Robust and Elastic Lunar and Martian Structures from 3D-Printed Regolith Inks

Abstract

Here, we present a comprehensive approach for creating robust, elastic, designer Lunar and Martian regolith simulant (LRS and MRS, respectively) architectures using ambient condition, extrusion-based 3D-printing of regolith simulant inks. The LRS and MRS powders are characterized by distinct, highly inhomogeneous morphologies and sizes, where LRS powder particles are highly irregular and jagged and MRS powder particles are rough, but primarily rounded. The inks are synthesized via simple mixing of evaporant, surfactant, and plasticizer solvents, polylactic-co-glycolic acid (30% by solids volume), and regolith simulant powders (70% by solids volume). Both LRS and MRS inks exhibit similar rheological and 3D-printing characteristics, and can be 3D-printed at linear deposition rates of 1–150 mm/s using 300 μm to 1.4 cm-diameter nozzles. The resulting LRS and MRS 3D-printed materials exhibit similar, but distinct internal and external microstructures and material porosity (~20–40%). These microstructures contribute to the rubber-like quasi-static and cyclic mechanical properties of both materials, with young’s moduli ranging from 1.8 to 13.2 MPa and extension to failure exceeding 250% over a range of strain rates (10–1−102 min−1). Finally, we discuss the potential for LRS and MRS ink components to be reclaimed and recycled, as well as be synthesized in resource-limited, extraterrestrial environments.

“Tissue Papers” from Organ‐Specific Decellularized Extracellular Matrices

“…These moduli are several orders of magnitude greater than native soft tissues, [45] but fall within the same range of 10 0 –10 1 MPa exhibited by previously described 3D-printed hydroxyapatite-, graphene-, metal-and metal oxide-, and Lunar- and Martian-regolith-simulant PLGA material systems produced using this general ink approach, [35,36,38,42] indicating that the mechanical load in the TPs is primarily carried by the elastomeric polymer matrix, PLGA. The variation in mechanical properties among TPs, however, is likely due to the mesostructural variation in porosity and dECM-particle/PLGA-matrix distribution within individual tissue paper types, rather than variations in the mechanical properties of the dECM itself, which do not play a significant role in carrying or transmitting mechanical loads.…”

“…These data illustrate the unique topographical characteristics of each TP type. Although photographs, scanning electron microscopy, or topographical fluorescence mapping reveal the micro- and mesostructures of the tissue papers, they do not elucidate the interaction between the dECM powder particles and the PLGA; we hypothesize, based on our previous work with related ink and 3D-printed systems, [24,34–38] that the PLGA forms a continuous matrix throughout the TP materials, physically encapsulating dECM particles, but not covalently bonding with them.…”

“…As a control, commercially available purified bovine collagen flakes (Type I from Achilles tendon) were milled and also transformed into CTP. dECM powders (65 vol% by solids content) derived from these specific tissues and organs were suspended in a trisolvent mixture containing dichloromethane (DCM), 2-butoxyethanol (surfactant), and dibutyl phthalate (plasticizer) in addition to solubilized PLGA (82:18 lactic acid to glycolic acid; 35 vol% by solids), to create dECM “inks.” This procedure, along with the importance and function of each solvent, is an extension of a process we have previously described for synthesizing 3D-printable particle-laden inks, [34–38,42] thus the reasoning for referring to the resulting dECM suspensions as inks.…”

“…Tissue papers were fabricated based on previously reported methods for making 3D-printable inks [24,34–38] and an estimated specific gravity of collagen (≈1.05 g cm −3 ), the primary component in the tissues. dECM powder was suspended in 2-butoxyethanol (Sigma, USA; 0.3 g per 0.35 g dECM), dibutyl phthalate (Sigma, USA; 0.15 g per 0.35 g dECM), and dichloromethane (Sigma, USA; 3 mL for every 0.35 g of dECM powder).…”

“…The process outlined in this work is an extension of a methodology we have previously demonstrated for creating 3D-inks for 3D-printing osteogenic, [34] neurogenic, [35] and mixed-functionality synthetic biomaterials, [36] as well as metals, [24,37] extraterrestrial soil simulants, and ceramics. [38] We evaluated, in parallel, the microstructural, mechanical, physical, and in vitro biological characteristics of TPs fabricated from decellularized porcine heart (HTP), kidney (KTP), liver (LTP), muscle (MTP), bovine ovary (OTP) and uterus (UTP), and purified collagen (CTP) as a control material.…”