Experimental Characterization Of Electrical Current Leakage In Poly(Dimethylsiloxane) Microfluidic Devices

Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microchannel wall can be treated as an electrically insulated boundary in an applied electric field. However, in certain layouts of microfluidic networks, electrical leakage through the PDMS microfluidic channel walls may not be negligible, which must be carefully considered in the microfluidic circuit design. In this paper, we report on the experimental characterization of the electrical leakage current through PDMS microfluidic channel walls of different configurations. Our numerical and experimental studies indicate that for tens of microns thick PDMS channel walls, electrical leakage through the PDMS wall could significantly alter the electrical field in the main channel. We further show that we can use the electrical leakage through the PDMS microfluidic channel wall to control the electrolyte flow inside the microfluidic channel and manipulate the particle motion inside the microfluidic channel. More specifically, we can trap individual particles at different locations inside the microfluidic channel by balancing the electroosmotic flow and the electrophoretic migration of the particle

SiO2-Coated Porous Anodic Alumina Membranes for High Flow Rate Electroosmotic Pump

ABSTRACT Electroosmotic pumping has been extensively used in biomedical lab-on-a-chip devices and micropumps for critical applications such as microelectronic cooling. In many applications, a high flow rate is a key requirement in desired performance so constant efforts have been made to increase the pumping flow rate through unit area to achieve the compact design. We report here an attempt of using SiO 2 -coated anodic porous alumina membrane as the material to achieve high electroosmotic pumping flow rate. High quality porous alumina membranes of controllable pore diameter in the range of 20-300 nm and pore length of 60 -100 µm have been fabricated with electrochemical anodization. The pores are uniform and hexagonally packed with a high porosity of up to 50% and a tortuosity of a bare minimum of unity. In addition, the inner surface of the pores could be conformally coated with a thin layer (~ 5 nm) of SiO 2 with sol-gel chemistry to achieve a high zeta potential. Scanning electron microscopy of the cross section of the membrane verified these facts. Electroosmotic pumping performance of these membranes has been investigated using standard relevant aqueous electrolyte buffer solutions and results showed that SiO 2 -coated porous alumina could achieve a higher flow rate compared with other microporous materials such as glass frit and porous silicon reported in the literature

Modification of structural and dielectric properties of polycrystalline Gd-doped BFO–PZO

(1−y)(BiFe1−xGdxO3)–y(PbZrO3) composites (y=0.5), having four different Gd concentrations (x=0.05, 0.1, 0.15, and 0.2), were synthesized and their structural, dielectric, and ferroelectric properties have been studied using different characterization techniques. In addition, to investigate the effect of ion implantation on the microstructure and dielectric properties, these composites were exposed to 2MeV He+-ions. Modifications of the structure, surface morphology and electrical properties of the samples before and after ion exposure were demonstrated using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) technique, and LCR meter. The compositional analysis was carried out using energy dispersive X-ray spectrometry (EDS). XRD results demonstrated a decrease in the intensity profile of the dominant peak by a factor of 6 showing a degradation of the crystallinity. Willliamson–Hall (WH) plots reveal reduction in the grain size after irradiation along with an increase in strain and dislocation density. A decrease in the dielectric constant and loss has been recorded after ion beam exposure with reduction in ac conductivity value. The contribution of grain and grain boundary effect in conduction mechanism has been addressed using Nyquist plots. All the samples demonstrate a lossy ferroelectric loop which shows a clear modification upon irradiation. The role of structural defects modifying the physical properties of the composite materials is discussed in this work

Electrical leakage through thin PDMS microchannel walls and its applications

PDMS is usually considered as a dielectric material and PDMS microchannel walls can be treated as an electrically insulated boundary. However, in certain layouts of microfluidic networks, electrical leakage through PDMS walls could significantly alter the electrical field in the microfluidic circuits, which must be carefully considered in microfluidic circuit design. We report on our experimental characterization of electrical leakage through PDMS microfluidic channel walls. Numerical modeling clearly disclosed the alteration of electrical field and electroosmotic velocity in the microfluidic channels because of the electrical leakage through the thin PDMS wall. In addition, we demonstrate that the electrical leakage through the PDMS channel wall can be used to realize trapping of individual particles at different locations inside the mcirofluidic channel by balancing the electroosmotic flow and electrophoretic migration of the particle. Copyright © 2008 by ASME

Bright Photon Upconversion on Composite Organic Lanthanide Molecules through Localized Thermal Radiation

Converting low-energy photons via thermal radiation can be a potential approach for utilizing infrared (IR) photons to improve photovoltaic efficiency. Lanthanide-containing materials have achieved great progress in IR-to-visible photon upconversion (UC). Herein, we first report bright photon, tunable wavelength UC through localized thermal radiation at the molecular scale with low excitation power density (<10 W/cm²) realized on lanthanide complexes of perfluorinated organic ligands. This is enabled by engineering the pathways of nonradiative de-excitation and energy transfer in a composite of ytterbium and terbium perfluoro­imidodi­phosphinates. The IR-excited thermal UC and wavelength control is realized through the terbium activators sensitized by the ytterbium sensitizers having high luminescence efficiency. The metallic molecular composite thus can be a potential energy material in the use of the IR solar spectrum for thermal photovoltaic applications

Quantifying nanodiamonds biodistribution in whole cells with correlative iono-nanoscopy

10.1038/s41467-021-25004-9NATURE COMMUNICATIONS121Complete