Hot Electron Detection under C..
It is well known that hot electrons, which are electrons that gain high kinetic energy during an chemical reaction, are the key elements to determine the reaction mechanism in heterogenous catalysis. However, direct detection of the hot electrons generated on the metal catalysts during the surface reactions is challenging because of their quick thermalization. To overcome this technical limitation, we have developed a novel catalytic nanodiode consisting of a thin metal catalyst deposited onto a semiconductor support, and succeeded in real-time detection of the hot electrons created in the course of catalytic reaction at atmospheric pressure or liquid phase. This finding may not only lead to the fundamental understanding in the mechanism of the catalytic reactions, but also provide a chance to develop next-generation catalysts with remarkably enhanced catalytic performance.
Protein delivery via engineere..
Nanoparticle-mediated delivery of functional macromolecules is a promising method for treating a variety of human diseases. Among nanoparticles, cell-derived exosomes have recently been highlighted as a new therapeutic strategy for the in vivo delivery of nucleotides and chemical drugs. Here we describe a new tool for intracellular delivery of target proteins, named ‘exosomes for protein loading via optically reversible protein–protein interactions’ (EXPLORs). By integrating a reversible protein–protein interaction module controlled by blue light with the endogenous process of exosome biogenesis, we are able to successfully load cargo proteins into newly generated exosomes. Treatment with protein-loaded EXPLORs is shown to significantly increase intracellular levels of cargo proteins and their function in recipient cells in vitro and in vivo. These results clearly indicate the potential of EXPLORs as a mechanism for the efficient intracellular transfer of protein-based therapeutics into recipient cells and tissues.
Development of environment-fri..
Recently, as part of environmental-friendly and sustainable development, there have been an increase in social and research demands for replacing chemical ground improvement materials such as cement, in the field of geotechnical engineering. This study was carried out to verify the microscopic interaction, feasibility, and strengthening mechanism of ground improvement using environmental-friendly microbial biopolymers, which is the world's first attempt applying microbial biopolymers as geotechnical engineering binders. In this regard, KAIST successfully secured numerous research achievements (8 SCI papers and 11 intellectual property rights at domestic and international, as well as developing a 100％ bio-based soil binder which is named as KABS (KAist Bio-Soil) binder. With KABS binder, KAIST has performed several field applications along with industrial technology transfer. Moreover, KAIST is cooporating with Korea Expressway Corporation and LH Corporation for further commercialization, nowadays.
Birefractive Stereo Imaging fo..
Depending on the polarization state of light, the incident light on a birefringent material such as calcite can be refracted into two different angles. This physical phenomenon is called double refraction. While traditional cameras capture just color pictures, we propose a novel 3D imaging method that allows us to capture not only color pictures, but also corresponding depth images. Whereas traditional stereo imaging requires at least two stereo cameras, our 3D imaging method can capture depth from a single picture of double refraction. This proposed 3D imaging technique can be applicable to many graphics and computer vision applications such as AR/VR applications that require color and depth information simultaneously.
Development of Pulse-Echo Lase..
We have world first developed a mobile laser ultrasonic propagation imaging system which is capable of 1000 point inspection per second and visualization of pulse-echo ultrasonic wave through the thickness of solid medium. This novel ultrasonic propagation visualization system has been successfully prototyped for the application of in-situ and in-process nondestructive evaluation of aerospace structures. The real world proof-of-concept has been done by testing the new system in the inspection of a space launcher fuselage (KSLV-II), control surfaces of military transport (CN-235), brake disk of F-16, guided weapon fuselage. In addition, the system has passed F-16 standard specimen test done by Korea Air Force. The prototype developed during the two years has been successfully delivered to Korea Air Force. Furthermore, the prototype development project has been introduced to The Boeing Inc. and KAIST OESL has been selected as the Boeing-KAIST technical contact lab and got a grant for 2 years from the Boeing Inc. The 2nd prototype is expected to be rent to the Boeing in 2017. The 3rd prototype will be delivered to KOPI and used as a standard inspection instrument. The ripple effect of this system and technology will be continued because another TRL improvement projects are running based on the sponsorship of KAI, Hankuk Fiber and so on.
Sub–10 nm ultrahigh–resolution..
In 2031, an ample supply of low–cost, high–performance nano–transfer printing technology has facilitated the detection and identification of various chemicals, such as disease–causing substances, drugs, and pesticides, for the last 15 years. Upon suspicion that a food has been contaminated by toxic substances, such as pesticide residue, tests can be done easily using detection kits based on printed electronics technology. Furthermore, self–diagnoses for a range of health conditions can be conducted easily with only a drop of blood. This is a revolution in detection and diagnosis technology that has enhanced food safety and promoted public health. Nano–transfer printing is an effective technology that, through a simple fabrication process, can enable the mass production of transistors, metamaterials, skin sensors, and other next–generation devices. However, printing sub–50 nm structures has not been researched, as it is physically difficult to both replicate and transfer the patterns. Our team has succeeded in realizing a nano–transfer printing technique that is applicable to virtually any surface by using a bilayer polymer that is effective at reproducing sub–10 nm patterns and applying the principle of selectively weakening surface adhesion. This technique was used to fabricate a working high–performance gas sensor that is capable of detecting explosive gases and nondestructively detecting pesticide residue on fruits. Printed electronics are electronic devices created using a printing fabrication method. Being able to fabricate devices using this method facilitates mass production through automated processes, giving such devices the advantages of being low– cost, environment–friendly, flexible, scalable, and applicable to low– temperature environments and simple processes. Consequently, they are expected to be used in a wide range of applications. The nanotechnology– based printed electronics fabrication method is anticipated to be utilized for a broad range of new products, such as RFIDs, memory chips, displays, batteries, lighting, sensors, and organic transistors. Based on related industries, the market value is predicted to be USD 57 billion. Accordingly, printed electronics processes for improving the performance and density of devices are expected to be applicable to high–value industries. Our team has found that, unlike conventional elastic molds, certain polymers can replicate ultrafine nano–patterns. Using this to replicate fine surface patterns, we were able to develop a series of key technologies to fabricate sub–10 nm , ultrafine nano–materials. Moreover, through this research, the principles of interface energy control in the so–called “super–lubrication effect,” based on organic solvents in vapor form, were discovered. Using this effect, a novel nano–transfer printing technology was developed, enabling the printing of an aligned nano–structure on virtually any substrate without surface treatments. The newly developed nano–transfer printing method is done in two steps. In the first step, a polymer film is coated on a template substrate with a patterned surface, peeled off using adhesive film to form a replicated thin–film mold, and deposited using functional materials to form a nano–structure. In this process, self–assembly technology can be used on the sub–10 nm master mold, and our team has recently reported an in situ directed self–assembly technology that maximizes processing convenience. In the application step, the polymer films replicate the nano–patterns on the template surface in sub– 10 nm resolution, and this is used to form sub– 10 nm ultrafine nano–structures. In the second step, an organic solvent vapor is introduced into the interface between the adhesive film and the replicated film mold, which selectively reduces adhesion between the two polymer films and prints the nano–structure on various substrates. The printed nano– structure is then utilized as a core material in the fabrication of devices. Through these attempts, our team has successfully implanted ultrafine nano– structures on various surfaces, from conventional silicon wafer substrates, flexible substrates, and curved substrates to biosurfaces like human skin. Using this ultrafine nano–transfer printing technique, a high–performance hydrogen sensor for the rapid detection of explosive gases was fabricated. Also, we became the first to successfully detect traces of pesticide residue on the surfaces of fruits in a nondestructive way. The novel nano–transfer printing technology developed by our team holds great significance. It is both a foundational technology, allowing the low–cost production of high–density sensors and semiconductor devices, and a state–of–the–art technology, making it possible to fabricate nano–materials and devices on various substrates. Furthermore, as this technique requires low investment and processing costs, it is expected to lead to significant reductions in the overall cost of device fabrication.
Role of Tau Regulating Force b..
Metaphor – In the morning of 2050, a motor protein named of “Kinesin” starts engine to transport neurotransmitter from the body of cell down to the end of axon. He is listening to morning news saying that highways is collapsed as symptom of Alzheimer’s. But he is not in worry because he knows 119 would fix it by signaling Tau to be expressed more with the recipe of short: medium: long Tau = 4:5:1. In an hour, Kinesin is driving through highway 101. cytoskeletal filaments assembled from αβ–tubulin heterodimers. Tau, an unstructured protein found in neuronal axons, binds to MTs and regulates their dynamics. Aberrant Tau behavior is associated with neurodegenerative dementias, including Alzheimer’s disease. We report on a direct force measurement between MTs coated with Tau by synchrotron small angle X–ray scattering (SAXS) under osmotic pressure. Tau with longer N–terminal tails sterically stabilizes MTs, preventing bundling up to ∼10,000– 20,000 Pa, an order of magnitude larger than bare MTs. This study suggests an isoform–dependent biological role for regulation by Tau, with longer isoforms conferring MT steric stabilization against aggregation either with other biomacromolecules or into tight bundles, preventing loss of function in the crowded axon environment. MTs, structural components of the eukaryotic cytoskeleton, are protein nanotubes involved in a range of cell functions, including intracellular trafficking, cell motility, segregating chromosomes, and establishing cell shape. MTs are composed of straight protofilaments (PFs), which are head to tail assemblies of globular αβ–tubulin heterodimers that selforganize, with lateral PF–PF interactions stabilizing the hollow MT. MT structure and assembly dynamics are regulated and functionally differentiated in vivo by MT–associated protein (MAP) Tau that is primarily localized to the axons of mature vertebrate neurons. Although Tau is involved in numerous functions, which remain to be fully elucidated, a well– characterized function of Tau on binding to MTs in mature neurons is in the modulation of MT dynamic instability by enhancing tubulin assembly while suppressing MT depolymerization. This modulation of MT dynamic instability ensures proper trafficking of modifications of Tau, including hyper–phosphorylation and mutations leading to loss of function, have been implicated in Alzheimer’s disease and a wide range of neurodegenerative disorders, including Fronto–Temporal Dementia with Parkinsonism linked to chromosome 17, Pick’s, supranuclear palsy, and more recently, chronic traumatic encephalopathy in athletes suffering concussions. We have investigated Tau–mediated forces between MTs using SAXS subjected to osmotic pressure. This study has revealed that Tau fundamentally alters the repulsive forces between MTs in an isoform–dependent manner. In particular, the jump in osmotic pressure required to bundle MTs coated with –M and –L Tau isoforms reveals a gain of function of Tau isoforms with longer N–terminal tails inimparting steric stabilization to individual MTs against bundling. What is highly significant in this work is the demonstration of the functional property of the charged projection domain (PD) in sterically stabilizing MTs on undergoing a transition to a brush state. Previous identification of Tau’s PD was based entirely on its lack of binding affinity to MTs and did not give insight to its biophysical functions. Steric stabilization against cellular biomacromolecules is essential in preventing MT loss of function in the crowded axon environment. Furthermore, the conformation of Tau on the MT surface is intrinsically connected to its coverage. The discovery of two distinct conformation states of MT–bound Tau, namely mushroom or brush, further emphasizes the need for future biophysical measurements of MT–bound Tau to be conducted in both regimes. It is interesting to note that the expression of six different Tau isoforms is developmentally regulated, where fetal brain expresses only the shortest isoform (3RS), whereas the adult brain expresses an ∼1:1 ratio of 3R and 4R Tau. This observation would suggest that the 3RS isoform is likely to be expressed at a higher level in fetal brain, enabling steric stabilization of fetal MTs at higher coverage, where 3RS Tau would be in a more extended brush conformation. With respect to the adult brain, although the composition of different isoforms is not known at different points along the length of the axon, our finding points to a minimum coverage needed by the longer isoforms (either –M or –L) to impart steric stabilization to MTs. This minimum coverage required for MT steric stabilization by Tau could also shed light on a possible pathway for neurodegeneration. In the diseased state, Tau is often found to be hyperphosphorylated, with a weaker binding affinity to MTs. MTs lose sufficient Tau coverage to the degree where PDs transition from brush to mushroom and fail to sterically stabilize MTs, intracellular trafficking on MTs could be significantly hampered by the nonphysiological close–bundled state in the crowded axonal environment. At high pressures in the MT bundled–phase regime, the polyampholytic nature of Tau resulted in a coverage–dependent electrostatic attraction between MTs. This regime of “tight bundles,” resisted by longer PDs, may conceivably be accessed in vivo in the presence of excess molecular crowding forces. Tight bundles would have negative consequences for organelle trafficking by MTs, where thesmall MT wall to wall spacing, ranging between 3 and 5 nm, would be expected to interfere with motors carrying cargo. In addition to the biological interest in MT–associated protein Tau as a key component of the axonal cytoskeleton, the directed assembly of MTs by intrinsically disorder protein Tau is also of broad interest from a biomolecular materials and biophysics perspective. The unique manifestation of short–range attraction and long–range repulsion by Tau of MTs gives inspiration for the design of biomaterials with multiple interaction motifs. The microtubule–associated protein Tau is known to stabilize microtubules against depolymerization in neuronal axons, ensuring proper trafficking of organelles along microtubules in long axons. Abnormal interactions between Tau and microtubules are implicated in Alzheimer’s disease and other neurodegenerative disorders. We directly measured forces between microtubules coated with Tau isoforms by synchrotron smallangle X–ray scattering of reconstituted Tau–microtubule mixtures under osmotic pressure (mimicking molecular crowding in cells). We found that select Tau isoforms fundamentally alter forces between microtubules by undergoing a conformational change on microtubule surfaces at a coverage indicative of an unusually extended Tau state. This gain of function by longer isoforms in imparting steric stabilization to microtubules is essential in preventing microtubule aggregation and loss of function in organelle trafficking.
Micro Chained Radar System for..
Unmanned aerial vehicles (UAVs), commonly known as drones, are difficult to detect using conventional radar systems. In this research, a precise radar system that can detect and identify small UAVs has been developed. Researchers succeeded in detecting them at ranges up to 1 km and extracting information of interest such as velocity and location. It is expected to improve technological readiness and achieve global competitiveness in the radar industry. Recently, North Korea has deployed a fleet of indigenous small UAVs.As the North Korean military poses a serious threat to the Republic of Korea (ROK), particular attention should be given to surveillance systems. The ROK Army and Air Force are currently using a low–altitude surveillance radar system that has difficulty in tracking small UAVs and has limitations imposed by mountainous terrain of ROK. For this reason, several experiments were conducted usingother radars imported from the UK and Israel but all failed. It is therefore necessary to develop an improved radar system whose resolution and sensitivity are high enough to accurately detect small UAVs. Researchers have developed a 4–channel radar system for the detection of small UAVs with our own technologies. It can detect UAVs having little radar cross section (≤0.03m2) whereas those of an existing radar system of the ROK army are about 2.0m2 , which means the detection performance is improved greatly (60 times). Also, it is possible to identify UAVs using the discrepancy compared to birds and other clutters. The development of the radar system includes fabricating Ku–band antennas, designing RF circuitry and its synchronization, and implementing a tracking algorithm and real–time data processing. This system has 1 transmitter in the center and 4 receivers in the four cardinal directions to find out the exact location of the target. This optimum placement forms conical beam patterns and determines the range of air surveillance. Researchers succeeded in enhancing the overall performance of the system by utilizing digital signal processing. Not only has the stability and dynamic range of the system been improved, but the size of the system has been smaller and the cost has also been reduced compared to analog–based systems. This radar system has a bandwidth of 150 MHz and the radial resolution is 1 m. Researchers have a number of experiments to verify its performance. During both trials, it successfully detected and tracks all eleven various drones prepared. This radar system can be used to guard the Military Demarcation Line and key national infrastructure as one of core technologies for the national security. As civil drones are increasingly being used, it is possible to apply the system for civilian demands.
Photonic oscillators with a ti..
Oscillators generate highly periodic clock signals that are used to synchronize the operation of systems. Today, high–performance oscillators play an important role not only in information and communication systems, but also for large–scale scientific facilities, measurement, defense, GPS, and navigation systems, to name only a few. For the development of ultrahigh–performance yet simple and robust oscillators, we demonstrate an all–fiber photonic oscillator with a three–femtosecond (3x10–15 seconds) timing error over a period of 0.1 seconds, the equivalent stability of which corresponds to an error of only one second in one million years. Lower noise oscillators can not only improve the performance of existing timing systems, but also allow new high–precision applications that were not possible before. Today’s state–of–the–art low–noise oscillators are based on specially designed and manufactured microwave or optical cavities that are both highly complex and expensive, limiting the breadth of their application. In this study, we pursued a new method of generating ultralow–noise clock signals using an all–fiber photonic oscillator that is cheaper and features a simpler design. Free–running mode–locked lasers can generate optical pulse trains with sub– femtosecond timing jitter on a fast time scale. However, the jitter of free–running lasers rapidly diverges over longer time scales. For example, a recent study showed that the absolute RMS jitter of free–running fiber lasers reaches 20 picoseconds over a period of one second despite exhibiting only 710 attoseconds of jitter within 100 microseconds. Therefore, maintaining attosecond–level absolute timing jitter over much longer time scales (e.g., 10 milliseconds or longer) could significantly increase the performance of many existing applications and open up new applications inprecision timing both in optics and electronics. To suppress the repetition–rate phase noise at lower Fourier frequencies, free–running mode–locked lasers can be locked to an ultrahigh–quality–factor (Q) radio frequency(rf), microwave, or optical reference. However, these previous state–of–the–art techniques are not only complex and expensive, but also fragile and alignment–sensitive. Therefore, a simpler, more robust repetition–rate stabilization method that can still achieve both ultralow phase noise/timing jitter and ultrahigh frequency stability is highly desirable. Here, we demonstrate a new all–fiber–based method for the repetition–rate stabilization of mode–locked lasers without using any cw lasers, spectral broadening, or fceo detection. This novel method is based on the direct repetition–rate stabilization of a mode–locked laser to a kilometer–scale fiber delay line. Using this method to stabilize a mode–locked erbium–doped fiber laser enables the all–fiber photonic generation of optical pulse trains with sub–femtosecond absolute timing jitter over a 0.01–second time scale, which is about 100 times longer than free–running lasers. Over a one–second time scale, the integrated absolute RMS timing jitter is suppressed by a factor of 500, from 10 picoseconds to only 20 femtoseconds. Such photonic oscillators and signal generators will find various applications inlarge–scale scientific facilities (e.g., free–electron lasers and radio astronomy), information systems (e.g., analog–to–digital converters and optical interconnection), space technology (e.g., navigation/time–keeping and satellite payload), defense systems (e.g., photonic radar and lidar), and environmental technology (e.g., remote sensing and dual–comb spectroscopy).
World's first handheld so..
Most car drivers have had the experience of hearing a noise while driving but not being able to determine its source. A sound camera, which visualizes sound in color contours similar to how a thermal camera displays temperature with visual images, can be an ideal tool to pinpoint the exact location of a noise when it is generated. Together with SM Instruments, Inc., a venture company started in the KAIST Technology Business Incubation Center, we developed and commercialized a handheld sound camera, which is the first of its kind in the world. The sound camera, SeeSV-S205, weighs only 1.78kg with a width of 39cm and a height of 38cm. Three ergonomically designed grips at the back of the camera provide excellent usability and mobility. For its innovative design, last February, SeeSV-S205 won a Red Dot Award: Product Design 2013, one of the three most prestigious international design awards in the world.
Development of a wall–climbing..
CAROS (Climbing Aerial RObot System) is a drone–type wall–climbing robot that can be used to inspect the surfaces of buildings and superstructures by changing its configuration and attaching itself to all types of surfaces. It is an efficient means of cleaning and conducting maintenance on buildings. CAROS has been extended to FAROS (Fireproof Aerial RObot System) that has been designed to enter large buildings and quickly gather information in the event of a fire. Such data will assist firefighters in their rescue efforts. A drone–type wall–climbing robot system can access any surface of a structure by flying and attaching to the target area using a configuration–change and perching mechanism.The robot is also equipped with a mechanism that allows it to climb vertical surfaces, like other wall–climbing robots. It is expected to be used for up–close inspections and maintenance of structures of various shapes. The structural stability of large structures, such as bridges, high–rise buildings, wind turbines, and large These technologies are expected to be used for the inspection or maintenance of surfaces that are not easily accessible. They may also be used to perform various types of maintenance on urban structures, such as inspections of wind turbine blades and the cleaning of high–rise buildings and solar panels aircraft, is a major factor of social security. Nowadays, due to the aging of large structures and public concern regarding the potential of their collapse, interest in structural health monitoring has been increasing around the world. Though much research has been done on means of inspecting inaccessible parts of large structures using mobile robots, the fact that most existing robots require the installation of additional infrastructure or use magnetic–based technology or vacuum adhesion has made it difficult to use them on structures with diverse surface shapes and materials. We have proposed the first drone–type wall–climbing robot system that doesn’trequire the installation of additional infrastructure, thereby maximizing stability and mobility. Called CAROS (Climbing Aerial RObot System), this robot features greater mobility than existing wall–climbing robots. In particular, it has the advantage of being able to recover from falls caused by unexpected disturbances. Since the robot can attach to surfaces, it is capable of performing up–close inspections of and maintenance on structures of various types. - Wall–climbing drone design and analysis: The structure and mechanism of the drone were designed and analyzed to maximize flight stability and grip force. - Development of flying/climbing mode transformation and wall–climbing control algorithm: In order to allow the robot to attach to a wall while flying, a flying/climbing mode transformation and wall–climbing control algorithm was developed.Forward and backward kinematics were derived and applied to the algorithm. - Development of three–dimensional autonomous navigation technology: The autonomous navigation algorithm was developed using sensor information that allows the robot to sense a three–dimensional environment.
An Asynchronous Sampling-Based..
This paper presents a direct photon-counting X-ray image detector with a HgI2 photoconductor for high-quality medical imaging applications. The proposed sampling-based charge preamplifier with asynchronous self-reset enables a pixel to detect single X-ray photon energy with higher sensitivity and faster processing rate. The use of the correlated double sampling enabled by the sampling-based architecture also reduces flicker noise and contributes to the achievement of high pixel-to-pixel uniformity. Discrimination of the energy level of the detected X-rays is performed by the proposed compact in-pixel ADC with low power consumption. Three 15-bit counters in each pixel count up energy-discriminated photons for the reconstruction of multispectral X-ray images. A 128 × 128 X-ray image detector with a pixel size of 60 × 60 μm2 is implemented and measured using a 0.13-μm/0.35-μm standard CMOS process. It discriminates 3 energy levels of photon energy with a gain of 107 mV/ke- and a static power consumption of 4.6 μW/pixel. The measured equivalent noise charge (ENC) and minimum detectable energy level of the detector pixel are 68 e- rms and 290 e-, respectively. The measured maximum threshold dispersion in the pixel array is 164 e- rms without any calibration. The functionality of our chip is also successfully demonstrated using real X-ray images.