Soft Deployable Structures via Core-Shell Inflatables.

Deployable structures capable of significant geometric reconfigurations are ubiquitous in nature. While engineering contraptions typically comprise articulated rigid elements, soft structures that experience material growth for deployment mostly remain the handiwork of biology, e.g., when winged insects deploy their wings during metamorphosis. Here we perform experiments and develop formal models to rationalize the previously unexplored physics of soft deployable structures using core-shell inflatables. We first derive a Maxwell construction to model the expansion of a hyperelastic cylindrical core constrained by a rigid shell. Based on these results, we identify a strategy to obtain synchronized deployment in soft networks. We then show that a single actuated element behaves as an elastic beam with a pressure-dependent bending stiffness which allows us to model complex deployed networks and demonstrate the ability to reconfigure their final shape. Finally, we generalize our results to obtain three-dimensional elastic gridshells, demonstrating our approach's applicability to assemble complex structures using core-shell inflatables as building blocks. Our results leverage material and geometric nonlinearities to create a low-energy pathway to growth and reconfiguration for soft deployable structures.

Bubble casting soft robotics.

Inspired by living organisms, soft robots are developed from intrinsically compliant materials, enabling continuous motions that mimic animal and vegetal movement1. In soft robots, the canonical hinges and bolts are replaced by elastomers assembled into actuators programmed to change shape following the application of stimuli, for example pneumatic inflation2-5. The morphing information is typically directly embedded within the shape of these actuators, whose assembly is facilitated by recent advances in rapid prototyping techniques6-11. Yet, these manufacturing processes have limitations in scalability, design flexibility and robustness. Here we demonstrate a new all-in-one methodology for the fabrication and the programming of soft machines. Instead of relying on the assembly of individual parts, our approach harnesses interfacial flows in elastomers that progressively cure to robustly produce monolithic pneumatic actuators whose shape can easily be tailored to suit applications ranging from artificial muscles to grippers. We rationalize the fluid mechanics at play in the assembly of our actuators and model their subsequent morphing. We leverage this quantitative knowledge to program these soft machines and produce complex functionalities, for example sequential motion obtained from a monotonic stimulus. We expect that the flexibility, robustness and predictive nature of our methodology will accelerate the proliferation of soft robotics by enabling the assembly of complex actuators, for example long, tortuous or vascular structures, thereby paving the way towards new functionalities stemming from geometric and material nonlinearities.

Differences in the recruitment of DNA repair proteins at subtelomeric and interstitial I-SceI endonuclease-induced DNA double-strand breaks.

Telomeres are nucleoprotein structures that are required to protect chromosome ends. Dysfunctional telomeres are recognized as DNA double-strand breaks (DSBs), and elicit the activation of a DNA damage response (DDR). We have previously reported that DSBs near telomeres are poorly repaired, resulting in a high frequency of large deletions and gross chromosome rearrangements (GCRs). Our previous genetic studies have demonstrated that this sensitivity of telomeric regions to DSBs is a result of excessive processing. In the current study, we have further investigated the sensitivity of telomeric regions to DSBs through the analysis of repair proteins associated with DSBs at interstitial and telomeric sites. Following the inducible expression of I-SceI endonuclease, chromatin immunoprecipitation (ChIP) and real-time quantitative PCR were used to compare the recruitment of repair proteins at I-SceI-induced DSBs at interstitial and subtelomeric sites. We observed that proteins that are specifically associated with processing of DSBs during homologous recombination repair, RAD51, BRCA1, and CtIP, are present at a much greater abundance at subtelomeric DSBs. In contrast, Ku70, which is specifically involved in classical nonhomologous end joining, showed no difference at interstitial and subtelomeric DSBs. Importantly, ATM was lower in abundance at subtelomeric DSBs, while ATR was in greater abundance at subtelomeric DSBs, consistent with the accumulation of processed DSBs near telomeres, since processing is accompanied by a transition from ATM to ATR binding. Combined, our results suggest that excessive processing is responsible for the increased frequency of large deletions and GCRs at DSBs near telomeres.