3D Printing for Low-Cost and Versatile Attenuated Total Reflection Infrared Spectroscopy.

In this work, we present a fully 3D-printed module for attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy ready for use in commercial FTIR spectrometers. The developed setup stands out in terms of robustness and ease of sample application. Rapid prototyping paired with theoretical considerations were employed to design and fabricate the module. Cost-efficient commercial available silicon and germanium ATR crystals prepared from double-sided polished wafers were mounted in the setup. While low-noise levels and stability bear comparison with commercial systems, the multibounce ATR crystal's long interaction pathlengths as well as their interchangeability turns the presented ATR module into an even more sophisticated tool. The versatility of the proposed setup is demonstrated for various spectroscopic challenges: Curing of a cyanoacrylate and a two-component epoxy based adhesive was monitored by tracking polymerization processes at room and high temperatures. To emphasize potential applications of the disposable ATR module in life science studies exploring potential biohazardous samples, mid-IR spectra of Escherichia coli and bovine serum albumin were recorded. The total printing time of the ATR module is 10.5 h, enabling overnight fabrication at a total cost ranging from 150 to 613 €, making the high versatility of ATR spectroscopy accessible to a broader audience. This proves the potential of 3D printing to generate optical instruments tailored to the needs of individual analytical problems.