Developing 3D-Printed Electrospray Sources for Mass Spectrometry Instrumentation

Researchers from the Massachusetts Institute of Technology have unveiled novel three-dimensional (3D)-printed electrospray sources for mass spectrometry (MS), offering double the signal strength of mainstream counterparts, according to a new study published in the Journal of the American Society of Mass Spectrometry (1).

In the chromatography space, 3D printing has been viewed as a technological innovation that would propel forward liquid chromatography (LC) (2). However, 3D printing methods have numerous limitations, particularly when it comes to resolution. Numerous printing methods that are commonly used, such as stereolithography and selective laser sintering, often operate with resolutions to the order to of 20–100 µm (2). Because of this operation parameter, printing methods generally feature porous bed sizes greater than 300 µm, which is two orders of magnitude (100 times) short of the feature sizes that are necessary for use in HPLC columns, for example, approximately 3 µm (2).

There have been several studies done to improve 3D printing technology. Several of these studies successfully combined traditional techniques to improve 3D printing of analytical columns (3,4). Recently, 3D printing technology has been taken a step further and used to mass produce electrospray emitters.

This study, led by Luis Fernando Velasquez-Garcia, investigated using 3D-print technology to improve electrospray emitters for MS analysis. Velasquez-Garcia and the research team successfully fabricated nano- and microscale-featured electrospray emitters in bulk, marking a significant stride towards scalable integration in clinically relevant diagnostics (1). The devised solution not only enhances device performance, but it also paves the way for advancements in medical diagnostics and beyond.

The emitters were created from stainless steel using binder jetting. They were coated with a conformal, hydrothermally grown zinc oxide nanowire (ZnONW) forest (1). This coating, combined with precise tuning of surface hydrophilicity, solvent evaporation, and geometry, contributed to the optimal performance of the 3D-printed electrospray sources (1).

What makes the electrospray emitters the team developed unique is their extractor electrode design. This new design makes operation easier at larger voltages and significantly improves the emitters’ functionality compared to other emitters (1). The MS data revealed the detection of therapeutically relevant targets at concentrations as low as 1 μg/ml, using a variety of solvents (1).

Of particular significance is the performance of nicardipine, a commonly used medication. The 3D-printed emitters achieved an astounding 116% higher signal-to-noise (S/N) ratios and exhibited far greater stability, which helped show their potential for applications in pharmaceutical research and clinical diagnostics (1).

The printed emitters were designed as surface mount devices. This means that they allow for direct soldering to printed circuit boards equipped with built-in digital microfluidics (1). This feature facilitates automated device assembly, further enhancing their utility and accessibility in various analytical settings (1).

References

(1) Velasquez-Garcia, L. F.; Kachkine, A. High-Performance, Low-Cost, Additively Manufactured Electrospray Ion Sources for Mass Spectrometry. J. Am. Soc. Mass Spectrom. 2024, ASAP. DOI: 10.1021/jasms.3c00409

(2) Nawada, S.; Budel, T. Novel 3D-Printing Method to Create Liquid Chromatography Columns. LCGC N. Am. 2021, 39 (9), 414–417.

(3) De Malsche, W.; Matheuse, F.; Broeckhoven, K.; et al. Current and Future Chromatographic Columns: Is One Column Enough to Rule Them All? LCGC Special Issue 2018, 36 (6), 9–17.

(4) Nawada, S. EU patent: EP 19170376.8-1022, 19 April 2019.