Person: Hamedi, Mahiar Max
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Hamedi
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Mahiar Max
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Hamedi, Mahiar Max
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Publication Electroanalytical devices with pins and thread(Royal Society of Chemistry (RSC), 2016) Glavan, Ana; Ainla, Alar; Hamedi, Mahiar Max; Fernández-Abedul, M. Teresa; Whitesides, GeorgeThis work describes the adaptive use of conventional stainless steel pins—used in unmodified form or coated with carbon paste—as working, counter, and quasi-reference electrodes in electrochemical devices fabricated using cotton thread or embossed omniphobic RF paper to contain the electrolyte and sample. For some applications, these pin electrodes may be easier to modify and use than printed electrodes, and their position and orientation can be changed as needed. Electroanalytical devices capable of multiplex analysis (thread-based arrays or 96-well plates) were easily fabricated using pins as electrodes in either thread or omniphobic RF paper.Publication Electrically Activated Paper Actuators(Wiley-Blackwell, 2016) Hamedi, Mahiar Max; Campbell, Victoria; Rothemund, Philipp Josef Michael; Guder, Firat; Christodouleas, Dionysios; Bloch, Jean-Francis; Whitesides, GeorgeThis paper describes the design and fabrication of electrically controlled paper actuators that operate based on the dimensional changes that occur in paper when the moisture absorbed on the surface of the cellulose fibers changes. These actuators are called “Hygroexpansive Electrothermal Paper Actuators” (HEPAs). The actuators are made from paper, conducting polymer, and adhesive tape. They are lightweight, inexpensive, and can be fabricated using simple printing techniques. The central element of the HEPAs is a porous conducting path (used to provide electrothermal heating) that changes the moisture content of the paper and causes actuation. This conducting path is made by embedding a conducting polymer (PEDOT:PSS) within the paper, and thus making a paper/polymer composite that retains the porosity and hydrophilicity of paper. Different types of HEPAs (straight, precurved, and creased) achieved different types of motions (e.g., bending motion, accordion type motion). A theoretical model for their behavior is proposed. These actuators have been used for the manipulation of liquids and for the fabrication of an optical shutter.Publication Integrating Electronics and Microfluidics on Paper(Wiley-Blackwell, 2016) Hamedi, Mahiar Max; Ainla, Alar; Guder, Firat; Christodouleas, Dionysios; Fernández-Abedul, M. Teresa; Whitesides, GeorgeThe fields of paper microfluidics and printed electronics have developed independently, and are incompatible in many of their aspects (e.g. printed electronic thin films are not designed to tolerate the flows of liquids, and especially of water, nor are water filled-channels designed to conduct electrons). This work demonstrates monolithic integration of microfluidics and electronics on paper, by extending the use of paper microfluidics to the fabrication of electrical conductors by the wicking of aqueous conducting inks inside microfluidic channels. These conductors are unique in that they can act as wires, electrodes, and microfluidic channels at the same time. These techniques, make it possible to print both two- and three-dimensional fluidic, electrofluidic, and electrical components using simple methods, and thus to design new paper devices. This paper demonstrates the fabrication of three classes of devices: i) 3D paper “printed circuit boards”, ii) vertical-flow electroanalytical devices, and iii) foldable, all-organic paper batteries.Publication Coated and uncoated cellophane as materials for microplates and open-channel microfluidics devices(Royal Society of Chemistry (RSC), 2016) Hamedi, Mahiar Max; Unal, Baris; Kerr, Emily; Glavan, Ana C.; Fernandez-Abedul, M. Teresa; Whitesides, GeorgeThis communication describes the use of uncoated cellophane (regenerated cellulose films) for the fabrication of microplates, and the use of coated cellophane for the fabrication of open-channel microfluidic devices. The microplates based on uncoated cellophane are particularly interesting for applications that require high transparency in the ultraviolet (UV) regime, and offer a low-cost alternative to expensive quartz-well plates. Uncoated cellophane is also resistant to damage by various solvents. The microfluidic devices, based on coated cellophane, can have features with dimensions as small as 500 μm, and complex, non-planar geometries. Electrodes can be printed on the surface of the coated cellophane, and embedded in microfluidic devices, to develop resistive heaters and electroanalytical devices for flow injection analysis, and continuous flow electrochemiluminescence (ECL) applications. These open-channel devices are appropriate for applications where optical transparency (especially in the visible regime), resistance to damage by water, biocompatibility and biodegradability are important. Cellophane microfluidic systems complement existing cellulose-based paper microfluidic systems, and provide an alternative to other materials used in microfluidics, such as synthetic polymers or glass. Cellulose films are plausible materials for uses in integrated microfluidic systems for diagnostics, analyses, cell-culture, and MEMS.Publication Paper-Based Potentiometric Ion Sensing(American Chemical Society (ACS), 2014) Lan, Wen-Jie; Zou, Xu U.; Hamedi, Mahiar Max; Hu, Jinbo; Parolo, Claudio; Maxwell, E. Jane; Bühlmann, Philippe; Whitesides, GeorgeThis paper describes the design and fabrication of ion-sensing electrochemical paper-based analytical devices (EPADs) in which a miniaturized paper reference electrode is integrated with a small ion-selective paper electrode (ISPE) for potentiometric measurements. Ion-sensing EPADs use printed wax barriers to define electrochemical sample and reference zones. Single-layer EPADs for sensing of chloride ions include wax-defined sample and reference zones that each incorporate a Ag/AgCl electrode. In EPADs developed for other electrolytes (potassium, sodium, and calcium ions), a PVC-based ion-selective membrane is added to separate the sample zone from a paper indicator electrode. After the addition of a small volume (less than 10 μL) of sample and reference solutions to different zones, ion-sensing EPADs exhibit a linear response, over 3 orders of magnitude, in ranges of electrolyte concentrations that are relevant to a variety of applications, with a slope close to the theoretical value (59.2/z mV). Ion-selective EPADs provide a portable, inexpensive, and disposable way of measuring concentrations of electrolyte ions in aqueous solutions.