Programmable Nano–Bio Interfaces for Functional Biointegrated Devices

A large amount of evidence has demonstrated the revolutionary role of nanosystems in the screening and shielding of biological systems. The explosive development of interfacing bioentities with programmable nanomaterials has conveyed the intriguing concept of nano–bio interfaces. Here, recent advances in functional biointegrated devices through the precise programming of nano–bio interactions are outlined, especially with regard to the rational assembly of constituent nanomaterials on multiple dimension scales (e.g., nanoparticles, nanowires, layered nanomaterials, and 3D‐architectured nanomaterials), in order to leverage their respective intrinsic merits for different functions. Emerging nanotechnological strategies at nano–bio interfaces are also highlighted, such as multimodal diagnosis or “theragnostics”, synergistic and sequential therapeutics delivery, and stretchable and flexible nanoelectronic devices, and their implementation into a broad range of biointegrated devices (e.g., implantable, minimally invasive, and wearable devices). When utilized as functional modules of biointegrated devices, these programmable nano–bio interfaces will open up a new chapter for precision nanomedicine.     

Overcoming the Interfacial Limitations Imposed by the Solid–Solid Interface in Solid‐State Batteries Using Ionic Liquid‐Based Interlayers

Li‐garnets are promising inorganic ceramic solid electrolytes for lithium metal batteries, showing good electrochemical stability with Li anode. However, their brittle and stiff nature restricts their intimate contact with both the electrodes, hence presenting high interfacial resistance to the ionic mobility. To address this issue, a strategy employing ionic liquid electrolyte (ILE) thin interlayers at the electrodes/electrolyte interfaces is adopted, which helps overcome the barrier for ion transport. The chemically stable ILE improves the electrodes‐solid electrolyte contact, significantly reducing the interfacial resistance at both the positive and negative electrodes interfaces. This results in the more homogeneous deposition of metallic lithium at the negative electrode, suppressing the dendrite growth across the solid electrolyte even at high current densities of 0.3 mA cm^?2. Further, the improved interface Li/electrolyte interface results in decreasing the overpotential of symmetric Li/Li cells from 1.35 to 0.35 V. The ILE modified Li/LLZO/LFP cells stacked either in monopolar or bipolar configurations show excellent electrochemical performance. In particular, the bipolar cell operates at a high voltage (≈8 V) and delivers specific capacity as high as 145 mAh g^?1 with a coulombic efficiency greater than 99%.     

Utilization of Peroxide Reduction Reaction at Air–Liquid–Solid Joint Interfaces for Reliable Sensing System Construction

The utilization of hydrogen peroxide (H₂O₂) cathodic reaction is an ideal approach to develop reliable biosensors that are immune to interferences arising from oxidizable endogenous/exogenous species in biological solutions. However, practical application of such a detection scheme is limited due to the significantly fluctuating oxygen levels in solutions, as oxygen can be reduced at similar potentials. Herein, this limitation is addressed by developing a novel electrode system with superhydrophobicity‐mediated air–liquid–solid joint interfaces, which allows the rapid and continuous transport of oxygen from the air phase to the electrode surface and provides a fixed interfacial oxygen concentration. Using cathodic measurement of the enzymatic product H₂O₂, the sensing platform is applied to detect glucose, a model analyte, achieving a remarkably high selectivity (≈2% signal modulation due to common biologic interferents), sensitivity (18.56 µA cm^?2 mm ^?1), and a dynamic linear range up to 80 × 10^?3m . The utility of H₂O₂ reduction reaction at triphase interface to achieve reliable sensing platforms is general, and hence has broad potential in the fields of medical research, clinical diagnosis, and environmental analysis.     

Directed Self‐Assembly of Liquid‐Crystalline Molecular Building Blocks for Sub‐5 nm Nanopatterning

The thin‐film directed self‐assembly of molecular building blocks into oriented nanostructure arrays enables next‐generation lithography at the sub‐5 nm scale. Currently, the fabrication of inorganic arrays from molecular building blocks is restricted by the limited long‐range order and orientation of the materials, as well as suitable methodologies for creating lithographic templates at sub‐5 nm dimensions. In recent years, higher‐order liquid crystals have emerged as functional thin films for organic electronics, nanoporous membranes, and templated synthesis, which provide opportunities for their use as lithographic templates. By choosing examples from these fields, recent progress toward the design of molecular building blocks is highlighted, with an emphasis on liquid crystals, to access sub‐5 nm features, their directed self‐assembly into oriented thin films, and, importantly, the fabrication of inorganic arrays. Finally, future challenges regarding sub‐5 nm patterning with liquid crystals are discussed.     

Signal Output of Triboelectric Nanogenerator at Oil–Water–Solid Multiphase Interfaces and its Application for Dual‐Signal Chemical Sensing

A liquid–solid contact triboelectric nanogenerator (TENG) based on poly(tetrafluoroethylene) (PTFE) film, a copper electrode, and a glass substrate for harvesting energy in oil/water multiphases is reported. There are two distinctive signals being generated, one is from the contact electrification and electrostatic induction between the liquid (water/oil) and the PTFE film (V_TENG and I_TENG); and the other is from the electrostatic induction in the copper electrode by the oil/water interfacial charges (ΔV_interface and I_interface), which is generated only when the liquid–solid contact TENG is inserted across the oil/water interface. The two signals show interesting opposite changing trends that the V_TENG and I_TENG decrease while the oil/water interfacial signals of ΔV_interface and I_interface increase after coating a layer of polydopamine on the surfaces of PTFE and glass via self‐polymerization. As an application of the observed phenomena, both the values of I_TENG and I_interface have a good linear relationship versus the natural logarithm of the concentration of the dopamine. Based on this, the first self‐powered dual‐signal detection of dopamine using TENG is demonstrated.     

Sculpting Asymmetric,Hollow‐Core,Three‐Dimensional Nanostructures Using Colloidal Particles

Colloidal elements have historically played a key role in “bottom‐up” self‐assembly processes for nanofabrication. However, these elementary components can also interact with light to generate complex intensity distributions and facilitate “top‐down” lithography. Here, a nanolithography technique is demonstrated based on oblique illuminations of colloidal particles to fabricate hollow‐core 3D nanostructures with complex symmetry. The light–particle interaction generates an angular light distribution as governed by Mie scattering, which can be compounded by multiple illuminations to sculpt novel 3D structures in the underlying photoresist. The fabricated geometry can be controlled by the particle parameters and illumination configurations, enabling the fabrication of a large variety of asymmetric hollow nanostructures. The proposed technique has high pattern versatility, is low cost and high throughput, and can find potential application in nanoneedles, nanonozzles, and materials with anisotropic properties.     

Temperature Gradients Drive Bulk Flow Within Microchannel Lined by Fluid–Fluid Interfaces

Surface tension gradients induce Marangoni flow, which may be exploited for fluid transport. At the micrometer scale, these surface‐driven flows can be quite significant. By introducing fluid–fluid interfaces along the walls of microfluidic channels, bulk fluid flows driven by temperature gradients are observed. The temperature dependence of the fluid–fluid interfacial tension appears responsible for these flows. In this report, the design concept for a biocompatible microchannel capable of being powered by solar irradiation is provided. Using microscale particle image velocimetry, a bulk flow generated by apparent surface tension gradients along the walls is observed. The direction of flow relative to the imposed temperature gradient agrees with the expected surface tension gradient. The phenomenon's ability to replace bulky peripherals, like traditional syringe pumps, on a diagnostic microfluidic device that captures and detects leukocyte subpopulations within blood is demonstrated. Such microfluidic devices may be implemented for clinical assays at the point of care without the use of electricity.     

Modulation of Mesenchymal Stem Cells Mechanosensing at Fluid Interfaces by Tailored Self‐Assembled Protein Monolayers

Mechanical cues of cellular microenvironments can modulate cell functions including cell spreading and differentiation. Most studies of cellular functions are performed using a solid substrate, and it is thought that cells cannot spread on fluid substrates because of rapid relaxation, which cannot resist against actomyosin‐based cell contractility. Here, the spreading and growth of anchorage‐dependent cells such as human mesenchymal stem cells at the liquid interface between a perfluorocarbon fluid and the culture medium are observed. It is demonstrated that a monomolecular protein nanosheet self‐assembled at a fluid interface is sufficiently rigid to support cell spreading without additional treatment. Fine tuning of the packing of these proteins at the liquid interface permits tailoring of the mechanics of the protein layer, ultimately allowing for the regulation of cell spreading. The greater stiffness of the protein nanosheets triggers cell spreading, adhesion growth, and yes‐associated protein nuclear translocation. Cell behavior at the fluid interface is explained within the framework of the molecular clutch model. In addition, the freestanding ultrathin protein nanosheets are extremely flexible, easily deformed, and perceived by cells as being much softer. The findings are expected to provide a new perspective for insights into cell–material interactions.