Chang Kyu Jeong

Highly‐Efficient, Flexible Piezoelectric PZT Thin Film Nanogenerator on Plastic Substrates

A highly-efficient, flexible piezoelectric PZT thin film nanogenerator is demonstrated using a laser lift-off (LLO) process. The PZT thin film nanogenerator harvests the highest output performance of ∼200 V and ∼150 μA·cm(-2) from regular bending motions. Furthermore, power sources generated from a PZT thin film nanogenerator, driven by slight human finger bending motions, successfully operate over 100 LEDs.

Self-Powered Cardiac Pacemaker Enabled by Flexible Single Crystalline PMN-PT Piezoelectric Energy Harvester

A flexible single-crystalline PMN-PT piezoelectric energy harvester is demonstrated to achieve a self-powered artificial cardiac pacemaker. The energy-harvesting device generates a short-circuit current of 0.223 mA and an open-circuit voltage of 8.2 V, which are enough not only to meet the standard for charging commercial batteries but also for stimulating the heart without an external power source.

A Hyper‐Stretchable Elastic‐Composite Energy Harvester

C. K. Jeong, G.-T. Hwang, D. Y. Park, J. H. Park, Dr. M. Byun, Prof. K. J. Lee Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST) 291 Daehak-ro , Yuseong-gu , Daejeon 305-701 , South Korea E-mail: keonlee@kaist.ac.kr Dr. J. Lee, Dr. S. Han, Prof. S. H. Ko Department of Mechanical Engineering Seoul National University 1 Gwanak-ro , Gwanak-gu , Seoul 151-742 , South Korea E-mail: maxko@snu.ac.kr Dr. J. Lee, Prof. S. S. Lee Department of Mechanical Engineering Korea Advanced Institute of Science and Technology (KAIST) 291 Daehak-ro , Yuseong-gu , Daejeon 305-701 , South Korea Dr. J. Ryu Functional Ceramic Group Korea Institute of Materials Science (KIMS) 797 Changwon-daero Seongsan-gu Changwon , Gyeongsangnam-do 642–831 , South Korea

Topographically-designed triboelectric nanogenerator via block copolymer self-assembly.

Herein, we report a facile and robust route to nanoscale tunable triboelectric energy harvesters realized by the formation of highly functional and controllable nanostructures via block copolymer (BCP) self-assembly. Our strategy is based on the incorporation of various silica nanostructures derived from the self-assembly of BCPs to enhance the characteristics of triboelectric nanogenerators (TENGs) by modulating the contact-surface area and the frictional force. Our simulation data also confirm that the nanoarchitectured morphologies are effective for triboelectric generation.

Virus-Directed Design of a Flexible BaTiO3 Nanogenerator

Biotemplated synthesis of functional nanomaterials has received increasing attention for applications in energy, catalysis, bioimaging, and other technologies. This approach is justified by the unique abilities of biological systems to guide sophisticated assembly and organization of molecules and materials into distinctive nanoscale morphologies that exhibit physicochemical properties highly desirable for specific purposes. Here, we present a high-performance, flexible nanogenerator using anisotropic BaTiO3 (BTO) nanocrystals synthesized on an M13 viral template through the genetically programmed self-assembly of metal ion precursors. The filamentous viral template realizes the formation of a highly entangled, well-dispersed network of anisotropic BTO nanostructures with high crystallinity and piezoelectricity. Even without the use of additional structural stabilizers, our virus-enabled flexible nanogenerator exhibits a high electrical output up to ∼300 nA and ∼6 V, indicating the importance of nanoscale structures for device performances. This study shows the biotemplating approach as a facile method to design and fabricate nanoscale materials particularly suitable for flexible energy harvesting applications.

Flexible Piezoelectric Thin-Film Energy Harvesters and Nanosensors for Biomedical Applications

The use of inorganic-based flexible piezoelectric thin films for biomedical applications has been actively reported due to their advantages of highly piezoelectric, pliable, slim, lightweight, and biocompatible properties. The piezoelectric thin films on plastic substrates can convert ambient mechanical energy into electric signals, even responding to tiny movements on corrugated surfaces of internal organs and nanoscale biomechanical vibrations caused by acoustic waves. These inherent properties of flexible piezoelectric thin films enable to develop not only self-powered energy harvesters for eliminating batteries of bio-implantable medical devices but also sensitive nanosensors for in vivo diagnosis/therapy systems. This paper provides recent progresses of flexible piezoelectric thin-film harvesters and nanosensors for use in biomedical fields. First, developments of flexible piezoelectric energy-harvesting devices by using high-quality perovskite thin film and innovative flexible fabrication processes are addressed. Second, their biomedical applications are investigated, including self-powered cardiac pacemaker, acoustic nanosensor for biomimetic artificial hair cells, in vivo energy harvester driven by organ movements, and mechanical sensor for detecting nanoscale cellular deflections. At the end, future perspective of a self-powered flexible biomedical system is also briefly discussed with relation to the latest advancements of flexible electronics.

Self-powered fully-flexible light-emitting system enabled by flexible energy harvester

Energy-harvesting technology utilising mechanical energy sources is a promising approach for the sustainable, independent, and permanent operation of a variety of flexible electronics. A new concept of a fully-flexible light-emitting system, self-powered by a high-performance piezoelectric thin-film energy harvester has been first established by manipulating highly-robust, flexible, vertically structured light emitting diodes (f-VLEDs). The f-VLEDs fabricated by anisotropic conductive film bonding and entire wafer etching show stable and durable performances during periodic mechanical deformations. A high-output energy harvester capable of generating up to 140 V and 10 μA can be fabricated via laser lift-off (LLO) process widely used in industries, in a safe and robust manner. In particular, this LLO process is of great benefit for the fabrication of mechanically stable, flexible piezoelectric devices, without causing any degradation of piezoelectric properties. In this process, self-powered all-flexible electronic system with light emittance can be spontaneously achieved by the electricity produced from flexible thin-film generator by applying slight biomechanical energy without any externally applied energy storage. This conceptual technology of self-powering based on the conversion of mechanical energy to electrical energy can open a facile and robust avenue for diverse, self-powered, bio-implantable applications, as well as commercial display applications.

Self-powered deep brain stimulation via a flexible PIMNT energy harvester

Deep brain stimulation (DBS) is widely used for neural prosthetics and brain–computer interfacing. Thus far in vivo implantation of a battery has been a prerequisite to supply the necessary power. Although flexible energy harvesters have recently emerged as alternatives to batteries, they generate insufficient energy for operating brain stimulation. Herein, we report a high performance flexible piezoelectric energy harvester by enabling self-powered DBS in mice. This device adopts an indium modified crystalline Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIMNT) thin film on a plastic substrate to transform tiny mechanical motions to electricity. With slight bending, it generates an extremely high current reaching 0.57 mA, which satisfies the high threshold current for real-time DBS of the motor cortex and thereby could efficiently induce forearm movements in mice. The PIMNT based flexible energy harvester could open a new avenue for future in vivo healthcare technology using self-powered biomedical devices.

Performance Enhancement of Electronic and Energy Devices via Block Copolymer Self‐Assembly

The use of self-assembled block copolymers (BCPs) for the fabrication of electronic and energy devices has received a tremendous amount of attention as a non-traditional approach to patterning integrated circuit elements at nanometer dimensions and densities inaccessible to traditional lithography techniques. The exquisite control over the dimensional features of the self-assembled nanostructures (i.e., shape, size, and periodicity) is one of the most attractive properties of BCP self-assembly. Harmonic spatial arrangement of the self-assembled nanoelements at desired positions on the chip may offer a new strategy for the fabrication of electronic and energy devices. Several recent reports show the great promise in using BCP self-assembly for practical applications of electronic and energy devices, leading to substantial enhancements of the device performance. Recent progress is summarized here, with regard to the performance enhancements of non-volatile memory, electrical sensor, and energy devices enabled by directed BCP self-assembly.

Flexible highly-effective energy harvester via crystallographic and computational control of nanointerfacial morphotropic piezoelectric thin film

Controlling the properties of piezoelectric thin films is a key aspect for designing highly efficient flexible electromechanical devices. In this study, the crystallographic phenomena of PbZr1–xTixO3 (PZT) thin films caused by distinguished interfacial effects are deeply investigated by overlooking views, including not only an experimental demonstration but also ab initio modeling. The polymorphic phase balance and crystallinity, as well as the crystal orientation of PZT thin films at the morphotropic phase boundary (MPB), can be stably modulated using interfacial crystal structures. Here, interactions with MgO stabilize the PZT crystallographic system well and induce the texturing influences, while the PZT film remains quasi-stable on a conventional Al2O3 wafer. On the basis of this fundamental understanding, a high-output flexible energy harvester is developed using the controlled-PZT system, which shows significantly higher performance than the unmodified PZT generator. The voltage, current, and power densities are improved by 556%, 503%, and 822%, respectively, in comparison with the previous flexional single-crystalline piezoelectric device. Finally, the improved flexible generator is applied to harvest tiny vibrational energy from a real traffic system, and it is used to operate a commercial electronic unit. These results clearly indicate that atomic-scale designs can produce significant impacts on macroscopic applications.