From Real Soils to 3D-Printed Soils: Reproduction of Complex Pore Network at the Real Size in a Silty-Loam Soil

Abstract

Pore complexity and micro-heterogeneity are pivotal in characterizing biogeochemical processes in soils. Recent advances in X-ray computed microtomography (microCT) allow the 3D soil morphology characterization of undisturbed samples, although its geometrical reproduction at very small spatial scales is still challenging. Here, by combining X-ray microCT with 3D multijet printing technology, we aimed to evaluate the reproducibility of 3D-printing soil structures at the original scale with a resolution of 80 µm and compare the hydraulic properties of original soil samples with those obtained from the soil-like prototypes. Results showed that soil-like prototypes were similar to the original samples in terms of total porosity and pore shape. By contrast the pore connectivity was reduced by the incomplete wax removal from pore cavities after the 3D printing procedure. Encouraging results were also obtained in terms of hydraulic conductivity since measurements were successfully conducted on five out of six samples, showing positive correlation with experimental data. We are confident that future developments of 3D-printing technologies and of their combination with microCT will help to further the understanding of soil microheterogeneity and its effects on soil-water dynamics.

Benefits and limitations of three-dimensional printing technology for ecological research

“…For example, acrylonitrile butadiene styrene (ABS), a type of filament, was used for printing artificial flowers [30], artificial zebrafish [28, 45], and models of lizards [13], while resin was used for printing artificial soils with fine-scale pore structure in a hydrology study [34]. It is also worth considering the type of scaffolding involved with a specific printer/print material combination.…”

“…18[29] Social behavior of zebrafish in response to varying stimuliZebrafish ( Danio rerio )Predatory fish model robot shoals comprising 3 zebrafish that varied in body size plus anchoring materials biologically-inspired zebrafish replicaABS plasticABS plasticABS plastic14 shoals1[68][28] [45] Influence of female body size on mate choice by malesNorthern map turtles ( Graptemys geographica )Replicas of female turtles that differed in body sizeABS plastic4[32] Evaluation of 3D printing as suitable method for field predation model studiesBrown anole ( Anolis sagrei )Lizard models using 2 print media, covered in clay, and field-tested for predationABS plastic, plastic-wood hybrid filament17This studyThermal ecology Comparing thermodynamics of 3D printed and copper lizard modelsTexas horned lizard ( Phrynosoma cornutum )Thermal models of lizardsABS plastic10[13]Tools—experimental areas Evaluation of 3D printed soil as suitable for fungal colonizationPlant pathogenic fungus ( Rhizoctonia solani )Artificial soil from 3D scans of soil with varying micropore structureNylon 1210[33] Comparing hydraulic properties of 3D printed soil relative to real soilSoilArtificial soil from 3D scans of soilResin (Visijet Crystal EX 200 Plastic Material)14[34] Microscale bacterial cell–cell interactions Pseudomonas aeruginosa and Staphlylococcus aureus “Designer” bacterial ecosystems that vary in size, geometry and spatial distance with exact starting quantities of P. aeruginosa and S. aureus GelatinNR[47, 48] Effect of interstitial space on predator–prey interactionsBlue crab ( Cal...…”

“…In the field of soil ecology, 3D printing has been used to print artificial soil structures which accurately replicate the macropore structure of soil (Table 1) [33, 34]. These artificial soils are ideal replicate experimental mesocosms for soil macro- and/or microorganisms.…”

Landmark Papers: No. 9 Jarvis, N.J. 2007. A review of non‐equilibrium water flow and solute transport in soil macropores: Principles, controlling factors and consequences for water quality. European Journal of Soil Science, 58, 523–546

“…Therefore, combined observations of soil macropore networks (i.e., form) and preferential flow and solute transport via macropores (i.e., function) can establish the relationship that links patterns, responses and functions to better describe and model a hydrological system. Model systems, such as combining 3D-imaging techniques with 3D-printing of reconstructed macropore networks, might overcome the current limitation that solute transport experiments cannot be repeated with identical networks under a range of initial hydraulic and boundary conditions (Bacher, Schwen, & Koestel, 2015;Dal Ferro & Morari, 2015;Otten et al, 2012).…”

Visual representation and characterization of three-dimensional hydrofracturing cracks within heterogeneous rock through 3D printing and transparent models

“…Second, the printing process can be repeated, making it is possible to produce multiple identical specimens. These advantages in specimen preparation make 3D printing suitable for manufacturing complicated transparent 3D solids (Miller et al 2011;Campbell and Ivanova 2013;Dal Ferro and Morari 2015).…”