Subcutaneous power supply by NIR-II light.

Implantable medical devices are wished to be recharged via contactless power transfer technologies without interventional operations. Superior to subcutaneous power supply by visible light or electromagnetic wave, second near-infrared (NIR-II) light is predicted to possess 60 times subcutaneous power transmission but hard to be utilized. Here we report a photo-thermal-electric converter via the combination of photothermal conversion and thermoelectric conversion. It is able to generate an output power as high as 195 mW under the coverage of excised tissues, presenting advantages of non-invasion, high output power, negligible biological damage, and deep tissue penetration. As an in vivo demonstration, the output power of a packaged converter in the abdominal cavity of a rabbit reaches 20 mW under NIR-II light irradiation through the rabbit skin with a thickness of 8.5 mm. This value is high enough to recharge an implanted high-power-consumption wireless camera and transfer video signal out of body in real-time.

Thermal Nociception of Ionic Skin: TRPV1 Ion Channel-Inspired Heat-Activated Dynamic Ionic Liquid.

The artificial reproduction of the tactile sensory function of natural skin is crucial for intelligent sensing, human-computer interaction, and medical health. Thermal nociception is an essential human tactile function to avoid noxious thermal stimuli, which depends on the specific heat-activation of the TRPV1 ion channel. Inspired by the TRPV1, a dynamic ionic liquid with heat-activation characteristics is designed and prepared, which can be activated at 45 °C, which is near the physiological noxious temperature, accompanied by a steep rise in electrical response signals. Its electrical behavior can be deemed to be the extreme version of temperature sensation similar to the natural thermal nociceptor. The heat-activation mechanism is confirmed as a feasible strategy to regulate the thermal response behavior of ions, and this reported dynamic ionic liquid has an unprecedented intrinsic temperature response sensitivity of up to 156.79%/°C. In consideration of the similarity between the heat-activated dynamic ionic liquid and the TRPV1 ion channel in terms of heat-activation characteristics, electrical output signal, and ultrathermal sensitivity, an all-liquid ionic skin with the ability of thermal nociception is further fabricated, which shows considerable potential to assist patients with tactile desensitization to avoid noxious thermal stimuli.

An injectable bioink with rapid prototyping in the air andin-situmild polymerization for 3D bioprinting.

Bioprinting is an attractive technology for building tissues from scratch to explore entire new cell configurations, which brings numerous opportunities for biochemical research such as engineering tissues for therapeutic tissue repair or drug screening. However, bioprinting is faced with the limited number of suitable bioinks that enable bioprinting with excellent printability, high structural fidelity, physiological stability, and good biocompatibility, particularly in the case of extrusion-based bioprinting. Herein, we demonstrate a composite bioink based on gelatin, bacterial cellulose (BC), and microbial transglutaminase (mTG enzyme) with outstanding printing controllability and durable architectural integrity. BC, as a rheology modifier and mechanical enhancer component, endows the bioink with shear-thinning behavior. Moreover, the printed structure becomes robust under physiological conditions owing to thein situchemical crosslinking catalyzed by mTG enzyme. Lattice, bowl, meniscus, and ear structures are printed to demonstrate the printing feasibility of such a composite bioink. Furthermore, the 3D-printed cell-laden constructs are proved to be a conducive biochemical environment that supports growth and proliferation of the encapsulated cellsin vitro. In addition, thein vivostudies convince that the composite bioink possesses excellent biocompatibility and biodegradation. It is believed that the innovation of this new composite bioink will push forward the bioprinting technology onto a new stage.

Renatured hydrogel painting.

Hydrogel coatings pave an avenue for improving the lubricity, biocompatibility, and flexibility of solid surfaces. From the viewpoint of practical applications, this work establishes a scalable method to firmly adhere hydrogel layers to diverse solid surfaces. The strategy, termed as renatured hydrogel painting (RHP), refers to adhering dehydrated xerogel to a surface with appropriate glues, followed by the formation of a hydrogel layer after rehydration of the xerogel. With the benefits of simplicity and generality, this strategy can be readily applied to different hydrogel systems, no matter what the substrate is. Hydrogel adhesion is demonstrated by its tolerance against mechanical impact with hydrodynamic shearing at 14 m/s. This method affords powerful supplements to renew the surface chemistry and physical properties of solid substrates. In addition, we show that the RHP technique can be applied to living tissue, with potential for clinical applications such as the protection of bone tissue.

Self-Powered and Green Ionic-Type Thermoelectric Paper Chips for Early Fire Alarming.

Early fire alarming is of vital importance to lower the damages led by forest fires. Thus far, methods to monitor the forest fires at their early stage are mainly focused on artificial ground patrol, unmanned aerial vehicle cruise monitoring, observation by watchtower, or satellite inspection, whereas these methods are practically encountered with the problems of untimely feedback before the forest fires are out of control. This work proposes a particular kind of self-powered, low-cost, and green thermoelectric paper chips based on the principle of self-assembly and disassembly of ionic liquids on the surface of gold electrodes. By adjustment of the species of ionic liquids, both "n- and p-type" thermoelectric behaviors have been exploited that correspond to the opposite open-circuit voltages. Owing to the fluidic nature of ionic liquids, those "n- and p-type" thermoelectric units can be readily connected in series on one paper chip, leading to remarkable voltage signals in the presence of the temperature difference of 35 K. Followed by signal acquisition and transmission, such a thermoelectric paper chip successfully affords immediate electrical alarming at the early stage of an afire circumstance.

Redox-Driven Spontaneous Double Emulsion.

The formation of spontaneous double emulsions is a peculiar phenomenon in emulsion systems. When compared to the traditional one-step and two-step methods for preparing double emulsions, spontaneous emulsification can not only steadily load uniform water droplets into an oil phase, but can also facilitate the preparation of emulsions with higher stability. However, the limited solubility of salts, which are typically used to modify osmotic pressure, in organic oils has inhibited the viability of this method for the preparation of W/O/W double emulsions. In this paper, a redox-driven spontaneous emulsification method is developed and investigated. Instead of employing oil-soluble salts, an oxidation reaction is implemented in the oil phase, which produces cation radicals and iodide counterions to generate osmotic pressure. Additionally, amphiphilic polymer chains are harnessed as stabilizers for the newly formed W/O interfaces. Various characterization methods have been used to elucidate the mechanism of both the oxidation reaction and the spontaneous formation of double emulsions.

Natural Rice Starch Granules for Green Cleaning.

Detergents are steadily becoming one of the necessities in our daily life. However, synthetic detergents are threatening the global environment and human health, as most of them are derived from petrochemicals. Inspired by one of the ancient Asian traditions that the rice-washing water served as a natural detergent for bathing and washing, this work provides insights into the mechanism of the detergent effect of rice-washing water. It is proposed that starch granules existing in the rice-washing water are interfacially active, which can facilitate the formation of O/W Pickering emulsions. This principle is successfully extended to rice flour that is made by mechanical media milling in a large scale. Pickering emulsions loading different organic solvents as dispersed phase can be stabilized by these food-grade granules without adding other chemical additives. Practical trails of removing pesticide residues and meat cleaning confirm the possibilities to render these natural rice starch granules as sustainable detergents for food cleaning with high safety assurance.

An Intrinsic Photothermal Liquid for Light Detection and Energy Storage.

Photothermal materials (PTMs) have been intensively investigated in the fields of photothermal conversion. Superior to solid PTMs, liquid PTMs are leading the trends in satisfying the demands of high flexibility and easy recycling. Successful examples of liquid PTMs are mostly formulated by dispersing solid PTMs in solvents, but suffer from the problems of phase segregation and solvent pollution. In this work, a low-cost formulation is proposed, which involves an oxidative product of ethyl oleate by iodine. It is an intrinsic liquid PTM, preserving the fluidic nature as well as possessing considerable ability for photothermal conversion. In addition to understanding the mechanism of light absorption in the visible and even near infrared windows, two examples are presented to demonstrate the great potential of liquid PTMs in broad areas such as light sensing and energy storage.

Crystal-confined freestanding ionic liquids for reconfigurable and repairable electronics.

Liquid sensors composed of ionic liquids are rising as alternatives to solid semiconductors for flexible and self-healing electronics. However, the fluidic nature may give rise to leakage problems in cases of accidental damages. Here, we proposed a liquid sensor based on a binary ionic liquid system, in which a flowing ionic liquid [OMIm]PF6 is confined by another azobenzene-containing ionic liquid crystalline [OMIm]AzoO. Those crystal components provide sufficient pinning capillary force to immobilize fluidic components, leading to a freestanding liquid-like product without the possibility of leakage. In addition to owning ultra-high temperature sensitivity, crystal-confined ionic liquids also combine the performances of both liquid and solid so that it can be stretched, bent, self-healed, and remolded. With respect to the reconfigurable property, this particular class of ionic liquids is exploited as dynamic circuits which can be spatially reorganized or automatically repaired.

Interfacial Diffusion Printing: An Efficient Manufacturing Technique for Artificial Tubular Grafts.

Despite great progresses in bioprinting materials and technologies, immense challenges still remain when printing tubular tissues or organs with satisfying mechanical and chemical properties, such as blood vessel, colon, and trachea. Herein, a promising extrusion system based on an interfacial diffusion printing (IDP) technique for one-step printing of tubular tissue grafts is proposed. Specifically, this technique offers great convenience to prepare hollow hydrogel fibers with excellent mechanical properties and satisfactory biocompatibility. The tubular diameter can be readily adjusted within 6 mm, which renders the possibility of these hydrogel tubes to serve as small-diameter vascular grafts. In the model of animal trials, the hydrogel grafts with the capability of enduring arterial pressure are mechanically stable in rabbit carotid artery replacement. Because of its intrinsic simplicity and generality, the IDP technique is considered to be one of the reliable choices for more complicated bioengineering.

Body Compatible Thermometer Based on Green Electrolytes.

With the use of coordinated complexes between aliphatic diols and calcium chloride (CaCl2) as green electrolytes, a body compatible, ecofriendly and low-cost thermometer is successfully developed. This particular conductive liquid possesses unique features of ultrafast response and high sensitivity against temperature change. The influences of CaCl2 concentration and the category of aliphatic diols on conductivity change reveal that the thermal sensing abilities of such green electrolytes are positively relevant to the viscosity change along with temperature change. Owing to the advantages of stability, reliability, and security, the thermometer can implement long-term and continuous temperature monitoring, which can fully meet the requirements of application of medical monitors, diagnostics, and therapies. Moreover, the inherent advantages of thermometers, including satisfactory biocompatibility and nontoxicity, afford great promise for applications in invasive and inflammatory devices.

Spider-Inspired Multicomponent 3D Printing Technique for Next-Generation Complex Biofabrication.

The shortage of tissue resources is currently a serious challenge that limits the clinical therapy to patients with tissue loss or end-stage organ failure. The booming development of 3D printing offers unprecedented hope for tissue engineering since it can construct cells and biomaterials into a 3D tissue-mimicking object with precise control over size and shape. However, it is still challenging to fabricate artificial living tissues or organs due to the extreme complexity of biological tissues. Herein, we propose a new concept of spider-inspired 3D printing technique (SI-3DP) for continuous multicomponent 3D printing based on in situ gelation at a multibarrel printing nozzle. The printing process allows for rapid construction of 3D architectures composed of different inks in the desired position. To present the potential in biomedical applications, the SI-DIP also prints vessel-like hollow hydrogel microfibers and cell-laden hollow fibers, indicating good biocompatibility of this technique. The newly developed SI-3DP technique is envisioned to promote the development of next-generation complex biofabrication.

Multichannel Dynamic Interfacial Printing: An Alternative Multicomponent Droplet Generation Technique for Lab in a Drop.

Generation of uniform emulsion droplets mixed with multiple components is one of the key issues in the field of lab in a drop. Traditionally, droplet microfluidic chips are often served as the prime choice while designing and fabricating microfluidic chips always rely on skilled technician and specialized equipment, severely restricting its wide accessibility. In this work, an alternative technique, called multichannel dynamic interfacial printing (MC-DIP), was proposed for multicomponent droplet generation. The MC-DIP device was designed modularly and could be set up manually without any microfabrication process, exhibiting full accessibility for freshmen after a brief training. This new technique owns advantages in the generation of droplets with predictable sizes and composites. Quantitative experiments of measuring minimum inhibitory concentration (MIC) value via mixing microbes and antibiotics into droplet were conducted to proving its application potential for lab in a drop. Further research on a clinical pathogenic strain revealed that this technique could be potentially applied in the clinical laboratory for antibiotic susceptibility testing.

P-N Conversion in a Water-Ionic Liquid Binary System for Nonredox Thermocapacitive Converters.

An intriguing p-n conversion of thermoelectric property was observed in a water-ionic liquid ([EMIm][Ac]) binary system with precise control over water content. The highest p-type and n-type Seebeck coefficient were optimized at water-[EMIm][Ac] molar ratio of 2:1 and 4:1, respectively. DFT calculation illustrates that a configuration of solvent separation ion pairs is preferred at the water-[EMIm][Ac] molar ratio of 4:1, leading to the p-n conversion through weakening interaction between anion clusters and gold electrodes. Furthermore, p-n thermocapacitive converters were integrated to enhance the output Seebeck voltages. This work opens up new perspectives for harvesting low grade heat with the use of fluidic materials.

Ultrafast Paper Thermometers Based on a Green Sensing Ink.

With the use of an ionic liquid as the ultrathermosensitive fluid, a paper thermometer is successfully developed with intrinsic ability of ultrafast response and high stability upon temperature change. The fluidic nature allows the ionic liquid to be easily deposited on paper by pen writing or inkjet printing, affording great promise for large-scale fabrication of low-cost paper sensors. Owing to the advantages of nonvolatilization, excellent continuity and deformability, the thermosensitive ink trapped within the cellulose fibers of paper matrix has no leakage or evaporation at open states, ensuring the excellent stability and repeatability of thermal sensing against arbitrary bending and folding operation. By shortening the heat exchange distance between ionic liquid and samples, it takes only 8 s for the thermometer to reach an electrical equilibrium at a given temperature. Moreover, the paper thermometer can be applied to remotely monitor temperature change with the combination of a wireless communication technology.