Impedance plethysmography-based method in the assessment of subclinical atherosclerosis.

BACKGROUND AND AIMS: The aim of this study was to examine an association of individual and combined pulse waveform parameters derived from bioimpedance measurements, that is pulse waves from a distal impedance plethysmographic (IPG), a whole-body impedance cardiographic (ICG) and transformed distal impedance plethysmographic (tIPG) signals, with markers of subclinical atherosclerosis, i.e. carotid intima-media thickness (cIMT), brachial artery flow-mediated dilation (FMD) and carotid artery distensibility (Cdist). The level of the association was also compared for arterial pulse wave velocity (PWV) and cIMT, FMD, and Cdist. METHODS: IPG, ICG, tIPG signals were measured from 1741 Finnish adults aged 30-45 years. The association between pulse wave parameters and cIMT, FMD and Cdist was studied using bootstrapped stepwise Akaike's Information Criterion method resulting in selection of parameters other than PWV, i.e. parameters having stronger association with cIMT, FMD and Cdist than PWV, in the model. Then risk scores were calculated from the selected pulse wave parameters and their association between cIMT, FMD and Cdist was studied with multivariable linear regression analysis. RESULTS: The risk score was found to be the third strongest predictor of subclinical atherosclerosis as indicated by cIMT measurement, the second strongest predictor of FMD and the strongest predictor of Cdist. These findings show that several individual pulse wave parameters were associated more strongly with cIMT, FMD, and Cdist than PWV when adjusted with clinical risk factors. CONCLUSIONS: Impedance based pulse waveform analysis provides a useful tool for assessing cardiovascular risk and estimating presence of structural changes in the vasculature.

Drying-Mediated Self-Assembly of Graphene for Inkjet Printing of High-Rate Micro-supercapacitors.

Scalable fabrication of high-rate micro-supercapacitors (MSCs) is highly desired for on-chip integration of energy storage components. By virtue of the special self-assembly behavior of 2D materials during drying thin films of their liquid dispersion, a new inkjet printing technique of passivated graphene micro-flakes is developed to directly print MSCs with 3D networked porous microstructure. The presence of macroscale through-thickness pores provides fast ion transport pathways and improves the rate capability of the devices even with solid-state electrolytes. During multiple-pass printing, the porous microstructure effectively absorbs the successively printed inks, allowing full printing of 3D structured MSCs comprising multiple vertically stacked cycles of current collectors, electrodes, and sold-state electrolytes. The all-solid-state heterogeneous 3D MSCs exhibit excellent vertical scalability and high areal energy density and power density, evidently outperforming the MSCs fabricated through general printing techniques.

Printed Flexible Microelectrode for Application of Nanosecond Pulsed Electric Fields on Cells.

Medical treatment is increasingly benefiting from biomedical microsystems, especially the trending telemedical application. A promising modality for tumor therapy showed the application of nanosecond pulsed electric fields (nsPEF) on cells to achieve nanoporation, cell death, and other cell reactions. A key technology for this method is the generation of pulsed fields in the nanosecond range with high-field strengths in the range of several kilovolts per centimeter. For further biomedical applications, state-of-the-art setups need to decrease in size and improve their capability of integration into microsystems. Due to demanding electronic requirements, i.e., using high voltages and fast pulses, miniaturization and low-cost fabrication of the electrode is first considered. This paper proposes a proof-of-concept for a miniaturized printed flexible electrode that can apply nsPEF on adherent fibroblast cells. The interdigital gold electrode was printed on polyimide with line-width of about 10 µm using an electrohydrodynamic inkjet printer. Furthermore, an electrical circuit was developed to generate both electrical pulses in the nano-second range and voltages up to 180 V. The electrode was integrated into an experimental setup for in-vitro application to human fibroblasts. Field strengths up to 100 kV/cm with 45 ns pulse duration were applied, depending on the degree of cell confluence. The cells show contraction, detachment from the electrode, and lethal reactions after the nsPEF treatment. Furthermore, this printed miniaturized electrode was found to be suitable for subsequent microsystem integration and further cell experiments to optimize pulse parameters for control of cell reaction and behavior.

Inkjet printing technology for increasing the I/O density of 3D TSV interposers.

Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (-40 °C to +125 °C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.