김석 교수

Nanofabrication, a pivotal technology at the intersection of nanoscale engineering and high-resolution patterning, has substantially advanced over recent decades. This technology enables the creation of nanopatterns on substrates crucial for developing nanophotonic devices and other applications in diverse fields including electronics and biosciences. Here, this mega-review comprehensively explores various facets of nanofabrication focusing on its application in nanophotonics. It delves into hig

Stimuli-responsive surfaces with tunable fluidic and optical properties utilizing switchable surface topography are of significant interest for both scientific and engineering research. This work presents a surface involving silicon scales on a magnetically responsive elastomer micropillar array, which enables fluid and light manipulation. To integrate microfabricated silicon scales with ferromagnetic elastomer micropillars, transfer printing-based deterministic assembly is adopted. The function

Scalable and cost-effective protocols to pattern and integrate colloidal quantum dots (QDs) with high resolution have been challenging to establish. While their solubility can facilitate certain processes such as spin-casting into thin films, it also makes them incompatible with many conventional patterning techniques including photolithography that require solution processing. In this work, we present "photoresist (PR) contact patterning", a dry means to pattern QD films over large areas with h

Although many recent studies demonstrate surfaces with switchable wettability under various external stimuli, a deliberate effort to self-propel liquid droplets utilizing a surface wetting mode switch between slippery lotus and adhesive rose petal states via a mechanical strain has not been made yet, which would otherwise further benefit microfluidic applications. In this work, we present a black silicon/elastomer (bSi/elastomer) composite surface which shows switchable wettability and adhesion

The advantages of utilizing the polymeric shape memory effect for deterministic assembly of microscale objects are explored in this letter. The assembly is performed by transfer printing, which involves a polymeric stamp with reversible adhesion as a manipulator. The dynamic rigidity control afforded by heating or cooling a shape memory polymer (SMP) stamp across its glass transition temperature allows for a dramatic increase in adhesion during pick-up. Furthermore, the shape-fixing and recovery

Abstract Dry adhesives are believed to be inadequate to achieve high adhesion to a wet or submerged surface due to liquid layers intercalated at the contact interface. Here, the reversible dry adhesion of a thermoresponsive shape memory polymer (SMP) performing under water and other liquids such as oil is presented. It is revealed that applying pressure to the SMP in its compliant rubbery state enables to squeeze out the liquid from its contact interface, and that the interface is then maintaine

While methods for dynamic tuning of surface wettability to manipulate water droplets have been widely explored for many applications including digital microfluidics, those based on dynamically changeable surface morphology have remained challenging to achieve. In this work, we present a structured shape memory polymer (SMP) surface which shows dynamically tunable surface wettability through changeable surface morphology in order to manipulate water droplets. The structured SMP surface involves a

Droplet manipulation has garnered significant attention in various fields due to its wide range of applications. Among many different methods, magnetic actuation has emerged as a promising approach for remote and instantaneous droplet manipulation. In this study, we present the bidirectional droplet manipulation on a magnetically actuated superhydrophobic ratchet surface. The surface consists of silicon strips anchored on elastomer ridges with superhydrophobic black silicon structures on the top

Hydrophobic-hydrophilic hybrid surfaces, sometimes termed biphilic surfaces, have shown potential to enhance condensation and boiling heat transfer, anti-icing, and fog harvesting performance. However, state of art techniques to develop these surfaces have limited substrate selection, poor scalability, and lengthy and costly fabrication methods. Here, we develop a simple, scalable, and rapid stamping technique for hybrid surfaces with spatially controlled wettability. To enable stamping, rationa

Direct transfer of pre-patterned device-grade nano-to-microscale materials highly benefits many existing and potential, high performance, heterogeneously integrated functional systems over conventional lithography-based microfabrication. We present, in combined theory and experiment, a self-delamination-driven pattern transfer of a single crystalline silicon thin membrane via well-controlled interfacial design in liquid media. This pattern transfer allows the usage of an intermediate or mediator

Switchable control of adhesion is an important feature of many desired applications such as robotic manipulation, medical adhesives, and scalable microassembly. We present the study of the switchable dry adhesion of a shape memory polymer surface comprising nanotips which is based on not only overcoming but also exploiting the adhesion paradox, i.e., controlling surface roughness via the shape memory effect. Here, densely packed sharp nanotips causing an initial high surface roughness are flatte

A shape memory polymer (SMP) adhesive forms a conformal and hermetic contact with a target surface at the soft, rubbery state and provides a high-strength dry adhesion at the rigid, glassy state. In particular, recent SMP adhesive studies show SMP's ability to adhere to various rough and even underwater yet rigid surfaces. However, achieving and retaining the strong adhesion on flexible target surfaces such as common fabrics has not been reported since a flexible target surface would easily be p

A hybrid tip-tilt-piston micromirror driven by electrostatic actuation is presented in this letter. The micromirror involves a highly doped silicon mirror and a conductive elastomeric universal joint, which are mechanically bonded and electrically interconnected. This device takes advantage of two distinct materials to achieve a high-quality reflective surface using single-crystal silicon and a highly flexible universal joint using an elastomer. To realize this hybrid system, micromasonry techni

Microfabrication technology is further being advanced with the assistance of the deterministic assembly of small‐scale materials or microobjects through transfer printing which utilizes a stamp to transfer microobjects. However, the growing trend of miniaturization in microfabrication technologies poses challenges in achieving precise and high‐yield transfer of microobjects with diverse compositions, sizes, and shapes. This work describes the study of a novel approach utilizing a geometrically s

Atomic force microscopy (AFM) has been widely utilized to gain insight into various material and structural functionalities on the nanometer scale, leading to numerous discoveries and technologies. Despite the phenomenal success in applying AFM to the simultaneous characterization of topological and functional properties of materials, it has continuously suffered from the crosstalk between the observables, causing undesirable artifacts and complicated interpretations. Here, we introduce a two-fi