The fabrication process of the microneedle based on Micro Electro Mechanical Systems (MEMS) technologies was summarized in this review article. Firstly, the Si microneedle was produced by applying the photolithography and the etching processes, and the pyramidal- and the circular cone-shaped microneedles were fabricated by the wet- and dry-etching, respectively. The mechanical grinding process was applied instead of the photolithography to produce the arrayed Si microneedle with high aspect ratio and high density by the wet-etching. The candle-like Si microneedle was produced by applying the multi-steps dry-etching. Recently, the molding process was embedded into the MEMS technologies to transfer the microneedle material. The micro-machined Si needle was used as the master, and its copied microneedle was produced by the mold applying the metal or resin as the materials. Metal female die produced by the arrayed Si microneedle was produced to increase the pyramidal shaped needle density in the case of the mold. The tip-separable microneedles array made of the biodegradable material was proposed by stacking the pyramidal shaped microneedle applying the transdermal drug delivery system.

Nanoimprint lithography (NIL) is one of promising micro- and nano-fabrication methods from single-digit nanometers. In this paper, we introduce the following topics: process and history, challenges for single-digit-nanometer patterning, practical issues, and a “print-and-imprint” method. The concept like NIL was first reported by Japanese researchers in 1977, and its feasibility for the fabrication of nanostructures has been demonstrated since 1995. NIL consists of nanoimprinting and lithography processes: the former is the transformation of micro- and nano-structures on a mold surface onto resistant materials and the latter is the pattern transfer from the molded mask to a substrate surface. Owing to its easy-to-use and high-throughput features, NIL has been studied in a broad range of fields such as semiconductors, optics, plasmonics, biology, and fluidic devices. Its potential of single-digit-nanometer scale resolution was confirmed in both thermal and ultraviolet (UV) NIL in 2000s. Practical micro- and nano-fabrication by NIL often faces issues at multi-level sizes; for example, flatness of a mold and substrate, burrs in periphery, residual layer thickness, and pattern defects derived from trapped air bubbles, pull-out of resistant materials during demolding, and impurity particles in ambient condition. We propose a new technology of “print-and-imprint” method involving laser-drilled screen printing and UV-NIL, which could provide several solutions for the practical issues.

Metal and metal oxide micropatterns were fabricated in ambient atmosphere by femtosecond laser-pulse-induced reductive sintering using metal oxide nanoparticles. First, metal oxide nanoparticle inks consisting of the nanoparticles, dispersant, and reductant agents, were coated on glass substrates. Then, in the case of using linear optical absorption, femtosecond laser pulses were focused onto the surface of the ink films to induce thermochemical reduction. In the case of using nonlinear optical absorption, femtosecond laser pulses were focused into the inks which exhibited high transparency at the laser wavelength. Finally, non-sintered nanoparticles were removed by rinsing the samples in ethylene glycol and ethanol. Cu/Cu2O composite temperature sensors and thermoelectric sensors were fabricated using CuO nanoparticle inks and CuO/NiO nanoparticle inks, respectively. The degree of the reduction from the inks was controlled by the laser irradiation conditions such as the laser pulse energy and the scanning speed. These direct writing process of the sensors in the air allows us to fabricate various sensors on the surface of the arbitral elements.

Surface-mount techniques primarily depend on soldering. However, soldering techniques have encountered some challenges in recent years. The reflow process in electronic assembly needs high-temperature processes, which result in undesired thermal damages and residual stress at a bonding interface. Therefore, there is an urgent requirement to attach electronic parts to circuit boards with good mechanical and electrical properties at room temperature. We recently developed a metallic nanowire surface fastener (NSF) to resolve the abovementioned problems. This fastener can connect electronic components on a substrate at room temperature using the van der Waals force between each nanowire. In this paper, we introduce a preparing method of a high-density nanowire array constituting the NSF. The NSF fabricated through the simple template method showed the room temperature bonding ability. The NSF’s adhesion strength and electrical properties were investigated by adjusting the nanowire parameters, such as diameter, length, density (number per area), preload, and shape. We also introduce some NSF applications, such as 64-pin NSF that behaves like a ball grid array for application to actual electronic devices and the fabrication of an NSF on a flexible substrate.

Microfluidic devices are technologies that integrate micro- and nano-meter sized structures in a microchannel using a microfabrication technique. In this article, I focused on the fabrication process of our developed microfluidic device which is based on the principle of size exclusion chromatography for DNA separation. Since this device has microfence structures and nanoslit structures in a microchannel, its fabrication process consists of a photolithography and a reactive ion etching for creating the microfence structures and a focused ion beam milling for creating the nanoslit structures. Additionally, I introduced the experimental results of DNA separation using our fabricated microfluidic device. Beyond the research field of analytical chemistry, microfluidic devices have been utilized to other research fields such as rheology for the measurement of viscosity and flow distribution of liquids. I hope that this article will be of interest to the readership in the research field of tribology.

The effective utilization of wood is important in order to achieve environmental protection or the Sustainable Development Goals (SDGs). Recently, research and development using tribological phenomena for wood processing has been done to expand the application of wood. The paper focuses on such research and development and reports the vista of wood processing technology utilizing tribological phenomena. Recent research investigated the use of rubbing wood together for wood processing. Rubbing wood together at high speed has succeeded in gluing wood without any adhesives and improving the surface hardness of wood. In addition, the new wood surface treatment method of rubbing wood with a smooth metal surface is considered. In the series of studies for the above new wood processing, the effect of high-speed friction on thermal and mechanical effects were investigated. Moreover, it is revealed that an ultra-smooth wood surface is generated by high-speed friction wood surface treatment technology. From recent achievements, the production of highly functional wood with surface treatment technology which utilizing tribology phenomena might be possible.

Since rolling bearing materials are subjected to repeated contact pressure of several GPa, heat treatment is applied to obtain a hardness that can bear such pressure. SUJ2 is the most widely used steel for rolling bearings, and it is heat treated under conditions that maximize the sub-surface initiated flaking life. In recent years, dent-initiated flaking life is getting more important, and for this purpose, carbonitriding and/or grain refinement is applied. Carbonitriding treatment has also been found to be effective against the failure due to hydrogen embrittlement. Heat treatment is a process that has a high environmental load, thus change to a high-efficiency heating source such as induction heating is being considered. In the case of induction heating, the conditions of higher temperature and short time than the case of furnace is employed. The appropriate heating conditions that can obtain the mechanical properties equivalent to those of the bearings heated in the furnace have been found.

In tribology, most phenomena are basically based on interfacial properties involving microscopic physics especially in dynamic motion such as friction, lubrication, and wear. Wettability is an index to describe how much a surface has high affinity to liquid, and is useful for assessing liquid adhesion, liquid-film formation, and lubrication. We previously proposed an air-injection mediated liquid exclusion (AILE) method for assessing the wettability dynamics by removing the liquid covering the target surface instead of measuring the contact angle of liquid droplets on the surface. To date, we have applied the method to various areas among biology, the environment, and biomaterials. The method reveals the difference of wettability on cultivated cells among culture conditions for the first time. And this method is widely used for assessing the wettability of surfaces such as biofilms and biomedical polymer for medical devices which are hard to be evaluated in wet state by previous approaches like the contact angle measurement. This article introduces the method which describes the microscopic dynamics of surface molecules from macroscopic view.