Blood, sweat, and tears: extraterrestrial regolith biocomposites with in vivo binders

Abstract

The proverbial phrase 'you can't get blood from a stone' is used to describe a task that is practically impossible regardless of how much force or effort is exerted. This phrase is well-suited to humanity's first crewed mission to Mars, which will likely be the most difficult and technologically challenging human endeavor ever undertaken. The high cost and significant time delay associated with delivering payloads to the Martian surface means that exploitation of resources in situ - including inorganic rock and dust (regolith), water deposits, and atmospheric gases - will be an important part of any crewed mission to the Red Planet. Yet there is one significant, but chronically overlooked, source of natural resources that will - by definition - also be available on any crewed mission to Mars: the crew themselves. In this work, we explore the use of human serum albumin (HSA) - a common protein obtained from blood plasma - as a binder for simulated Lunar and Martian regolith to produce so-called 'extraterrestrial regolith biocomposites (ERBs).' In essence, HSA produced by astronauts in vivo could be extracted on a semi-continuous basis and combined with Lunar or Martian regolith to 'get stone from blood', to rephrase the proverb. Employing a simple fabrication strategy, HSA-based ERBs were produced and displayed compressive strengths as high as 25.0 MPa. For comparison, standard concrete typically has a compressive strength ranging between 20 and 32 MPa. The incorporation of urea - which could be extracted from the urine, sweat, or tears of astronauts - could further increase the compressive strength by over 300% in some instances, with the best-performing formulation having an average compressive strength of 39.7 MPa. Furthermore, we demonstrate that HSA-ERBs have the potential to be 3D-printed, opening up an interesting potential avenue for extraterrestrial construction using human-derived feedstocks. The mechanism of adhesion was investigated and attributed to the dehydration-induced reorganization of the protein secondary structure into a densely hydrogen-bonded, supramolecular β-sheet network - analogous to the cohesion mechanism of spider silk. For comparison, synthetic spider silk and bovine serum albumin (BSA) were also investigated as regolith binders - which could also feasibly be produced on a Martian colony with future advancements in biomanufacturing technology.

Keywords: 3D-printing; BSA, Bovine Serum Albumin; Biopolymer-bound soil composites; CD, Circular Dichroism; ERB, Extraterrestrial Regolith Biocomposite; FE-SEM, Field-emission Scanning Electron Microscopy; HSA, Human Serum Albumin; Human serum albumin; Hybrid materials; In situ resource utilization; LHS-1, Lunar Highlands Simulant 1; MGS-1, Martian Global Simulant 1; MSA, Mammalian Serum Albumin; Recombinant spider silk.

Graphical abstract

Fig. 1

A hypothetical block diagram depicting how HSA could be produced in vivo from in situ resources available on Mars, and — technological advancements permitting — eventually supplemented or replaced with an ultra-high reliability self-contained bioreactor (dashed yellow arrows) that could have additional uses [28,30]. Abbreviations: Environmental Control and Life Support (ECLS), Mars Ascent Vehicle (MAV).

Fig. 2

Scheme depicting the typical fabrication procedure for producing HSA-based ERBs.

Fig. 3

(a) Relationship between HSA solution concentration and calculated binder content. (b) Relationship between HSA solution concentration and UCS of the ERBs. (c) Relationship between elastic modulus under compression and HSA solution concentration for MGS-1 and (d) for LHS-1.

Fig. 4

(a) CD spectra of a 5 wt% HSA solution laminated between two quartz substrates over a 20 h period with (b) corresponding changes to secondary structure. (c) CD spectra of a 0.1 wt% HSA solution from 25 °C to 85 °C with (d) corresponding changes to secondary structure. (e) CD spectra of the 0.1 wt% HSA solution from 85 °C to 25 °C with (f) corresponding changes to secondary structure.

Fig. 5

(a) Relationship between urea concentration and UCS for ERBs employing 30 wt% HSA with MGS-1 and (b) LHS-1. (c) Stress-strain curves EBRs employing 30 wt% HSA and 3 M urea with MGS-1 and (d) LHS-1.

Fig. 6

Visible light images of recombinant spider silk-based ERBs: (a) LHS-1 and (b) MGS-1. FE-SEM images of recombinant spider silk-based ERBs: (c) LHS-1 ×100 magnification, (d) LHS-1×5000 magnification (e) MGS-1×100 magnification, (f) MGS-1×5000 magnification.

Fig. 7

Visible light images of the 3D-printed HSA-ERB based on MGS-1. (a) after fabrication, (b) during compression testing, and (c) after compression testing.

Fig. 8

Life-cycle process flow diagram for HSA/Urea-based ERBs.