Search Results (5)

The wireless capture of analog differential signals from fully passive (battery-less) sensors is technically challenging but it can allow for the seamless capture of differential biosignals such as an electrocardiogram (ECG). This paper presents a novel design for the wireless capture of analog differential signals using a novel conjugate coil pair for a wireless resistive analog passive (WRAP) ECG sensor. Furthermore, we integrate this sensor with a new type of dry electrode, namely conductive polymer polypyrrole (PPy)-coated patterned vertical carbon nanotube (pvCNT) electrodes. The proposed circuit uses dual-gate depletion-mode MOSFETs to convert the differential biopotential signals to correlated drain-source resistance changes and the conjugate coil wirelessly transmits the differences of the two input signals. The circuit rejects (17.24 dB) common mode signals and passing only differential signals. We have integrated this novel design with our previously reported PPy-coated pvCNT dry ECG electrodes, fabricated on a stainless steel substrate with a diameter of 10 mm, which provided a zero-power (battery-less) ECG capture system for long duration monitoring. The scanner transmits an RF carrier signal at 8.37 MHz. The proposed ECG WRAP sensor uses only two complementary biopotential amplifier circuits, each of which has a single-depletion MOSFET. The amplitude-modulated RF signal is envelope-detected, filtered, amplified, and transmitted to a computer for signal processing. ECG signals are collected using this WRAP sensor and compared with a commercial counterpart. Due to the battery-less nature of the ECG WRAP sensor, it has the potential to be a body-worn electronic circuit patch with dry pvCNT electrodes that stably operate for a long period of time. Full article

In nature, solar energy is captured by different types of light harvesting protein–pigment complexes. Two of these photoactivatable proteins are bacteriorhodopsin (bR), which utilizes a retinal moiety to function as a proton pump, and photosystem I (PSI), which uses a chlorophyll antenna to catalyze unidirectional electron transfer. Both PSI and bR are well characterized biochemically and have been integrated into solar photovoltaic (PV) devices built from sustainable materials. Both PSI and bR are some of the best performing photosensitizers in the bio-sensitized PV field, yet relatively little attention has been devoted to the development of more sustainable, biocompatible alternative counter electrodes and electrolytes for bio-sensitized solar cells. Careful selection of the electrolyte and counter electrode components is critical to designing bio-sensitized solar cells with more sustainable materials and improved device performance. This work explores the use of poly (3,4-ethylenedioxythiophene) (PEDOT) modified with multi-walled carbon nanotubes (PEDOT/CNT) as counter electrodes and aqueous-soluble bipyridine cobalt^II/III complexes as direct redox mediators for both PSI and bR devices. We report a unique counter electrode and redox mediator system that can perform remarkably well for both bio-photosensitizers that have independently evolved over millions of years. The compatibility of disparate proteins with common mediators and counter electrodes may further the improvement of bio-sensitized PV design in a way that is more universally biocompatible for device outputs and longevity. Full article

Carbon nanotubes (CNTs) and polyelectrolyte poly(allylamine hydrochloride) (PAH) composite modified indium tin oxide (ITO) electrodes, by a layer-by-layer (LBL) self-assembly technique, was evaluated as an anode for microbial fuel cells (MFCs). The bioelectrochemistry of Shewanella loihica PV-4 in an electrochemical cell and the electricity generation performance of MFCs with multilayer (CNTs/PAH)_n-deposited ITO electrodes as an anode were investigated. Experimental results showed that the current density generated on the multilayer modified electrode increased initially and then decreased as the deposition of the number of layers (n = 12) increased. Chronoamperometric results showed that the highest peak current density of 34.85 ± 2.80 mA/m² was generated on the multilayer (CNTs/PAH)₉-deposited ITO electrode, of which the redox peak current of cyclic voltammetry was also significantly enhanced. Electrochemical impedance spectroscopy analyses showed a well-formed nanostructure porous film on the surface of the multilayer modified electrode. Compared with the plain ITO electrode, the multilayered (CNTs/PAH)₉ anodic modification improved the power density of the dual-compartment MFC by 29%, due to the appropriate proportion of CNTs and PAH, as well as the porous nanostructure on the electrodes. Full article

Conventional electrode-based technologies, such as the electrocardiogram (ECG), capture physiological signals using an electrolyte solution or gel that evaporates shortly after exposure, resulting in a decrease in the quality of the signal. Previously, we reported a novel dry impedimetric electrode using patterned vertically-aligned Carbon NanoTubes (pvCNT) for biopotential measurement applications. The mechanical adhesion strength of the pvCNT electrode to the substrate was weak, hence, we have improved this electrode using a thin coating of the conductive polymer polypyrrole (PPy) that strengthens its mechanical properties. Multiwall CNTs were grown vertically on a circular stainless-steel disc (⌀ = 10 mm) substrate of 50 µm thickness forming patterned pillars on a square base (100 µm × 100 µm) with an inter-pillar spacing of 200 µm and height up to 1.5 mm. The PPy coating procedure involves applying 10 µL of PPy mixed with 70% ethyl alcohol solution and rapid drying at 300 °C using a hot air gun at a distance of 10 cm. A comparative study demonstrated that the coated pvCNT had higher impedance compared to a non-coated pvCNT but lower impedance compared to the standard gel electrode. The PPy-coated pvCNT had comparable signal capture quality but stronger mechanical adhesion to the substrate. Full article

Microbial fuel cells (MFCs) are promising devices for sustainable energy production, wastewater treatment and biosensors. Anode materials directly interact with electricigens and accept electrons between cells, playing an important role in determining the performance of MFCs. In this study, a novel carbon nanotubes (CNTs) and polyaniline (PANI) nanocomposite film modified Indium-tin oxide (ITO) anode was fabricated through graft polymerization of PANI after the modification of γ-aminopropyltriethoxysilane (APTES) on ITO substrate, which was followed by layer-by-layer (LBL) self-assembling of CNTs and PANI alternatively on its surface. (CNTs/PANI)_n/APTES/ITO electrode with low charge transfer resistance showed better electrochemical behavior compared to the bare ITO electrode. Twelve layers of CNTs/PANI decorated ITO electrode with an optimal nanoporous network exhibited superior biocatalytic properties with a maximal current density of 6.98 µA/cm², which is 26-fold higher than that of conventional ITO electrode in Shewanella loihica PV-4 bioelectrochemical system. MFCs with (CNTs/PANI)₁₂/APTES/ITO as the anode harvested a maximum output power density of 34.51 mW/m², which is 7.5-fold higher than that of the unmodified ITO electrode. These results demonstrate that (CNTs/PANI)_12/APTES/ITO electrode has superior electrochemical and electrocatalytic properties compared to the bare ITO electrode, while the cellular toxicity of CNTs has an effect on the performance of MFC with (CNTs/PANI)_n/APTES/ITO electrode. Full article