy from fluid flow may be used to create vibrations capable of detection by an operator of aspiration system 10. A variety of designs may be used for flow oscillator 20 including, but not limited to, feedback-channel fluid oscillators, and the like. [0061] In some examples, flow oscillator 20 may be configured to allow bidirectional flow with unidirectional flow indication. For example, flow oscillator 20 may be configured to oscillate fluid flow in a first flow direction and refrain from oscillating fluid flow in a second flow direction. For example, flow oscillator 20 may be configured to generate vibrations capable of unaided haptic detection by a human for flow in a first direction and generate vibrations that are not capable of unaided haptic detection by a human for flow in a second direction. In some examples, flow oscillator 20 is configured to oscillate the flow of the fluid above a haptic threshold in a first flow direction and not oscillate the flow of the fluid above the haptic threshold in a second flow direction. For example, vibrations produced by flow oscillator 20 capable of unaided detection by a clinician may be correspond to a “haptic threshold,”above in which the vibrations may be detected by the clinician and below which the vibrations may not be detected by the clinician. While this haptic threshold may vary depending on a sensitivity of the clinician, the difference between the vibrations produced by flow of fluid in the first flow direction and the vibrations produced by flow of fluid in the second flow direction may be of such a degree (e.g., an order of magnitude or periodicity) that the clinician would note a difference between fluid flowing in the first flow direction and the second flow direction.