Biomimetic patterned surfaces for controllable friction in micro- and nanoscale devices

Kahp-Yang Suh,Arvind Singh

doi:10.1186/2213-9621-1-6

Abstract

Biomimetics is the study and simulation of biological systems for desired functional properties. It involves the transformation of underlying principles discovered in nature into man-made technologies. In this context, natural surfaces have significantly inspired and motivated new solutions for micro- and nano-scale devices (e.g., Micro/Nano-Electro-Mechanical Systems, MEMS/NEMS) towards controllable friction, during their operation. As a generic solution to reduce friction at small scale, various thin films/coatings have been employed in the last few decades. In recent years, inspiration from ‘Lotus Effect’ has initiated a new research direction for controllable friction with biomimetic patterned surfaces. By exploiting the intrinsic hydrophobicity and ability to reduce contact area, such micro- or nano-patterned surfaces have demonstrated great strength and potential for applications in MEMS/NEMS devices. This review highlights recent advancements on the design, development and performance of these biomimetic patterned surfaces. Also, we present some hybrid approaches to tackle current challenges in biomimetic tribological applications for MEMS/NEMS devices.

Highlights

MEMS/NEMS are miniaturized devices that are built at micro/nano-scale and are operated by various electrical, mechanical, and optical principles
The issues of smooth operation and long-term reliability have remained un-resolved owing to high friction that arises at micro/nano-scale [3]
As described earlier, the area-to-volume ratio is extremely large at micro/nano-scale, leading us to conclude that friction depends on surface properties rather than bulk material properties

Summary

Introduction

MEMS/NEMS are miniaturized devices that are built at micro/nano-scale and are operated by various electrical, mechanical, and optical principles. If one wants to reproduce the detailed surface topography of real leaves with high accuracy, it would be difficult, costly, and time-consuming, and further may not contribute to lower friction force at small scale To explain this further, micro- and nano-scale roughness on surfaces, i.e. dual-scale hierarchical surfaces provides superhydrophobicity (e.g. Figure 9A [27]). Micro-pillars fabricated on silicon wafers by photolithography were seen to reduce friction by 2.8 times compared to that of silicon flat surface They underwent wear owing to the brittle nature of silicon as well due to increased contact pressure (at any given load, patterned surfaces experience higher contact pressures than flat surfaces due to lower contact areas). In other applications such as optoelectronics and photonics, polymer patterns are increasingly employed [31] for engineering reliable mechanical motion

Discussion

Conclusions