Hiroaki Jinno


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Jinno

First Name

Hiroaki

ORCID

0000-0003-0998-6489

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2021 - 20253
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Publications 1 - 3 of 3
  • Self-powered ultraflexible photonic skin for continuous bio-signal detection via air-operation-stable polymer light-emitting diodes
    Item type: Journal Article
    Jinno, Hiroaki; Yokota, Tomoyuki; Koizumi, Mari; et al. (2021)
    Nature Communications
    Ultraflexible optical devices have been used extensively in next-generation wearable electronics owing to their excellent conformability to human skins. Long-term health monitoring also requires the integration of ultraflexible optical devices with an energy-harvesting power source; to make devices self-powered. However, system-level integration of ultraflexible optical sensors with power sources is challenging because of insufficient air operational stability of ultraflexible polymer light-emitting diodes. Here we develop an ultraflexible self-powered organic optical system for photoplethysmogram monitoring by combining air-operation-stable polymer light-emitting diodes, organic solar cells, and organic photodetectors. Adopting an inverted structure and a doped polyethylenimine ethoxylated layer, ultraflexible polymer light-emitting diodes retain 70% of the initial luminance even after 11.3 h of operation under air. Also, integrated optical sensors exhibit a high linearity with the light intensity exponent of 0.98 by polymer light-emitting diode. Such self-powered, ultraflexible photoplethysmogram sensors perform monitoring of blood pulse signals as 77 beats per minute.
  • Strong repulsive Lifshitz-van der Waals forces on suspended graphene
    Item type: Journal Article
    Vagli, Gianluca; Tian, Tian; Naef, Franzisca; et al. (2025)
    Nature Communications
    Understanding surface forces of two-dimensional (2D) materials is of fundamental importance as they govern molecular dynamics in nanoscale proximity. Despite recent understanding of substrate-supported 2D monolayers, the intrinsic surface properties of 2D materials remain vague. Here we report on a repulsive Lifshitz-van der Waals force generated in proximity to the surface of suspended graphene. In combination with our theoreticalmodel taking into account the flexibility of graphene, we directly measured repulsive forces using atomic force microscopy. An average repulsive force of up to 1.4 kN/m² has been detected at separations of 8.8 nm between a gold-coated tip and a sheet of suspended graphene, more than two orders of magnitude greater than the long-range Casimir-Lifshitz repulsion demonstrated in fluids. Our findings imply that suspended 2D materials could exert repulsive forces on any approaching electroneutral object in close proximity, resulting in substantially lower wettability. This could offer technological opportunities such as molecular actuation and quantum levitation.
  • Indoor Self-Powered Perovskite Optoelectronics with Ultraflexible Monochromatic Light Source
    Item type: Journal Article
    Jinno, Hiroaki; Shivarudraiah, Sunil B.; Asbjörn, Rasmussen; et al. (2024)
    Advanced Materials
    Self-powered skin optoelectronics fabricated on ultrathin polymer films is emerging as one of the most promising components for the next-generation Internet of Things (IoT) technology. However, a longstanding challenge is the device underperformance owing to the low process temperature of polymer substrates. In addition, broadband electroluminescence (EL) based on organic or polymer semiconductors inevitably suffers from periodic spectral distortion due to Fabry–Pérot (FP) interference upon substrate bending, preventing advanced applications. Here, ultraflexible skin optoelectronics integrating high-performance solar cells and monochromatic light-emitting diodes using solution-processed perovskite semiconductors is presented. n–i–p perovskite solar cells and perovskite nanocrystal light-emitting diodes (PNC-LEDs), with power-conversion and current efficiencies of 18.2% and 15.2 cd A⁻¹, respectively, are demonstrated on ultrathin polymer substrates with high thermal stability, which is a record-high efficiency for ultraflexible perovskite solar cell. The narrowband EL with a full width at half-maximum of 23 nm successfully eliminates FP interference, yielding bending-insensitive spectra even under 50% of mechanical compression. Photo-plethysmography using the skin optoelectronic device demonstrates a signal selectivity of 98.2% at 87 bpm pulse. The results presented here pave the way to inexpensive and high-performance ultrathin optoelectronics for self-powered applications such as wearable displays and indoor IoT sensors.
Publications 1 - 3 of 3