Shusuke Kanazawa

Photoluminescence and Optical Gain Properties of a Crystalline Thiophene/Phenylene Co-oligomer

We have successfully demonstrated a significant fluorescence property in an organic crystal made of a thiophene/phenylene co-oligomer called AC5. The crystal showed no non radiative transition, meaning it has 100% internal fluorescent quantum efficiency. The crystal also showed high quantum efficiency of photoluminescence of 23±1%. Furthermore, it showed an amplified spontaneous emission at a threshold energy of 21.3 µJ/cm2 and subsequently showed a quite high optical gain of 52.3 cm-1. These features are attractive in many areas in the organic optics field such as organic light emitting diodes, organic lasers, and so on.

Direct observation of microcontact behaviours in pattern-generation step of reverse offset printing

In this study, we investigate the static and dynamic aspects of the nip formed during roll-to-sheet-type reverse offset printing. First, we show that several modes of roof collapses (bottom contact defects) could be formed depending on the poly(dimethylsiloxane) (PDMS) blanket thickness and pattern size. We regulate the manifestation of the defect modes driven by the local pile-up of the incompressible PDMS, as modelled by the contact mechanics formulation, together with a complementary numerical simulation. In dynamics, we first differentiate between the static nip and dynamic nip during printing, where the width is extended by the kinetically controlled adhesion of the blanket PDMS. Further, we observe that depending on the pattern structure, there was spatial deviation of the microscopic contact and subsequent separation behaviours of the cliche from a macroscopically recognizable nip, and consequently, local detachment rates were heterogeneous in the pattern-generation process of the reverse offset printing, even with a constant machine speed. In addition, we found that the parts of a pattern where the ink transfer fails in a high-speed patterning condition corresponded to the region of the locally enhanced detachment rates found during direct observation.

Novel printing process for the fabrication of cantilever structures by the partially controlled sintering of ink

We present a novel process for manufacturing cantilever structures by the additive stacking of ink layers. The three-dimensional transfer of printed mechanical parts was achieved by optimizing the ink-sintering conditions to guarantee the structural integrity of the printed parts and provide adequate differences in adhesion strengths between the receiver and donor interfaces. A metal–insulator–metal cantilever structure with a bottom electrode, air insulator, and cantilevered top electrode was fabricated on a flexible film, forming a successful capacitive bending sensor for use on human bodies. This process allows highly efficient device fabrication in the MEMS field.

Improved transfer process for fabrication of cantilever with precise air-gap formation

In this paper, an improved transfer process to fabricate a cantilever structure with a precise air gap is reported. For this fabrication, a planar imprinting method was used and the drying conditions of the cantilever precursor ink were controlled. The air gap between the cantilevered top and bottom electrodes was formed with an estimated error of less than 3%. An operational force gauge with a changeable capacitance was obtained by applying a force to the cantilevered top electrode. This process can facilitate the eco-friendly fabrication of micro-devices with three-dimensional structures.

One-batch transfer process for the additive manufacturing of a cantilever with a weight

An improved transferring process that can be used to additively fabricate a cantilever with a weight is reported. By using a poly(dimethylsiloxane) template with a cavity relief structure for the weight formation, an increase in the number of process steps was not required. A capacitive acceleration sensor was successfully manufactured using the described process. Enhanced responsiveness of the sensor was clearly shown to result from the effect of the weight. The one-batch transfer process has the potential to significantly simplify the manufacturing process of highly responsive hollow structures and could be applied in the fabrication of various microelectromechanical system sensors.

Fabrication of a Textile-Based Wearable Blood Leakage Sensor Using Screen-Offset Printing

We fabricate a wearable blood leakage sensor on a cotton textile by combining two newly developed techniques. First, we employ a screen-offset printing technique that avoids blurring, short circuiting between adjacent conductive patterns, and electrode fracturing to form an interdigitated electrode structure for the sensor on a textile. Furthermore, we develop a scheme to distinguish blood from other substances by utilizing the specific dielectric dispersion of blood observed in the sub-megahertz frequency range. The sensor can detect blood volumes as low as 15 μL, which is significantly lower than those of commercially available products (which can detect approximately 1 mL of blood) and comparable to a recently reported value of approximately 10 μL. In this study, we merge two technologies to develop a more practical skin-friendly sensor that can be applied for safe, stress-free blood leakage monitoring during hemodialysis.

Imaging the patterning step of R2S microcontact printing

Microcontact printing is a technique that is widely used in the patterning of various materials ranging from small molecules to polymers and nanoparticles. In industrial applications, the roof-collapse of the stamp due to printing pressure is known to cause defective printing. To address this problem, a direct observation system for the patterning step of R2S microcontact printing was devised and used in conducting investigations. Results showed that several modes of roof-collapse were a function of the stamp thickness and area of the raised surface during the patterning step. In developing a model for this relationship, contact mechanics was investigated taking into account the effect of the finite thickness of the deformable poly(dimethylsiloxane).