Developing energy harvesting devices is crucial to mitigate the dependence on conventional and rigid batteries in wearable electronics, ensuring their autonomous operation. Nanogenerators offer a cost‐effective solution for enabling continuous operation of wearable electronics. Herein, this study proposes a novel strategy that combines freeze‐casting, freeze‐drying, and printing technologies to fabricate a fully printed triboelectric nanogenerator (TENG) based on polyvinylidene fluorid‐etrifluoroethylene P(VDF‐TrFE) porous aerogel. First, the effects of porosity and poling on the stretchability and energy harvesting capabilities of P(VDF‐TrFE) are investigated, conducting a comprehensive analysis of this porous structure's impact on the mechanical, ferroelectric, and triboelectric properties compared to solid P(VDF‐TrFE) films. The results demonstrate that structural modification of P(VDF‐TrFE) significantly enhances stretchability increasing it from 7.7% (solid) to 66.4% (porous). This modification enhances output voltage by 66% and generated charges by 48% for non‐poled P(VDF‐TrFE) porous aerogel films compared to their non‐poled solid counterparts. Then, a fully printed TENG is demonstrated using stretchable materials, exhibiting a peak power of 62.8 mW m⁻² and an average power of 9.9 mW m⁻² over 100 tapping cycles at 0.75 Hz. It can illuminate light‐emitting diodes (LEDs) through the harvesting of mechanical energy from human motion. This study provides a significant advance in the development of energy harvesting devices.

In this contribution, we propose a fully printed charge amplifier for on-skin biosignal measurements. The amplifier is fabricated on an ultra-thin parylene substrate and consists of organic transistors, integrated bias and feedback resistors, and a feedback capacitor. The fabrication process utilizes inkjet-printed Ag ink for source, drain, gate, and capacitor electrode metallization as well as for the interconnects between the amplifier elements. Dispensed polystyrene, 2,7-dihexyl-dithieno2,3-d;2’,3’-d’benzo1,2-b;4,5-b’dithiophene (PS:DTBDT-C6), is used as the transistor channel material, dispensed poly(3-hexylthiophene) (P3HT) as the high-resistivity material for the printed resistors, and parylene as the capacitor dielectric. A pass band optimized for pulse-wave measurement (60 mHz to 36 Hz) is achieved with a maximum charge amplification of 1.6 V/nC. To demonstrate the potential of the proposed printed amplifier, a radial arterial pulsewave signal recorded with a printed piezoelectric poly(vinylidenefluoride-cotrifluoroethylene) (PVDF-TrFE) sensor was fed to it and the output was analyzed to quantify the similarity of the pulse-wave features calculated from the original signal and the amplifier output. The amplified signal contains all the essential features of a pulse wave, such as both systolic waves, the dicrotic notch, and diastolic wave, which enable the accurate derivation of the clinically relevant indices utilized in the evaluation of vascular health.

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.

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. 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. 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. Impedance based pulse waveform analysis provides a useful tool for assessing cardiovascular risk and estimating presence of structural changes in the vasculature.

Flexible piezoelectric energy harvesters have the potential to be used as power sources for wearable electronics. This study presents a simple printing-based fabrication process for a flexible piezoelectric energy-harvesting module with an integrated and optimized surface mount device (SMD)-based full-wave diode bridge rectifier. We investigate the effect of the electrode configuration on the energy-harvesting performance of the piezoelectric elements. Two types of piezoelectric elements are fabricated [a metal–insulator–metal (MIM) structure and an interdigitated electrode (IDE) structure] for comparison. The electrodes are inkjet printed using poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT: PSS), and the piezoelectric layer is bar-coated using poly (vinylidene-fluoride-co-trifluoroethylene) (P(VDF-TrFE)). The results show that a higher output power density can be obtained with the MIM-based energy harvester ( $7.8~\mu \text{W}$ /cm ³ ) when compared to the IDE-based harvester (20.8 nW/cm ³ ). Simulation results show that this is explained by the higher current output (i.e., charge generation ability) of the MIM-based structure.

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.