Eiji Iwase

Recently, a new technology has come to the fore, namely four-dimensional (4D) printing. Conventional research has, however, mostly been in a glass state after a shape change such as self-folding of 4D printing, because the heat shrinkage or shape memory effect of polymers is used. Therefore, the 4D printed hinges are rigid and cannot be folded or unfolded after 4D printing below the glass transition temperature of the shape memory polymer (SMP). Hence, in this study, we proposed a hybrid hinge s

In this paper, we have developed a process for multistep sequential batch assembly of complex three-dimensional (3-D) ferromagnetic microstructures. The process uses the magnetic torque generated by an external magnetic field perpendicular to the substrate to lift hinged structures. We found that a dimensionless factor that depends on the volume of the magnetic material and the stiffness of the hinges determines the sensitivity of the hinged microstructures to a magnetic field. This factor was u

In this paper we describe a general method to avoid stress-induced buckling of thin and large freestanding membranes. We show that using properly designed supports, in the form of microbeams, we can reduce the out-of-plane deflection of the membrane while maintaining its stiffness. As a proof of principle, we used a silicon-on-insulator (SOI) platform to fabricate 30 mu m wide, 220 nm thick, free-standing Si membranes, supported by four 15 mu m long and 3 mu m wide microbeams. Using our approach

A stretchable thermoelectric (TE) generator was developed by using rigid BiTe-based TE elements and a non-stretchable substrate with origami-like folding deformation. Our stretchable TE generator contains flat sections, on which the rigid TE elements are arranged, and folded sections, which produce and guarantee the stretchability of a device. First, a simple stretchable device with a single pair of p-type and n-type BiTe-based TE elements was designed and fabricated. The TE elements were sandwi

This study demonstrates a method to mount electronic components using gallium-based liquid metals (LMs) with reduced contact resistivity between the LM and a copper (Cu) electrode. Gallium-based LMs have low volume resistivity and low melting points, and they are used as electronic components such as interconnects and sensors of stretchable electronic devices. However, the high contact resistivity of the oxide layer on the surface of the Ga-based LMs becomes a problem when the Ga-based LMs are u

We designed a kirigami structure with a particular shape at both ends to provide a large uniform deformation region when stretched. When a kirigami structure is stretched, non-deformation regions, where the regions' cuts do not open, and non-uniform deformation regions, where the regions' cuts are not uniformly deformed, are produced. The extent of the non-deformation and non-uniform deformation regions increases in proportion to the number of cut cycles in the width direction <i>n</i> <sub>w</s

A self-folding method that can fold a thick (~10 μm) metal layer with a large curvature (>1 mm−1) and is resistant to repetitive folding deformation is proposed. Given the successful usage of hinged origami/kirigami structures forms in deployable structures, they show strong potential for application in stretchable electronic devices. There are, however, two key difficulties in applying origami/kirigami methods to stretchable electronic devices. The first is that a thick metal layer used as the

This paper proposes a micro self-folding using a self-rolling up deformation. In the fabrication method at micro scale, self-folding is an especially useful method of easily fabricating complex three-dimensional (3D) structures from engineered two-dimensional (2D) sheets. However, most self-folded structures are limited to 3D structures with a hollow region. Therefore, we made 3D structures with a small hollow region by self-rolling up a 2D sheet consisting of SU-8 and a temperature-responsive h

This paper reports complex three-dimensional (3-D) MEMS devices (polydimethylsiloxane) fabricated on PDMS by a parts-transfer method. Our target size of parts is 100-μm-order in our parts-transfer method. First, we evaluate the transfer yield and the positioning accuracy. Secondly, we assemble a hidden vertical comb-drive actuator, including comb-electrodes and a support beam underneath its upper plate. Finally, we measure the drive characteristics of the actuator. Our actuators are the first de

We modeled a kirigami structure by considering the influence of non-uniform deforming cuts in order to theoretically design the mechanical characteristics of the structure. It is known that the end regions of kirigami structures are non-uniformly deformed when stretched, because the deformation is inhibited at the regions close to both the ends connected to the uncut region in the longitudinal direction. The non-uniform deformation affects the overall mechanical characteristics of the structure.

Liquid metals (LMs) are used as stretchable conductors in various stretchable electronic devices. Moreover, such devices using Ga-based LMs have attracted considerable attention. Herein, we propose a method for accurately determining the contact resistance (<i>R</i>_c) between galinstan and Cu electrodes by considering the current-density distribution in transfer length method (TLM) measurement. Conventional TLM measurements assume that the sheet resistance of the metal electrode (<i>R

The flexibility of thermoelectric generators (TEGs) is important for low-contact thermal resistance to curved heat sources. However, approaches that depend on soft materials, which are used in most existing studies, have the problem of low performance in terms of the substrate's thermal conductivity and the thermoelectric conversion efficiency of the thermoelectric (TE) elements. In this study, we propose a method to fabricate "Origami-TEG", a TEG with an origami structure that enables both flex

This paper describes three-dimensional (3-D) microstructure assembly using an external magnetic field. An external magnetic field perpendicular to a substrate lifts up a hinged structure due to the shape magnetic anisotropy. Micro flap structures (4.5 /spl mu/m-thick electroplated Permalloy) having 0.2 /spl mu/m-thick nickel elastic hinges with various lengths and widths are bent in out-of-plane direction in a magnetic field up to 50 kA/m. The volume of magnetic material and the stiffness of the

Recently, some studies have addressed the use of a folded substrate to realize stretchable electronic devices including stretchable thermoelectric generators (TEGs). However, the utilization of the folded substrate as a heat radiation fin has not been achieved. Herein, we have proposed the construction of a TEG with an origami-like folded structure substrate called an "origami-fin" that can achieve a high heat radiation performance and is also highly stretchable. The origami-fin increases the st