3D Printed Stainless Steel Microreactor

International researchers are exploring the creation of microreactors in ‘Simple 3D printed stainless steel microreactors for online mass spectrometric analysis.’ In this study, they analyze the functionality of a stainless steel microreactor, using an inverse electron demand Diels-Alder and subsequent retro Diels-Alder reaction for testing.

Because only a small number of reagents are required to analyze chemical reactions with microfluidic devices, they can be invaluable—especially when a lab may not have extensive funding—or when such reagents are not commercially available. Microreactors are often connected with mass spectrometry, NMR spectroscopy, liquid chromatography, and UV-Vis spectroscopy.

“Flow chemistry allows for the use of a non-destructive detection method in series with mass spectrometry,” state the researchers. “The most common mass spectrometric method used with microreactors has been electrospray ionization – mass spectrometry (ESI-MS), which has been done either by attaching the microreactor to a commercial ESI ion source or by integrating an ESI tip with the reactor.”

Stainless steel microreactor with an ESI tip. (a) 3D model of the microreactor and X-ray image, (b) photograph of a microreactor with a 1 euro coin for size comparison, and (c) optical micrograph of a channel cross section of a reactor with similar channel design as the microreactor in Fig. 2a-b.

Miniature reactors and microfluidics are created via microtechnologies—requiring both steps in lithography and bonding. There may only be one set of chips available also, from silicon to glass to another type of polymer. 3D printing is, of course, also an up and coming technology for microfluidics; however, there are few made from metal.

For testing in the study, the team used an EOS instrument. The channels were created with an equilateral triangular profile with a 1.2-mm side, along with the volume being determined by weight, water, and more.

“Before attempting to use the microreactor in conjunction with a mass spectrometer, we determined the flow rates at which electrospray can be obtained. An 80:20 mixture of acetonitrile: water with 0.1 vol % of formic acid was pumped into the microreactor, which was attached to a high voltage power supply.”

Flow rates were noted before others could use the microreactor, with the researchers noting that there are many limitations of ESI—even stating that it does not generally work very well with solvents comprised of high salt content.

Here are some important advantages:

• Improved temperature control
• Shorter mixing times
• Good temperature control in the reactor
• Low volume of reactants
• Analytical detection techniques can be combined with online detection

“Despite the issues mentioned above, the simple stainless steel microreactors could already now be useful as disposable devices in some applications. They are not perfectly suited for studying reaction kinetics and mechanisms due to the memory effects caused by the rough surfaces in the channels, but can perform the same reaction repeatedly or continuously, especially with a much longer reaction channel and better-defined tip structure for ESI,” concluded the researchers.

“The fact that fabrication of the device requires no cleanroom work, is an additional benefit. Another benefit is the fact that the device can be easily tailored to suit specific needs through the process of rapid prototyping. Some researchers may also find very advantageous the fact that the devices are made of a mechanically robust material that can easily be heated to hundreds of degrees Celsius, to enhance the rate of reactions. For these reasons we foresee further research into improving these stainless steel microreactors.”

Stainless steel is used for a variety of applications in 3D printing today, with different grades, alloys, and filaments. Find out more about its uses with microreactors here. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.