Shunsuke Yamada

In the era of a trillion sensors, a tremendous number of sensors will be consumed to collect information for big data analysis. Once they are installed in a harsh environment or implanted in a human/animal body, we cannot easily retrieve the sensors; the sensors for these applications are left unattended but expected to decay after use. In this paper, a disposable temperature sensor that disappears with contact with water is reported. The gel electrolyte based on an ionic liquid and a water-solu

We develop an environmentally benign supercapacitor, which decomposes by contact with water, incorporating an ionic liquid, carbon powder, a cellulose separator, and a molybdenum electrode. The ionic liquid is dispersed into a water-dissolvable polymer, poly(vinyl alcohol), to produce a solid electrolyte, so-called ionic gel. A carbon composite mixed with the ionic liquid maintains a gel form. The ionic gel and the carbon composite enable an all-solid-state supercapacitor, which can be charged a

Field-effect-transistor (FET) is combined with an ionic gel to realize a pressure sensitive ionic-gel field-effect-transistor (PSG-FET) of high sensitivity and low operational voltage. The ionic gels form a layer of charge accumulation in a nanometric scale called the electrical double layer (EDL) on each electrode upon voltage application and exhibit quite high capacitance. The source-drain current through the ZnO channel increases from the initial 44 nA (without pressure) to 783 μA (with press

A water-dissolvable electrolyte is developed by combining an ionic liquid (IL) with poly(vinyl alcohol) (PVA), which decays over time by contact with water. An IL generally consists of two species of ions (anion and cation), and forms an electrical double layer (EDL) of a large electrostatic capacitance due to the ions accumulated in the vicinity of a conductive electrode when voltage is applied. In a similar manner, the ionic gel developed in this work forms an EDL due to the ions suspended in

Domain formation or compartmentalization in a lipid bilayer membrane has been thought to take place dynamically in cell membranes and play important roles in the spatiotemporal regulation of their physiological functions. In addition, the membrane skeleton, which is a protein assembly beneath the cell membrane, also regulates the properties as well as the morphology of membranes because of its role as a diffusion barrier against constitutive molecules of the membrane or as a scaffold for physiol

A pseudo-capacitor with transient behavior is applied in implantable, disposable, and bioresorbable devices, incorporating an Na ion-doped bioderived ionic liquid, molybdenum trioxide (MoO₃ )-covered molybdenum foil, and silk sheet as the electrolyte, electrode, and separator, respectively. Sodium lactate is dissolved in choline lactate as a source of Na ions. The Experimental results reveal that the Na ions are intercalated into the van der Waals gaps in MoO₃ , and the pse

Choline lactate, an ionic liquid composed of bioderived materials, offers an opportunity to develop biodegradable electrochemical devices. Although ionic liquids possess large potential windows, high conductivity, and are nonvolatile, they do not exhibit electrochemical characteristics such as intercalation pseudocapacitance, redox pseudocapacitance, and electrochromism. Herein, bioderived ionic liquids are developed, including metal ions, Li, Na, and Ca, to yield ionic liquid with electrochemic

With the development of wireless sensor networks, electrical waste that remains in the environment is an inevitable issue in achieving sustainability and progress in electronics. Transient electronics that disappear after a prescribed time are of interest in electronics and material sciences. Such devices comprise naturally sourced materials that degrade without harmful or toxic substances during biodegradation. Although there are reports on transient electronic devices, including transistors, s

Primary batteries are the fundamental power sources in small electronic gadgets and bio/ecoresorbable batteries. They are fabricated from benign and biodegradable materials and are of interest in environmental sensing and implants because of their low toxicity toward the environment and human body during decomposition. However, current bio/ecoresorbable batteries suffer from low operating voltages and output powers because of the occurrence of undesired hydrogen evolution reactions (HERs) at cat

A facile, benign, and rapid dealloying method was employed to synthesize nanoporous Cu using an ammonium chloride (NH4Cl) saline solution and Mg as an etchant and a sacrificial metal, respectively. The large difference between the standard electrode potentials of Mg and Cu (−2.36 and +0.34 V, respectively) resulted in rapid etching at 10 nm/min and 303 K. Dealloying for 15 min yielded a nanoporous Cu foil, exhibiting a specific surface area of 24.1 m2/g. The raw materials Mg and NH4Cl are natura

To boost the output of the vibration energy harvester an order of magnitude higher, we devised a high-performance energy harvester taking advantages of the two characteristics of ionic liquid, namely variable deformation of liquid and the electrical double layer between ionic liquid and metal. The electrical double layer is approximately 1nm thick and works as insulator within the voltage range of ±2.0V. Therefore, we can obtain quite high capacitance(1- 10μ/cm2). Squeezing and drawing ionic liq

Unlike typical sensor electronics that always require a voltage source for sensors, amplifiers, and analog-digital converters, we use a mechano-electric transducer as a sensor and also in place of a power source to drive the rest of the electronics, thereby realizing an autonomous self-powered artificial sensory nervous system. A piezoelectric (lead zirconate titanate oxide) PZT is used as an inertia sensor that produces a voltage signal as a function of the acceleration of incoming vibrations.

We propose a high power-output vibrational energy harvesting based on ionic liquid. Ionic liquid enables very large capacitance (1.0-10 μF cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ) on the electrode at bias voltage less than 1.9 V due to its extremely thin (~ 1 nm) electrical double layer. By mechanical squeezing and drawing the ionic liquid, that was solidified with a polymer additive, between a pair of electrodes at 15 Hz, we st