Monday, November 18, 2013

Patterning aluminum with the photoresist "lift-off" method

I show how the photoresist "lift-off" method works to pattern thin films as they are deposited. In this case, I patterned aluminum on a microscope slide.


  1. Hi Ben,
    I really enjoy your projects! I had this idea to hack or re engineer a pulse ox sensor, mostly the O2 sensor to instead measure BAC. I've looked over patents by Qinetiq but they are written to broadly and I've never tried to reverse engineer something from a patent before. I found a formula to find the wavelength ethyl alcohol absorbs on but don't understand it and you understand electronics far better then me. I thought maybe a BAC spectrometer that can be made cheap and a product that can actively measure peak and rising BAC to help people be informed and make a better driving decision would be worth it. I have some reaserch done on this but was wondering if you'd like to take this on for your YouTube channel? Anyway, thanks for your time. David.

  2. David, thanks! One of the problems with detecting alcohol levels by absorption spectrometry of a fingertip, would be all of the other substances in the fingertip that have their own absorbance spectra. You'll need a fair amount of data processing, and calibration to make it work. Also, I'm guessing the peak absorbance is mid-IR, which could mean expensive sensors. In principle, it should work, though.

  3. Thanks for the reply Ben! Absolutely, the largest problem with fingers is that everything can contaminate the results. You're also correct about the wavelength being mid ir and the sensors being expensive. I have a lot of literature on what I need to measure, seemed to have the most specifics on what I need to be able to detect.

    What I've learned most in this is how truly broad the ir spectrum is. A lot of products operate outside of their primary purpose, like the camera on a cell phone picking up near ir. So I'm going through ir photo receptors looking for something that can detect 3-3.5micron light. Once I have the parts and can measure any difference in light absorption I can start writing software to dial it in. Finding volunteers I can breathalize while consuming alcohol to create data points for my software should be the easy part lol.

    Thanks for the chat and please share any thoughts you may have about this.

  4. this project has really help me alot thanks