A piezoresistive sensor for pressure monitoring at inkjet nozzle

This paper presents a MEMS piezoresistive sensor for monitoring the fluidic pressure at the nozzle of an inkjet during droplet generation. The device consists of a sensing membrane (150 μm wide and 1 μm thick) with a nozzle orifice (20 μm in diameter), and piezo-resistors placed around. The pressure information is useful in detecting missing droplets and estimating the size of the generated droplets. The device is fabricated on SOI wafers with an IC-compatible process. A resistance variation of 8.7% is measured with a 1 × 10
⁵
Pa applied pressure. The sensitivity is 3.9 × 10
^-7
V/Pa in a Wheatstone bridge configuration with 1 V supply voltage. The detected pressure signal can be used to implement a close-loop control to replace the open-loop control in most current commercial inkjet printheads, for better volume precision and system reliability.