Method for Wafer-Level Surface Micromachining to Reduce Stiction

A method of forming a superhydrophobic surface, the method comprising:

• providing a surface;
• providing an array of microbumps on the surface, wherein the array by itself is not superhydrophobic, and wherein the array comprises:
• a plurality of microbumps having a pitch of between 0.5 microns and 30 microns, and each bump having a height of at least 0.2 microns and width of at least 0.5 microns, and
• coating the array of microbumps with a non-superhydrophobic material,
• wherein the coating renders the array is superhydrophobic.

A method of fabricating a micromachined device having a superhydrophobic surface, the method comprising:

• providing a substrate having a first surface;
• adding a sacrificial layer on the first surface, the sacrificial layer having an exposed surface;
• etching an array of cavities into the exposed surface of the sacrificial layer;
• depositing a low surface-free-energy layer to the array of cavities, the low surface-free-energy material lining but not filling the cavities in the array of cavities such that the cavities are lined cavities;
• depositing a mass layer on the low surface-free-energy layer, such that the sacrificial layer and the low surface-free-energy layer are sandwiched between the substrate and an opposing surface of the mass layer, the mass layer occupying the plurality of lined cavities and forming a plurality of bumps;
• and
• removing the sacrificial layer;
• wherein the bumps protrude from the opposing surface of the mass layer in the direction of the substrate, and wherein the array has a contact angle of at least 140 degrees and a contact angle hysteresis of less than 15 degrees.

A method of fabricating a micromachined device having a superhydrophobic surface, the method comprising:

• providing a substrate having a first surface;
• providing an array of bumps on the first surface;
• adding a low surface-free-energy layer to the array, such that the low surface-free-energy layer coats the bumps but does not fill the space between the bumps;
• adding a sacrificial layer on the low surface-free-energy layer, the sacrificial layer having an exposed surface;
• depositing a mass layer on the exposed surface of the sacrificial layer such that the sacrificial layer is sandwiched between the substrate and an opposing surface of the mass layer;
• and
• removing the sacrificial layer, thereby exposing the coated array,
• wherein the bumps of the array protrude from the substrate in the direction of the opposing surface of the mass layer, and wherein the array has a contact angle of at least 140 degrees and a contact angle hysteresis of less than 15 degrees.