Modeling and Experimental Verification of Nano Positioning System for Nanomanufacturing

Modeling and Experimental Verification of Nano Positioning System for Nanomanufacturing

Sagil James (Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA), Lauren Blake (Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA) and Murali M. Sundaram (Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH, USA)
DOI: 10.4018/ijmmme.2013100101
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Abstract

Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) is a novel nanomachining process that combines the principles of vibration-assisted abrasive machining and tip-based nanomachining has been developed by the authors to perform target specific nano abrasive machining of hard and brittle materials. One of the critical factors in achieving nanoscale precision during the VANILA process is to maintain an optimal machining gap between the tool and the workpiece surface. Piezoelectric crystal based positioning systems is a proven method for achieving ultraprecision control, however the application of such a system for controlling the nanoscale machining gap during a machining process is not explored. In this paper, the possibility of using a piezoelectric crystal based nano positioning setup to achieve the desired gap during the VANILA process is explored. This research thus finds a new application for the nanopositioning systems in order enhance the capability of existing VANILA process. Analytical models based on piezoelectric theory are done to predict the vibrational behavior of the piezoelectric crystal in the nano-positioning setup under different machining conditions. Further experiments are conducted to validate the model and study the mass-loading effect on the piezoelectric crystal. The model developed is agreeing within 20% with the experimentally determined values and thus the model forms the basis for using the nano-positioning system for maintaining optimal gap between the tool tip and the workpiece surface.
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Introduction

One of the most prominent techniques in conducting nanomachining is Scanning probe microscopy, such as scanning-tunneling microscopy (STM) (Della Pia & Costantini 2013) and atomic force microscopy (AFM) (Lin, Chen et al., 2011). SPMs are used for manipulating materials down to the nanometer scale because of their inherent capability of working at atomic levels. Recently, there has been a tremendous increase in the usage of STMs and AFMs well beyond their originally intended nano metrological applications, which have opened up a variety of practical routes for ultra-precision machining. AFM, in particular has proved to be a versatile tool for conducting mechanical modification, local anodic oxidation (Lee, Ahn et al., 2012), atoms manipulation and thermal–mechanical writing (Malshe, Rajurkar et al., 2010) Many different processes have been developed based on AFM to conduct sophisticated lithography such as nanocutting, nanoscratching, and nano electro-machining (Malshe, Rajurkar et al., 2010). However, these processes have limitations regarding the type of work material, tool wear and profile of machined cavity.

Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) process - a tip-based nanomachining process that uses a single-point AFM probe with loose abrasives and vibration assistance has been investigated and can be used to perform target specific impact-based machining of nanoscale features on hard and brittle materials such as glass and ceramics materials (James and Sundaram 2012). The process was developed based on an AFM platform in which slurry of nano diamond abrasive particles is introduced between the tool and the workpiece. The machining is conducted in tapping mode where the tool probe continuously hammers the abrasive nanoparticles, suspended in liquid medium, which in turn impacts the workpiece surface. A schematic of the VANILA process is shown in Figure 1.

Figure 1.

Schematic of VANILA process, a) Tool striking the abrasive particle, b) Abrasive particle impacting workpiece surface, c) Material removal from the workpiece

The feasibility of nanoscale machining using the VANILA process was successfully demonstrated experimentally on Silicon and Borosilicate Glass substrates. Nano-cavities with circular cross-sections having depths in the range of 5-100 nm and diameters in the range of 50-300 nm were obtained on these substrates. In addition, patterns of nano-cavities, shown in Figure 2 were successfully machined to demonstrate the controllability and repeatability of the process.

Figure 2.

AFM images of nano-cavity pattern machined using the VANILA Process, a) on Silicon Substrate (James & Sundaram 2012), (b) on Borosilicate Glass Substrate

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