Hoon Eui Jeong

Ulsan National Institute of Science and Technology | UNIST · Department of Mechanical Engineering

Stretchable and self-adhesive conductive hydrogels hold significant importance across a wide spectrum of applications, including human–machine interfaces, wearable devices, and soft robotics. However, integrating multiple properties, such as high stretchability, strong interfacial adhesion, self-healing capability, and sensitivity, into a single ma...

Soft robotic grippers excel at achieving conformal and reliable contact with objects without the need for complex control algorithms. However, they still lack in grasp and manipulation abilities compared with human hands. In this study, we present a sensorized multi-fingered soft gripper with bioinspired adhesive fingertips that can provide both fi...

We demonstrate the facile fabrication of metal-wire-embedded microtrenches interconnected with semiconducting ZnO nanowires (ZNWs) through the continuous mechanical machining of micrograting trenches, the mechanical embedding of solution-processable metal wires therein, and the metal-mediated hydrothermal growth of ZNWs selectively thereto. The ent...

Microscale and nanoscale cilia are ubiquitous in natural systems where they serve diverse biological functions. Bioinspired artificial magnetic cilia have emerged as a highly promising technology with vast potential applications, ranging from soft robotics to highly precise sensors. In this review, we comprehensively discuss the roles of cilia in n...

Microparticles with multiple internal chambers hold great promise as drug delivery systems due to their ability to sustain the release of drugs with short half‐lives. However, conventional batch methods used for their fabrication have limitations in terms of encapsulation efficiency and particle size distributions, while microfluidic methods suffer...

Achieving exceptional water-repellency and reliable reversible adhesion is crucial for the development of wearable flexible electronics. However, simultaneously achieving these properties presents a significant challenge, as water-repellency requires maximizing the presence of air while robust adhesion necessitates enhancing the solid fraction. In...

As point‐of‐care testing (POCT) is becoming the new paradigm of medical diagnostics, there is a growing need to develop reliable POCT devices that can be conveniently operated in a minimally invasive manner. However, the clinical potential of POCT diagnostics is yet to be realized, mainly due to the limited and inconsistent amount of collected samp...

Ionotronic hydrogels have attracted significant attention in emerging fields such as wearable devices, flexible electronics, and energy devices. To date, the design of multifunctional ionotronic hydrogels with strong interfacial adhesion, rapid self-healing, three-dimensional (3D) printing processability, and high conductivity are key requirements...

Inspired by mucus‐secreting organisms, biomimetic slippery surfaces have been studied in various engineering fields. The liquid‐infused polymer surface (LIPS) has received considerable interest because of its ability to store lubricants inside the polymer itself, facile fabrication, and high scalability. However, the conventional LIPS easily loses...

Biological cilia have exquisitely organized dynamic ultrafine structures with submicron diameters and exceptional aspect ratios, which are self-assembled with ciliary proteins. However, the construction of artificial cilia with size and dynamic functions comparable to biological cilia remains highly challenging. Here, we propose a self-assembly tec...

For decades, bioinspired functional materials have been attracting the interest of many researchers for their remarkable characteristics. In particular, some plant leaves are well known for their inherent superhydrophobic nature. Salvinia molesta, a free-floating aquatic fern, has egg-beater-shaped hierarchical trichomes on its surface of leaves. D...

Over the past few decades, extensive research efforts have been devoted to developing surfaces with unique functionalities, such as controlled wettability, antibiofouling, antifogging, and anti-icing behavior, for applications in a wide range of fields, including biomedical devices, optical instruments, microfluidics, and energy conservation and ha...

Nanocilia In article number 2200185, Hoon Eui Jeong and co‐workers develop a programmable self‐assembly strategy that can direct magnetic nanoparticles into a highly ordered, field‐responsive, artificial nanocilia array. The self‐assembled nanocilia can maintain their structural integrity through the interplay of interparticle interactions. Interes...

We present a solution-processable Ag nanostructure (SPAN) fabrication protocol for thin metallic nanoarchitectures exhibiting tunable optical and electrical properties as well as strong adhesion to general materials, including transparent, flexible, and fabric substrates and graphene-coated surfaces. The SPAN film can be fabricated in a scalable, v...

Polyurethane (PU) is the most extensively used soft backbone substrate for wearable applications. However, even with biocompatibility and stretchability, PU-based wearable devices are unsuitable for epidermal devices because they lack of adhesive properties. To impart adhesive properties to PU, commercial adhesive additives are required or the mixi...

Self‐assembly of nanoparticles (NPs) is a powerful route to construct higher‐order structures. However, the programmed self‐assembly of NPs into non‐close‐packed, three‐dimensional (3D), shape‐morphing nanocilia arrays remains elusive, whereas dynamically actuated nanometer cilia are universal in living systems. Here, we present a programmable self...

Recently, temperature monitoring with practical colorimetric sensors has been highlighted because they can directly visualize the temperature of surfaces without any power sources or electrical transducing systems. Accordingly, several colorimetric sensors that convert the temperature change into visible color alteration through various physical an...

Living creatures often adopt multiple strategies that utilize materials, structures, and dynamic motions to efficiently prevent surface fouling. However, previous synthetic antifouling materials are typically based on single strategies using materials, structures, or physical motions, which lead to limited antifouling performance. Here, we present...

Ice buildup occurs through multiple routes of frost formation, condensate freezing, and supercooled raindrops. Therefore, it is crucial to integrate multiple anti- and de-icing functionalities in the design of next-generation ice-free materials. Herein, a multifunctional magneto-responsive photothermal composite cilia array (MRPA) exhibiting remark...

Minimizing the thermal contact resistance (TCR) at the boundary between two bodies in contact is critical in diverse thermal transport devices. Conventional thermal contact methods have several limitations, such as high TCR, low interfacial adhesion, a requirement for high external pressure, and low optical transparency. Here, a self-interfacing fl...

Bioinspired adhesives that emulate the unique dry and wet adhesion mechanisms of living systems have been actively explored over the past two decades. Synthetic bioinspired adhesives that have recently been developed exhibit versatile smart adhesion capabilities, including controllable adhesion strength, active adhesion control, no residue remainin...

The stability of air plastron entrapped in a submerged superhydrophobic (SHPo) surface determines the sustainability of the surface properties including drag reduction, self-cleaning, and anti-icing. To increase the stability for high water pressure, various microstructures have been adopted for SHPo surfaces. A re-entrant structure is a typical ex...

Biofouling of tubular fluidic devices limits the stability, accuracy, and long-term uses of lab on-a-chip systems. Healthcare-associated infection by biofilm formations on body-indwelling and extracorporeal tubular medical devices is also a major cause of mortality and morbidity in patients. Although diverse antifouling techniques have been develop...

Flexible tactile sensors are required to maintain conformal contact with target objects and to differentiate different tactile stimuli such as strain and pressure to achieve high sensing performance. However, many existing tactile sensors do not have the ability to distinguish strain from pressure. Moreover, because they lack intrinsic adhesion cap...

In winter, electric power facilities such as solar panels, substations, power towers, and power lines suffer from freezing or ice accumulation problems due to exposure to harsh external environments. These problems result in unstable power supply, high maintenance costs, and severe economic and social losses. To address these problems, diverse anti...

Repeatedly changing dressings during wound healing can cause unbearable physical pain for patients with chronic skin injury. In this study, we designed a tough hydrogel-based dressing that can be degraded in an on-demand fashion for advanced chronic wound care. The resultant hydrogel dressing could be rapidly dissolved within 100 s after wetting wi...

Biomedical patches have been known as important biomaterial-based medical devices for the clinical treatment of tissue and organ diseases. Inspired by the extracellular matrix-like aligned nanotopographical pattern as well as the unique physical and biocompatible properties of gelatin, we developed strength-enhanced biomedical patches by coating ge...

A variety of sensor systems have been developed to monitor the structural health status of buildings and infrastructures. However, most sensor systems for structural health monitoring (SHM) are difficult to use in extreme conditions, such as a fire situation, because of their vulnerability to high temperature and physical shocks, as well as time-co...

The development of a flexible electronic skin (e-skin) highly sensitive to multimodal vibrations and a specialized sensing ability is of great interest for a plethora of applications, such as tactile sensors for robots, seismology, healthcare, and wearable electronics. Here, we present an e-skin design characterized by a bio-inspired, microhexagona...

Flexible, transparent, conductive electrodes are key elements of emerging flexible electronic and energy devices. Such electrodes should form an intimate physical contact with various active components of flexible devices to ensure stable, low‐resistant electrical contacts. However, contact formation techniques are based largely on conventional sol...

Extensive efforts have been devoted toward developing antibiofilm materials that can efficiently suppress bacterial attachment and subsequent biofilm formation. However, many of the previous approaches are based on non-biocompatible, non-degradable, and environmentally harmful synthetic materials. Herein, we report an efficient and sustainable biof...

Diverse bioinspired antifouling strategies have demonstrated effective fouling-resistant properties with good biocompatibility, sustainability, and long-term activity. However, previous studies on bioinspired antifouling materials have mainly focused on material aspects or static architectures of nature without serious consideration of kinetic topo...

Vertically aligned nanomaterials, such as nanowires and nanoneedles, hold strong potential as efficient platforms onto which living cells or tissues can be interfaced for use in advanced biomedical applications. However, their rigid mechanical properties and complex fabrication processes hinder their integration onto flexible, tissue-adaptable, and...

Measuring shear displacement and pressure simultaneously is essential for various applications, such as tactile sensors for robotic finger tips, shoe soles for gait monitoring, etc. We present a simple means of transducing shear displacement and pressure change to flexible composite sensor. The presented sensor consists of an array of cylindrical p...

Eggshell membrane (ESM) is usually regarded as an agricultural by-product waste, even though it has unique properties as a biomaterial. In particular, ESM has a flexible and highly pure microfibrous network structure that can be used as an artificial extracellular matrix (ECM) platform for engraftment or as a tissue-engineered scaffold. In this stu...

In article number 1902720, Hoon Eui Jeong and co‐workers develop an ultra‐adaptable and wearable photonic skin based on a shape‐memory, responsive cellulose derivative. The photonic skin can firmly adhere to diverse substrates including the human skin and building walls and directly visualize external mechanical stimuli from the substrates.

A flexible microneedle patch that can transdermally deliver liquid-phase therapeutics would enable direct use of existing, approved drugs and vaccines, which are mostly in liquid form, without the need for additional drug solidification, efficacy verification, and subsequent approval. Specialized dissolving or coated microneedle patches that delive...

Many research groups have studied biomimetic functional surfaces for practical applications. Dry adhesives inspired by the gecko foot consist of hierarchical and numerous micro/nano hairs and can achieve pull-off strengths for vertical and shear adhesion of up to 20 N cm-2. However, since detachment of nearly dry adhesive is carried out by peeling,...

The laser-induced synthesis of nanostructures provides an innovative and unique way to shorten the overall processing time in comparison to traditional methods, while allowing precise control of the growth. This is the novel research to report continuous laser beam-assisted uniform growth of aligned nanowires, nanorods and nanotubes on woven carbon...

Photonic skins enable a direct and intuitive visualization of various physical and mechanical stimuli with eye‐readable colorations by intimately laminating to target substrates. Their development is still at infancy compared to that of electronic skins. Here, an ultra‐adaptable, large‐area (10 × 10 cm²), multipixel (14 × 14) photonic skin based on...

We report directional switchable adhesion behavior inspired by the locomotion mechanism of gecko lizard. The robust mushroom-like polydimethylsiloxane microline arrays are fabricated by using silicon based over-etching process and replica molding. The line gecko patterns attached to the glass substrate exhibit strong shear adhesion forces in parall...

Bioinspired dry adhesives with micropillar arrays can be harnessed for precise and environment-friendly manufacturing. This study presents a simple and robust approach for developing synthetic dry adhesives with significantly enhanced adhesion strength without sophisticated structural modification or chemical surface treatment. We show that when dr...

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-as...

In article number 1803411, Hoon Eui Jeong and co‐workers develop a high‐performance flexible electronic skin by incorporating a piezoresistive carbon nanotube composite into a hierarchical topography of micropillar–wrinkle hybrid architectures. The hybrid architectures‐based electronic skin exhibits versatile and superior sensing performance.

Low‐dimensional nanomaterials are widely adopted as active sensing elements for electronic skins. When the nanomaterials are integrated with microscale architectures, the performance of the electronic skin is significantly altered. Here, it is shown that a high‐performance flexible and stretchable electronic skin can be produced by incorporating a...

Stable and reversible adhesion to wet surfaces is challenging owing to water molecules at the contact interface. In this study, we develop a hydrogel-based wet adhesive, which can exhibit strong and reversible adhesions to wet and underwater surfaces as well as to dry surfaces. The remarkable wet adhesion of the hydrogel adhesive is realized based...

Thermotherapy is a widespread technique that provides relief for muscle spasms and joint injuries. A great deal of energy is used to heat the surrounding environment, and heat emitted by the human body is wasted on our surroundings. Herein, a woven Kevlar fiber (WKF)-based personal thermal management device was fabricated by directly growing vertic...

Thermotherapy is a widespread technique that provides relief for muscle spasms and joint injuries. A great deal of energy is used to heat the surrounding environment, and heat emitted by the human body is wasted on our surroundings. Herein, a woven Kevlar® fiber (WKF)-based personal thermal management device was fabricated by directly growing verti...

In this study, we reported continuous partial curing and tip-shaped modification methods for continuous production of dry adhesive with microscale mushroom-shaped structures. Typical fabrication methods of dry adhesive with mushroom-shaped structures are less productive due to the failure of large tips on pillar during demolding. To solve this prob...

Anti-icing materials that can efficiently limit ice formation have a strong potential to replace existing anti-icing techniques, such as Joule heating, chemical release, or mechanical removal, which are usually inefficient, expensive, and environmentally harmful. In this study, an anti-icing material based on a magnetically responsive hierarchical...

Structural supercapacitors provide a variety of opportunities for woven carbon fibers in portable electronics, hybrid automobiles and aerospace applications. We describe herein the synthesis of bimetallic Cu-Co selenide nanowires based on woven carbon fibers, and their use as electrodes in supercapacitors. Woven Kevlar fiber is used as separator fo...

This study presents a wet-responsive and biocompatible smart hydrogel adhesive that exhibits switchable and controllable adhesions on demand for the simple and efficient transfer printing of nanomembranes. The prepared hydrogel adhesives show adhesion strength as high as ≈191 kPa with the aid of nano- or microstructure arrays on the surface in the...

A wet‐responsive, reconfigurable and biocompatible hydrogel adhesive that exhibits switchable and controllable adhesion on demand is reported by Hoon Eui Jeong and co‐workers in article number 1706498. Based on the smart adhesion capabilities, diverse metallic and semiconducting nanomembranes can be transferred from donor substrates to either rigid...

Actuator-based Micro-Electro-Mechanical Systems (MEMS) are confounded by tribological issues such as strong adhesion, friction and wear that undermine the smooth operation of their moving elements/components. As solutions to mitigate the tribological issues, thin films/coatings have been traditionally researched. In recent times, polymeric topograp...

A skin adhesive patch is the most fundamental and widely used medical device for diverse health‐care purposes. Conventional skin adhesive patches have been mainly utilized for routine medical purposes such as wound management, fixation of medical devices, and simple drug release. In contrast to traditional skin adhesive patches, recently developed...

This study presents wet-responsive, shape-reconfigurable, and flexible hydrogel adhesives that exhibit strong adhesion under wet environments based on reversible interlocking between reconfigurable microhook arrays. The experimental investigation on the swelling behavior and structural characterization of the hydrogel microstructures reveal that th...

Engineered surfaces that have high friction under wet or lubricated conditions are important in many practical applications. However, it is not easy to achieve stable high friction in wet conditions because a layer of fluid prevents direct solid-solid contact. Here, we report a micropatterned elastomeric surface with superior wet friction. The surf...

Bioinspired dry adhesives have attracted considerable attention over the last decade because of their superiority in properties, such as adhesion strength, repeatable and reversible adhesion, rough surface adaptation, self-cleaning, and directional adhesion. However, previous manufacturing techniques of bioinspired dry adhesives based on lithograph...

Gecko lizards have superior locomotive capabilities to walk on ceilings and walls of varying angles. Furthermore, their skin has superior water-repellency due to hierarchical hairy structures on it. With these remarkable capabilities, their wide range of locomotion is effective even in rainy and wet environments, leading to enhanced survival capabi...

Caterpillars are very successful soft-bodied climbers that navigate in complex environments. This paper develops a multi-segmented robot climbing on vertical surfaces using dry adhesive pads, inspired by caterpillar locomotion. The miniaturized robot consists of four segments, and each segment uses a solenoid actuator with a permanent magnet plunge...

We present rheological and mechanical behaviors of a partially cured photopolymer. When an ultraviolet (UV)-curable resin is exposed to UV light in atmospheric conditions, a partially cured layer is formed on the top of the resin owing to inhibitory effects of oxygen. Interestingly, such a partially cured resin behaves like a Bingham plastic with a...

Bioinspired dry adhesives with protruding tips offer strong, repeatable, and reversible adhesion both in normal and shear directions owing to the presence of a thin spatulate layer. However, the temperature range in which they can be used is limited because most of them are made of polymeric materials that have inherently poor thermomechanical stab...

We present the scalable fabrication of a novel transparent heater (TH) architecture by continuously creating metallic micromesh patterns on a flexible substrate via Photo Roll Lithography (PRL). The optimal TH structure is explored by systematically investigating the heating and transmittance characteristics depending on the metal material, thickne...

We present a method to induce cell directional behavior using slanted nanocilia arrays. NIH-3T3 fibroblasts demonstrated bidirectional polarization in a rectangular arrangement on vertical nanocilia arrays and exhibited a transition from a bidirectional to a unidirectional polarization pattern when the angle of the nanocilia was decreased from 90°...

We present a simple yet scalable method with detailed process protocols for fabricating dry adhesives with mushroom-shaped micropillars of controlled tip geometries. The method involves using photo-lithography with a bilayer stack combining SU-8 and lift-off resist, and subsequent replica molding process. This approach utilizes widely used and comm...

The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces. Although a variety of droplet manipulation techniques have been proposed, active, fast and reversible manipulation of pure discrete droplets remains elusive due to the technical limitations of previous techniques. Her...

We present a simple method of fabricating bio-inspired multiscale structure by combining replica molding and surface wrinkling. With this technique, we demonstrates that our fabrication method is manageable to fabricate various types of substrate with various orientations of nanopatterns on microwrinkle structure, resulting perfectly conform the wr...

Gecko-like dry adhesive using high aspect ratio polymeric nanohairs has insuperable limitations, although it has huge potential in many applications. Repeated harsh contacts on a target substrate lead to physical collapse of nanohairs and significant degradation of the adhesion property, because the polymeric nanohairs are quite fragile due to poor...

Engineering complex extracellular matrix (ECM) is an important challenge for cell and tissue engineering applications as well as for understanding fundamental cell biology. We developed the methodology for fabrication of precisely controllable multiscale hierarchical structures using capillary force lithography in combination with original wrinklin...

We present a straightforward method to realize a wettability-controlled stainless steel surface via wire electrical discharge machining. Samples of AISI 304 stainless steel were prepared, having various depth of groove, while width and pitch of groove were set to be 500 μm and 600 μm. Wetting properties of the fabricated samples were quantified by...

We present an application of high-aspect-ratio (high-AR) silicon structures (black silicon) with high water repellency and good wettability by oils and solvents. The fabrication of black silicon consists of a deep reactive-ion etching process for extremely-high-AR silicon structures and surface treatment with C4F8 gas. Such high-AR structures were...

Inspired by the remarkable adhesion properties of gecko lizards, bio-inspired dry adhesives with smart adhesion properties have been developed in the last decade. Compared to earlier dry adhesives, the recently developed ones exhibit excellent adhesion strength, smart directional adhesion, and structural robustness. With these unique adhesion prope...

A simple yet scalable strategy for fabricating dry adhesives with mushroom-shaped micropillars is achieved by a combination of the roll-to-roll process and modulated UV-curable elastic poly(urethane acrylate) (e-PUA) resin. The e-PUA combines the major benefits of commercial PUA and poly(dimethylsiloxane) (PDMS). It not only can be cured within a f...

Stem cell-based therapy has been proposed as an enabling alternative not only for the treatment of diseases but also for the regeneration of tissues beyond complex surgical treatments or tissue transplantation. In this study, we approached a conceptual platform that can integrate stem cells into a multiscale patterned substrate for bone regeneratio...

Multiscale, hierarchically patterned surfaces, such as lotus leaves, butterfly wings, adhesion pads of gecko lizards are abundantly found in nature, where microstructures are usually used to strengthen the mechanical stability while nanostructures offer the main functionality, i.e., wettability, structural color, or dry adhesion. To emulate such hi...

Understanding how living cells interact with nanostructures is integral to a better understanding of the fundamental principles of biology and the development of next-generation biomedical/bioenergy devices. Recent studies have demonstrated that mammalian cells can recognize nanoscale topographies and respond to these structures. From this perspect...

We present a simple method for fabricating robust dry adhesives by coating a soft polydimethyl siloxane (PDMS) thin layer on rigid backbone micropillars of polyurethane acrylate (PUA). These core–shell type micropillars demonstrated enhanced durability both in normal and shear adhesion over more than 100 cycles of attachment and detachment. Relativ...