Search for: All records

We synthesized and characterized the advanced multifunctional features of mycelium–coir-based composites as a replacement for fossil-based foams used in building insulation. 

AbstractMycelium is crucial in decomposing biomass and cycling nutrients in nature. While various environmental factors can influence mycelium growth, the role of substrate mechanics is not yet clear. In this study, we investigate the effect of substrate stiffness on mycelium growth. We prepared agar substrates of different concentrations to grow the mycelium, but kept other environmental and chemical conditions consistent. We made a time-lapse recording of the growing history with minimum interruption. We repeated our tests for different species. Our results generally support that mycelium grows faster on a stiffer substrate,Ganoderma lucidumgives the highest growth rate andPleurotus eryngiiis most sensitive to substrate stiffness. We combined experimental characterization and computational simulation to investigate the mechanism and discovered that mycelium concentrates on the surface of a rigid substrate, but penetrates the soft one. Our Monte Carlo simulations illustrate that such a penetration allows mycelium to grow in the three-dimensional space, but effectively slows down the surface occupation speed. Our study provides insights into fungal growth and reveals that the mycelium growth rate can be tuned through substrate stiffness, thus reducing the time for producing mycelium-based composites. Impact statementWe used agar substrates and tuned its stiffness to culture mycelium and compared tune its stiffness to culture mycelium and compare its growth in a well-controlled condition. Our results revealed that mycelium grows faster on stiffer substrates, thus fully occupying the petri dish surface more quickly. We repeated our study several times by testing four species,P. eryngii,G. lucidum,Trametes versicolor,and Flammulina velutipes,and the stiffest substrate always gives the highest mean growing rate than others. TheG. lucidumshows the highest spreading rate that is obtained on the stiffest substrate as 39.1 ± 2.0 mm²/h. We found that the mycelium on a soft substrate will grow into the substrate instead of spreading on the stiffer surface. Our Monte Carlo simulations further show that once the fibers grow into a three-dimensional substrate, its growth is slower than growing on a two-dimensional surface, providing a microscopic mechanism of the substrate stiffness effect. This study’s analysis of how substrate stiffness impacts mycelium growth is new, bridging a critical knowledge gap in understanding the relationship between substrate mechanics and fungal ecology. The knowledge from this study has a potential in accelerating sustainable manufacturing of mycelium-based composite by adjusting substrate mechanics. Graphical Abstract 

2D materials such as graphene, monolayer MoS2 and MXene are highly functional for their unique mechanical, thermal and electrical features and are considered building blocks for future ultrathin, flexible electronics. However, they can easily fracture from flaws or defects and thus it is important to increase their toughness in applications. Here, inspired by natural layered composites and architected 3D printed materials of high toughness, we introduce architected defects to the 2D materials and study their fracture in molecular dynamics simulations. We find that the length of the defects in the shape of parallel bridges is crucial to fracture toughness, as long bridges can significantly increase the toughness of graphene and MoS2 but decrease the toughness of MXene, while short bridges show opposite effects. This strategy can increase the toughness of 2D materials without introducing foreign materials or altering the chemistry of the materials, providing a general method to improve their mechanics. 

The distribution of material phases is crucial to determine the composite's mechanical property. While the full structure-mechanics relationship of highly ordered material distributions can be studied with finite number of cases, this relationship is difficult to be revealed for complex irregular distributions, preventing design of such material structures to meet certain mechanical requirements. The noticeable developments of artificial intelligence (AI) algorithms in material design enables to detect the hidden structure-mechanics correlations which is essential for designing composite of complex structures. It is intriguing how these tools can assist composite design. Here, we focus on the rapid generation of bicontinuous composite structures together with the stress distribution in loading. We find that generative AI, enabled through fine-tuned Low Rank Adaptation models, can be trained with a few inputs to generate both synthetic composite structures and the corresponding von Mises stress distribution. The results show that this technique is convenient in generating massive composites designs with useful mechanical information that dictate stiffness, fracture and robustness of the material with one model, and such has to be done by several different experimental or simulation tests. This research offers valuable insights for the improvement of composite design with the goal of expanding the design space and automatic screening of composite designs for improved mechanical functions. 

Collagen, a vital protein that provides strength to various body tissues, has a triple helix structure containing three polypeptide chains. The chains are composed mostly of a tripeptide of glycine (G), proline (P), and hydroxyproline (O). Using molecular dynamics simulations and theoretical analysis, the study examines the mechanical response of collagen triple helix structures, made up of three different tripeptide units, when subjected to different fracture loading modes. The results show that collagen with GPO tripeptide units at their C-terminal are mechanically stronger than the POG and OGP units with a single amino-acid frame shift. Our work shows that the N-terminal has less effect on collagen fracture than the C-terminal. The differences in mechanical response are explained by the heterogenous rigidity of the amino acid backbone and the resulting shear lag effect near the terminal. The findings have potential applications in developing tough synthetic collagen for building materials and may stimulate further studies on the connection between terminal repeats and the mechanical-thermal behavior of other structural proteins such as silk, elastin, fibrin, and keratin. 

Abstract Cis-peptide bonds are rare in proteins, and building blocks less favorable to the trans-conformer have been considered destabilizing. Although proline tolerates the cis-conformer modestly among all amino acids, for collagen, the most prevalent proline-abundant protein, all peptide bonds must be trans to form its hallmark triple-helix structure. Here, using host-guest collagen mimetic peptides (CMPs), we discover that surprisingly, even the cis-enforcing peptoid residues (N-substituted glycines) form stable triple-helices. Our interrogations establish that these peptoid residues entropically stabilize the triple-helix by pre-organizing individual peptides into a polyproline-II helix. Moreover, noting that the cis-demanding peptoid residues drastically reduce the folding rate, we design a CMP whose triple-helix formation can be controlled by peptoid cis-trans isomerization, enabling direct targeting of fibrotic remodeling in myocardial infarction in vivo. These findings elucidate the principles of peptoid cis-trans isomerization in protein folding and showcase the exploitation of cis-amide-favoring residues in building programmable and functional peptidomimetics.