NiTi Shape Memory Alloy Based Microgripper

Principal investigator: Mr Tan Jun Ping

Co-investigator:As/Prof. Huang Weimin

Funding:

Date started: 11/1998

Date completed:

Objective

To design and develop a Microgripper using Shape Memory Alloys (SMA) thin film.

What is SMA?

At a low temperature, a SMA can be seemingly “plastically” deformed, but this “plastic” strain can be recovered by increasing the temperature. This is called the Shape Memory Effect (SME). At a high temperature, a large deformation can be recovered simply by releasing the applied force. This behavior is known as Superelasticity (SE).

pic 1
Fig. 1: (a) Shape Memory Effect and (b) Superelasticity

Working Principle

The working of SMA Microgripper includes two steps:

  1. When SMA thin film is cooled, it is deformed by the cantilever beams and the microgripper is opened.
  2. When SMA thin film is heated, it recovers is shape. Thus the cantilever beams bend toward each other and the microgripper is closed.

pic 2
Fig. 2: (a) SMA is Cooled and (b) SMA is Heated

Structure of Microgripper

The SMA microgripper consists of three parts:

  1. A silicon cantilever beams with SMA thin film (brown)
  2. One silicon spacer that separates the cantilever beams.
  3. Another silicon cantilever beams with SMA thin film (brown)

The three parts are aligned and bonded together. The excess silicon frames are removed. Two cantilever beams (1647um x 922um x 15um) were adhered together to create a microgripper [Figure 4]. Each cantilever beam was capable of achieving a tip deflection of 373 um [Figure 5].

pic 4/P>

pic 5/P>

Main Advantages

Publication

Last updated: 20.10.99
Webmaster