3D fabricated PDMS digital pressure controllers for miniature pneumatic systems

Automatic and programmable pressure controllers are critical to miniature pneumatic systems employing pressurized air to transport and manipulate fluidic samples. We have successfully demonstrated (1) a digital pressure control scheme containing active converters and passive regulators that can be readily miniaturized and automated, (2) a 3D PDMS fabrication and integration scheme that can realize on-chip and self-contained pressure controllers for miniature pneumatic systems, and (3) pressure controllers that can switch downstream air pressure between specific levels on demand. In the proposed pressure controller, a regulator is utilized to yield a steady air output, whose pressure is determined by a serial digital-to-analog converter and switched between specific levels on demand. More specifically, a converter guided diaphragm bypasses a certain portion of the input air to reduce and stabilize the output pressure. In the prototype demonstration, PDMS structures were duplicated using 3D-printed molds, bonded and integrated on chip or into self-contained pressure controllers of 25 cm3 in volume. Four-digit converters were employed to realize pressure output at 16 evenly spaced levels. The errors of the measured output pressure were less than 2.4 % of the target pressure while the fluctuations were below 1.2 %. It was also demonstrated that the switching time between pressure levels was less than 0.3 s when digital valves operating at 10 Hz were utilized. As such, the demonstrated miniature pressure controllers could replace their bulky/costly counterparts, and automatic and programmable control of pneumatically driven systems could potentially be realized.