A system comprising: a hydrodynamic separation element comprising one or more hydrodynamic separators each defining a curved microfluidic channel in fluid communication, each microfluidic channel defining: an inlet configured to receive a first fluid and particles dispersed in the first fluid, wherein the particles have a different composition than the first fluid, and an outlet comprising a first flow branch and a second flow branch, wherein at a predetermined flow rate, each microfluidic channel is configured to direct any particles exceeding a corresponding threshold size into the second flow branch and any remaining particles into both the first flow branch and the second flow branch; a particle sensor positioned along the one or more hydrodynamic separators configured to provide signal data representing a signal corresponding to the first fluid and the particles in the first fluid; and characterized in that the system includes a controller operably coupled to the particle sensor to receive the signal data and operably couplable to a fluid pump in fluid communication with the hydrodynamic separation element, the controller being configured to: control the fluid pump to direct the first fluid through the hydrodynamic separation element, determine whether a threshold level of particles is present in at least one microfluidic channel based on the signal data from the particle sensor, and control a flow rate through the hydrodynamic separation element, in response to determining that the threshold level of particles is present in the at least one microfluidic channel, to direct the first fluid at the predetermined flow rate through the hydrodynamic separation element to focus any particles exceeding the corresponding threshold size to the second flow branch of the at least one microfluidic channel, wherein the system further comprises a source reservoir in fluid communication with the inlet and second flow branch, wherein the first fluid and the particles are pumpable from the source reservoir to the hydrodynamic separation element and selectively back to the source reservoir through the second flow branch. a hydrodynamic separation element comprising one or more hydrodynamic separators each defining a curved microfluidic channel in fluid communication, each microfluidic channel defining: an inlet configured to receive a first fluid and particles dispersed in the first fluid, wherein the particles have a different composition than the first fluid, and an outlet comprising a first flow branch and a second flow branch, wherein at a predetermined flow rate, each microfluidic channel is configured to direct any particles exceeding a corresponding threshold size into the second flow branch and any remaining particles into both the first flow branch and the second flow branch; an inlet configured to receive a first fluid and particles dispersed in the first fluid, wherein the particles have a different composition than the first fluid, and an outlet comprising a first flow branch and a second flow branch, wherein at a predetermined flow rate, each microfluidic channel is configured to direct any particles exceeding a corresponding threshold size into the second flow branch and any remaining particles into both the first flow branch and the second flow branch; a particle sensor positioned along the one or more hydrodynamic separators configured to provide signal data representing a signal corresponding to the first fluid and the particles in the first fluid; and characterized in that the system includes a controller operably coupled to the particle sensor to receive the signal data and operably couplable to a fluid pump in fluid communication with the hydrodynamic separation element, the controller being configured to: control the fluid pump to direct the first fluid through the hydrodynamic separation element, determine whether a threshold level of particles is present in at least one microfluidic channel based on the signal data from the particle sensor, and control a flow rate through the hydrodynamic separation element, in response to determining that the threshold level of particles is present in the at least one microfluidic channel, to direct the first fluid at the predetermined flow rate through the hydrodynamic separation element to focus any particles exceeding the corresponding threshold size to the second flow branch of the at least one microfluidic channel, control the fluid pump to direct the first fluid through the hydrodynamic separation element, determine whether a threshold level of particles is present in at least one microfluidic channel based on the signal data from the particle sensor, and control a flow rate through the hydrodynamic separation element, in response to determining that the threshold level of particles is present in the at least one microfluidic channel, to direct the first fluid at the predetermined flow rate through the hydrodynamic separation element to focus any particles exceeding the corresponding threshold size to the second flow branch of the at least one microfluidic channel, wherein the system further comprises a source reservoir in fluid communication with the inlet and second flow branch, wherein the first fluid and the particles are pumpable from the source reservoir to the hydrodynamic separation element and selectively back to the source reservoir through the second flow branch.