Lubrication of MEMS under vacuum

The concept of replenishing lubrication provided by a pair of bound/mobile hydrocarbon-based lubricants has been extended to silicon-based MEMS in vacuum (∼ 1.3 × 10− 4 Pa). Several bound/mobile pairs of lubricants were evaluated to study the effects of bound phase end-group and mobile phase chemical functionality towards performance. The bound species studied were derived from 1-decanol and 1,7-heptanediol. Mobile phases investigated were, a pentaerythritol ester, a multiply alkylated cyclopentane, Pennzane®, and a polysilane developed for spacecraft application. Lubricant performance was compared with data generated in dry air earlier, and also with fresh Fomblin Zdol® under identical conditions of vacuum. The best performance from among those studied was provided by a mixture of bound 1,7-heptanediol and the pentaerythritol ester. An explanation for its superior performance is advanced based on intermolecular hydrogen bonding.