Effective Approach for Fabricating Highly Precise High-Curvature Structural Patterns via Air-Bubble Induction.

Developing a new master mold-based patterning technology that can be used to accurately, precisely, and uniformly create large-area micropatterns while controlling the micropatterns of curved structures is essential for promoting innovative developments in various application fields. This study develops a new top-down lithographic process that can effectively produce structural patterns with high curvatures by growing isolated microbubbles in the master pattern holes. The isolated air-pocket lithography (IAL) we developed is based on the controlled behavior of micrometer-sized air pockets trapped between the grooves of the master pattern and the curable polymer. We successfully fabricated a concave array polydimethylsiloxane (PDMS) film and a convex array polymer film. In addition, the IAL mechanism was proven by confirming the expansion process of micrometer-sized air pockets trapped between the deep groove of the silicon master pattern and the PDMS coating film by using optical microscopy images. We successfully obtained complex three-dimensional structural patterns containing both 3D hollow spherical concave and ring-shaped two-dimensional convex patterns. This simple, fast, and effective high-curvature patterning technique is expected to provide innovative solutions for future applications such as nanoelectronics, optical devices, displays, and photovoltaics.

Easy-To-Wear Auxetic SMA Knot-Architecture for Spatiotemporal and Multimodal Haptic Feedbacks.

Wearable haptic interfaces prioritize user comfort, but also value the ability to provide diverse feedback patterns for immersive interactions with the virtual or augmented reality. Here, to provide both comfort and diverse tactile feedback, an easy-to-wear and multimodal wearable haptic auxetic fabric (WHAF) is prepared by knotting shape-memory alloy wires into an auxetic-structured fabric. This unique meta-design allows the WHAF to completely expand and contract in 3D, providing superior size-fitting and shape-fitting capabilities. Additionally, a microscale thin layer of Parylene is coated on the surface to create electrically separated zones within the WHAF, featuring zone-specified actuation for conveying diverse spatiotemporal information to users with using the WHAF alone. Depending on the body part it is worn on, the WHAF conveys either cutaneous or kinesthetic feedback, thus, working as a multimodal wearable haptic interface. As a result, when worn on the forearm, the WHAF intuitively provides spatiotemporal information to users during hands-free navigation and teleoperation in virtual reality, and when worn on the elbow, the WHAF guides users to reach the desired elbow flexion, like a personal exercise advisor.

A Dual-Responsive Magnetoactive and Electro-Ionic Soft Actuator Derived from a Nickel-Based Metal-Organic Framework.

There is growing demand for multiresponsive soft actuators for the realization of natural, safe, and complex motions in robotic interactions. In particular, soft actuators simultaneously stimulated by electrical and magnetic fields are always under development owing to their simple controllability and reliability during operation. Herein, magnetically and electrically driven dual-responsive soft actuators (MESAs) derived from novel nickel-based metal-organic frameworks (Ni-MOFs-700C), are reported. Nanoscale Ni-MOFs-700C has excellent electrochemical and magnetic properties that allow it to be used as a multifunctional material under both magnetoactive and electro-ionic actuations. The dual-responsive MESA exhibits a bending displacement of 30 mm and an ultrafast rising time of 1.5 s under a very low input voltage of 1 V and also exerts a bending deflection of 12.5 mm at 50 mT under a high excitation frequency of 5 Hz. By utilizing a dual-responsive MESA, the hovering motion of a hummingbird robot is demonstrated under magnetic and electrical stimuli.

Fabrication of junction-free Cu nanowire networks via Ru-catalyzed electroless deposition and their application to transparent conducting electrodes.

Over the past few years, metal nanowire networks have attracted attention as an alternative to transparent conducting oxide materials such as indium tin oxide for transparent conducting electrode applications. Recently, electrodeposition of metal on nanoscale template is widely used for formation of metal network. In the present work, junctionless Cu nanowire networks were simply fabricated on a substrate by forming a nanostructured Ru with 80 nm width as a seed layer, followed by direct electroless deposition of Cu. By controlling the density of Ru nanowires or the electroless deposition time, we readily achieve desired transmittance and sheet resistance values ranging from ∼1 kΩ sq-1at 99% to 9 Ω sq-1at 89%. After being transferred to flexible substrates, the nanowire networks exhibited no obvious increase in resistance during 8000 cycles of a bending test to a radius of 2.5 mm. The durability was verified by evaluation of its heating performance. The maximum temperature was greater than 180 °C at 3 V and remained constant after three repeated cycles and for 10 min. Transmission electron microscopy and x-ray diffraction studies revealed that the adhesion between the electrolessly deposited Cu and the seed Ru nanowires strongly influenced the durability of the core-shell structured nanowire-based heaters.

Universal Nanopatterning Technique Combining Secondary Sputtering with Nanoscale Electroplating for Fabricating Size-Controllable Ultrahigh-Resolution Nanostructures.

Here, we describe a next-generation lithographic technique for fabricating ultrahigh-resolution nanostructures. This technique makes use of the secondary sputtering phenomenon of plasma ion etching and of nanoscale electroplating to finely control the resolution of the fabricated structures from ten nanometers to hundreds of nanometers from a single microsized master pattern. In contrast to previously described techniques that incorporate a recently developed secondary sputtering lithography (SSL) patterning approach, which could only yield 10 nm-resolution structures, in the current technique, we used an improved SSL approach to produce various-sized, high-resolution structures. Additionally, this improved SSL approach was used to fabricate size-controllable 3D patterns on various types of substrates, in particular, a silicon wafer, transparent glass, and flexible polycarbonate (PC) film. Thus, this method can serve as a new-concept patterning method for the efficient mass production of ultrahigh-resolution nanostructures.