Organic light emitting board for dynamic interactive display

Interactive displays involve the interfacing of a stimuli-responsive sensor with a visual human-readable response. Here, we describe a polymeric electroluminescence-based stimuli-responsive display method that simultaneously detects external stimuli and visualizes the stimulant object. This organic light-emitting board is capable of both sensing and direct visualization of a variety of conductive information. Simultaneous sensing and visualization of the conductive substance is achieved when the conductive object is coupled with the light emissive material layer on application of alternating current. A variety of conductive materials can be detected regardless of their work functions, and thus information written by a conductive pen is clearly visualized, as is a human fingerprint with natural conductivity. Furthermore, we demonstrate that integration of the organic light-emitting board with a fluidic channel readily allows for dynamic monitoring of metallic liquid flow through the channel, which may be suitable for biological detection and imaging applications.

Electrothermal soft manipulator enabling safe transport and handling of thin cell/tissue sheets and bioelectronic devices

“Living” cell sheets or bioelectronic chips have great potentials to improve the quality of diagnostics and therapies. However, handling these thin and delicate materials remains a grand challenge because the external force applied for gripping and releasing can easily deform or damage the materials. This study presents a soft manipulator that can manipulate and transport cell/tissue sheets and ultrathin wearable biosensing devices seamlessly by recapitulating how a cephalopod’s suction cup works. The soft manipulator consists of an ultrafast thermo-responsive, microchanneled hydrogel layer with tissue-like softness and an electric heater layer. The electric current to the manipulator drives microchannels of the gel to shrink/expand and results in a pressure change through the microchannels. The manipulator can lift/detach an object within 10 s and can be used repeatedly over 50 times. This soft manipulator would be highly useful for safe and reliable assembly and implantation of therapeutic cell/tissue sheets and biosensing devices

Interactive structural color displays of nano-architectonic 1-dimensional block copolymer photonic crystals FOCUS ISSUE REVIEW

For changing environmental circumstances, interactive structural color (SC) observation is a promising strategy to store and express external information. SCs based on self-assembled block copolymer (BCP) photonic crystals have been a research focus due to their facile and diverse nanostructures relying on the volume ratio of blocks. Their unique nano-architectonics can reflect incident light due to constructive interference of the two different dielectric constituents. Their excellent ability to change nano-architectonics in response to external stimuli (i.e. humidity, temperature, pH, and mechanical force) allows for a programmable and stimuli-interactive BCP SC display. In this review, recent advances in programmable and stimuli-interactive SC displays with the 1-dimensional self-assembled BCP nano-architectonics are comprehensively discussed. First, this review focuses on the development of programmable BCP SCs that can store various information. Second, stimuli-interactive BCP SCs capable of responding reversibly to external stimuli are also addressed. Particularly, reversible BCP SC changes are suitable for rewritable displays and emerging human-interactive BCP SC displays that detect various human information through changes in electric signals with the simultaneous alteration of the BCP SCs. Based on previously reported literature, the current challenges in this research field are further discussed, and the perspective for future development is presented in terms of material, nano-architectonics, and process.Funding Agencies|Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) - Ministry of Science and ICT [2018M3D1A1058536]; National Research Foundation of Korea (NRF) - Korean government (MEST) [2020R1A2B5B03002697]; Korea Medical Device Development Fund grant - Korea government (Ministry of Health Welfare) [1711174508, KMDF_PR_20200901_0077]; Korea Medical Device Development Fund grant - Korea government (Ministry of Food and Drug Safety) [1711174508, KMDF_PR_20200901_0077]; National Research Foundation of Korea (NRF) - Korea government (MSIT) [2021R1I1A1A01048298]; Korea Medical Device Development Fund grant - Korea government (the Ministry of Science and ICT) [1711174508, KMDF_PR_20200901_0077]; Korea Medical Device Development Fund grant - Korea government (Ministry of Trade, Industry and Energy) [1711174508, KMDF_PR_20200901_0077]</p

Dual Functionalization of Hexagonal Boron Nitride Nanosheets Using Pyrene-Tethered Poly(4-vinylpyridine) for Stable Dispersion and Facile Device Incorporation

Owing to its favorable solution processability, the development of a stable dispersion of two-dimensional (2D) boron nitride (BN) has received significant attention for cutting-edge optic/electronic applications. Herein, we report an efficient method to disperse BN nanosheets (BNNSs) in polar solvents via dual noncovalent interactions using pyrene-tethered poly(4-vinylpyridine) (P4VP-Py). As a dispersion agent, P4VP-Py enables bifunctionalization with BNNS through ??????? and Lewis acid???base interactions arising from the pyrene and pyridine moiety, respectively, resulting in highly stable BNNS dispersions in different polar solvents. The blend of P4VP-Py-functionalized BNNS with the pristine P4VP matrix resulted in increased thermal conductivity and dielectric constant combined with superior thermal stability by forming a compatible interface between the P4VP-Py matrix and the BNNS adjacent to the P4VP-Py. We demonstrated that dual noncovalent functionalization of BNNSs based on molecular design presents a strategy to achieve high dispersion of 2D materials into various media, ranging from polar solvents to solid matrices, for the expansion of advanced optic/electronic applications using BNNSs

Rheology-tailored stable aramid nanofiber suspensions for fabricating ultra-strong and electrically insulated additive-free nanopapers

Although aramid nanofiber paper (ANF-P) is a promising alternative to conventional electrical insulation paper, its performance requires further optimization. This study aimed to establish an optimal nanopaper-fabrication process by using rheology-controlled suspensions to achieve remarkably strengthened pure ANF-Ps. The ANF-P was fabricated in two steps: 1) preparing ANF suspension (ANF-SH???O) by precipitating ANF/dimethyl sulfoxide (DMSO) (ANF-DDMSO), and 2) preparing ANF-P by vacuum-filtrating ANF-SH2O. Under an in-situ homogenization-assisted precipitation in step 1, the concentration of ANF-DDMSO predominantly affected both the suspension stability and nanopaper performance. Semi-dilute ANF-DDMSOs (0.1???0.7 wt%) produced stable suspensions and strong ANF-Ps (mechanical modulus and strength of 4.5???5.1 GPa and 221.4???243.4 MPa, respectively), while concentrated ANF-DDMSOs (1.0???2.0 wt%) yielded unstable suspensions and weak ANF-Ps (0.3???3.2 GPa and 12.6???139.0 MPa, respectively). The former ANF-SH2Os comprised branched or sheet-like precipitated particles that were favorable for structuring the paper, whereas the latter ones consisted of irregular particles. Particularly at a thickness of 17 ??m, ANF-Ps from 0.3 wt% ANF-DDMSO exhibited record-high mechanical performances (modulus, strength, and toughness of 7.4 GPa, 382.3 MPa, and 32.5 MJ???m???3, respectively) compared to previously reported pure ANF-Ps. In addition, ANF-Ps exhibited a remarkable dielectric breakdown strength of ???200.3 kV???mm???1. Rheologically, ANF-SH2Os from semi-dilute ANF-DDMSOs provided a higher scaling exponent of elastic modulus, indicating a higher degree of particle entanglement. Moreover, the strain-induced modulus overshoot phenomena revealed a highly structured suspension network. Therefore, linear- and nonlinear-suspension rheology provide a fundamental guideline for fortifying the foundation of industrial production of high-performance nanopapers

Thermal and Flame Retardant Properties of Phosphate-Functionalized Silica/Epoxy Nanocomposites

We report a flame retardant epoxy nanocomposite reinforced with 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide (DOPO)-tethered SiO2 (DOPO-t-SiO2) hybrid nanoparticles (NPs). The DOPO-t-SiO2 NPs were successfully synthesized through surface treatment of SiO2 NPs with (3-glycidyloxypropyl)trimethoxysilane (GPTMS), followed by a click reaction between GPTMS on SiO2 and DOPO. The epoxy nanocomposites with DOPO-t-SiO2 NPs as multifunctional additive exhibited not only high flexural strength and fracture toughness but also excellent flame retardant properties and thermal stability, compared to those of pristine epoxy and epoxy nanocomposites with a single additive of SiO2 or DOPO, respectively. Our approach allows a facile, yet effective strategy to synthesize a functional hybrid additive for developing flame retardant nanocomposites

RTA-Treated Carbon Fiber/Copper Core/Shell Hybrid for Thermally Conductive Composites

In this paper, we demonstrate a facile route to produce epoxy/carbon fiber composites providing continuous heat conduction pathway of Cu with a high degree of crystal perfection via electroplating, followed by rapid thermal annealing (RTA) treatment and compression molding. Copper shells on carbon fibers were coated through electroplating method and post-treated via RTA technique to reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated carbon fiber composites with Cu shell of 12.0 vol % prepared via simple compression molding, revealed 18 times larger thermal conductivity (47.2 W m^–1 K^–1) in parallel direction and 6 times larger thermal conductivity (3.9 W m^–1 K^–1) in perpendicular direction than epoxy/carbon fiber composite. Our novel composites with RTA-treated carbon fiber/Cu core/shell hybrid showed heat conduction behavior of an excellent polymeric composite thermal conductor with continuous heat conduction pathway, comparable to theoretical values obtained from Hatta and Taya model

Enhanced outcoupling in down-conversion white organic light-emitting diodes using imprinted microlens array films with breath figure patterns

We demonstrate high-performance down-conversion microlens array (DC-MLA) films for white organic light-emitting diodes (OLEDs). The DC-MLA films are readily fabricated by an imprinting method based on breath figure patterns, which are directly formed on the polymer substrate with a novel concept. The DC-MLA films result in high-quality white light as well as enhanced light outcoupling efficiency for white OLEDs. The external quantum efficiency and power efficiency of OLEDs with DC-MLA films are increased by a factor of 1.35 and 1.86, respectively, compared to OLEDs without outcoupling films. Moreover, the white OLEDs with DC-MLA films achieve a high color-rendering index of 84.3. It is anticipated that the novel DC-MLA films fabricated by the simple imprinting process with breath figure patterns can contribute to the development of efficient white OLEDs

Copper Shell Networks in Polymer Composites for Efficient Thermal Conduction

Thermal management of polymeric composites is a crucial issue to determine the performance and reliability of the devices. Here, we report a straightforward route to prepare polymeric composites with Cu thin film networks. Taking advantage of the fluidity of polymer melt and the ductile properties of Cu films, the polymeric composites were created by the Cu metallization of PS bead and the hot press molding of Cu-plated PS beads. The unique three-dimensional Cu shell-networks in the PS matrix demonstrated isotropic and ideal conductive performance at even extremely low Cu contents. In contrast to the conventional simple melt-mixed Cu beads/PS composites at the same concentration of 23.0 vol %, the PS composites with Cu shell networks indeed revealed 60 times larger thermal conductivity and 8 orders of magnitude larger electrical conductivity. Our strategy offers a straightforward and high-throughput route for the isotropic thermal and electrical conductive composites