고려대학교 전자재료연구실
ELECTRO CERAMICS LABORATORY
KOREA UNIVERSITY COLLEGE OF ENGINEERING

In-Wheel Piezoelectric DC Power Generator With Zero Resistive Torque

Self-actuated thermomagnetic agitator for advanced immersion cooling in data centers

Influence of sample thickness on polarization hysteresis and energy storage in lead-free Bi0.5Na0.5TiO3-based relaxor ceramics

Artificial Morphotropic Phase Boundary Associated with Nano-Clustering in Lead Zirconate - Lead Titanate Composite Films

Thermoelectric and pyroelectric cancer therapy

Ultrasound-Driven Triboelectric Technology for Functional Wireless Power Transfer

A Body Conformal Ultrasound Receiver for Efficient and Stable Wireless Power Transfer in Deep Percutaneous Charging

Form Factor Free Magneto Triboelectric Generator for Standalone Power Line IoT Applications

High-power piezoelectric ceramics with superior figure-of-merits through tailored grain engineering

Interface Engineering of LaSrCoO-N-CDs-FeOOH Composites for Synergistic Water-Splitting Catalysis

Electric field-induced strain enhancement in Pb-free Na0. 46Bi0. 47La0. 01Ba0. 05TiO3 ceramics modified by (Al0. 50Nb0. 50) 4+ complex ions

Brief Review of Lead-Free Piezoelectric Ceramics for High-Power Applications

Artificially intelligent nasal perception for rapid sepsis diagnostics

Magnetic Control of Multiscale Ligand Nanoarchitecture Regulates Stem Cell Fate

Simultaneously achieving large transducer figure-of-merits and high curie temperature through acceptor doping in PMN-PAN-PZT ternary system for high power applications

Low-voltage driven ferroelectric thermal switch

Piezoelectric DC Generator Through Sequential In Phase Polarization Variation

UV-activated seed strategy for promoting textured colossal grain growth in templated ceramic processing

Boosting the Luminescence Performance of Magneto-Mechano-Luminescence Devices by Leveraging Self-Generated Electric Potentials

Overcoming Moisture-Induced Charge Decay in Tribo-Materials

A review on piezoelectric energy harvesting: materials, methods, and circuits

Recent advances in triboelectric nanogenerators: from technological progress to commercial applications

Microstructure and piezoelectric properties of 0.95 (Na0. 5K0. 5) NbO3–0.05 BaTiO3 ceramics

Cellular auxetic structures for mechanical metamaterials: A review

Ultra-low resonant piezoelectric MEMS energy harvester with high power density

Pyroelectric energy conversion and its applications—flexible energy harvesters and sensors

Piezoelectric energy harvesting design principles for materials and structures: material figure‐of‐merit and self‐resonance tuning

3D printed graphene-based self-powered strain sensors for smart tires in autonomous vehicles

Microstructure and Piezoelectric Properties of (1− x )(Na 0.5 K 0.5 )NbO 3 – x LiNbO 3 Ceramics

Effect of MnO 2 on the Piezoelectric Properties of (1- x )(Na 0.5 K 0.5 )NbO 3 – x BaTiO 3 Ceramics

Effect of ZnO and CuO on the sintering temperature and piezoelectric properties of a hard piezoelectric ceramic

Polarization-controlled PVDF-based hybrid nanogenerator for an effective vibrational energy harvesting from human foot

Broadband dual phase energy harvester: Vibration and magnetic field

Energy harvesting and strain sensing in smart tire for next generation autonomous vehicles

Multilayer piezoelectric energy scavenger for large current generation

Low-grade waste heat recovery scenarios: Pyroelectric, thermomagnetic, and thermogalvanic thermal energy harvesting

Lead-free piezoelectric materials and composites for high power density energy harvesting

Automatic resonance tuning mechanism for ultra-wide bandwidth mechanical energy harvesting

Thermo-magneto-electric generator arrays for active heat recovery system

Optimization of piezoelectric polymer composites and 3D printing parameters for flexible tactile sensors

Shashank Priya

Sunghoon Hur

Jeong Min Baik

Jungho Ryu

Kyung-Hoon Cho

Jun Chen

Hyun-Cheol Song

Piezoelectric microelectromechanical systems (PiezoMEMS) are attractive for developing next generation self-powered microsystems. PiezoMEMS promises to eliminate the costly assembly for microsensors/microsystems and provide various mechanisms for recharging the batteries, thereby, moving us closer towards batteryless wireless sensors systems and networks. In order to achieve practical implementation of this technology, a fully assembled energy harvester on the order of a quarter size dollar coin (diameter=24.26 mm, thickness=1.75 mm) should be able to generate about 100 μW continuous power from low frequency ambient vibrations (below 100 Hz). This paper reviews the state-of-the-art in microscale piezoelectric energy harvesting, summarizing key metrics such as power density and bandwidth of reported structures at low frequency input. This paper also describes the recent advancements …

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it …

For 0.95 (Na 0.5 K 0.5) Nb O 3–0.05 Ba Ti O 3 (0.95 NKN-0.05 BT) ceramics sintered at 1040–1075 C⁠, abnormal grain growth occurred but the grain size decreased when the sintering temperature exceeded 1075 C⁠. The dielectric constant (ϵ 3 T∕ ϵ 3)⁠, electromechanical coupling factor (k p)⁠, and piezoelectric constant (d 33) were considerably increased with increasing relative density and grain size. Evaporation of Na 2 O deteriorated the piezoelectric properties by decreasing the resistivity. To minimize Na 2 O evaporation, specimens were muffled with 0.95 NKN-0.05 BT powders during the sintering. Improved piezoelectric properties of d 33= 225 pC∕ N⁠, k p= 36%⁠, and ϵ 3 T∕ ϵ 3= 1058 were obtained for specimen sintered at 1060 C for 2 h with muffling.

Recent advances in lithography technology and the spread of 3D printers allow us a facile fabrication of special materials with complicated microstructures. The materials are called “designed materials” or “architectured materials” and provide new opportunities for material development. These materials, which owing to their rationally designed architectures exhibit unusual properties at the micro- and nano-scales, are being widely exploited in the development of modern materials with customized and improved performance. Meta-materials are found to possess superior and unusual properties as regards static modulus (axial stress divided by axial strain), density, energy absorption, smart functionality, and negative Poisson’s ratio (NPR). However, in spite of recent developments, it has only been feasible to fabricate a few such meta-materials and to implement them in practical applications. Against such a backdrop, a broad review of the wide range of cellular auxetic structures for mechanical metamaterials available at our disposal and their potential application areas is important. Classified according to their geometrical configuration, this paper provides a review of cellular auxetic structures. The structures are presented with a view to tap into their potential abilities and leverage multidimensional fabrication advances to facilitate their application in industry. In this review, there is a special emphasis on state-of-the-art applications of these structures in important domains such as sensors and actuators, the medical industry, and defense while touching upon ways to accelerate the material development process.

We demonstrate a microscale vibration energy harvester exhibiting an ultra-low resonance frequency and high power density. A spiral shaped microelectromechanical system (MEMS) energy harvester was designed to harvest ambient vibrations at a low frequency (<;200 Hz) and acceleration (<;0.25 g). High quality Pb(Zr 0.48 Ti 0.52 )O 3 (PZT) film with 1.8 μm-thickness exhibiting remanent polarization of 36.2 μC/cm 2 and longitudinal piezoelectric constant of 155 pm/V was synthesized to achieve high efficiency mechanical to electrical conversion. The experimental results demonstrate an ultra-low natural frequency of 48 Hz for MEMS harvester. This is one of the lowest resonance frequency reported for the piezoelectric MEMS energy harvester. Further, the position of the natural frequency was controlled by modulating the number of spiral turns and weight of the proof mass. The vibration mode shape and stress …

Among the various forms of natural energies, heat is the most prevalent and least harvested energy. Scavenging and detecting stray thermal energy for conversion into electrical energy can provide a cost-effective and reliable energy source for modern electrical appliances and sensor applications. Along with this, flexible devices have attracted considerable attention in scientific and industrial communities as wearable and implantable harvesters in addition to traditional thermal sensor applications. This review mainly discusses thermal energy conversion through pyroelectric phenomena in various lead-free as well as lead-based ceramics and polymers for flexible pyroelectric energy harvesting and sensor applications. The corresponding thermodynamic heat cycles and figures of merit of the pyroelectric materials for energy harvesting and heat sensing applications are also briefly discussed. Moreover, this study provides guidance on designing pyroelectric materials for flexible pyroelectric and hybrid energy harvesting.

Piezoelectric energy harvesters (PEHs) aim to generate sufficient power to operate targeting device from the limited ambient energy. PEH includes mechanical‐to‐mechanical, mechanical‐to‐electrical, and electrical‐to‐electrical energy conversions, which are related to PEH structures, materials, and circuits, respectively; these should be efficient for increasing the total power. This critical review focuses on PEH structures and materials associated with the two major energy conversions to improve PEH performance. First, the resonance tuning mechanisms for PEH structures maintaining continuous resonance, regardless of a change in the vibration frequency, are presented. Based on the manual tuning technique, the electrically‐ and mechanically‐driven self‐resonance tuning (SRT) techniques are introduced in detail. The representative SRT harvesters are summarized in terms of tunability, power consumption …

The transition of autonomous vehicles into fleets requires an advanced control system design that relies on continuous feedback from the tires. Smart tires enable continuous monitoring of dynamic parameters by combining strain sensing with traditional tire functions. Here, we provide breakthrough in this direction by demonstrating tire-integrated system that combines direct mask-less 3D printed strain gauges, flexible piezoelectric energy harvester for powering the sensors and secure wireless data transfer electronics, and machine learning for predictive data analysis. Ink of graphene based material was designed to directly print strain sensor for measuring tire-road interactions under varying driving speeds, normal load, and tire pressure. A secure wireless data transfer hardware powered by a piezoelectric patch is implemented to demonstrate self-powered sensing and wireless communication capability …

(1− x )(Na 0.5 K 0.5 )NbO 3 – x LiNbO 3 [(1− x )NKN– x LN] ceramics were produced by the conventional solid‐state sintering method, and their microstructure and piezoelectric properties were investigated. The formation of the liquid phase and K 6 Li 4 Nb 10 O 30 second phase that were observed in the (1− x )NKN– x LN ceramics was explained by the evaporation of Na 2 O during the sintering. A morphotropic phase boundary (MPB) was observed in the specimens with 0.05< x <0.08. Promising piezoelectric properties were obtained for the specimens with x =0.07. Therefore, the piezoelectric properties of this 0.93NKN–0.07LN ceramic were further investigated and were found to be influenced by their relative density and grain size. In particular, grain size considerably affected the d 33 value. Two‐step sintering was conducted at different temperatures to increase the grain size. Piezoelectric properties of d 33 =240 (pC/N) and k p =0 …

(Na 0.5 K 0.5 )NbO 3 (NKN) and BaTiO 3 (BT) ceramics form a homogeneous solid solution. The relative density of the (1- x )NKN– x BT solid solutions significantly decreased when x ≤0.07. Although the relative density of the 0.95NKN–0.05BT ceramic was very low, it had a high d 33 value of 134 pC/N. MnO 2 was added to improve the piezoelectric properties of the 0.95NKN–0.05BT ceramics by enhancing their sinterability. The addition of MnO 2 increased the density of the specimens, as well as improving the piezoelectric properties. The 0.9 mol % MnO 2 added 0.95NKN–0.05BT ceramics showed the good piezoelectric properties of k p =0.31, d 33 =194 pC/N and ε 3 T / ε 0 = 800.

Hard piezoelectrics with high dielectric and piezoelectric constants are used for high‐power applications. However, the sintering temperature of these ceramics is high, around 1200°C, restricting the usage of cheap base metal electrodes in fabrication of multi‐layer components. This study investigates the effect of CuO and ZnO on the sintering temperature of a hard piezoelectric, APC 841, which is a MnO 2 ‐ and Nb 2 O 5 ‐modified PZT. The addition of CuO decreased the sintering temperature through the formation of a liquid phase. However, the piezoelectric properties of the CuO‐added ceramics sintered at ≤950°C were lower than the desired values. The addition of ZnO resulted in a significant improvement in the piezoelectric properties. This enhancement was attributed to the formation of a homogeneous microstructure with large grains. The APC 841+0.2 wt% CuO+1.1 wt% ZnO ceramics sintered at 950°C …

The effective conversion of vibrational energy from the motion of human body into electricity has been considered as one of the most promising technologies for charging portable electronic devices. Here, we report an electric polarization-controlled PVDF-based hybrid triboelectric-piezoelectric nanogenerator (TP-NG) as for an effective energy harvesting of various mechanical vibrations from human foot. The hybrid TP-NG simply consists of PVDF, Al, and acrylic, and the triboelectric NG component is vertically stacked on the piezoelectric NG component. We observed the strong electric-polarization-dependent electric power due to the modulated surface potential and negative piezoelectricity of PVDF. We also observed the in-phase power generation due to the vertical stacking of two flat NGs, irrespective of various loading rate, contact time, force, and frequency. Three hybrid TP-NGs were embedded at the forefoot …

Broadband mechanical energy harvesting implies stable output power over a wide range of source frequency. Here we present a cost-effective solution towards achieving broadband response by designing a magnetically coupled piezoelectric energy harvester array that exhibits a large power density of 243 μW/cm 3 g 2 at natural frequency and bandwidth of more than 30 Hz under 1 g acceleration. The magnetically coupled piezoelectric energy harvester array exhibits dual modes of energy harvesting, responding to both stray magnetic field as well as ambient vibrations, and is found to exhibit the output power density of 36.5 μW/cm 3 Oe 2 at 79.5 Hz under the ambient magnetic field while maintaining the broadband nature. The magnetically coupled piezoelectric energy harvester array was demonstrated to harvest continuous power from a rotary pump vibration, an automobile engine vibration and a …

We demonstrate the feasibility of the strain energy harvesting from the automobile tires, powering wireless data transfer with enhanced frame rates, and self-powered strain sensing. For this, we used a flexible organic piezoelectric material for continuous power generation and monitoring of the variable strain experienced by a tire under different driving conditions. Power output of ∼580 µW at 16 Hz (∼112 km/h) from the energy-harvester and mounted on a section of a tire, is sufficient to power 78 LEDs. We further demonstrate that the stored energy was sufficient to power the wireless system that transmits tire deformation data with an enhanced frame rate to control system of a vehicle. Using sensors mounted on a tire of a mobile test rig, measurements were conducted on different terrains with varying normal loads and speeds to quantify the sensitivity and self-powered sensing operation. These results provide a …

Piezoelectric energy harvesting system is promising to the energy source of wireless sensor nodes for ubiquitous sensor networks. The piezoelectric material has been usually considered as a high voltage and low current source. When charging current into the thin film battery or supercapacitor, a larger current is needed to shorten the charging time. In order to increase the current in the piezoelectric energy harvesting, multilayer ceramics were fabricated. N -layer multilayer ceramics decreased the voltage but increased the current N times. The impedance of the multilayer ceramics are matched to 1 kΩ which is similar to the impedance of general electrical devices. The multilayer piezoelectric generator could be directly employed for electrical device without the additional electrical circuit to improve efficiency.

Identifying reliable and sustainable sources of electricity is a significant challenge of the present time. However, most energy-generation mechanisms produce unavoidable low-grade waste heat as a byproduct while harvesting (or converting) electrical energy from conventional or renewable energy sources. Each year, over 60% of the primary energy is wasted as heat. Accordingly, considerable efforts are being made to convert this waste heat into usable electrical energy using diverse energy conversion materials. In this review, three actively investigated energy conversion mechanisms beyond thermoelectrics, i.e . , (1) pyroelectric, (2) thermomagnetic, and (3) thermogalvanic generators, are reviewed and compared from the viewpoint of fundamental theories, critical parameters for high energy conversion efficiency, and current status of materials and devices. The challenges and opportunities in low-grade waste …

In the emerging era of Internet of Things (IoT), power sources for wireless sensor nodes in conjunction with efficient and secure wireless data transfer are required. Energy harvesting technologies are promising solution toward meeting the requirements for sustainable power sources for the IoT. In this review, we focus on approaches for harvesting stray vibrations and magnetic field due to their abundance in the environment. Piezoelectric materials and piezoelectric–magnetostrictive [magnetoelectric (ME)] composites can be used to harvest vibration and magnetic field, respectively. Currently, such harvesters use modified lead zirconate titanate (or lead-based) piezoelectric materials and ME composites. However, environmental concerns and government regulations require the development of a suitable lead-free replacement for lead-based piezoelectric materials. In the past decade, several lead-free piezoelectric …

Piezoelectric energy harvesters typically exhibit sharp peak in output power around resonance frequency (small bandwidth), which presents complexity in harvesting ambient vibrations that normally comprise of multiple frequencies. Prior attempts in designing energy harvesters with broadband response have met with practical challenges in terms of low output power, large mass and weight, and small improvements in bandwidth. Here, we report a breakthrough in demonstrating ultra-wide bandwidth piezoelectric energy harvesters through the automatic resonance tuning (ART) phenomenon. ART provides energy harvester ability to adjust its natural frequency in conjunction with ambient vibration without human intervention or additional tuning energy. The ART energy harvester utilizes the motion of the mobile proof mass in a doubly clamped oscillating beam structure to modulate the natural frequency of the beam …

Continued emphasis on development of thermal cooling systems is being placed that can cycle low grade heat. Examples include solar powered unmanned aerial vehicles (UAVs) and data storage servers. The power efficiency of solar module degrades at elevated temperature, thereby, necessitating the need for heat extraction system. Similarly, data centres in wireless computing system are facing increasing efficiency challenges due to high power consumption associated with managing the waste heat. We provide breakthrough in addressing these problems by developing thermo-magneto-electric generator (TMEG) arrays, composed of soft magnet and piezoelectric polyvinylidene difluoride (PVDF) cantilever. TMEG can serve dual role of extracting the waste heat and converting it into useable electricity. Near room temperature second-order magnetic phase transition in soft magnetic material, gadolinium, was …

Optimization of the formulation and processability of 3D-printable ceramic polymer composites offers a solution to piezoelectric materials with high printability and piezoelectric responses. Our approach is based on both 3D-printable piezoelectric composite formulation and auxetic structural design. The optimal formulation exhibited strong interfacial adhesion, high dispersion stability, low viscosity, and a smooth surface, resulting in a high piezoelectricity. In addition, processing parameters, such as the intensity and application time of the UV laser, were optimized for processability. The simulated structures were designed to further enhance the piezoelectric response, and several auxetic structures were compared. A printed piezoelectric composite with an auxetic structure, including a functionalized piezoelectric ceramic powder and a dispersant, showed good flexibility, a high piezoelectric coefficient ( d 33 ), and an …

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In-Wheel Piezoelectric DC Power Generator With Zero Resistive Torque

Self-actuated thermomagnetic agitator for advanced immersion cooling in data centers

Influence of sample thickness on polarization hysteresis and energy storage in lead-free Bi0.5Na0.5TiO3-based relaxor ceramics

연구실 보유 특허

대학별 입시끈

우리 연구실 모집

교수님 소개

송 현 철

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

In-Wheel Piezoelectric DC Power Generator With Zero Resistive Torque

Self-actuated thermomagnetic agitator for advanced immersion cooling in data centers

Influence of sample thickness on polarization hysteresis and energy storage in lead-free Bi0.5Na0.5TiO3-based relaxor ceramics

연구실 보유 특허

최근 3년간 연구실적 높은 연구실

대학별 입시끈

우리 연구실 모집