Blood, Sweat and Tears: Extraterrestrial Regolith Biocomposites with in Vivo Binders

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 produce a concrete-like material. 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 can 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 reorganisation 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.