An apparatus for controlling flow of ER fluid. The apparatus has a first channel 10 for conveying carrier fluid 1 of a first dielectric constant and droplets 2 of a second dielectric constant in the carrier fluid. The apparatus further comprises a second channel 20 conveying the ER fluid and a first conductor 100 for conveying an electrical potential from the second channel to the first channel. A circuit 61 is provided for applying potential difference between the first and second channels. When a droplet is present in the first channel, the ER fluid is solidified in the second channel; when no droplet is present, the ER fluid flows as liquid in the second channel. Therefore the apparatus acts as an IF gate. Arrangements for other types of fluidic logic gate are also disclosed.

A flow rate control device (100) comprises: a pressure control valve (6) provided in a flow path; a flow rate control valve (8) provided downstream side of the pressure control valve; and a first pressure sensor (3) for measuring pressure on the downstream side of the pressure control valve and on the upstream side of the flow rate control valve. The flow rate control valve has a valve element (13) seated on/separated from a valve seat (12); a piezoelectric element (10b) for moving the valve element so as be seated on/separated from the valve seat; and a strain sensor (20) provided on a side surface of the piezoelectric element. The pressure control valve (6) is configured to control the pressure control valve (6) on the basis of a signal output from the first pressure sensor (3), and to control the driving of the piezoelectric element of the flow rate control valve (8) based on a signal output from the strain sensor (20).

A flow rate control device (100) comprises: a pressure control valve (6) provided in a flow path; a flow rate control valve (8) provided downstream side of the pressure control valve; and a first pressure sensor (3) for measuring pressure on the downstream side of the pressure control valve and on the upstream side of the flow rate control valve. The flow rate control valve has a valve element (13) seated on/separated from a valve seat (12); a piezoelectric element (10b) for moving the valve element so as be seated on/separated from the valve seat; and a strain sensor (20) provided on a side surface of the piezoelectric element. The pressure control valve (6) is configured to control the pressure control valve (6) on the basis of a signal output from the first pressure sensor (3), and to control the driving of the piezoelectric element of the flow rate control valve (8) based on a signal output from the strain sensor (20).