Force sensing at cadherin-mediated adhesions is critical for their proper function. α-Catenin, which links cadherins to actomyosin, has a crucial role in this mechanosensing process. It has been hypothesized that force promotes vinculin binding, although this has never been demonstrated. X-ray structure further suggests that α-catenin adopts a stable auto-inhibitory conformation that makes the vinculin-binding site inaccessible. Here, by stretching single α-catenin molecules using magnetic tweezers, we show that the subdomains MI vinculin-binding domain (VBD) to MIII unfold in three characteristic steps: a reversible step at ~5 pN and two non-equilibrium steps at 10-15 pN. 5 pN unfolding forces trigger vinculin binding to the MI domain in a 1:1 ratio with nanomolar affinity, preventing MI domain refolding after force is released. Our findings demonstrate that physiologically relevant forces reversibly unfurl α-catenin, activating vinculin binding, which then stabilizes α-catenin in its open conformation, transforming force into a sustainable biochemical signal.

A comprehensive review on the five levels of hierarchical structures of silk materials and the correlation with macroscopic properties/performance of the silk materials, that is, the toughness, strain‐stiffening, etc., is presented. It follows that the crystalline binding force turns out to be very important in the stabilization of silk materials, while the β‐crystallite networks or nanofibrils and the interactions among helical nanofibrils are two of the most essential structural elements, which to a large extent determine the macroscopic performance of various forms of silk materials. In this context, the characteristic structural factors such as the orientation, size, and density of β‐crystallites are very crucial. It is revealed that the formation of these structural elements is mainly controlled by the intermolecular nucleation of β‐crystallites. Consequently, the rational design and reconstruction of silk materials can be implemented by controlling the molecular nucleation via applying sheering force and seeding (i.e., with carbon nanotubes). In general, the knowledge of the correlation between hierarchical structures and performance provides an understanding of the structural reasons behind the fascinating behaviors of silk materials.

such as increasing the mechanical flexibility, [3,4] sensitivity [5,6] and accuracy, [7] lowering down the operating voltage, [8,9] response speed, [1,10,11] etc. To realize the close-fitting to human bodies and the long-term monitoring, mechanical flexibility has become one of the most critical properties for wearable devices [12] and on-skin sensors. [13][14][15][16] Previously, conventional flexible devices usually applied thin polymer films as the substrates, such as poly(ethylene terephthalate), [17][18][19][20] poly(d imethylsiloxane), [21] and polyimide. [9] It is noted that some problems exist for such polymer-based substrates. For instance, the aforementioned polymers are nondegradable so that they would give rise to large amount of electronic waste. Besides, compared with the natural skin which serves as the transportation routine for nutrients and body fluids, most of the polymer-based substrates are neither biocompatible nor air/water permeable, suggesting they would damage the skin when continuously paste such polymer-based substrates on skin.In this regard, it is in great demand for developing advanced substrate materials which maintain good biocompatibility, tight adherence to biological tissues, and ideal air/water permeability. Recently, owing to the superior biocompatibility and relatively low cost, silk fibroin (SF) has become one of the most promising candidates for the future flexible substrate materials which display both high dielectric property and excellent mechanical compliance. [5,22,23] Moreover, the excellent air permeability of SF films (in the wet state), which is even comparable to that of natural human skin, also triggers their potential for application in artificial skin systems. [13,23] Despite the superior natural biodegradability and biocompatibility, the development of SF-based on-skin electronics is still at a preliminary stage due to the following reasons: First, the intrinsic brittleness and poor chemical stability of SF films prevent the fabrication of SF-based electronics through traditional techniques. Although the mechanical/chemical stability can be improved to a certain extent by doping polyurethane, [24] polyvinylalcohol (PVA), [25,26] glycerol, [27] or metal ions, [28] it is still far from the demand of real applications. Second, except for mechanical/chemical stability, the SF film served as the substrate is also supposed to be stretchable, so that they can be comfortably cling to skin. [29][30][31][32][33] Similarly, the conducting film on SF substrate should also be Due to the natural biodegradability and biocompatibility, silk fibroin (SF) is one of the ideal platforms for on-skin and implantable electronic devices. However, the development of SF-based electronics is still at a preliminary stage due to the SF film intrinsic brittleness as well as the solubility in water, which prevent the fabrication of SF-based electronics through traditional techniques. In this article, a flexible and stretchable silver nanofibers (Ag NFs)/SF based electrode is synthesized th...

Functionalization of flexible materials based on mesoscopic reconstruction is a key strategy in fabricating biocompatible flexible electronics. This work is to acquire new mesoscopic bioelectronic hybrid materials of silk fibroin (SF)-Ag nanoclusters (AgNCs@BSA; BSA: bovine serum albumin), which enhance significantly the performance of silk memristors. It is to build AgNCs@BSA into SF mesoscopic networks by templated β-crystallization. Atomic force microscopy potential probing indicates that AgNCs@BSA serve as electronic potential wells that change completely the transport behavior of charge particles within the SF films. This leads to significant enhancement in the switching speed (≈10 ns), very good switching stability, extremely low set/reset voltages (0.3/−0.18 V) of SF meso-hybrid memristors, compared with the original and other organic memristors, and displays unique synapse characteristics and the capability of synapse learning. Classical density functional theory Poisson-Nernst-Planck simulations indicate that the enhanced performance is subject to the low potential paths interconnecting the AgNCs@BSA, which guide charges' transport (Ag + ) and deposition in SF films.