Llibertat Abad

The growing demand for autonomous, sustainable, and delocalized power sources for low-power-consuming electronic devices is driving a significant research effort on energy harvesting technologies. Among these, micro-thermoelectric generators (µTEGs) emerge as an appealing solution because of the abundance of residual latent heat sources. This paper proposes an approach to combine high-performance thermoelectric oxides with Si-based µTEGs, leveraging the miniaturization and high-density integration of CMOS-like technologies. The approach is applied to the integration of niobium-doped strontium titanate (Nb:STO) thin films on Si-based planar µTEG structures. The Nb:STO-based µTEG achieves a specific power density Γ = 0.36 nW·cm⁻²·K⁻² under controlled temperature gradients, which is below state-of-the-art performance probably due to lower electrical conductivity from polycrystalline growth. When the chips were tested under realistic operating conditions – placed on a hot surface at 175°C – a maximum power output of p = 0.07 nW was obtained. Nonetheless, by implementing a technological solution for thermal dissipation, the temperature gradient across the thermoelectric material improved by a factor of 110, resulting in a significantly higher extracted power of p = 7.75 nW.

Modulation of magnetic properties through voltage-driven ion motion and redox processes, i.e., magneto-ionics, is a unique approach to control magnetism with electric field for low-power memory and spintronic applications. So far, magneto-ionics has been achieved through direct electrical connections to the actuated material. Here we evidence that an alternative way to reach such control exists in a wireless manner. Induced polarization in the conducting material immersed in the electrolyte, without direct wire contact, promotes wireless bipolar electrochemistry, an alternative pathway to achieve voltage-driven control of magnetism based on the same electrochemical processes involved in direct-contact magneto-ionics. A significant tunability of magnetization is accomplished for cobalt nitride thin films, including transitions between paramagnetic and ferromagnetic states. Such effects can be either volatile or non-volatile depending on the electrochemical cell configuration. These results represent a fundamental breakthrough that may inspire future device designs for applications in bioelectronics, catalysis, neuromorphic computing, or wireless communications.

Nanocrystalline zinc oxide:vanadium (ZnO:V) films were deposited over thoroughly cleaned glass substrates using the reactive direct current magnetron sputtering technique. The deposited ZnO:V films were analyzed for their structural, morphological, optical and electrical properties using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), UV-visible spectrophotometry and the two-probe method, respectively. Microstructural parameters of the films varied with respect to substrate temperature, substrate bias and sputtering powers. FE-SEM micrographs of the films showed that the prepared films were porous when compared with pure ZnO films. ZnO:V films were highly transparent and the optical band gap value of the films varied between 3·1 and 3·37 eV. Piezoelectric generation of the ZnO:V films was tested by different testing methodologies. The lab-scale device fabricated in the present work generated 100 µV upon applying vibration. Scaling up this device would yield piezoelectricity of higher orders of voltages.

A spatially controlled synthesis of nanowire bundles of the functional crystalline coordination polymer (CP) Ag(I)TCNQ (tetracyanoquinodimethane) from previously fabricated and trapped monovalent silver CP (Ag(I)Cys (cysteine)) using a room-temperature microfluidic-assisted templated growth method is demonstrated. The incorporation of microengineered pneumatic clamps in a two-layer polydimethylsiloxane-based (PDMS) microfluidic platform was used. Apart from guiding the formation of the Ag(I)Cys coordination polymer, this microfluidic approach enables a local trapping of the in situ synthesized structures with a simple pneumatic clamp actuation. This method not only enables continuous and multiple chemical events to be conducted upon the trapped structures, but the excellent fluid handling ensures a precise chemical activation of the amino acid-supported framework in a position controlled by interface and clamp location that leads to a site-specific growth of Ag(I)TCNQ nanowire bundles. The synthesis is conducted stepwise starting with Ag(I)Cys CPs, going through silver metal, and back to a functional CP (Ag(I)TCNQ); that is, a novel microfluidic controlled ligand exchange (CP → NP → CP) is presented. Additionally, the pneumatic clamps can be employed further to integrate the conductive Ag(I)TCNQ nanowire bundles onto electrode arrays located on a surface, hence facilitating the construction of the final functional interfaced systems from solution specifically with no need for postassembly manipulation. This localized self-supported growth of functional matter from an amino acid-based CP shows how sequential localized chemistry in a fluid cell can be used to integrate molecular systems onto device platforms using a chip incorporating microengineered pneumatic tools. The control of clamp pressure and in parallel the variation of relative flow rates of source solutions permit deposition of materials at different locations on a chip that could be useful for device array preparation. The in situ reaction and washing procedures make this approach a powerful one for the fabrication of multicomponent complex nanomaterials using a soft bottom-up approach.

This work demonstrates the design and fabrication of an all cyclo‐olefin polymer based microfluidic device capable of capturing magnetic beads and performing electrochemical detection in a series of gold electrodes. The size of chip is of a microscope slide and features six independent measuring cells for multianalyte detection purposes. The aim of this work is to show that rapid prototyping techniques can be instrumental in the development of novel bioassays, particularly in clinical diagnosis applications. We show the successful determination of troponin‐T, a cardiac disease marker, in the clinically relevant range of 0.05–1.0 ng/mL. This methodology achieves a detection limit of 0.017 ng/mL in PBS solutions, and is capable of detecting less than 1 ng/mL in a 1:50 human serum dilution.