Principal investigator: Mr Tan Jun Ping
Co-investigator:As/Prof. Huang Weimin
Date started: 11/1998
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).
Fig. 1: (a) Shape Memory Effect and (b) Superelasticity
The working of SMA Microgripper includes two steps:
- When SMA thin film is cooled, it is deformed by the cantilever beams and the microgripper is opened.
- When SMA thin film is heated, it recovers is shape. Thus the cantilever beams bend toward each other and the microgripper is closed.
Fig. 2: (a) SMA is Cooled and (b) SMA is Heated
Structure of Microgripper
The SMA microgripper consists of three parts:
- A silicon cantilever beams with SMA thin film (brown)
- One silicon spacer that separates the cantilever beams.
- 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].
- Can be mass produced at very low cost.
- Structurally simple thus high reliability.
- Can be produced into very small sizes.
- Flexibility in design.
- Very large deflection.