(Photo ©Earl Zubkoff)

Dr. Ahmed and scientists from NIST and American University are researching the use of metal organic frameworks (MOFs) as the basis for an inexpensive, easy-to-build gas sensing technology. The problem they faced is that newly made MOFs are tiny particles that, in bulk, have the consistency of dust.

Tech Briefs: What got you started on this research?

Dr. Zeeshan Ahmed: A lot of the work we do is to make very precise measurements of physical states of matter. The seed for this project began with a challenge: could we make cost-effective, disposable sensors that are good enough for everyday measurements? We came up with the idea of adopting 3D printing to make sensors that anyone, anywhere could make.

Tech Briefs: Why did you choose MOFs as the sensing element?

Dr. Ahmed: There are varieties of MOF products that have differing affinities and different binding constants for gases such as carbon dioxide or methane. You could put them in a stream and each would capture a different gas. If the gas adheres, it changes the refractive index of the local environment, and we could detect that slight change. We can look at the frequency of resonance of the device and say certain gas molecules are present or not.

Another way is to make an entire sensor out of these 3D-printed pieces with the MOF embedded. When gas molecules go in and change the mechanical properties, the permittivity, or the refractive index of the entire piece, you’re able to look at the frequency of your sensor and determine whether and how much of the gas molecules of interest are present.

Tech Briefs: How do you mix the MOF with the plastic?

Dr. Ahmed: The blending of MOF powder with the plastic — finding out the concentrations you can mix in — was a large part of what we did. If you have too much powder, things don’t mix together, the plastic doesn’t flow, and you can’t print. If you have too little, you don’t have the properties of interest. We tried to figure out where you could mix in the powders and they would disperse evenly, wouldn’t clump together, and would provide the desired crystal structure and size.

Tech Briefs: How will these gas sensors compare with existing sensors?

Dr. Ahmed: We hope that they will be at least as good. The big advantage is that anyone, anywhere can make them as long as they have the CAD file and a 3D printer. We make the CAD file, and it’s out there for anyone to use.

Tech Briefs: What excites you about this research?

Dr. Ahmed: People anywhere in the world can use this technology and innovate on top of it. Since it’s easily scalable to small labs, or even individuals, you’ve opened up the possibility of advancing the field much more quickly than with a traditional technique.