Optical Detection of Micro-Cantilever Deflection

Kellen Chase, Richard Colonna, Michael Humphreys, Joseph Ortiz, Grace Shih

Dr. Eniko Enikov, AMEDr. Stanley Pau, OSC

February 27th, 2007

Agenda

• Purpose

• Background

• Design

• Progress

• Questions

Statement of Purpose

• To fabricate an inexpensive optical detection system for a MEMS (micro-electrical mechanical structure) to detect changes in the surface stress of an individual cantilever.

Visions

• Short Term– Utilized in a joint mechanical/optical graduate student

laboratory– Students will fabricate and test lithographic masks by

attempting to detect an “known” chemical deposited on the cantilever

• Long Term– Create commercialized product with chemical

database to be used outside of an academic setting– Medical use for quick identification of organic

compounds

Background

• Chemicals bond to gold– Wet=0º– Dry=30º

• Surface stress causes power in cantilever– Changes spot centroid

• Published paper with calibration data– Berger et al., Science,

Vol. 276, no. 5321, 2021-2024, 1997

Design

• Utilize “optical lever” technique– Same principle as atomic force microscopy– Accuracy is determined by separation of

Position Sensitive Device (PSD)– Accuracy is limited by PSD active area

• Subassemblies– Laser– Cantilever– PSD

Design

Subassembly-Laser

Subassembly-Cantilever

Cantilever Deposition Chamber

Goniometer

Lockable Rotation Stage

Translation Stages

Dovetail Rail Clamp

Cantilever Deposition Chamber

Goniometer

Lockable Rotation Stage

Translation Stages

Dovetail Rail Clamp

Subassembly-PSD

Procedure

• Run MATLAB code

• Align laser, cantilever, & PSD– Adjust 4 DoF on cantilever subassembly – Maximize intensity and center spot on PSD

• Capture initial PSD reading

• Deposit chemicals– Secured syringe and tubing

• Capture final PSD reading

Progress

• Completed Tasks– Have all mechanical & optical parts in lab– Machined and assembled all parts– Obtained array of cantilevers for testing– Acquired chemicals from ChEE Department

• In Progress– MatLab software code– Circuitry for PSD– Compile lab manual

• Detailed deposition and alignment techniques

Summary of Goals

• Create inexpensive laboratory apparatus to measure changes in surface stress of micro-cantilevers

• Uses “optical lever” technique

• 2 discrete measurements to determine Δσ

• Possible future uses include:– Organic & non-organic chemical detection

Questions

http://classes.engr.arizona.edu/engr498a/2006/optomems

Members

• Kellen Chase (520-490-9516)– chased1k@gmail.com

• Richard Colonna (520-349-9760)– colonna@email.arizona.edu

• Michael Humphreys (520-603-4762)– michael.r.humphreys@gmail.com

• Joseph Ortiz (520-250-1826)– jortiz@email.arizona.edu

• Grace Shih (520-331-1444)– grashi@gmail.com