Yudai Ogawa

Organic transdermal iontophoresis patch with built-in biofuel cell.

A completely organic iontophoresis patch is reported. A built-in biofuel cell is mounted on the patch that generates transdermal iontophoretic administration of compounds into the skin. The amplitude of transdermal current is tuned by integrating a conducting polymer-based stretchable resistor of predetermined resistance.

Stretchable biofuel cell with enzyme-modified conductive textiles.

A sheet-type, stretchable biofuel cell was developed by laminating three components: a bioanode textile for fructose oxidation, a hydrogel sheet containing fructose as fuel, and a gas-diffusion biocathode textile for oxygen reduction. The anode and cathode textiles were prepared by modifying carbon nanotube (CNT)-decorated stretchable textiles with fructose dehydrogenase (FDH) and bilirubin oxidase (BOD), respectively. Enzymatic reaction currents of anode and cathode textiles were stable for 30 cycles of 50% stretching, with initial loss of 20-30% in the first few cycles due to the partial breaking of the CNT network at the junction of textile fibers. The assembled laminate biofuel cell showed power of ~0.2 mW/cm(2) with 1.2 kΩ load, which was stable even at stretched, twisted, and wrapped forms.

Porous polymer microneedles with interconnecting microchannels for rapid fluid transport

A porous polymer microneedle array with an average pore diameter of ∼1 μm was fabricated by photopolymerization of an acrylate monomer in the presence of a porogen within a mold. Porosity measurement and water absorption testing revealed that the pores are interconnected throughout the microneedle, which enabled rapid wetting of the microneedle by capillary action. The porosity of the polymer microneedles can be modulated by varying porogen content, and this allowed balancing fast water absorption speed and sufficient mechanical strength to penetrate a skin. The developed porous polymer microneedle array is a potentially versatile tool for rapid fluid transport from and into a body through the skin.

Surfactant-assisted direct electron transfer between multi-copper oxidases and carbon nanotube-based porous electrodes.

The effects of pre-treatment with surfactants on the electrocatalytic reaction of multi-copper oxidases were quantitatively evaluated using a well-structured carbon nanotube forest electrode. It was found that both the charge polarity of the head group and the aromatics in the tail part of the surfactants affect the efficiency of enzymatic electrocatalysis.

An energy-autonomous, disposable, big-data-based supply-sensing biosensor using bio fuel cell and 0.23-V 0.25-μm Zero-Vth all-digital CMOS supply-controlled ring oscillator with inductive transmitter

This study demonstrates an energy-autonomous disposable supply-sensing biosensor platform for big-data-based healthcare application for the first time. The proposed supply-sensing biosensor platform is based on bio fuel cells and a 0.23-V 0.25-μm zero-Vth all-digital CMOS supply-controlled ring oscillator with a current-driven pulse-interval-modulated inductive-coupling transmitter. The all-digital and current-driven architecture using zero-Vth transistors enables low-voltage operation and small footprint even in the cost-competitive legacy CMOS, which enables converterless energy-autonomous operation using bio fuel cell for disposable healthcare application. To verify its effectiveness, a test chip was fabricated using 0.25-μm CMOS technology. The measured results successfully demonstrated operation under a 0.23-V supply, which is the lowest supply voltage among reported proximity transmitters. In addition, an energy-autonomous biosensing operation using organic bio fuel cells for transdermal patch was successfully demonstrated.

Accelerated Wound Healing on Skin by Electrical Stimulation with a Bioelectric Plaster

Wound healing on skin involves cell migration and proliferation in response to endogenous electric current. External electrical stimulation by electrical equipment is used to promote these biological processes for the treatment of chronic wounds and ulcers. Miniaturization of the electrical stimulation device for wound healing on skin will make this technology more widely available. Using flexible enzymatic electrodes and stretchable hydrogel, a stretchable bioelectric plaster is fabricated with a built-in enzymatic biofuel cell (EBFC) that fits to skin and generates ionic current along the surface of the skin by enzymatic electrochemical reactions for more than 12 h. To investigate the efficacy of the fabricated bioelectric plaster, an artificial wound is made on the back skin of a live mouse and the wound healing is observed for 7 d in the presence and absence of the ionic current of the bioelectric plaster. The time course of the wound size as well as the hematoxylin and eosin staining of the skin section reveals that the ionic current of the plaster leads to faster and smoother wound healing. The present work demonstrates a proof of concept for the electrical manipulation of biological functions by EBFCs.

Intrinsically Stretchable Electrochromic Display by a Composite Film of Poly(3,4-ethylenedioxythiophene) and Polyurethane

A stretchable, electrochromic film of a uniform composite of poly(3,4-ethylenedioxythiophene):p-toluene sulfonic acid (PEDOT:PTS) and polyurethane (PU) (PEDOT/PU) was fabricated, and its integration with a hydrogel as a free-standing, stretchable electrochromic (EC) display was demonstrated. The PEDOT/PU composite film was prepared by the spin coating of a solution containing an EDOT monomer and PU, followed by oxidative polymerization using iron(III) tosylate at elevated temperature. The fabricated film showed reversible electrochromism without an external conductive support. The color change of the film can be used to quantify the progress of the redox reactions by means of digital camera image analysis and a custom mobile phone app.

Dynamic characteristics of the middle ear in neonates.

OBJECTIVE Early diagnosis and treatment of hearing disorders in neonates is highly effective for realization of linguistic competence and intellectual development. To objectively and quickly evaluate the dynamic characteristics of the middle ear, a sweep frequency impedance (SFI) meter was developed, which allowed the diagnosis of middle-ear dysfunctions in adults and children. However, this SFI meter was not applicable to neonates since the size of the measurement probe was too large. In the present study, therefore, the SFI meter was improved, i.e., the diameter of the probe was reduced to that of the neonatal external ear canal. By using this newly designed SFI meter, SFI tests were performed in healthy neonates. METHODS A sound of the sweeping sinusoidal frequency between 0.1 kHz and 2.0 kHz in 0.02-kHz step intervals is presented to the ear canal by an SFI probe while the static pressure of the ear canal is kept constant. During this procedure, the sound pressure level (SPL) is measured. The measurements are performed at 50-daPa intervals of static pressure from 200 daPa to -200 daPa. RESULTS Measurements were conducted in 10 ears of 9 neonates. The SPL showed two variations at 0.26 ± 0.03 kHz and 1.13 ± 0.12 kHz. Since the SPL is known to show a variation at frequencies from 1.0 kHz to 1.6 kHz due to the resonance of the middle ear in adults and children with normal hearing, the second variation is probably related to such resonance in neonates. The measurement of gel models, which mimics the neonatal external ear canal, showed a variation in SPL at around 0.5 kHz. This implies that the source of the first variation may possibly be related to the resonance of the external ear canal wall. CONCLUSIONS SFI tests revealed that there were two variations in the SPL curve in neonates, one at 0.26 ± 0.03 kHz and the other at 1.13 ± 0.12 kHz, the former and the latter being possibly related to the resonance of the external ear canal wall and that of the middle ear, respectively. This result suggests that the dynamic characteristics of the middle ear in neonates are different from those in adults.

Design of an energy-autonomous bio-sensing system using a biofuel cell and 0.19V 53μW integrated supply-sensing sensor with a supply-insensitive temperature sensor and inductive-coupling transmitter

This paper presents an energy-autonomous bio-sensing system with the capability of wireless communication. The proposed system includes a biofuel cell as a power source and sensing frontend associated with the integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, supply-insensitive time-domain temperature sensor, and inductive-coupling transmitter. A test chip using 65-nm CMOS technology was operated with a supply of 0.19 V and consumed 53 μW to successfully demonstrate wireless communication with an asynchronous receiver.

An energy-autonomous bio-sensing system using a biofuel cell and 0.19V 53μW 65nm-CMOS integrated supply-sensing sensor with a supply-insensitive temperature sensor and inductive-coupling transmitter

This paper presents an energy-autonomous bio-sensing system with the capability of proximity communication. The proposed biosensor includes a bio-fuel cell as a power source and sensing front-end associated with the integrated supply-sensing sensor. The sensor consists of a digital-based gate leakage timer, supply-insensitive time-domain temperature sensor, and current-driven inductive-coupling transmitter and achieves low-voltage operation. The timer converts the output supply-voltage from a bio-fuel cell to period output. The supply-insensitive temperature sensor provides PWM output without dependency of the supply voltage. The following inductive-coupling transmitter enables proximity communication. A test chip using 65-nm CMOS technology was operated with a supply of 0.19 V and consumed 53 μW to successfully demonstrate proximity communication with an asynchronous receiver. The measurement results show the possibility of energy-autonomous operation using bio-fuel cells.