Cracking pressure control of parylene checkvalve using slanted tensile tethers

MEMS check valves with fixed cracking pressures are important in micro-fluidic applications where the pressure, flow directions and flow rates all need to be carefully controlled. This work presents a new surface-micromachined parylene check valve that uses residual thermal stress in the parylene to control its cracking pressure. The new check valve uses slanted tethers to allow the parylene tensile stress to apply a net downward force on the valving seat against the orifice. The angle of the slanted tethers is made using a gray-scale mask to create a sloped sacrificial photoresist with the following tether parylene deposition. The resulted check valves have both the cracking pressures and flow profiles agreeable well with our theoretical analysis

The effects of firm-initiated clawback provisions on earnings management

Thesis (Ph.D.)--Boston UniversityThis paper examines whether the adoption of clawback provisions decreases earnings management. Clawback provisions are intended to discourage managers' opportunistic behavior by enabling companies to recoup erroneously awarded compensation in the event of an accounting restatement. Using firms that voluntarily implement clawback provisions, I find that clawback-adopters experience a reduction in both accrual-based and real earnings management in the post-adoption period, relative to non-adopters. These results are robust to multiple approaches controlling for endogeneity of the clawback decision. In addition, these results are also consistent within subsamples of firms facing high level of incentives to manage earnings, suggesting that clawback provisions remain effective in curbing accrual-based earnings management even when managers are under more pressure to manipulate earnings. Overall, the findings are consistent with clawback adoption signaling a move towards overall higher reporting quality

Parylene stiction

This paper presents a preliminary study into stiction between parylene C and substrate surfaces for biocompatible check-valve applications. During fabrication, parylene C is used as the structural material for the check-valve. The substrate surfaces studied include Au, Al, Si, parylene C, XeF_2 treated Si, and silicon dioxide. Stiction between different surfaces is created after sacrificial photoresist etching. Then, the stiction is measured using blister tests, and stiction mechanisms for different materials are investigated. The devices are released with different recipes to examine their effects. Finally, the results of the study reveal methods to control the cracking pressure of parylene check-valves