3D‐Printing of Functionally Graded Porous Materials Using On‐Demand Reconfigurable Microfluidics

Tailoring the morphology of macroporous structures remains one of the biggest challenges in material synthesis. Herein, we present an innovative approach for the fabrication of custom macroporous materials in which pore size varies throughout the structure by up to an order of magnitude. We employed a valve‐based flow‐focusing junction (vFF) in which the size of the orifice can be adjusted in real‐time (within tens of milliseconds) to generate foams with on‐line controlled bubble size. We used the junction to fabricate layered and smoothly graded porous structures with pore size varying in the range of 80–800 μm. Additionally, we mounted the vFF on top of an extrusion printer and 3D‐printed constructs characterized by a predefined 3D geometry and a controlled, spatially varying internal porous architecture, such as a model of a bone. The presented technology opens new possibilities in macroporous material synthesis with potential applications ranging from tissue engineering to aerospace industry and construction.     

PEG–Anthracene Hydrogels as an On‐Demand Stiffening Matrix To Study Mechanobiology

There is a growing interest in materials that can dynamically change their properties in the presence of cells to study mechanobiology. Herein, we exploit the 365 nm light mediated [4+4] photodimerization of anthracene groups to develop cytocompatible PEG‐based hydrogels with tailorable initial moduli that can be further stiffened. A hydrogel formulation that can stiffen from 10 to 50 kPa, corresponding to the stiffness of a healthy and fibrotic heart, respectively, was prepared. This system was used to monitor the stiffness‐dependent localization of NFAT, a downstream target of intracellular calcium signaling using a reporter in live cardiac fibroblasts (CFbs). NFAT translocates to the nucleus of CFbs on stiffening hydrogels within 6 h, whereas it remains cytoplasmic when the CFbs are cultured on either 10 or 50 kPa static hydrogels. This finding demonstrates how dynamic changes in the mechanical properties of a material can reveal the kinetics of mechanoresponsive cell signaling pathways that may otherwise be missed in cells cultured on static substrates.     

An Auto‐Switchable Dual‐Mode Seawater Energy Extraction System Enabled by Metal–Organic Frameworks

Harvesting energy directly in oceans by electrochemical devices is essential for driving underwater appliances such as underwater vehicles or detectors. Owing to the extreme undersea environment, it is important but difficult to use the devices with both a high energy density and power density simultaneously. Inspired by marine organisms that have switchable energy extraction modes (aerobic respiration for long‐term living or anaerobic respiration to provide instantaneously high output power for fast movement), an auto‐switchable dual‐mode seawater energy extraction system is presented to provide high energy density and power density both by initiatively choosing different solutes in seawater as electron acceptors. With assistance from metal–organic frameworks, this device had a theoretical energy density of 3960 Wh kg^?1, and a high practical power density of 100±4 mW cm^?2 with exceptional stability and low cost, making practical applications in seawater to be possible.     

Stimulus‐Induced Conformational Transformation of a Cyclic Peptide for Selective Cell‐Targeting On–Off Gatekeeper for Mesoporous Nanocarriers

α_vβ₃ Integrin is upregulated on many cancer cells. We designed a dual functional cyclic peptide gatekeeper with a capability of stimuli‐responsive conformational transformation which could serve as a selective cell‐targeting on–off gatekeeper for mesoporous nanocarriers. The advantage of employing the motif of stimuli‐induced conformational transformation of cyclic peptides is that they could be utilized not only as an on–off gatekeeper for the triggered release of cargo drugs but also as a targeting ligand of the carriers to desired cells with their respective binding receptors. The peptide gatekeepers on the surface of nanocarriers exhibited on–off gatekeeping via conformational transformation triggered by intracellular glutathione levels of the cancer cells. The cyclic RGD sequence of the peptide gatekeepers enhanced the intracellular uptake into tumor cells (A549) and the therapeutic efficacy of the nanocarrier.     

Oxidative Neutralization of Mustard‐Gas Simulants in an On‐Board Flow Device with In‐Line NMR Monitoring

The fast and effective neutralization of the mustard‐gas simulant 2‐chloroethyl ethyl sulfide (CEES) using a simple and portable continuous flow device is reported. Neutralization takes place through a fully selective sulfoxidation by a stable source of hydrogen peroxide (alcoholic solution of urea–H₂O₂ adduct/MeSO₃H freshly prepared). The reaction progress can be monitored with an in‐line benchtop NMR spectrometer, allowing a real‐time adjustment of reaction conditions. Inherent features of millireactors, that is, perfect control of mixing, heat and reaction time, allowed the neutralization of 25 g of pure CEES within 46 minutes in a 21.5 mL millireactor (t ^R =3.9 minutes). This device, which relies on affordable and nontoxic reagents, fits into a suitcase, and can be deployed by police/military forces directly on the attack site.     

An Optically and Thermally Switchable Electronic Structure Based on an Anthracene–BODIPY Conjugate

An optically and thermally responsive boron dipyrromethene (BODIPY) dye, namely, meso‐2‐(9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dione) (DK)‐linked, bicyclo[2.2.2]octadiene (BCOD)‐fused BODIPY ( BCOD‐DK ), was synthesized. The weakly luminous structure of BCOD‐DK can be changed quantitatively to that of the strongly fluorescent BODIPY BCOD‐Ant by optical excitation at the DK unit, which induces double decarbonylation of the DK unit to give an anthracene unit. The solvent effect on the fluorescence properties of BCOD‐DK suggests that the dramatic change in fluorescence intensity is controlled by intramolecular electron transfer from the BODIPY moiety to the meso‐DK substituent. BCOD‐DK is converted to meso‐ DK benzene‐fused BODIPY ( Benzo‐DK ) by heating at 220 °C with 64–70 nm redshift of absorption and fluorescence peaks without changing the fluorescence quantum yield of Φ_F=0.08 in dichloromethane. Benzo‐DK can be converted to strongly fluorescent meso ‐ anthracene benzene‐fused BODIPY Benzo‐Ant by optical excitation. Thus, BCOD‐DK can show four different optical performances simply by irradiation and heating, and hence may be applicable for optical data storage and security data encryption.     

An Ion‐Responsive Pincer‐Crown Ether Catalyst System for Rapid and Switchable Olefin Isomerization

Rapid, selective, and highly controllable iridium‐catalyzed allylbenzene isomerization is described, enabled by tunable hemilability based on alkali metal cation binding with a macrocyclic “pincer‐crown ether” ligand. An inactive chloride‐ligated complex can be activated by halide abstraction with sodium salts, with the resulting catalyst [κ ⁵‐(^15c5NCOP^{i Pr})Ir(H)]⁺ exhibiting modest activity. Addition of Li⁺ provides a further boost in activity, with up to 1000‐fold rate enhancement. Ethers and chloride salts dampen or turn off reactivity, leading to three distinct catalyst states with activity spanning several orders of magnitude. Mechanistic studies suggest that the large rate enhancement and high degree of tunability stem from control over substrate binding.