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.

No abstract

No abstract

Ultrathin sensing devices utilizing piezoelectric materials have emerged as potential candidates to develop highly skin-conformable and energy-efficient continuous biosignal monitoring systems. However, biocompatible, cost-efficient, and simple fabrication processes still need to be investigated to enable wider adoption of such devices. This study proposes a simple two-step printing process for the fabrication of a piezoelectric biosignal sensor that utilizes readily available and biocompatible polymer-based materials for the substrate (i.e., Parylene-C), electroactive layer (i.e., poly­(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)), and interdigitated electrodes (i.e., poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS)). The proposed interdigitated electrode architecture improves upon the conventional metal–insulator–metal architecture by (1) increasing the thickness-normalized output voltage and (2) enabling the detection of bending orientation. The performance of the proposed sensor structure is demonstrated with the measurement of the arterial pulse waveform signal and limb movement detection. The presented results pave the way for cost-effective and continuous unobtrusive on-skin biosignal monitoring.

In this contribution, we evaluate the performance of an additively fabricated piezoelectric poly(vinylidenefluoride-cotrifluoroethylene) (P(VDF-TrFE)) based dynamic pressure sensor in non-invasive arterial pulse wave (PW) measurement. Additively fabricated piezoelectric sensors have high potential for the realization of affordable and unobtrusive PW measurement systems which could enable the long-term monitoring of patients with cardiovascular diseases (CVDs). However, the accuracy and reliability of such sensors have not been extensively studied before. We propose an additive fabrication process for a P(VDF-TrFE) PW-sensor, measure PW from the radial artery at the wrist from 22 healthy volunteer subjects, calculate clinically relevant parameters based on the PW waveform and compare their values to the values obtained from concurrent measurement with an electromechanical film (EMFi) based reference sensor, used earlier in several clinical studies. We show that the signals recorded with the two sensors, as well as the radial augmentation index (rAIx) and the stiffness index (SI) calculated from them, are in good agreement with each other. These results demonstrate that the additively fabricated P(VDF-TrFE) PW sensors can reach a suitable level of accuracy and reliability for clinical use.Index Terms-Printed electronics, pulse wave measurement, radial artery, piezoelectric dynamic pressure sensor, P(VDF-TrFE), electret material, EMFi Korkeakoulunkatu 3, 33720, Tampere, Finland. M.-M. Laurila is the