PUBLICATIONS

PUBLICATIONS

Journals

Patents

Journals

  • 14

    Soft implantable drug delivery device integrated wirelessly with wearable devices to treat fatal seizures

    Abstract

    Personalized biomedical devices have enormous potential to solve clinical challenges in urgent medical situations. Despite this potential, a device for in situ treatment of fatal seizures using pharmaceutical methods has not been developed yet. Here, we present a novel treatment system for neurological medical emergencies, such as status epilepticus, a fatal epileptic condition that requires immediate treatment, using a soft implantable drug delivery device (SID). The SID is integrated wirelessly with wearable devices for monitoring electroencephalography signals and triggering subcutaneous drug release through wireless voltage induction. Because of the wireless integration, bulky rigid components such as sensors, batteries, and electronic circuits can be moved from the SID to wearables, and thus, the mechanical softness and miniaturization of the SID are achieved. The efficacy of the prompt treatment could be demonstrated with animal experiments in vivo, in which brain damages were reduced and survival rates were increased.
    Link
  • 13

    Shear Stress-Triggered Deformation of Microparticles in a Tapered Microchannel

    Abstract

    We demonstrate that it is possible to produce microparticles with high deformability while maintaining a high effective volume. For significant particle deformation, a particle must have a void region. The void fraction of the particle allows its deformation under shear stress. Owing to the importance of the void fraction in particle deformation, we defined an effective volume index (V*) that indicates the ratio of the particle’s total volume to the volumes of the void and material structures. We chose polyethylene glycol diacrylate (Mn ~ 700) for the fabrication of the microparticles and focused on the design of the particles rather than the intrinsic softness of the material (E). We fabricated microparticles with four distinct shapes: discotic, ring, horseshoe, and spiral, with various effective volume indexes. The microparticles were subjected to shear stress as they were pushed through a tapered microfluidic channel to measure their deformability. The deformation ratio R was introduced as R = 1−Wdeformed/Doriginal to compare the deformability of the microparticles. We measured the deformation ratio by increasing the applied pressure. The spiral-shaped microparticles showed a higher deformation ratio (0.901) than those of the other microparticles at the same effective volume index.
    Link
  • 12

    Ternary MOF-Based Redox Active Sites Enabled 3D-on-2D Nanoarchitectured Battery-Type Electrodes for High-Energy-Density Supercapatteries

    Abstract

    Designing rationally combined metal-organic frameworks (MOFs) with multifunctional nanogeometries is of significant research interest to enable the electrochemical properties in advanced energy storage devices. Herein, we explored a new class of binder-free dual-layered Ni-Co-Mn-based MOFs (NCM-based MOFs) with three-dimensional (3D)-on-2D nanoarchitectures through a polarity-induced solution-phase method for high-performance supercapatteries. The hierarchical NCM-based MOFs having grown on nickel foam exhibit a battery-type charge storage mechanism with superior areal capacity (1311.4 μAh cm-2 at 5 mA cm-2), good rate capability (61.8%; 811.67 μAh cm-2 at 50 mA cm-2), and an excellent cycling durability. The superior charge storage properties are ascribed to the synergistic features, higher accessible active sites of dual-layered nanogeometries, and exalted redox chemistry of multi metallic guest species, respectively. The bilayered NCM-based MOFs are further employed as a battery-type electrode for the fabrication of supercapattery paradigm with biomass-derived nitrogen/oxygen doped porous carbon as a negative electrode, which demonstrates excellent capacity of 1.6 mAh cm-2 along with high energy and power densities of 1.21 mWh cm-2 and 32.49 mW cm-2, respectively. Following, the MOF-based supercapattery was further assembled with a renewable solar power harvester to use as a self-charging station for various portable electronic applications.

    Link
  • 11

    Unveiling one-dimensional mixed-metallic oxysulfide nanorods as an advanced cathode material for hybrid supercapacitors

    Abstract

    Mixed-metallic oxyphosphides and oxysulfides are prominent electrode candidates for energy storage devices owing to the synergistic benefits of metal oxides and metal sulfides. Herein, we explore nickel-molybdenum oxyphosphides and oxysulfides (NMOP/NMOS) by a one-step hydrothermal technique, followed by an anion exchange process. As a result, the materials consist of one-dimensional nanorods (1D NRs) which promote charge transportation. Both the materials with 1D NR morphology exhibit superior electrochemical performance to the nickel-molybdenum oxides (NMO) NRs due to the incorporation of phosphorus and sulfur anions. Particularly, the NMOS material demonstrates better specific capacity (38.3 mA h/g, 338.7 F/g) compared with the NMO and NMOP materials. The feasibility of NMOS NRs as a cathode material is explored by fabricating the hybrid supercapacitor (HSC). By exploiting an intriguing feature of NMOS (cathode) and activated carbon (anode) materials, the HSC delivers maximum energy and power densities of 58.9 W h/kg and 3502.5 W/kg, respectively. An HSC shows excellent cycling stability even after 10,000 cycles (90.6% retention). The suitability of HSC in real-time applications is also verified by powering various electronic components. This work promotes the rational design of novel mixed-metallic oxysulfides-based electrode materials with beneficial morphologies for high-capacity SCs.

    Graphical abstract

    Synopsis: One-dimensional mixed-metallic oxysulfide nanorods as a cathode material for hybrid supercapacitors.

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    Link
  • 10

    Improved performance of nanogenerator via synergetic piezo/triboelectric effects of lithium niobate microparticles embedded composite films

    Abstract

    Harvesting energy from renewable energy resources is an emerging research area to fulfil the globally rising energy demand owing to the enormous usage of various portable electronic systems. Mechanical energy is one of them and available abundantly in everyday human life such as ocean wave, human motion, raindrop fall, rotation energy, etc. Herein, the ferroelectric lithium niobate (LiNbO3) microparticles are prepared by a solid-state reaction technique and further utilized for the fabrication of nanogenerator to efficiently harvest these mechanical energies. Ferroelectric materials exhibit much higher piezoelectric coefficients and a strong electric dipole movement, thus resulting in higher electrical performance of corresponding nanogenerators. Therefore, the as-prepared LiNbO3 is used to comparatively study the electrical performance of piezoelectric, triboelectric, and hybrid nanogenerators, respectively. In this regards, a composite layer is developed by incorporating the LiNbO3 into the triboelectric polymer (i.e., polydimethylsiloxane) to develop distinct types of nanogenerators and their electrical output performance is examined. Consequently, the hybrid nanogenerator (HNG) exhibits relatively higher performance as compared to the others, thanks to synergetic piezoelectric and triboelectric effects. Furthermore, the concentration of LiNbO3 added into the composite is further optimized to realize the highest electrical performance of HNG and it also exhibits good electrical stability and mechanical durability. Eventually, practical applications of the power generated by the HNG are further demonstrated to operate portable electronics.

    Link
  • 9

    Porous Co-MoS2@Cu2MoS4 three-dimensional nanoflowers via in situ sulfurization of Cu2O nanospheres for electrochemical hybrid capacitors

    Abstract

    Engineering novel transition metal dichalcogenide (TMDC) materials with three-dimensional (3D) porous nanostructures have demonstrated exceptional electrochemical performance in energy storage due to their synergistic special morphological features and conductive metal ions. Herein, hetero-network-based MoS2@Cu2MoS4-210 (MS@CMS-210; obtained at 210 °C) 3D nanoflowers (NFs) and Co-nanoparticles-containing MS@CMS-210 (Co-MS@CMS-210) 3D NFs were prepared by a hydrothermal synthesis method without calcination. We used uniform Cu2O nanospheres (NSs) obtained via a co-precipitation method as a template to synthesize the hierarchical MS@CMS-210 3D NFs. The unique MS@CMS-210 3D NF morphology was obtained due to the in situ sulfurization effect of Cu2O NSs at the reaction temperature of 210 °C and further detailed growth process was explored. The electrochemical performances of Cu2O NSs, sulfurized MS@CMS products prepared at the reaction temperatures of 180, 190, 200, and 210 °C, and Co-MS@CMS-210 hetero-network-based electrodes were investigated. The Co-nanoparticles introduced into the optimized MS@CMS-210 3D NFs provided a higher specific surface area of 128.58 m2 g−1, further exhibiting a greater specific capacity (220 mA h g−1 at 1 A g−1) and enhanced cycling stability (~96% retention at 10 A g−1) compared to the other electrodes. The better electrochemical results were obtained due to the developed rich electroactive sites and rapid redox reactions from the rational combination of Co-MS@CMS-210 3D NF morphology and conductive natured TMDC hybrid composite. Additionally, a pouch-type electrochemical hybrid capacitor (Co-MS@CMS-210//activated carbon) device was constructed and it provided maximum energy and power density values of 41.6 W h kg−1 and 6240 W kg−1, respectively, along with greater cycling stability. Finally, several portable electronics such as green/red light-emitting diodes and timer displays were successfully tested to demonstrate the practical utility of the device in the area of energy storage.

    Link
  • 8

    Boosting a Power Performance of a Hybrid Nanogenerator via Frictional Heat Combining a Triboelectricity and Thermoelectricity toward Advanced Smart Sensors

    Abstract

    The demand for a well-equipped healthcare system is increasing due to the requirement of instant treatment in emergency situations. Particularly, patients are advised to employ fall-detection sensors and touch-activated emergency alarms to reduce the mortality rate arising from unexpected falls and emergency conditions. Herein, smart sensors are successfully developed by scavenging the human motions and heat energy with the combination of a triboelectric nanogenerator (TENG) and a thermoelectric generator (TEG). The frictional heat energy produced from the contact and separation of TENG can be utilized as an input source for TEG. Thus, the hybrid tribo-thermoelectric nanogenerator (HTTNG) generates two electrical outputs with a single primary input. As evidence of this, the flexible HTTNG delivers high output due to the synergistic effect of two generators, that is, through the high output voltage and current in TENG and TEG, respectively. The feasibility of HTTNG as a touch-activated emergency alarm and a human fall-detection sensor is successfully demonstrated. Furthermore, the HTTNG can be a promising self-powered sensing device without any additional power source as well as a power supplier in the Internet of Things era. This hybrid nanogenerator can pave the way for efficient utilization in healthcare systems.

    Link
  • 7

    Rational Design of Bimetallic Oxide Multi-Nanoarchitectures for High-Rate and Durable Hybrid Supercapacitors

    Abstract

    Designing porous multi-nanoarchitectures can be advantageous to reduce the ion impregnation and enhance the electrokinetics in the active materials of electrochemical energy storage devices. Herein, the nickel cobaltite (NiCo2O4) hybrid nanoarchitecture (NCO HNA) is prepared by using a facile wet-chemical method, followed by calcination. The effect of surfactants on the evolution of morphology is comprehensively investigated. The NCO HNA prepared with both the carbamide and methenamine as surfactants (NCO-C+M) demonstrates 1D nanorods along with 2D hexagonal nanosheets. Owing to its advantageous structural features, the NCO-C+M electrode exhibits maximum areal capacity of 154.7 μAh cm−2 compared to the other electrodes, with decent capacity retention of 86.7% after 10 000 cycles. The hybrid supercapacitor (HSC) device is fabricated with NCO-C+M as a positive electrode and activated carbon as a negative electrode. The fabricated HSC device delivers a superior areal capacitance of 221.7 mF cm−2 at 1.5 mA cm−2 and still retains 93.2% at a high current density. Besides, the HSC displays a high energy density of 67.8 μWh cm−2 and a high power density of 19545 µW cm−2, with good cycling efficiency (81.3%) after 10 000 cycles. The practicability of HSC is further tested by powering-up various electronic components.

    Link
  • 6

    Rational Design of Bimetallic Oxide Multi-Nanoarchitectures for High-Rate and Durable Hybrid Supercapacitors

    Abstract

    Designing porous multi-nanoarchitectures can be advantageous to reduce the ion impregnation and enhance the electrokinetics in the active materials of electrochemical energy storage devices. Herein, the nickel cobaltite (NiCo2O4) hybrid nanoarchitecture (NCO HNA) is prepared by using a facile wet-chemical method, followed by calcination. The effect of surfactants on the evolution of morphology is comprehensively investigated. The NCO HNA prepared with both the carbamide and methenamine as surfactants (NCO-C+M) demonstrates 1D nanorods along with 2D hexagonal nanosheets. Owing to its advantageous structural features, the NCO-C+M electrode exhibits maximum areal capacity of 154.7 μAh cm−2 compared to the other electrodes, with decent capacity retention of 86.7% after 10 000 cycles. The hybrid supercapacitor (HSC) device is fabricated with NCO-C+M as a positive electrode and activated carbon as a negative electrode. The fabricated HSC device delivers a superior areal capacitance of 221.7 mF cm−2 at 1.5 mA cm−2 and still retains 93.2% at a high current density. Besides, the HSC displays a high energy density of 67.8 μWh cm−2 and a high power density of 19545 µW cm−2, with good cycling efficiency (81.3%) after 10 000 cycles. The practicability of HSC is further tested by powering-up various electronic components.

    Link
  • 5

    Gradient-Wrinkled Microparticle with Grayscale Lithography Controlling the Cross-Linking Densities for High Security Level Anti-Counterfeiting Strategies

    Abstract

    Physical unclonable functions (PUFs) enable different characteristics according to the purpose, such as easy to access identification, high security level, and high code capacity, against counterfeiting a product. However, most multiplex approaches have been implemented by embedding several security features rather than one feature. In this paper, we present a high security level anti-counterfeiting strategy using only labyrinth wrinkle patterns with different complexities, which can be used as unique and unclonable codes. To generate codes with different levels in a microtaggant, we fabricated wrinkle patterns with characteristic wavelength gradients using grayscale lithography. The elastic modulus of the polymer substrate and corresponding wavelength after the wrinkling process were controlled by designing the gray level of each subcode region in a gray-level mask image for photopolymerization of the microparticle substrate. We then verified the uniqueness of the extracted minutia codes through a cross-correlation analysis. Finally, we demonstrated the authentication strategies by decoding different minutia codes according to the scanning resolution during the decoding. Overall, the presented patterning method can be widely used in security code generation.

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