Temperature gradients are generated by the sun and a vast array of technologies and can induce molecular concentration gradients in solutions via thermodiffusion (Soret effect). For ions, this leads to a thermovoltage that is determined by the thermal gradient ΔT across the electrolyte, together with the ionic Seebeck coefficient αi. So far, redox-free electrolytes have not been explored in thermoelectric applications due to a lack of strategy to harvest the energy from the Soret effect. Here, we demonstrate the conversion of heat into stored charge via the ionic Soret effect in an IonicThermoelectric Supercapacitor (ITESC), thus providing a new means to harvest energy from intermittent heat sources. We show that the stored electrical energy of the ITESC is proportional to (ΔTαi) 2 and that its αi reaches beyond 10 mV/K. The resulting ITESC can convert and store several thousand times more energy as compared to a traditional thermoelectric generator connected in series with a supercapacitor. INTRODUCTIONVarious thermoelectric concepts are currently under investigation for conversion of thermal energy into electrical energy, with the goal to provide efficient thermoelectric systems. First, electronic charge carriers in a conductor thermodiffuse when subjected to a temperature gradient, which leads to a thermovoltage known as the Seebeck voltage. Thermoelectric generators (TEGs) that utilize the Seebeck effect are typically composed of semi-metals [1, 2], inorganic semiconductors [3, 4], and electronically conducting polymers have also recently been explored [5]. Secondly, thermovoltages can originate from the thermogalvanic effect, which results from temperature-dependent entropy changes during electron transfer between a redox molecule and an electrode [6]. Hence, thermogalvanic cells are based on electrolytes with redox couples, such as ferricyanide/ferrocyanide. The Soret effect [7] of redox free electrolyte, i.e. from ionic charge carriers constitute yet a third thermoelectric concept that, to the best of our knowledge, has not previously been considered for energy harvesting.Analogous to the electronic Seebeck effect, the Soret effect is a result of thermo-diffusion of ions in an ionic solid [8, 9] or electrolyte [10]. This produces an ionic concentration gradient and a corresponding thermo-voltage that is governed by the temperature difference across the material and the ionic Seebeck coefficient αi.For a traditional thermoelectric leg, composed of a semiconductor and two metal contacts, a constant electrical power can be provided to an external load by imposing a temperature gradient along the metal-semiconductor-metal stack. The same harvesting principle is, however, not directly applicable if the semiconductor is replaced by an electrolyte solution with ions as charge carriers. The reason for this is that the thermo-diffused ions are blocked at the surface of the metal electrode and cannot pass through the external circuit. Instead, the ions will be accumulated in excess at the metal surface where th...

Measuring temperature and heat flux is important for regulating any physical, chemical, and biological processes. Traditional thermopiles can provide accurate and stable temperature reading but they are based on brittle inorganic materials with low Seebeck coefficient, and are difficult to manufacture over large areas. Recently, polymer electrolytes have been proposed for thermoelectric applications because of their giant ionic Seebeck coefficient, high flexibility and ease of manufacturing. However, the materials reported to date have positive Seebeck coefficients, hampering the design of ultra-sensitive ionic thermopiles. Here we report an “ambipolar” ionic polymer gel with giant negative ionic Seebeck coefficient. The latter can be tuned from negative to positive by adjusting the gel composition. We show that the ion-polymer matrix interaction is crucial to control the sign and magnitude of the ionic Seebeck coefficient. The ambipolar gel can be easily screen printed, enabling large-area device manufacturing at low cost.

Fluorescence recovery after photobleaching has been an established technique of quantifying the mobility of molecular species in cells and cell membranes for more than 30 years. However, under nonideal experimental conditions, the current methods of analysis still suffer from occasional problems; for example, when the signal/noise ratio is low, when there are temporal fluctuations in the illumination, or when there is bleaching during the recovery process. We here present a method of analysis that overcomes these problems, yielding accurate results even under nonideal experimental conditions. The method is based on circular averaging of each image, followed by spatial frequency analysis of the averaged radial data, and requires no prior knowledge of the shape of the bleached area. The method was validated using both simulated and experimental fluorescence recovery after photobleaching data, illustrating that the diffusion coefficient of a single diffusing component can be determined to within approximately 1%, even for small signal levels (100 photon counts), and that at typical signal levels (5000 photon counts) a system with two diffusion coefficients can be analyzed with <10% error.

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This paper presents the use of the localized surface plasmon resonance (LSPR) sensor concept to probe the formation of macroscopic and laterally mobile supported lipid bilayers (SLBs) on SiOx-encapsulated nanohole-containing Au and Ag films. A comparison between Au- and Ag-based sensor templates demonstrates a higher sensitivity for Au-based templates with respect to both bulk and interfacial refractive index (RI) changes in aqueous solution. The lateral mobility of SLBs formed on the SiOx-encapsulated nanohole templates was analyzed using fluorescence recovery after photobleaching (FRAP), demonstrating essentially complete (>96%) recovery, but a reduction in diffusivity of about 35% compared with SLBs formed on flat SiOx substrates. Furthermore, upon SLB formation, the temporal variation in extinction peak position of the LSPR active templates display a characteristic shape, illustrating what, to the best of our knowledge, is the first example where the nanoplasmonic concept is shown capable of probing biomacromolecular structural changes without the introduction of labels. With a signal-to-noise ratio better than 5 x 10(2) upon protein binding to the cell-membrane mimics, the sensor concept is also proven competitive with state-of-the-art label-free sensors.

Nanopores enable label-free detection and analysis of single biomolecules. Here, we investigate DNA translocations through a novel type of plasmonic nanopore based on a gold bowtie nanoantenna with a solid-state nanopore at the plasmonic hot spot. Plasmonic excitation of the nanopore is found to influence both the sensor signal (nanopore ionic conductance blockade during DNA translocation) and the process that captures DNA into the nanopore, without affecting the duration time of the translocations. Most striking is a strong plasmon-induced enhancement of the rate of DNA translocation events in lithium chloride (LiCl, already 10-fold enhancement at a few mW of laser power). This provides a means to utilize the excellent spatiotemporal resolution of DNA interrogations with nanopores in LiCl buffers, which is known to suffer from low event rates. We propose a mechanism based on plasmon-induced local heating and thermophoresis as explanation of our observations.

a fair comparison between electronic and ionic thermoelectric devices.The electronic Seebeck coefficient α e of a material is defined as the ratio between the open circuit potential V oc and the temperature difference ΔT (compensated for the Seebeck coefficient of the metal contacts). If electrons and holes thermodiffuse toward the colder side at identical rate no thermovoltage is generated. Hence, a nonnegligible Seebeck coefficient is obtained for materials with different conductivities for electrons and holes. This is illustrated for a material displaying majority hole (h + ) conduction in Figure 1a,b. The electronic Seebeck effect provides the basic principle of operation for thermoelectric generators (TEGs), which can provide a continuous output current and power ( Figure 1c). The efficiency of the heat-to-electricity conversion is directly related to ZT e 1+ , where ZT e is the dimensionless thermoelectric figure of merit, as introduced by A. F. Ioffe already in 1949. [4] ZT T e e e ( / 2 σ α λ = ) is defined by three fundamental properties of the thermoelectric material: the electrical conductivity σ e , the Seebeck coefficient α e , and the thermal conductivity λ. Today, there is an intense strive to optimize the interplay between those three properties and to maximize ZT e . [1] While the major effort is to achieve TEGs based on inorganic materials (ZT e = 1.2 at 300 K for Bi 2 Te 3 alloys), [5] recent studies also include oxides, carbon-based compounds, [6,7] and electronically conducting organic polymers entirely based on atomic elements of high natural abundance (ZT e = 0.2-0.4 at 300 K for poly(3, 4-ethylenedioxythiophene) (PEDOT)). [8][9][10] This opens up for mass production of thermoelectric modules using high-volume printing and extrusion technologies. [8] We now move from electronic to ionic electronic thermoelectric materials. Figure 1d shows an example of an ionic conductor (that is not electrochemically active, thus excluding any contribution from thermogalvanic effects) [11] that favors the transport of cations over anions when exposed to a thermal gradient. The Soret effect induces ionic concentration differences that generate a thermovoltage. The ionic Seebeck voltage α i of the ionic conductor is measured as the open circuit voltage V oc established between the two metal electrodes exposed to different temperatures (assuming a negligible Seebeck coefficient of the metal contacts). [12] The ionic thermoelectric effect occurs Thermoelectric materials enable conversion of heat to electrical energy. The performance of electronic thermoelectric materials is typically evaluated using a figure of merit ZT = σα2T/λ, where σ is the conductivity, α is the so-called Seebeck coefficient, and λ is the thermal conductivity. However, it has been unclear how to best evaluate the performance of ionic thermoelectric materials, like ionic solids and electrolytes. These systems cannot be directly used in a traditional thermoelectric generator, because they are based on ions that cannot pass the interface bet...

With the aim of developing a DNA sequencing methodology, we theoretically examine the feasibility of using nanoplasmonics to control the translocation of a DNA molecule through a solid-state nanopore and to read off sequence information using surface-enhanced Raman spectroscopy. Using molecular dynamics simulations, we show that high-intensity optical hot spots produced by a metallic nanostructure can arrest DNA translocation through a solid-state nanopore, thus providing a physical knob for controlling the DNA speed. Switching the plasmonic field on and off can displace the DNA molecule in discrete steps, sequentially exposing neighboring fragments of a DNA molecule to the pore as well as to the plasmonic hot spot. Surface-enhanced Raman scattering from the exposed DNA fragments contains information about their nucleotide composition, possibly allowing the identification of the nucleotide sequence of a DNA molecule transported through the hot spot. The principles of plasmonic nanopore sequencing can be extended to detection of DNA modifications and RNA characterization.