New types of laboratory reactors that are highly customizable, low-cost and easy to produce are needed to investigate low-temperature geochemical processes. We recently showed that desktop 3D printing stereolithography (SLA) can be used to efficiently fabricate a mixed flow reactor (MFR) with high dimensional accuracy comparable to traditional machining methods (Michel et al., 2018). We also showed that the SLA method allowed for the addition of complex features that are often beyond the capabilities of traditional methods. However, the stability of 3D printed parts at low-temperature geochemical conditions has not been fully evaluated. The objectives of this work were twofold: 1) to provide a framework for assessing the stability and compatibility of SLA printed materials at geochemically relevant conditions, and 2) to show how 3D printed specialty devices can enable new laboratory geochemical experiments. Part 1 of this Master's thesis presents findings for enhancing mechanical and solvent resistance properties of a commercial 3D printing material (Formlabs Clear) by UV post-curing procedures and also provide data showing its stability in aqueous solutions at pH 0, 5.7, and 12 for periods of up to 18 days. Thermal degradation patterns, mechanical analysis, and leachable fraction data are provided. Part 2 shows experiments coupling 3D printed reactors and flow devices for in situ small-angle x-ray scattering (SAXS). Schwertmannite (pH 2.7) and goethite (6.2) are precipitated from solution using various setups and observed differences in growth rates are discussed. The data show the potential of 3D printing for enabling novel laboratory geochemical experiments. / MS / New types of laboratory devices are needed to investigate environmental processes such as how minerals form, transform, and interact with their surroundings. These devices should be highly customizable, low-cost, and easy to produce. We have recently showed how 3D printing, specifically a technique called stereolithography (SLA), can be used to fabricate reactors with complex features that are often difficult to produce using traditional machining methods. However, in order to ensure that these materials don’t interfere with reactions of interest, we must assess the stability and compatibility of these materials in the relevant environmental conditions. As 3D printing techniques are still an emerging and rapidly developing technology, the methods we present will be useful for evaluating how new printer types and materials (i.e. resins) impact the suitability of 3D printed devices for future experimental studies. In part 1 of this thesis, the properties of a commercial 3D printing material were investigated by thermal and mechanical analyses; the propensity for leaching out material from the solid was also investigated. We show how exposing SLA printed materials to ultraviolet (UV) light post-printing can enhance material properties and minimize leaching. We then provide data showing the stability of the material after exposure to an array of acidic, neutral and basic conditions for a period of up to 18 days. In part 2, we describe experiments showing how novel 3D printed devices can be used to enhance laboratory investigations. Syntheses of two common iron oxide minerals using various custom reactor setups are presented. The setups were coupled with an analytical technique allowing for nanoscale observation of crystal growth in real-time. The data show how 3D printed specialty devices can be used to solve important questions in the geosciences such as the mechanisms of complex crystal formation.