Barnacle Cement Proteins-Inspired Tough Hydrogels with Robust,Long-Lasting,and Repeatable Underwater Adhesion

The development of adhesives that can achieve robust and repeatable adhesion to various surfaces underwater is promising; however, this remains a major challenge primarily because the surface hydration layer weakens the interfacial molecular interactions. Herein, a strategy is proposed to develop tough hydrogels that are robust, reusable, and long-lasting for underwater adhesion. Hydrogels from cationic and aromatic monomers with an aromatic-rich composition inspired by the amino acid residuals in barnacle cement proteins are synthesized. The hydrogels are mechanically strong and tough (elastic modulus 0.35 MPa, fracture stress 1.0 MPa, and fracture strain 720%), owing to the interchain π–π and cation–π interactions. In water, the hydrogels firmly adhere to diverse surfaces through interfacial electrostatic and hydrophobic interactions (adhesion strength of 180 kPa), which allows for instant adhesion and reversibility (50 times). Moreover, the hydrogel shows long-lasting adhesion in water for months (100 days). Novel adhesive hydrogels may be useful in many applications, including underwater transfer, water-based devices, underwater repair, and underwater soft robots.     

Microtemplated Electrowetting for Fabrication of Shape-Controllable Microdomes in Extruded Microsucker Arrays toward Octopus-Inspired Dry/Wet Adhesion

Inspired by the prominent adhesion ability of octopus suckers, many dry/wet adhesives with specific micro-structure have been fabricated for applications in smart robots, manipulators, and medical treatments. However, the reported octopus-inspired adhesive patches are either suction-assistant without tight-sealing, or suction-sealed but inefficient under both dry/wet environments. Here, a microtemplated electrowetting method is developed for the fabrication of reversible dry/wet adhesive pads consisting of extruded microsuckers with suction-enhanced microdomes and sealing-ring tips. The mechanism toward the morphology regulation of microdomes illustrates the uneven electrohydrodynamic force on the liquid–air interface that changes the liquid meniscus and achieves the precise regulation of the microdomes curvature ratio (from 0.45 to 0.74). The tip spacing can be controlled (from 0 to 50 µm) by using different templates. Theoretical and experimental insights into the mechanism of the microdomes morphology and the tip spacing on adhesion are discussed. With optimized microdomes and maximized sealing-tips, this adhesive patch generates strong and repeatable adhesion on a silicon wafer in both air (≈ 86 kPa) and underwater (≈ 61 kPa) environments. Besides, considerable adhesion to the rough surfaces are also revealed. Its adhesion ability is demonstrated with stable transportation of various objects under air/underwater environments, providing a potential application in cross-media operation.     

Bringing Hetero‐Polyacid‐Based Underwater Adhesive as Printable Cathode Coating for Self‐Powered Electrochromic Aqueous Batteries

The advent of electrochromic aqueous batteries represents a promising trend in the development of smart and environmentally friendly energy storage devices. However, it remains a great challenge to integrate electrochromic, flexible, and patterned features into a single battery unit through a simple operation. Herein, an entirely new class of hetero‐polyacid‐based underwater adhesives is designed and synthesized by combining the redox properties of hetero‐polyacids and the water‐resistant binding of adhesives in single system. The hybrid underwater adhesives not only serve as printable electrode coatings in aqueous solution but also offer unique electrochromic feature for guiding the convenient fabrication of self‐powered electrochromic aqueous battery. The reversible discharging and H₂O₂ assistant charging behavior is also demonstrated. This kind of wet and electrochromic adhesive with excellent toleration of mechanical deformation offers great promise in developing flexible and smart energy storage configuration, which provides a user‐device interface platform allowing one to evaluate the battery's charging state based on the naked eye–visible change in color.     

Polymer Pressure-Sensitive Adhesive with A Temperature-Insensitive Loss Factor Operating Under Water and Oil

Loss factor tan δ determines the viscoelasticity of a material. Higher or lower loss factor tanδ (>1 or <1) suggests a viscous or elastic material. Most polymer pressure-sensitive adhesives (PSAs) possess a limited operational temperature range (near room temperature), above which the PSAs trend to be more viscous (un-crosslinked) or more elastic (crosslinked), and below which PSAs become more elastic. These properties are unfavorable for PSA operation. Herein, an underwater PSA possessing short hydrophobic side chains and weak hydrogen bond interactions are described. Proper modulus and stable loss factor close to 1 contributes to an efficient adhesion underwater over a temperature range of 0–100 °C. Moreover, by introducing Teflon particles, the adhesion can be operated under silicon oil from room temperature to 150 °C due to the formation of a drainage surface structure and its temperature insensitivity.     

Self‐Hydrophobization in a Dynamic Hydrogel for Creating Nonspecific Repeatable Underwater Adhesion

Adhesive hydrogels are widely applied for biological and medical purposes; however, they are generally unable to adhere to tissues under wet/underwater conditions. Herein, described is a class of novel dynamic hydrogels that shows repeatable and long‐term stable underwater adhesion to various substrates including wet biological tissues. The hydrogels have Fe³⁺‐induced hydrophobic surfaces, which are dynamic and can undergo a self‐hydrophobization process to achieve strong underwater adhesion to a diverse range of dried/wet substrates without the need for additional processes or reagents. It is also demonstrated that the hydrogels can directly adhere to biological tissues in the presence of under sweat, blood, or body fluid exposure, and that the adhesion is compatible with in vivo dynamic movements. This study provides a novel strategy for fabricating underwater adhesive hydrogels for many applications, such as soft robots, wearable devices, tissue adhesives, and wound dressings.     

Pressure Sensitive Adhesion of an Elastomeric Protein Complex Extracted From Squid Ring Teeth

The pressure sensitive adhesion characteristic of a protein complex extracted from squid ring teeth (SRT), which exhibits an unusual and reversible transition from a solid to a melt, is studied. The native SRT is an elastomeric protein complex that has standard amino acids, and it does not function as adhesives in nature. The SRT can be thermally shaped into any 3D geometry (e.g., thin films, ribbons, colloids), and it has a glass transition temperature of 32 °C in water. Underwater adhesion strength of the protein film is approximately 1.5–2.5 MPa. The thermoplastic protein film could potentially be used in an array of fields, including dental resins, bandages for wound healing, and surgical sutures in the body.     

Superior Low-Temperature Reversible Adhesion Based on Bio-Inspired Microfibrillar Adhesives Fabricated by Phenyl Containing Polydimethylsiloxane Elastomers

Gecko-inspired microfibrillar adhesives have achieved great progress in microstructure design and adhesion improvement over the past two decades. Space applications nowadays show great interest in this material for the characteristics of reversible adhesion and universal van der Waals interactions. However, the impact of harsh environment of space on the performance of microfibrillar adhesives, especially the extreme low temperature, is rarely addressed. Herein, microfibrillar adhesives fabricated by phenyl containing polydimethylsiloxane (p-PDMS) elastomers with superior low-temperature reversible adhesion is proposed. p-PDMS elastomers are synthesized through one-pot anionic ring-opening copolymerization, and the resulting elastomers become non-crystallizable with excellent low-temperature elasticity. Low-temperature adhesion tests demonstrate that the adhesion strength of microfibrillar adhesives fabricated by p-PDMS elastomers can be well maintained to as low as −120 °C. In contrast, the adhesion strength of pure PDMS microfibrillar adhesive reduces more than 50% below its crystallization temperature. The low-temperature cyclic adhesion tests further demonstrate that p-PDMS microfibrillar adhesives exhibit superior reversible adhesion compared to that of PDMS microfibrillar adhesives, owing to the sustainable conformal contact and even distribution of loads over repeated cycles. This study provides a new fabrication strategy for microfibrillar adhesives, and is beneficial for the practical application of microfibrillar adhesives.     

Supramolecular β‐Sheet Suckerin–Based Underwater Adhesives

Nature has evolved several molecular strategies to ensure adhesion in aqueous environments, where artificial adhesives typically fail. One recently‐unveiled molecular design for wet‐resistant adhesion is the cohesive cross‐β structure characteristic of amyloids, complementing the well‐established surface‐binding strategy of mussel adhesive proteins based on 3,4‐l ‐dihydroxyphenylalanine (Dopa). Structural proteins that self‐assemble into cross β‐sheet networks are the suckerins discovered in the sucker ring teeth of squids. Here, light is shed on the wet adhesion of cross‐β motifs by producing recombinant suckerin‐12, naturally lacking Dopa, and investigating its wet adhesion properties. Surprisingly, the adhesion forces measured on mica reach 70 mN m^?1, exceeding those measured for all mussel adhesive proteins to date. The pressure‐sensitive adhesion of artificial suckerins is largely governed by their cross‐β motif, as evidenced using control experiments with disrupted cross‐β domains that result in complete loss of adhesion. Dopa is also incorporated in suckerin‐12 using a residue‐specific incorporation strategy that replaces tyrosine with Dopa during expression in Escherichia coli. Although the replacement does not increase the long‐term adhesion, it contributes to the initial rapid contact and enhances the adsorption onto model oxide substrates. The findings suggest that suckerins with supramolecular cross‐β motifs are promising biopolymers for wet‐resistant adhesion.     

Elastic Energy Storage Enabled Magnetically Actuated,Octopus-Inspired Smart Adhesive

Octopus suckers offer remarkable adhesion performance against nonporous surfaces and have inspired extensive research to develop artificial adhesives. However, most of existing octopus-inspired adhesives are either passive without an actuation strategy or active but not energy efficient. Here, a novel design of a magnetically actuated, energy-efficient smart adhesive with rapidly tunable, great switchable, and highly reversible adhesion strength inspired by the elastic energy storage mechanism in octopus suckers is reported. The smart adhesive features two cavities separated by an elastic membrane with the upper cavity filled with magnetic particles while the lower one empty. The deformation of the elastic membrane can be actively controlled by an external magnetic field to change the cavity volume, thus generating a cavity-pressure-induced adhesion. Systematically experimental and theoretical studies reveal the fundamental aspects of design and operation of the smart adhesive and give insights into the underlying adhesion mechanisms. Demonstrations of this smart adhesive in transfer printing and manipulation of various surfaces in both dry and wet environments illustrate the potential for deterministic assembly and industrial or robotic manipulation.     

水下实验有线测量技术综述

水下实验是海洋工程、船舶工程、海洋资源开发、水下兵器研制等诸多领域的必要手段,有线测量是水下实验和水下测量的重要手段,它为水下实验提供数据支撑和评判依据,是一项基础性的工作.本文针对水下实验领域特点,详细阐述了有线测量水下实验技术的特点和着重点,综合介绍了水下实验测量技术.     

Deep Eutectic Solvents-Based Ionogels with Ultrafast Gelation and High Adhesion in Harsh Environments

Adhesive materials have recently drawn intensive attention due to their excellent sealing ability, stimulating advances in materials science and industrial usage. However, reported adhesives usually exhibit weak adhesion strength, require high pressure for strong bonding, and display severe adhesion deterioration in various harsh environments. In this study, instead of water or organic solvents, a deep eutectic solvent (DES) is used as the medium for the photopolymerization of zwitterionic and polarized monomers, thus generating a novel ionogel with tunable mechanical properties. Multiple hydrogen bonds and electrostatic interactions between DES and monomers facilitated ultrafast gelation and instant bonding without any external pressure, which has rarely been reported previously. Furthermore, high adhesion in different harsh environments (e.g., water, acidic and basic buffers, and saline solutions) and onto hydrophilic (e.g., glass and tissues) and hydrophobic (e.g., polymethyl methacrylate, polystyrene, and polypropylene) adherends is demonstrated. Also, the high stretchability of the ionogel at extreme temperatures (−80 and 80 °C) indicates its widespread applications. Furthermore, the biocompatible ionogel shows high burst pressure onto stomach and intestine tissues to prevent liquid leakage, highlighting its potential as an adhesive patch. This ionogel provides unprecedented opportunities in the packaging industry, marine engineering, medical adhesives, and electronic assembly.     

A Mechanically Robust,Self-Healing,and Adhesive Biomimetic Camouflage Ionic Conductor for Aquatic Environments

Flexible conductive materials capable of simulating transparent ocean organisms have garnered interest in underwater motion monitoring and covert communication applications. However, the creation of underwater flexible conductors that possess mechanical robustness, adhesion, and self-healing properties remains a challenge. Herein, hydrophobic interaction is combined with electrostatic interaction to obtain a solvent-free transparent poly(ionic liquid) elastomer (PILE) fabricated using soft acrylate monomers and acrylate ionic liquids. The synergy of hydrophobic and electrostatic interactions can eliminate the hydration of water molecules underwater, giving the PILE adjustable fracture strength, good elasticity, high stretchability, high toughness, fatigue resistance, underwater self-healing ability, underwater adhesion, and ionic conductivity. As a result, the transparent iontronic sensor generated from the PILE can achieve multifunctional sensing and human motion detection with high sensitivity and stability. In particular, the sensor can also transmit information underwater through stretching, pressing, and non-contact modes, demonstrating its huge potential in underwater flexible iontronic devices.     

Towards the Next Level of Bioinspired Dry Adhesives: New Designs and Applications

This Feature Article aims to highlight our recent efforts to develop more robust gecko‐inspired dry adhesives and their applications. Due to recent progress in micro‐ and nanofabrication techniques, it is possible to fabricate highly sophisticated multiscale, hierarchical structures using various polymer materials. In addition, the adhesion strength of synthetic dry adhesives has been shown to be similar to or exceed that of real gecko foot‐hair by several times. Therefore, it is timely and appropriate to drive the research of gecko‐inspired dry adhesives into a new epoch by investigating more robust dry adhesive structures, efficient detachment mechanisms, and new applications. In this Feature Article, we present a series of our recent achievements to overcome some of the limitations of gecko‐like hair structures such as rough surface adaptation, durability, and controlled geometry, with particular emphasis on materials issues and detachment mechanism. For potential applications, a clean transportation device and a biomedical skin patch are briefly described to expand the application realm from the well‐known wall climbing robot.     

水下短距离微波无线通信实验探索

以上海市各区不同泳池为样本水源,使用微波谐振腔法获得样本的品质因数和电导率参数,建立了微波信号在泳池中传播的路径损耗模型,并评估了水下无线传输距离,选定水下无线通信实验的频率。设计加工了微波发射前端天线及相关电路模块并用于水下测试。实验综合运用了微波理论、天线技术、电磁场仿真设计、微波器件加工与测量等电磁场与微波技术专业知识,具有较强的工程应用价值。     

Bioinspired Mineral–Organic Bone Adhesives for Stable Fracture Fixation and Accelerated Bone Regeneration

The use of hydrogel‐based bone adhesives has the potential to revolutionize the clinical treatment of bone repairs. However, severe deficiencies remain in current products, including cytotoxicity concerns, inappropriate mechanical strength, and poor fixation performance in wet biological environments. Inspired by the unique roles of glue molecules in the robust mechanical strength and fracture resistance of bone, a design strategy is proposed using novel mineral–organic bone adhesives for strong water‐resistant fixation and guided bone tissue regeneration. The system leveraged tannic acid (TA) as a phenolic glue molecule to spontaneously co‐assemble with silk fibroin (SF) and hydroxyapatite (HA) in order to fabricate the inorganic–organic hybrid hydrogel (named SF@TA@HA). The combination of the strong affinity between SF and TA along with sacrificial coordination bonds between TA and HA significantly improves the toughness and adhesion strength of the hydrogel by increasing the amount of energy dissipation at the nanoscale. This in turn facilitated adequate and stable fixation of bone fracture in wet biological environments. Furthermore, SF@TA@HA promotes the regeneration of bone defects at an early stage in vivo. This work presents a type of bioinspired bone adhesive that is able to provide stable fracture fixation and accelerated bone regeneration during the bone remodeling process.     

Bio-Inspired Adhesive with Reset-On Demand,Reuse-Many (RORM) Modes

Development of tough, reusable adhesives is important, but remains a major challenge, especially in water. A tough reusable adhesive that resets entirely to its virgin condition when needed is reported using caffeic acid. Here, caffeic acid is employed as adhesive moiety to achieve such the functions due to its dual characteristics: an adhesive moiety from mussel-inspired catechol and a photo-reversible crosslink from cinnamic acid. Adhesion involves a two-step process. First, the caffeic acid-functionalized polymer is applied to the adherend, followed by UV irradiation (peak wavelength of light-emitting diode, λ_P: 365 nm) to form a durable pre-applied adhesive (PAA) layer through crosslinking among the caffeic acid moieties. Second, thermal activation of the PAA layer ensures repeated adhesion to a variety of adherends ( R euse- M any mode). The cyclic dimer of the caffeic acid moiety is de-crosslinked by UV irradiation at λ_P: 254 nm. This allows the complete removal of the adhesive residues from the adherends when the adhesive is no longer needed ( R eset- O n demand mode). Furthermore, using magnetic nanoparticles, the caffeic acid-functionalized polymer can be activated remotely under water by magnetic induction heating. This study paves the way for the rational design of bio-inspired adhesives that outperform nature using plant-derived raw materials.     

Fibrillar Elastomeric Micropatterns Create Tunable Adhesion Even to Rough Surfaces

Biologically inspired, fibrillar dry adhesives continue to attract much attention as they are instrumental for emerging applications and technologies. To date, the adhesion of micropatterned gecko‐inspired surfaces has predominantly been tested on stiff, smooth substrates. However, all natural and almost all artificial surfaces have roughnesses on one or more different length scales. In the present approach, micropillar‐patterned PDMS surfaces with superior adhesion to glass substrates with different roughnesses are designed and analyzed. The results reveal for the first time adhesive and nonadhesive states depending on the micropillar geometry relative to the surface roughness profile. The data obtained further demonstrate that, in the adhesive regime, fibrillar gecko‐inspired adhesive structures can be used with advantage on rough surfaces; this finding may open up new applications in the fields of robotics, biomedicine, and space exploration.     

Ambiently and Mechanically Stable Ionogels for Soft Ionotronics

Stretchable ionic conductors such as hydrogels and ionic-liquid-based gels (aka ionogels) have garnered great attention as they enable the development of soft ionotronics. Notably, soft ionotronic devices inevitably operate in humid environments or under mechanical loads. However, many previously reported hydrogels and ionogels, however, are unstable in environments with varying humidity levels owing to hydrophilicity, and their liquid components (i.e., ionic liquid, water) may leak easily from polymer matrices under mechanical loads, causing deterioration of device performance. This work presents novel hydrophobic ionogels with strong ionic liquid retention capability. The ionogels are ambiently and mechanically stable, capable of not absorbing moisture in environments with high relative humidity and almost not losing liquid components during long periods of mechanical loading. Moreover, the ionogels exhibit desirable conductivity (10⁻⁴–10⁻⁵ S cm⁻¹), large rupturing strain (>2000%), moderate fractocohesive length (0.51–1.03 mm), and wide working temperature range (−60 to 200 °C). An ionic skin is further designed by integrating the concept of sensory artificial skins and triboelectric nanogenerators, which can convert multiple stimuli into various types of signals, including resistance, capacitance, short-circuit current, and open-circuit voltage. This work may open new avenues for the development of soft ionotronics with stable performance.     

Phototunable Underwater Oil Adhesion of Micro/Nanoscale Hierarchical‐Structured ZnO Mesh Films with Switchable Contact Mode

Controllable surface adhesion of solid substrates has aroused great interest both in air and underwater in solving many challenging interfacial science problems such as robust antifouling, oil‐repellent, and highly efficient oil/water separation materials. Recently, responsive surface adhesion, especially switchable adhesion, under external stimulus in air has been paid more and more attention in fundamental research and industrial applications. However, phototunable underwater oil adhesion is still a challenge. Here, an approach to realize phototunable underwater oil adhesion on aligned ZnO nanorod array‐coated films is reported, via a special switchable contact mode between an unstable liquid/gas/solid tri‐phase contact mode and stable liquid/liquid/solid tri‐phase contact mode. The photo‐induced wettability transition to water and air exists (or does not) in the micro/nanoscale hierarchical structure of the mesh films, playing important role in controlling the underwater oil adhesion behavior. This work is promising in the design of novel interfacial materials and functional devices for practical applications such as photo‐induced underwater oil manipulation and release, with loss‐free oil droplet transportation.     

TAPE: A Medical Adhesive Inspired by a Ubiquitous Compound in Plants

Adhesives play an important role in industrial fields such as electronics, architectures, energy plantation, and others. However, adhesives used for medical purpose are rather under‐developed compared with those used in industry and consumer products. One key property required for medical adhesives is to maintain their adhesiveness in the presence of body fluid. Here, an entirely new class of medical adhesives called TAPE is reported; this is produced by intermolecular hydrogen bonding between a well‐known polyphenol compound, tannic acid, and poly(ethylene glycol). The preparation method of TAPE is extremely easy, forming a few liters at once by just the simple mixing of the two compounds without any further chemical synthetic procedures. TAPE shows a 250% increase in adhesion strength compared with fibrin glue, and the adhesion is well maintained in aqueous environments. It is demonstrated that TAPE is an effective hemostatic material and a biodegradable patch for detecting gastroesophageal reflux disease in vivo. Widespread use of TAPE is anticipated in various medical and pharmaceutical applications such as muco‐adhesives, drug depots, and others, because of its scalability, adhesion, and facile preparation.