Keon Jae Lee 교수

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.

A nanocomposite generator (NCG) is fabricated using piezoelectric BaTiO3 nanoparticles and universal graphitic carbons (carbon nanotubes and reduced graphene oxide). A piezoelectric nanocomposite is produced by the simple process of dispersing nanoparticles and carbon-based nanomaterials in a polydimethylsiloxane matrix and subsequent spin-casting onto a metal-coated plastic substrate. The NCG device generates an output voltage of ∼3.2 V and a current of ∼350 nA under periodic mechanical deforma

Continuous monitoring of an arterial pulse using a pressure sensor attached on the epidermis is an important technology for detecting the early onset of cardiovascular disease and assessing personal health status. Conventional pulse sensors have the capability of detecting human biosignals, but have significant drawbacks of power consumption issues that limit sustainable operation of wearable medical devices. Here, a self-powered piezoelectric pulse sensor is demonstrated to enable in vivo measu

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 and deformable elastic-composite generator is developed using a piezoelectric nanocomposite composed of (1−x){Pb(Mg1/3Nb2/3)O3}–x{PbTiO3} microparticles, carbon nanotubes, a silicone rubber matrix, and very long silver (Ag) nanowire percolation network electrodes. To date, this nanogenerator sets world records for output performance, strain capacity, mechanical stability, and commercial feasibility in the research field for stretchable and deformable piezoelectric energy harv

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 propertie

Recent technological advances in developing a diverse range of lasers have opened new avenues in material processing. Laser processing of materials involves their exposure to rapid and localized energy, which creates conditions of electronic and thermodynamic nonequilibrium. The laser-induced heat can be localized in space and time, enabling excellent control over the manipulation of materials. Metal oxides are of significant interest for applications ranging from microelectronics to medicine. N

The outstanding performance (sheet resistance of 5 Ω sq^-1 at transmittance of 90%) and strongly adhesive (30.7 J m^-2 ) silver nanowires (AgNWs) are fabricated using flash-induced plasmonic welding (FPW) based on theoretical research of photothermal interactions. The FPW-processed AgNWs are utilized as electrodes of a transparent flexible energy harvester, and this device exhibits excellent transmittance and high electric output performance. The FPW methodology provides a hi

For patients who suffer from sensorineural hearing loss by damaged or loss of hair cells in the cochlea, biomimetic artificial cochleas to remedy the dis­advantages of existing implant systems have been intensively studied. Here, a new concept of an inorganic‐based piezoelectric acoustic nanosensor (iPANS) for the purpose of a biomimetic artificial hair cell to mimic the functions of the original human hair cells is introduced. A trapezoidal silicone‐based membrane (SM) mimics the function of th

The lead‐free nanocomposite generator device for high‐output energy harvesting using piezoelectric alkaline niobate‐based particles (KNLN) and copper (Cu) nanorods filler is reported. To produce the piezoelectric nanocomposite (p‐NC), lead‐free KNLN particles synthesized using a solid‐state method and the Cu nanorods are distributed in a polydimethylsiloxane (PDMS) matrix. The lead‐free flexible nanocomposite generator (NCG) made by a simple spin‐casting method successfully converts mechanical e

A flexible piezoelectric energy harvester was demonstrated by an aerosol-deposited PZT film to realize a self-powered wireless sensor node system. The flexible harvesting device can generate a voltage of 200 V and a current of 35 μA. A self-powered wireless sensor node was constructed by integrating the PZT harvester, a rectifying/storage circuit, and a wireless temperature-sensor node to measure ambient temperature and wirelessly transmit the data to a monitor. As a service to our authors and r

A high-output large-area lead zirconate titanate (PZT)-based nanocomposite generator (NCG) device is demonstrated using a simple, low-cost, and scalable bar-coating method. The generated output reaches up to ≈100 V and ≈10 μA and powers 12 commercial light-emitting diodes (LEDs) without external energy-storage systems. This demonstrates the feasibility of using NCG devices to power consumer electronics, self-powered devices, and wireless sensor networks using irregular mechanical agitation.

Wearable blood-pressure sensors have recently attracted attention as healthcare devices for continuous non-invasive arterial pressure (CNAP) monitoring. However, the accuracy of wearable blood-pressure (BP) monitoring devices has been controversial due to the low signal quality of sensors, the absence of an accurate transfer function to convert the sensor signals into BP values, and the lack of clinical validation regarding measurement precision. Here, a wearable piezoelectric blood-pressure sen

Flexible resonant acoustic sensors have attracted substantial attention as an essential component for intuitive human-machine interaction (HMI) in the future voice user interface (VUI). Several researches have been reported by mimicking the basilar membrane but still have dimensional drawback due to limitation of controlling a multifrequency band and broadening resonant spectrum for full-cover phonetic frequencies. Here, highly sensitive piezoelectric mobile acoustic sensor (PMAS) is demonstrate

Abstract Inorganic‐based micro light‐emitting diodes (µLEDs) have witnessed significant improvements in terms of display and biomedical applications, which can shift the paradigm of future optoelectronic systems. In particular, µLED displays are on the verge of becoming the next big interface platform for visual communications, expanding to various internet of things and wearable/bioapplications. Novel µLED concepts need to be upgraded to be able to satisfy their potential optoelectric applicati