Hindered Urea Bonds Research Articles

Self-Healing Polyurethane-Urea Elastomers with High Strength and Toughness Based on Dynamic Hindered Urea Bonds and Hydrogen Bonds

Self-Healing Polyurethane-Urea Elastomers with High Strength and Toughness Based on Dynamic Hindered Urea Bonds and Hydrogen Bonds

Room temperature self-healing and reprocessing elastomer with dynamic bonds for flexible wearable sensor

The production of room-temperature (RT) self-healing elastomers with good mechanical properties is significant for application in soft electronics, yet remains a challenge in material design. Herein, we present an effective and feasible approach to create RT self-healing cross-linked elastomers (CEs) through photo-initiated copolymerization. A key feature is the incorporation of 2,7-dihydroxynaphthalene and alicyclic diisocyanate into the polymer backbone as hard domains, along with the rational optimization of the soft segments. In addition, urethane-based H-bonding interactions, acting as sacrificial bond, contribute to the high toughness of the CEs. The resulting CEs exhibit desirable mechanical performances, including a tensile strength of 12.9 MPa, an elongation at break of approximately 1243 %, and a high toughness of 68.64 MJ m–3. Furthermore, by integrating a flexible PTMEG-based polymeric chain and hindered urea bonds into the backbone, the chain mobility and dynamic nature of the CEs are improved. The CEs are capable of reprocessing and self-healing at RT within 30 min upon scratching, with a self-healing efficiency in toughness reaching 99.64 %. The dynamic networks are evidenced by rheological test, stress relaxation analysis, as well as creep and recovery experiments. These CEs, characterized by their superior properties, hold promise for applications in flexible wearable electronics.

Nanocomposites of Poly(n-Butyl Acrylate) with Fe3O4: Crosslinking with Hindered Urea Bonds, Reprocessing and Related Functional Properties.

In this contribution, we reported the synthesis of the nanocomposites of poly(n-butyl acrylate) with Fe3O4 nanoparticles (NPs) via dynamic crosslinking of poly(n-butyl acrylate)-grafted Fe3O4 NPs with hindered urea bonds (HUBs). Towards this end, the surfaces of Fe3O4 NPs were grafted with poly(n-butyl acrylate-ran-2-(3-tert-butyl-3-ethylureido)ethyl acrylate) chains [denoted as Fe3O4-g-P(BA-r-TBEA)] via living radical polymerization. Thereafter, 1,2-bis(tert-butyl)ethylenediamine was used as a crosslinker to afford the organic-inorganic networks with variable contents of Fe3O4 NPs and crosslinking densities. It was found that the fine dispersion of Fe3O4 NPs in the matrix of poly(n-butyl acrylate) was achieved. The nanocomposites exhibited excellent reprocessing properties, attributed to the introduction of HUBs. Owing to the crosslinking, the nanocomposites displayed excellent shape memory properties. Further, the nanocomposites possessed photo- and magnetic-thermal properties, which were inherited from Fe3O4 NPs. These functional properties allow triggering the shape shifting of the nanocomposites in an uncontacted fashion.

Non‐Isocyanate Synthesis of Covalent Adaptable Networks Based on Dynamic Hindered Urea Bonds: Sequential Polymerization and Chemical Recycling

AbstractThe development of environmentally sustainable processes for polymer recycling is of paramount importance in the polymer industry. In particular, the implementation of chemical recycling for thermoset polymers via covalent adaptable networks (CANs), particularly those based on the dynamic hindered urea bond (HUB), has garnered intensive attention from both the academic and industrial sectors. This interest stems from its straightforward chemical structure and reaction mechanism, which are well‐suited for commercial polyurethane and polyurea applications. However, a substantial drawback of these CANs is the requisite use of toxic isocyanate curing agents for their synthesis. Herein, we propose a new HUB synthesis pathway involving thiazolidin‐2‐one and a hindered amine. This ring‐opening reaction facilitates the isocyanate‐free formation of a HUB and enables sequential reactions with acrylate and epoxide monomers via thiol–Michael and thiol–epoxy click chemistry. The CANs synthesized using this methodology exhibit superior reprocessability, chemical recyclability, and reutilizability, facilitated by specific catalytic and solvent conditions, through the reversible HUB, thiol–Michael addition, and transesterification processes.

Bioinspired waterproof and self-healing Photonic-Ionic skin for underwater interactive sensing

Bioinspired photonic-ionic skins (PI-skins) possessing multiple signals considerably promote the development of soft ionoelectronics owing to the fascinating interactive sensing capabilities. Unfortunately, swelling and leakage in aqueous environments are significantly detrimental to the stability and durability of underwater sensing. Herein, a novel PI-skin with waterproof, self-healing, and highly resilient properties is ingeniously fabricated via integrating the photonic array and dynamically covalently crosslinking fluorine-rich ionogel. Benefiting from the strain-modulated nanostructure and ionic conduction, the PI-skin achieves unique dual-signal sensing capability with sensitive mechanochromic performance and synchronous electrical response. Furthermore, the synergistic water repellency of the trifluoromethyl on the skeleton and the long alkyl chain modified hydrophobic ionic liquid (IL) inhibit swelling and leakage, significantly enhancing underwater stability. Notably, the exchangeable hindered urea bonds (HUBs) were judiciously introduced to construct a stable dynamically covalently crosslinking network, achieving efficient self-healing and high resilience simultaneously. The PI-skin with excellent adhesion and durability demonstrates the application potential in dual-signal underwater sensing and wireless information transmission. This work offers innovative design inspirations for the advancement of multifunctional artificial skins, intelligent interactive devices, and high-performance wearable iontronics.

Non-Isocyanate Synthesis of Covalent Adaptable Networks Based on Dynamic Hindered Urea Bonds: Sequential Polymerization and Chemical Recycling.

The development of environmentally sustainable processes for polymer recycling is of paramount importance in the polymer industry. In particular, the implementation of chemical recycling for thermoset polymers via covalent adaptable networks (CANs), particularly those based on the dynamic hindered urea bond (HUB), has garnered intensive attention from both the academic and industrial sectors. This interest stems from its straightforward chemical structure and reaction mechanism, which are well-suited for commercial polyurethane and polyurea applications. However, a substantial drawback of these CANs is the requisite use of toxic isocyanate curing agents for their synthesis. Herein, we propose a new HUB synthesis pathway involving thiazolidin-2-one and a hindered amine. This ring-opening reaction facilitates the isocyanate-free formation of a HUB and enables sequential reactions with acrylate and epoxide monomers via thiol-Michael and thiol-epoxy click chemistry. The CANs synthesized using this methodology exhibit superior reprocessability, chemical recyclability, and reutilizability, facilitated by specific catalytic and solvent conditions, through the reversible HUB, thiol-Michael addition, and transesterification processes.

Design and preparation of low-temperature curable, tough, repairable epoxy containing hindered urea-based dynamic reversible bonds

ABSTRACT Traditional epoxy resins are of technological significance for structural adhesives and composite materials, as well as many others. However, brittleness limits its further development, and achieving a combination of toughness and rigidity in epoxy networks remains a great challenge. In this work, we designed and synthesized low-temperature curable, tough and repairable epoxy networks via hindered urea bond (HUB) crosslinking strategies. Mechanical testing revealed that the material exhibited simultaneously improved toughness and stiffness, and specifically, tensile strength, elongation at break, and toughness were able to reach 78.2 MPa, 8.61%, and 4.63 MJ · m−3, respectively. More importantly, the dynamic exchange of HUB dispersed between polymer chains enables HUB crosslinked epoxy with thermal-triggered reparability and recyclability. In addition, thermal properties, chemical stability and water resistance of toughened epoxy samples were also characterized. This work provides a practical guidance for the exploration of high-performance epoxy with the potential to be extended to other polymers.

Programmable, Self-Healable, and Photochromic Liquid Crystal Elastomers Based on Dynamic Hindered Urea Bonds for Biomimetic Flowers.

Recently, researchers have been exploring the use of dynamic covalent bonds (DCBs) in the construction of exchangeable liquid crystal elastomers (LCEs) for biomimetic actuators and devices. However, a significant challenge remains in achieving LCEs with both excellent dynamic properties and superior mechanical strength and stability. In this study, a diacrylate-functionalized monomer containing dynamic hindered urea bonds (DA-HUB) is employed to prepare exchangeable LCEs through a self-catalytic Michael addition reaction. By incorporating DA-HUB, the LCE system benefits from DCBs and hydrogen bonding, leading to materials with high mechanical strength and a range of dynamic properties such as programmability, self-healing, and recyclability. Leveraging these characteristics, bilayer LCE actuators with controlled reversible thermal deformation and outstanding dimensional stability are successfully fabricated using a simple welding method. Moreover, a biomimetic triangular plum, inspired by the blooming of flowers, is created to showcase reversible color and shape changes triggered by light and heat. This innovative approach opens new possibilities for the development of biomimetic and smart actuators and devices with multiple functionalities.

High performance, self-healable and recyclable epoxy thermosets by integrating dynamic hindered urea bonds

During recent decades, intrinsic self-healable thermosetting materials by integrating dynamic covalent bonds (DCBs) have been widely used. In this study, through the molecular structure design, a flexible polyurethane curing agent based on hindered urea bonds (HUBs) was successfully prepared by the reaction of Hexamethylene diisocyanate trimer (THDI) and sterically hindered secondary amine, which was further used as a curing agent to cure epoxy resin. Therefore, a new type of epoxy thermosetting material (TBEP) with dynamic hindered urea bond was synthesized and the preparation and performance of TBEP were confirmed and characterized by infrared spectroscopy, thermomechanical analysis and thermal stability test. The results show that the HUBs are successfully integrated into the epoxy resin and endow the epoxy thermosets with brilliant self-healable, reprocessable, recyclable and shape memory properties. Simultaneously, the existence of flexible polyurethane chain in the crosslinking network effectively solves the brittleness problem of epoxy resin, promotes the mechanical performance of epoxy thermosets, and further broadens the its application field. This work provides a simple and efficient method to design flexible and self-healable epoxy thermosets with brilliant mechanical performance, which solves the contradiction between outstanding mechanical properties and self-healing ability of epoxy resin to some extent, and is environmentally friendly and cost-effective in acquisition and application.

Biobased, self-healing, and recyclable polyurethane derived hydrogel-elastomer hybrids for efficient lubrication

Developing biobased hydrogel-elastomer hybrids with stable lubrication derived from self-healing and recyclable polymer matrix poses a key challenge in the field of medical devices. Herein, we reported a novel hydrogel-elastomer hybrid incorporating a tung oil (TO)-based, self-healing, and recyclable polyurethane (PU) substrate that exhibits exceptional hydrophilic and lubricating properties. Initially, a series of UV-curable PU elastomers containing dynamic hindered urea bonds (HUBs) derived from renewable TO were prepared. By adjusting the ratios of the cross-linking agent TO-based polyol and the chain-extending agent polytetramethyleneglycol, the mechanical and thermal properties of these elastomers could be tuned well. The as-prepared PU elastomers demonstrated remarkable dynamic properties, attributed to the dissociation and recombination of HUBs, enabling efficient self-healing and effective recycling through solvent or hot-pressing methods while preserving their mechanical properties. Furthermore, functional hydrogel-elastomer hybrids were obtained by applying UV-initiated polymerization method to generate hydrogel coatings onto the optimized PU elastomer surface. Compared to the pristine PU material, the resulting hydrogel-elastomer hybrids exhibited excellent lubricity in aqueous environments, resulting from the formation of a robust hydration layer facilitated by electrostatic forces. Overall, our current research work provides key design inspiration for developing next-generation medical devices from sustainable and recyclable functional biomaterials.

A photocurable polyurethane elastomer for digital light processing with comprehensive reusability based on dynamic hindered urea bonds

Digital Light Processing (DLP) 3D printing has emerged as a highly promising technique, enabling the fabrication of intricate geometric structures with ease and precision, without the need for complex mold-making processes. However, the printed objects are typically crosslinked photopolymers that cannot be reshaped, reprocessed and recycled. Herein, we successfully synthesize a dynamic soft polymer crosslinker containing hindered urea bonds (HUBs) composed of polyurethane acrylate prepolymer and tri-functional for recyclable DLP 3D printing. Contributing to the dynamic thermal response of HUBs, the printed objects can be recycled in the initial printing inks at 80 °C in 2h and the obtained recycled ink can be reprinted by DLP achieving a low viscosity and high printing resolution. In addition, the printed objects can be reprocessed by hot-press at 110 °C for 30 min upon a pressure of 5 MPa. By a reasonable proportion of monomer and crosslinker, a series of photocured elastomers were successfully prepared, in which mechanical properties could be tailored by changing the content of the crosslinker. The resulting products exhibited some fascinating attributes, such as excellent fatigue resistance, thermodynamic stability, and transparency. Significantly, the resin can regain initial 3D printing capability after undergoing solvent recycling, which maintains its printing resolution and excellent mechanical properties. This innovative design strategy not only alleviates environmental impact but also plays a pivotal role in developing the DLP 3D printing industry by tackling the long-standing issue of resin recyclability.

Reprocessed, shape-memory and self-healing robust epoxy resin by hindered urea bond

Given the fossil fuel energy crisis and serious environmental pollution in recent years, one way to alleviate the problem is to introduce dynamic covalent chemistry into thermosetting resins to give the material processable and recyclable properties, creating a new type of eco-friendly material. Hindered urea bonds can undergo reversible exchange reactions at high temperatures to decompose into amine and isocyanate. This reversible addition reaction is currently a prominent research focus in the development of reprocessable thermosets. In this work, we synthesize a novel curing agent with hindered urea bonds without any catalysts. Then characterize the resulting epoxy vitrimers based on hindered urea bond (HUG-EP) using FT-IR and 1H NMR, confirming the successful introduction of hindered urea bonds into the epoxy resin. A variety of tests are carried out, such as those to assess thermal stability, swelling, shape-memory, re-processability and tensile strength. The results demonstrate that HUG-EP can rapidly self-healed within 20 min at 160 °C, with the tensile strength was maintained at 87.15 % of the original during the welding experiments. Furthermore, it can also be reprocessed by hot-pressing several times at 160 °C. Thus, the introduction of hindered urea bonds into the crosslinked network proves to be an effective and practicable approach for producing thermosetting resins with reprocessing, self-healing, and shape memory capabilities.

Organic-inorganic polyureas with benzyl hindered urea bonds and POSS cages in the main chains: Synthesis, shape memory and reprocessing properties

The organic–inorganic polyureas with benzyl hindered urea bonds (HUBs) and POSS cages as the main-chain structural units were synthesized via the polyaddition of 4,4′-diphenylmethane diisocyanate with α,ω-dibenzyl diamines including α,ω-dibenzylamino-terminated poly(ethylene oxide), N,N’-dibenzylhexamethylene-1,6-diamine and 3,13-dibenzylaminoanilino double decker silsesquioxane. The organic–inorganic PUreas were microphase-separated, in which the POSS cages were self-assembled into the microdomains via POSS-POSS interactions. The POSS microdomains acted as the physical crosslinking points and thus the organic–inorganic PUreas behaved as the crosslinked elastomers; the physical crosslinking remained thermally stable even at elevated temperature as high as 200 °C. In spite of the high thermal stability, the networks can be reprocessed with the plasticity in solids via the dynamic exchange of benzyl HUBs. Due also to the physical crosslinking, the organic–inorganic PUreas possessed the excellent shape memory properties; the original shapes were re-configurable by taking advantage of the benzyl HUBs in the main chains.

Fast‐Photocurable, Mechanically Robust, and Malleable Cellulosic Bio‐Thermosets Based on Hindered Urea Bond for Multifunctional Electronics

AbstractMalleable thermosets as dynamic covalent cross‐linked polymers, simultaneously possessing the advantages of thermosets and thermoplastics, have attracted considerable attention. Although several reprocessing concepts have been demonstrated, the fabrication of fast‐curing bio‐based strong and tough malleable thermosets for advanced applications in electronics remains a great challenge. Herein, a novel construction strategy of combining hindered urea bonds (HUB) and radical polymerization is developed to prepare fast‐photocurable and mechanically robust cellulose‐based malleable bio‐thermosets (CMTs). In this strategy, the functional cellulose macromonomer simultaneously has acrylate groups and HUB is first synthesized and employed as a macro‐crosslinker to react with plant oil‐based monomer to construct the malleable bio‐thermosets with “soft (plant oil‐based polymer)” and “hard (rigid cellulose)” phase architecture through the fast photocuring. The CMTs exhibit excellent flexibility and high toughness (2.89 MJ m−3), and the introduction of dynamic HUB endows the CMTs with excellent malleability and reprocessability by heating compression molding or solvent regeneration, the recovery efficiency reached 94.7%. More impressively, the CMTs can be used as substrates to fabricate CMTs/silver composite for anti‐icing or de‐icing devices, and CMTs‐based capacitive sensors for monitoring environmental humidity or human health. This work paves a new strategy to develop new‐generation fast‐photocurable mechanically robust, malleable bio‐thermosets for multifunctional electronic devices.

Universal approach for developing reprocessable and reprintable plant oil-based resins for digital light processing 3D printing

Recently, researchers have shown great interest in the development of biobased and reprintable 3D printing materials for sustainable 3D printing. Herein, a method for developing plant oil (PO)-based digital light processing (DLP) printing resins that are both reprocessable and reprintable is proposed. Biobased UV-curable monomers (POPITs) containing dynamic hindered urea bonds (HUBs) from POs were synthesized via the thiol-ene click reaction. A range of DLP printing resins (POPIT-I) with high biobased content (52.6%–58.1%) were prepared by blending POPITs with the biobased dilute monomer isobornyl acrylate. These resins demonstrated good mechanical and thermal properties (e.g., tensile strength: 45.1–49.5 MPa and Tg: 74–92 °C), as well as high DLP printing quality. Reprocessable DLP printing was employed to fabricate large-volume parts through the dissociation and reorganization of HUBs, thereby reducing printing difficulty and printing time. Additionally, a powder blending and modification method was used to recycle and reprint printed materials. The printing materials, including printed green parts and discarded supporting materials, were milled into micron-sized powders and then blended with POPIT-I to prepare the powder blending resins. The milled powders in the powder blending resins were further modified by 2-(tert-butylamino) ethyl methacrylate to prepare reprinting resins. This process resulted in the grafting of C = C onto the powder surface, which eliminated heterogeneity between the powders and POPIT-I. The mechanical and thermal properties of the reprinting resins were comparable with those of POPIT-I even after three rounds of recycling. Furthermore, the reprinting method reported here is applicable to other dynamic covalent bond-based 3D printing systems.

Robust, self-healing, anti-corrosive waterborne polyurethane urea composite coatings enabled by dynamic hindered urea bonds

To meet the increasing concerns for health, safety, and the environment, traditional solvent coatings are gradually replaced by their waterborne counterparts and the development of robust and self-healing waterborne polymers is showing important application significance. Herein, waterborne polyurethane urea composite coatings (WPUU) with dynamic hindered urea bonds are reported. The dispersion of WPUU synthesized with hindered amine as the chain extender has a smaller particle size. The mussel-inspired polydopamine modification was applied to improve the dispersion and interfacial interactions of carbon nanotubes (CNTs) in the WPUU matrix. Due to the dynamic reversibility of the hindered urea and abundant hydrogen bonding, the resulting WPUU-2T2B can achieve self-healing at 70 °C, also showing good mechanical toughness, the tensile strength of 34.0 MPa and elongation at break of 530 %. After adding the modified CNTs, 10%PDA@CNTs/WPUU demonstrates the tensile strength of 22.4 MPa, elongation at break of 251 % and yield strength of 13.1 M Pa. The self-healing properties of nanocomposites are still retained. The maximum electrical conductivity of the composite coating reaches 56.8 S m−1. The composite coating can recover excellent corrosion resistance in the electrolyte environment after healing, which could ensure its safety and sustainability in the long-term service. We envisage this work offers an idea for the fabrication of environmentally friendly, self-healing, corrosion resistant and electrically conductive coatings with good thermal stability and robust mechanical properties.

Nanoscratch-healing of single and bilayer thin films of hindered urea bond-based self-healable copolymers

In this study, the effects of the surface properties of single and bilayer thin films of hindered urea bond (HUB)-based self-healable copolymers on their scratch-wound formation and self-healing were investigated. Initially, three prepolymers with bulky amine groups, PtB (control), PFtB (hydrophobic), and PMtB (hydrophilic), were synthesised by free-radical polymerisation. Subsequently, they were used to fabricate self-healing copolymers by crosslinking with HDI. The three crosslinked polymers (PtB-H, PFtB-H, and PMtB-H) showed contact angles of 80°, 93°, and 73°, respectively. Moreover, all the single-layer samples showed complete scratch healing within 2 h at ambient temperature, with PFtB-H and PMtB-H showing an initial elastic recovery immediately after scratch formation, unlike PtB-H. The formation of bilayer samples by stepwise coating was confirmed by X-ray photoelectron spectroscopy (XPS). Owing to HUB networks formed on their surface similar to the single-layer, bilayer coatings showed excellent scratch-healing performance at room temperature for nano-scratches with 40–50 nm depth, as indicated by AFM. PMtB-H@PtB-H showed a better scratch-healing performance than PFtB-H@PtB-H, and the scratch-healing ability of PMtB-H@PtB-H was improved by moisture. Their nano-scale self-healing ability was verified by micro-scale scratch tests; scratches with 4–12 µm depth healed completely with ∼100% SHE% at 60 °C.

Design of healable, porous polyurethane with large ionic liquids loading amounts towards ultra-durable pressure sensor

Flexible intelligent sensors have got booming development over the past decades, yet, it is still a huge challenge to construct advanced sensors with long service life and superb durability. Herein, a novel porous capacitance pressure sensor with ultra-durability via sugar template method was prepared successfully by impregnating non-volatile, highly conductive ionic liquids (ILs) into polyurethane (PU-DBTDA5) matrix. As a consequence of the rich hydrogen bonding networks and dynamic hindered urea bond in the polymer chain, the as-prepared PU-DBTDA5 matrix shows excellent self-healing ability (99 %). The ionic liquid-soluble polyethylene glycol (PEG1000) serving as soft segment endows PU-DBTDA5 with ultra-absorption ability of ILs (absorbing ILs over three times to its own weight within 5 min). The pressure sensor with porous structure shows outstanding anti-fatigue ability as well as good sensitivity (S1 = 0.82 kPa−1, S2 = 1.04 kPa−1), and it can even monitor tiny strain as low as 0.5 %. More importantly, due to the well combination of the PU-DBTDA5 with excellent self-healing ability and the non-volatile ionic liquids, not only the healed sensor, but the sensor stored at room environment over 100 days both exhibit stable electronic signals similar to that of freshly-prepared foam sensor in 3000 uninterrupted compression tests, being strong evidence of its ultra-durability.

3D printing of dynamic covalent polymer network with on-demand geometric and mechanical reprogrammability

Delicate geometries and suitable mechanical properties are essential for device applications of polymer materials. 3D printing offers unprecedented versatility, but the geometries and mechanical properties are typically fixed after printing. Here, we report a 3D photo-printable dynamic covalent network that can undergo two independently controllable bond exchange reactions, allowing reprogramming the geometry and mechanical properties after printing. Specifically, the network is designed to contain hindered urea bonds and pendant hydroxyl groups. The homolytic exchange between hindered urea bonds allows reconfiguring the printed shape without affecting the network topology and mechanical properties. Under different conditions, the hindered urea bonds are transformed into urethane bonds via exchange reactions with hydroxyl groups, which permits tailoring of the mechanical properties. The freedom to reprogram the shape and properties in an on-demand fashion offers the opportunity to produce multiple 3D printed products from one single printing step.

Vat photopolymerization 3D printing of transparent, mechanically robust, and self-healing polyurethane elastomers for tailored wearable sensors

As flexible sensors are soft and prone to damage in practical applications, stretchable conductors with self-healing capacity can extend their service life. However, existing vat photopolymerization (VP) 3D-printed self-healing elastomers generally have a tensile strength of less than 1 MPa, which limits the load-bearing capacity and application range of the flexible sensors. Herein, a photocurable oligomer comprising dynamic hindered urea bonds (HUBs) was synthesized to prepare self-healing elastomers. By using a surface-functionalized spherical nano-silica (Nano-SiO2) for reinforcement modification, the tensile strength and elongation at break of the 3D-printed elastomer were enhanced by 73.7% and 111.3%, respectively, without compromising the transparency and photopolymerization rate. The fractured elastomer exhibited a high tensile strength of 5.44 MPa and a stretchability of 372% after self-healing. Subsequently, a stretchable ionic conductive elastomer (SICE) with high transparency and self-healing properties was developed by incorporating ionic liquids into the 3D-printed elastomer. The high resolution of VP-based 3D printing allowed the construction of pyramid-Kelvin lattice microstructures in the pressure sensor, which enhanced the pressure sensitivity of the sensor several times compared to the pyramid structure. In addition, combining Voronoi tessellation and kirigami art to fabricate tailored wearable sensors with smart structures, broadens the application range and improves the wearing comfort of the sensors.