A microfluidic device, comprising: an inlet to receive a fluid sample from a fluid receiving structure; a vented microfluidic reservoir located on a bottom portion of the microfluidic device, wherein the fluid receiving structure is located on a top portion of the vented microfluidic reservoir; a channel between the fluid receiving structure and the vented microfluidic reservoir; a sensor in the channel: a nozzle; and an actuator disposed near a closed end of the channel downstream from the sensor and associated with the nozzle to cause flow of the fluid sample from the channel into the vented microfluidic reservoir; wherein the vented microfluidic reservoir comprises: a housing defining a volume of the vented microfluidic reservoir; and a vent coupled to the housing to vent air associated with the fluid sample communicated into the housing to an environment surrounding the microfluidic device, and where the housing and the volume include a grooved region located along a periphery of the housing to retain the fluid sample in communication with the vented microfluidic reservoir. an inlet to receive a fluid sample from a fluid receiving structure; a vented microfluidic reservoir located on a bottom portion of the microfluidic device, wherein the fluid receiving structure is located on a top portion of the vented microfluidic reservoir; a channel between the fluid receiving structure and the vented microfluidic reservoir; a sensor in the channel: a nozzle; and an actuator disposed near a closed end of the channel downstream from the sensor and associated with the nozzle to cause flow of the fluid sample from the channel into the vented microfluidic reservoir; wherein the vented microfluidic reservoir comprises: a housing defining a volume of the vented microfluidic reservoir; and a vent coupled to the housing to vent air associated with the fluid sample communicated into the housing to an environment surrounding the microfluidic device, and where the housing and the volume include a grooved region located along a periphery of the housing to retain the fluid sample in communication with the vented microfluidic reservoir. a nozzle; and an actuator disposed near a closed end of the channel downstream from the sensor and associated with the nozzle to cause flow of the fluid sample from the channel into the vented microfluidic reservoir; wherein the vented microfluidic reservoir comprises: a housing defining a volume of the vented microfluidic reservoir; and a vent coupled to the housing to vent air associated with the fluid sample communicated into the housing to an environment surrounding the microfluidic device, and where the housing and the volume include a grooved region located along a periphery of the housing to retain the fluid sample in communication with the vented microfluidic reservoir. a housing defining a volume of the vented microfluidic reservoir; and a vent coupled to the housing to vent air associated with the fluid sample communicated into the housing to an environment surrounding the microfluidic device, and where the housing and the volume include a grooved region located along a periphery of the housing to retain the fluid sample in communication with the vented microfluidic reservoir.