Review—A Pencil Drawing Overview: From Graphite to Electrochemical Sensors/Biosensors Applications

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Abstract

Much effort was made in the literature to put pencil-drawing as an attractive way to fabricate electrochemical sensors. The pencil drawing is one of the easiest, cost-effective, unique single-step methods for fabricating paper-based devices without necessitating any expensive instrumentation by merely transferring the carbon by exfoliation abrasion on paper. Additionally, much has to be done to improve the quality of this transfer carbon to achieve a suitable sensing platform for electrochemical measurements. Hence, this review article aims to bring the new approaches developed in the last five years to circumvent some fabrication problems and enhance this “carbonization” step for electrochemistry detection using paper-based sensors. We will start the discussion on the carbon materials moving to the substrate and finally discuss the strategies to produce the conductive tracks and enhance their properties for sensing applications.

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Re-epithelialization and immune cell behaviour in an ex vivo human skin model

Ana Rakita, Nenad Nikolić, Michael Mildner … (2020)

A large body of literature is available on wound healing in humans. Nonetheless, a standardized ex vivo wound model without disruption of the dermal compartment has not been put forward with compelling justification. Here, we present a novel wound model based on application of negative pressure and its effects for epidermal regeneration and immune cell behaviour. Importantly, the basement membrane remained intact after blister roof removal and keratinocytes were absent in the wounded area. Upon six days of culture, the wound was covered with one to three-cell thick K14+Ki67+ keratinocyte layers, indicating that proliferation and migration were involved in wound closure. After eight to twelve days, a multi-layered epidermis was formed expressing epidermal differentiation markers (K10, filaggrin, DSG-1, CDSN). Investigations about immune cell-specific manners revealed more T cells in the blister roof epidermis compared to normal epidermis. We identified several cell populations in blister roof epidermis and suction blister fluid that are absent in normal epidermis which correlated with their decrease in the dermis, indicating a dermal efflux upon negative pressure. Together, our model recapitulates the main features of epithelial wound regeneration, and can be applied for testing wound healing therapies and investigating underlying mechanisms.

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Advanced carbon electrode materials for molecular electrochemistry.

Richard L McCreery (2008)

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Carbon materials for supercapacitor application.

Elzbieta Frackowiak (2007)

The most commonly used electrode materials for electrochemical capacitors are activated carbons, because they are commercially available and cheap, and they can be produced with large specific surface area. However, only the electrochemically available surface area is useful for charging the electrical double layer (EDL). The EDL formation is especially efficient in carbon pores of size below 1 nm because of the lack of space charge and a good attraction of ions along the pore walls. The pore size should ideally match the size of the ions. However, for good dynamic charge propagation, some small mesopores are useful. An asymmetric configuration, where the positive and negative electrodes are constructed from different materials, e.g., activated carbon, transition metal oxide or conducting polymer, is of great interest because of an important extension of the operating voltage. In such a case, the energy as well as power is greatly increased. It appears that nanotubes are a perfect conducting additive and/or support for materials with pseudocapacitance properties, e.g. MnO(2), conducting polymers. Substitutional heteroatoms in the carbon network (nitrogen, oxygen) are a promising way to enhance the capacitance. Carbons obtained by one-step pyrolysis of organic precursors rich in heteroatoms (nitrogen and/or oxygen) are very interesting, because they are denser than activated carbons. The application of a novel type of electrolyte with a broad voltage window (ionic liquids) is considered, but the stability of this new generation of electrolyte during long term cycling of capacitors is not yet confirmed.