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Ainla, Alar

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Ainla

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Alar

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Ainla, Alar
Author's Publications: search.filters.isAuthorOfPublication.62ae2046-6d47-4007-b6d4-f69ab941eb92

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Now showing 1 - 9 of 9
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    Buckling of Elastomeric Beams Enables Actuation of Soft Machines
    (Wiley-Blackwell, 2015) Yang, Dian; Mosadegh, Bobak; Ainla, Alar; Lee, Ben; Khashai, Fatemeh; Suo, Zhigang; Bertoldi, Katia; Whitesides, George
    Soft, pneumatic actuators that buckle when interior pressure is less than exterior provide a new mechanism of actuation. Upon application of negative pneumatic pressure, elastic beam elements in these actuators undergo reversible, cooperative collapse, and generate a rotational motion. These actuators are inexpensive to fabricate, lightweight, easy to control, and safe to operate. They can be used in devices that manipulate objects, locomote, or interact cooperatively with humans.
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    Electroanalytical devices with pins and thread
    (Royal Society of Chemistry (RSC), 2016) Glavan, Ana; Ainla, Alar; Hamedi, Mahiar Max; Fernández-Abedul, M. Teresa; Whitesides, George
    This 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.
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    Paper-Based Electrical Respiration Sensor
    (Wiley-Blackwell, 2016) Guder, Firat; Ainla, Alar; Redston, Julia; Mosadegh, Bobak; Glavan, Ana; Martin, T. J.; Whitesides, George
    Current methods of monitoring breathing require cumbersome, inconvenient, and often expensive devices; this requirement sets practical limitations on the frequency and duration of measurements. This article describes a paper-based moisture sensor that uses the hygroscopic character of paper (i.e. the ability of paper to adsorb water reversibly from the surrounding environment) to measure patterns and rate of respiration by converting the changes in humidity caused by cycles of inhalation and exhalation to electrical signals. The changing level of humidity that occurs in a cycle causes a corresponding change in the ionic conductivity of the sensor, which can be measured electrically. By combining the paper sensor with conventional electronics, data concerning respiration can be transmitted to a nearby smartphone or tablet computer for post-processing, and subsequently to a cloud server. This means of sensing provides a new, practical method of recording and analyzing patterns of breathing.
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    Integrating Electronics and Microfluidics on Paper
    (Wiley-Blackwell, 2016) Hamedi, Mahiar Max; Ainla, Alar; Guder, Firat; Christodouleas, Dionysios; Fernández-Abedul, M. Teresa; Whitesides, George
    The 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.
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    A Paper-Based “Pop-up” Electrochemical Device for Analysis of Beta-Hydroxybutyrate
    (American Chemical Society (ACS), 2016) Wang, Chien-Chung; Hennek, Jonathan; Ainla, Alar; Kumar, Ashok Ashwin; Lan, Wen-Jie; Im, Judy S; Smith, Barbara S.; Zhao, Mengxia; Whitesides, George
    This paper describes the design and fabrication of a “pop-up” electrochemical paper-based analytical device (pop-up-EPAD) to measure beta-hydroxybutyrate (BHB)—a key biomarker for diabetic ketoacidosis—using a commercial glucometer. Pop-up-EPADs are inspired by pop-up greeting cards and children's books. They are made from a single sheet of paper folded into a three-dimensional (3D) device that changes shape, and fluidic and electrical connectivity, by simply folding and unfolding the structure. The reconfigurable 3D structure makes it possible to change the fluidic path and to control timing; it also provides mechanical support for the folded and unfolded structures that enables good registration and repeatability on folding. A pop-up-EPAD designed to detect BHB shows performance comparable to commercially available plastic test strips over the clinically relevant range of BHB in blood when used with a commercial glucometer that integrates the ability to measure glucose and BHB (combination BHB/glucometer). With simple modifications of the electrode and fluid path design, the pop-up-EPAD also detects BHB using a simple glucometer—a device that is much more available than combination BHB/glucometers. Strategies that use a “3D pop-up”—that is, large-scale changes a 3D structure and fluidic paths—by folding/unfolding add functionality (e.g., controlled timing, fluidic handling and path programming, control over complex sequences of steps, and alterations in electrical connectivity) to EPADs, and should enable the development of new classes of paper-based diagnostic de-vices.
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    Autocatalytic, bistable, oscillatory networks of biologically relevant organic reactions
    (Springer Nature, 2016) Semenov, Sergey; Kraft, Lewis J.; Ainla, Alar; Zhao, Mengxia; Baghbanzadeh, Mostafa; Campbell, Victoria; Kang, Kyungtae; Fox, Jerome Michael; Whitesides, George
    Networks of organic chemical reactions are centrally important in life, and were likely to have played a central role in its origins. Network dynamics regulate cell division, circadian rhythms, nerve impulses, chemotaxis, and guide development of organisms. Although out-of-equilibrium networks of chemical reactions have the potential to display emergent network dynamics such as spontaneous pattern formation, bistability, and periodic oscillations, the principles that enable networks of organic reactions to develop complex behaviors are incompletely understood. Here we describe a network of biologically relevant organic reactions (amide formation, thiolate-thioester exchange, thiolate-disulfide interchange, and conjugate addition) that displays bistability and oscillations in concentrations of organic thiols and amides. Oscillations arise from the interaction between three subcomponents of the network: (i) an autocatalytic cycle that generates thiols and amides from thioesters and dialkyl disulfides; (ii) a trigger that controls autocatalytic growth; and (iii) inhibitory processes that remove activating thiol species produced during the autocatalytic cycle. In contrast to previous studies demonstrating oscillations and bistability using highly evolved biomolecules (i.e., enzymes and DNA) or inorganic molecules of questionable biochemical relevance (e.g. those used in Belousov-Zhabotinsky-type reactions), the organic molecules used in our network are relevant to current metabolism and similar to those that might have existed on early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable, and oscillatory behavior, we identified principles that clarify how dynamic networks relevant to life might possibly have developed. In the future, modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks, and of synthetic self-regulating and evolving chemical systems.
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    Arthrobots
    (Mary Ann Liebert Inc, 2017) Nemiroski, Alex; Shevchenko, Yanina Y.; Stokes, Adam A.; Unal, Baris; Ainla, Alar; Albert, Sahradha; Compton, Gabrielle; MacDonald, Emily; Schwab, Yosyp; Zellhofer, Caroline; Whitesides, George
    This paper describes a class of robots—“arthrobots”— inspired, in part, by the musculoskeletal system of arthropods (spiders and insects, inter alia). An exoskeleton, constructed from thin organic polymeric tubes, provides lightweight structural support. Pneumatic joints modeled after the hydrostatic joints of spiders provide actuation and inherent mechanical compliance to external forces. An inflatable elastomeric tube (a “balloon”) enables active extension of a limb; an opposing elastic tendon enables passive retraction. A variety of robots constructed from these structural elements demonstrate i) crawling with one or two limbs, ii) walking with four or six limbs (including an insect-like triangular gait), iii) walking with eight limbs, or iv) floating and rowing on the surface of water. Arthrobots are simple to fabricate, inexpensive, light-weight, and able to operate safely in contact with humans.
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    Soft, Rotating Pneumatic Actuator
    (Mary Ann Liebert Inc, 2017) Ainla, Alar; Verma, Mohit S.; Yang, Dian; Whitesides, George
    This paper describes a soft pneumatic actuator that generates cyclical motion. The actuator consists of several (three, four, or five) chambers (arranged around the circumference of a circle surrounding a central rod) that can be actuated independently using negative pressure (or partial vacuum). Sequential actuation of the four-chamber device using reduced pressure moves the central rod cyclically in an approximately square path. We characterize the trajectory of the actuator and the force exerted by it, as we vary the material used for fabrication, the number of chambers, and the size of the actuator. We demonstrate two applications of this actuator: to deliver fluid while stirring (by replacing the central rod with a needle), and for locomotion that mimics a reptilian gait (by combining four actuators together).
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    Electrical Textile Valves for Paper Microfluidics
    (Wiley-Blackwell, 2017) Ainla, Alar; Hamedi, Mahiar M.; Güder, Firat; Whitesides, George
    This paper describes electrically-activated fluidic valves that operate based on electrowetting through textiles. The valves are fabricated from electrically conductive, insulated, hydrophobic textiles, but the concept can be extended to other porous materials. When the valve is closed, the liquid cannot pass through the hydrophobic textile. Upon application of a potential (in the range of 100–1000 V) between the textile and the liquid, the valve opens and the liquid penetrates the textile. These valves actuate in less than 1 s, require low energy (≈27 µJ per actuation), and work with a variety of aqueous solutions, including those with low surface tension and those containing bioanalytes. They are bistable in function, and are, in a sense, the electrofluidic analog of thyristors. They can be integrated into paper microfluidic devices to make circuits that are capable of controlling liquid, including autonomous fluidic timers and fluidic logic.