Fig. 3: Mechanical property characterization and performance comparison of BC sheet.

a Typical tensile strain-stress curve for static (control) and rotational BC sheets. b Statistical comparison of ultimate tensile stress (UTS), Young’s modulus (YM) and work of failure (WoF) of the BC sheets from static and rotational culture with the mean values noted atop. YM1 and YM2 represent the slopes of linear fits to the low-strain (<0.6%) and high-strain (>0.6%) regions, respectively. Bars represent mean values, and error bars indicate standard deviation (n = 3 independent samples per category). Statistical significance was determined using two-sided independent Welch’s t-tests. Asterisks indicate significance levels: p ≤ 0.05 (*), p ≤ 0.01 (**), and p ≤ 0.001 (***). Exact p values: UTS (p = 0.00713), YM1 (p = 0.00118), YM2 (p = 0.0286), and WoF (p = 0.000148). c Linear fittings to the strain-stress curve, shown in (a) for calculating YM1 (red line) and YM2 (black line). d Correlation between % improvement in YM and the degree of alignment using Krenchel analytical model (square symbol), our model prediction (circle symbol) and experimental data (pink shaded area). Inset shows two model BC sheets with 58.4% alignment (green) and random alignment (grey). Representative SEM image the fractured surface of BC sheets from (e) static culture and (f) rotational culture. Compared to the static grown BC, rotational device grown BC shows directional alignment and more fiber pull-out. Similar morphological features were consistently observed in three independently repeated experiments. g Comparison of tensile strength across various single-step synthesis methods for BC. Bars represent mean values, and error bars indicate standard deviation. h Ashby plot of strength and density shows that the BC grown from rotational culture has higher strength than polymers and glass (indicated in red star). i Ashby plot of Young’s modulus and density shows that BC (indicated in red star) has Young’s modulus higher than most of the natural materials and even comparable to some metals. j Cyclic tensile loading (10,000 cycles) rotational BC at 50 ± 30 MPa. Inset shows zoomed-in (red dotted area) cyclic loading for first 1 min of the cycling depicting triangle-shaped loading input. k Tensile stress–strain curves of the rotational BC before and after 10,000 cycles of loading.