Date of Graduation

5-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Microelectronics-Photonics (PhD)

Degree Level

Graduate

Department

Microelectronics-Photonics

Advisor/Mentor

Zou, Min

Committee Member

Salamo, Gregory J.

Second Committee Member

Meng, Xiangbo

Third Committee Member

Kim, Jin-Woo

Fourth Committee Member

Wise, Rick L.

Keywords

Bioinspiration; Microfabrication; Replication; Surface engineering; Tribology

Abstract

Up to one-fifth of all energy consumed each year goes directly to overcoming frictional effects. This waste will remain even if renewable energy becomes feasible as a large-scale replacement for conventional fuel sources. If that wasted energy could be saved instead, then overall energy consumption could either decrease or be redirected to where it would be most beneficial to human and environmental flourishing. To this end, there is a need for strategies and techniques to reduce frictional energy loss. It is well established that surface texturing can be used to reduce friction. There are many industrial methods in current use to accomplish this, but many of these techniques do not grant very good control over the final surface topography. It has been observed that many surfaces found in nature exhibit remarkable friction control through their surface textures. However, there has been limited success in direct replication of these surface textures at resolutions high enough to take advantage of their microstructuring. This work presents a method whereby arbitrary surfaces may be digitized with 3D laser scanning microscopy and fabricated through two-photon lithography to serve as masters for replication. In this way, natural surfaces may be replicated many times without the need for using existing direct replication methods, many of which are potentially destructive and limited in the surfaces they can copy. The presented method does not need to make physical contact with the original surface, preserving surface structures which may be fragile to replicate. Additionally, a method is presented whereby a small input area can be periodically repeated over a much larger area, reducing the need for large scan areas. The digitization method can replicate surfaces to micrometer accuracy. These printed surfaces demonstrated friction reduction compared to a flat substrate of up to 42%, as well as a statistically significant increase in the water contact angle. Additionally, a hexagonal groove-dimple texture was tested against an industrial liner which was replicated using the digitization method. This texture reduced friction by 22% compared to a flat control and by 10% compared to the industrial liner. These techniques grant access to quick replication and testing of natural surfaces so that the benefits from biological friction control can be more quickly realized. These advances will improve our understanding of friction reduction so that energy can be conserved instead of wasted in many different industries.

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