Conventional machines rely on rigid, centralized electronic components to make decisions, which limits complexity and scaling. Here, we show that decision making can be realized on the material-level without relying on semiconductor-based logic. Inspired by the distributed decision making that exists in the arms of an octopus, we present a completely soft, stretchable silicone composite doped with thermochromic pigments and innervated with liquid metal. The ability to deform the liquid metal couples geometric changes to Joule heating, thus enabling tunable thermo-mechanochromic sensing of touch and strain. In more complex circuits, deformation of the metal can redistribute electrical energy to distal portions of the network in a way that converts analog tactile ‘inputs’ into digital colorimetric ‘outputs’. Using the material itself as the active player in the decision making process offers possibilities for creating entirely soft devices that respond locally to environmental interactions or act as embedded sensors for feedback loops.

Electron transfer (ET) rate kinetics through n-alkanethiol self-assembled monolayers (SAMs) of alkanethiols of different chain lengths [Me(CH 2 ) n SH; n ) 8, 10, 11, 15] on Au and Hg surfaces and ferrocene (Fc)-terminated SAMs (poly-norbornylogous and HS(CH 2 ) 12 CONHCH 2 Fc) on Au were studied using cyclic voltammetry and scanning electrochemical microscopy (SECM). The SECM results allow determination of the ET kinetics of solution-phase Ru(NH 3 ) 6 3+/2+ through the alkanethiol SAMs on Au and Hg. A model using the potential dependence of the measured rate constants is proposed to compensate for the pinhole contribution. Extrapolated values of k o ML for Ru(NH 3 ) 6 3+/2+ using the model follow the expected exponential decay (β is 0.9) for different chain lengths. For a Fc-terminated poly-norbornyl SAM, the standard rate constant of direct tunneling (k o is 189 ( 31 s -1 ) is in the same order as the k o value of HS(CH 2 ) 12 CONHCH 2 Fc. In blocking and Fc SAMs, the rates of ET are demonstrated to follow Butler-Volmer kinetics with transfer coefficients R of 0.5. Lower values of R are treated as a result of the pinhole contribution. The normalized rates of ET are 3 orders of magnitude higher for Fc-terminated than for blocking monolayers. Scanning electron microscopy imaging of Pd nanoparticles electrochemically deposited in pinholes of blocking SAMs was used to confirm the presence of pinholes.

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Among all of the elements in the periodic table, there are only five metals that are liquid near room temperature: francium (Fr), cesium (Cs), rubidium (Rb), mercury (Hg), and gallium (Ga).The first three elements, however, are not practical for applications because they are either radioactive (Fr, Cs) or explosively reactive with air (Rb). Mercury was widely used in the past but is now avoided due to its toxicity. [1,2] By process of elimination, therefore, gallium and gallium-based alloys are the safest liquid metals at or near room temperature. [3] Gallium, discovered in 1875, has an extremely low vapor pressure even at high temperatures (effectively zero at room temperature and only 1 kPa at 1037 C; [4] by comparison, water has a vapor pressure of 1 kPa at 7 C). This low vapor pressure keeps the liquid from evaporating and eliminates the danger of vapor inhalation. While gallium should be found as solid at room temperature, because its melting point is 30 C, it is often liquid due to its ability to supercool. To assure a roomtemperature liquid phase, eutectic alloys containing at least one additional metal are commonly used to lower the melting point below room temperature. Two popular commercial alloys are Galinstan (68.5 wt% Ga, 21.5 wt% In, and 10.0 wt% Sn) and eutectic gallium indium (EGaIn, 75.5 wt% Ga and 24.5 wt% In), for which the melting point is 10.7 and 15.5 C, respectively. [5] In air, these alloys all form surface oxides within microseconds due to a high reactivity of gallium with oxygen. Because Ga oxidizes more readily than other components in these alloys, the surface oxides are dominated by gallium oxide species. These alloys thereby exhibit similar interfacial behavior to gallium in air. [6] Thus, we discuss these gallium-based alloys without distinguishing them by their bulk composition, except where warranted. Interfacial Tension ModulationMetals have significantly larger surface tension (>400 mN m À1 depending on the liquid metal [7] ) than common fluids such as water (72 mN m À1 ), as shown in Figure 1a. The large surface tension of metals is due to the metallic bonds. [4] Gallium is notable for having the highest surface tension (708 mN m À1 ) of any liquid in air near room temperature [8,9] and alloys of Ga, such as EGaIn, also have enormous surface tension (624 mN m À1 ). [10] We note the term "surface tension" refers to the tension of fluid interfaces in contact only with a vapor phase, whereas "interfacial tension" refers more broadly to the tension of fluids

Liquids typically form droplets when exiting a nozzle. Jets––cylindrical streams of fluid—can form transiently at higher fluid velocities, yet interfacial tension rapidly drives jet breakup into droplets via the Rayleigh–Plateau instability. Liquid metal is an unlikely candidate to form stable jets since it has enormous interfacial tension and low viscosity. We report that electrochemical anodization significantly lowers the effective tension of a stream of metal, transitioning it from droplets to long (long lifetime and length) wires with 100-μm diameters without the need for high velocities. Whereas surface minimization drives Rayleigh–Plateau instabilities, these streams of metal increase in surface area when laid flat upon a surface due to the low tension. The ability to tune interfacial tension over at least three orders of magnitude using modest potential (<1 V) enables new approaches for production of metallic structures at room temperature, on-demand fluid-in-fluid structuring, and new tools for studying and controlling fluid behavior.

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The development of simple, inexpensive, hand-held, user-friendly biosensor for high throughput and multiplexed genotyping of various single nucleotide polymorphisms (SNPs) in a single run experiment by a nonspecialist user is the main challenge in the analysis of DNA. Visualizing the signal and possibility to monitor SNPs by a digital camera opens a new horizon for the routine applications. In the present manuscript, a novel wireless electrochemiluminescence (ECL) DNA array is introduced for the visualized genotyping of different SNPs on the basis of ECL of luminol/hydrogen peroxide system on a bipolar electrode (BPE) array platform. After modification of anodic poles of the array with the DNA probe and its hybridization with the targets, genotyping of various SNPs is carried out by exposing the array to different monobase modified luminol-platinum nanoparticles (M-L-PtNPs). Upon the hybridization of M-L-PtNPs to mismatch sites, the ECL of luminol is followed using a photomultiplier tube (PMT) or digital camera and the images are analyzed by ImageJ software. This biosensor can detect even thermodynamically stable SNP (G-T mismatches) in the range of 2-600 pM. Also, by combining the advantages of BPE and the high visual sensitivity of ECL, it could be easily expected to achieve sensitive screening of different SNPs. The present biosensor demonstrates the capability for the discrimination between PCR products of normal, heterozygous, and homozygous beta thalassemia genetic disorders.

Electrochemical oxidation of catechol has been studied in the presence of secondary amines as nucleophiles in aqueous solution with various pH values using cyclic voltammetry and differential pulse voltammetry. Cyclic voltammetry of catechol in pure buffered solution (2.00 pH < 9.00) shows one anodic and corresponding cathodic peak which relates to the transformation of catechol to corresponding o-benzoquinone and vice versa within a quasireversible two electron transfer process. Also, a little amount of o-benzoquinone undergoes polymerization reaction. Cyclic voltammogram of catechol in the presence of nucleophilic amines, show one anodic peak in the first scan of potential but on the reverse scan the corresponding cathodic peak disappear and new peak is observed at less positive potential. In the second scan of potential also a new anodic peak is observed. On the other hand at high concentration of amines the redox peak attributable to formed polymer disappear showing that in this condition the polymerization reaction occurs at non-measurable extent. On the basis of these observations we propose an ECE mechanism for the electrochemical oxidation of catechol in the presence of secondary amines.