A hybrid surface tension seal for pneumatic and hydraulic microactuators

Abstract

Recent research revealed that microactuators driven by pressurized fluids are able to generate high power and force densities at microscale. One of the main technological barriers in the development of these actuators is the fabrication low friction seals. This paper presents a novel scalable seal technology, which resists the actuation pressure relying on a combination of a clearance seal and a surface tension seal. This approach allows to seal pressures of more than 800 kPa without leakage. The seal is tested on an actuator with a bore of 0.8 mm 2 and a length of 13 mm, which was able to generate forces up to 0.32 N.

Pneumatic and hydraulic microactuators: a review

“…Instead of using mercury as driving fluid, De Volder et al [124,129,130] proposed a gallium-based seal where the seal liquid is confined to a small circular cavity at the extremity of the cylinder (see figure 2( 16)). A first prototype was able to seal pressures up to 90 kPa without leakage using undercooled gallium as seal liquid [124], in a follow-up paper, the seal pressure was enhanced to more than 800 kPa with a pressure divider [131]. The latter combines a surface tension seal with a clearance seal and allows us to drastically increase the seal pressure while retaining leak-free operation.…”

“…Some exceptions are of course possible [72], but in general this is an important factor in the selection of the actuator type. Based on our own developments in piston-cylinder actuators [3,84,95,97,101,102,124,131,137], the authors developed a selection chart for seal technologies in piston-cylinder microactuators shown in figure 4. Although this graph is subject to changes depending on the implementation of the seal technology, it provides a first guideline in the selection process.…”

“…Reprinted from[4], copyright (1995), with permission from SPIE. (16) Reprinted from[95,131] (17). Reprinted from[128], copyright (2002), with permission from Elsevier (18).…”