In this article, we propose a strategy for the design of a wireless power transfer system consisting of a class-E inverter, a half-bridge class-DE rectifier, and two coupled coils. The system is optimized for maximum power transfer efficiency. The design is validated via a case study, for which a wireless power transfer link to a neuroprosthesis was designed. After circuit simulations, a prototype was realized and measured. There is a good agreement between the calculated, simulated and measured voltages and currents. The prototype delivers ${\text {80}}$ mW, ${\text {7}}$ V to a biomedical implant at ${\text {6.78}}$ MHz, the transfer efficiency is ${\text {52}}$ to 68%, depending on the alignment. The end-to-end efficiency, with the controller and gate driver also taken into account, is ${\text {39}}$ to 57%. Electromagnetic and thermal simulations were performed to verify compliance with relevant safety regulations on specific absorption rate (SAR) levels, magnetic field strength, and heat generation in the implant, for separation distances between the coils of ${\text {8}}$ to ${\text {15}}$ mm, and transverse misalignment from ${\text {0}}$ to $\text {15}$ mm.

Transcranial temporal interference stimulation (tTIS) has recently emerged as a non-invasive neuromodulation method aimed at reaching deeper brain regions than conventional techniques. However, many questions about its effects remain, requiring further experimental studies. This review consolidates the experimental literature on tTIS’s effects in the human brain, clarifies existing evidence, identifies knowledge gaps, and proposes future research directions to evaluate its potential. A systematic literature search was performed in PubMed, Web of Science, and Scopus for studies published up to 27 January 2025. Eligible studies applied tTIS to the human brain and examined its effects on neural, behavioral, and clinical outcomes. Of 127 publications screened, 18 met the inclusion criteria. Studies were analyzed for design, stimulation target, parameters, control conditions, and outcome measures. Included studies exhibited low bias or minor concerns using the Cochrane RoB2 and ROBINS-I tools. Ten studies targeted cortical regions (motor, occipito-parietal, fronto-parietal), and eight probed subcortical sites (striatum, hippocampus, globus pallidus, caudate). Motor-cortex tTIS enhanced motor-network connectivity, though the effect was similar to that of transcranial direct current stimulation. Beta-band stimulation envelopes (20 Hz) promoted learning-related plasticity, while gamma-band envelopes (70 Hz) yielded immediate performance improvements. Occipito-parietal tTIS did not modulate alpha power. Preliminary deep-target findings are promising: 5 Hz hippocampal tTIS improved episodic recall, 100 Hz striatal tTIS enhanced motor learning in older adults, and 100 Hz hippocampal-entorhinal tTIS aided spatial navigation. Two fMRI studies confirmed network-specific modulation, although one raised concerns about using a fixed montage between individuals. Clinical evidence remains limited, with two Parkinson’s pilots and one epilepsy study showing short-term benefits. Overall, tTIS shows potential to modulate human brain activity and behavior. However, current evidence is preliminary and predominantly focused on cortical rather than deep targets. Larger, well-controlled studies are needed to reliably determine whether tTIS can effectively engage subcortical structures and provide meaningful clinical benefits.

Conventional transcranial electric stimulation(tES) using standard anatomical positions for the electrodes and standard stimulation currents is frequently not sufficiently selective in targeting and reaching specific brain locations, leading to suboptimal application of electric fields. Recent advancements in in vivo electric field characterization may enable clinical researchers to derive better relationships between the electric field strength and the clinical results. Subject-specific electric field simulations could lead to improved electrode placement and more efficient treatments. Through this narrative review, we present a processing workflow to personalize tES for focal epilepsy, for which there is a clear cortical target to stimulate. The workflow utilizes clinical imaging and electroencephalography data and enables us to relate the simulated fields to clinical outcomes. We review and analyze the relevant literature for the processing steps in the workflow, which are the following: tissue segmentation, source localization, and stimulation optimization. In addition, we identify shortcomings and ongoing trends with regard to, for example, segmentation quality and tissue conductivity measurements. The presented processing steps result in personalized tES based on metrics like focality and field strength, which allow for correlation with clinical outcomes.

Integration of vibration energy harvesters (VEHs) with small-scale electronic devices may form an attractive alternative for relatively large batteries and can, potentially, increase their lifespan. However, the inherent mismatch between a harvester's high-frequency resonance, typically in the range 100−1000 Hz, relative to the available low-frequency ambient vibrations, typically in the range 10–100 Hz, means that low-frequency power generation in microscale VEHs remains a persistent challenge. In this work, we model a novel electret-based, electrostatic energy harvester (EEH) design. In this design, we combine an out-of-plane gap-closing comb (OPGC) configuration for the low-frequency oscillator with an in-plane overlap comb configuration for the high-frequency oscillator and employ impact for frequency up-conversion. An important design feature is the tunability of the resonance frequency through the electrostatic nonlinearity of the low-frequency oscillator. Impulsive normal forces due to impact are included in numerical simulation of the EEH through Moreau's time-stepping scheme which has, to the best of our knowledge, not been used before in VEH design and analysis. The original scheme is extended with time-step adjustments around impact events to reduce computational time. Using frequency sweeps, we numerically investigate power generation under harmonic, ambient vibrations. Results show improved low-frequency power generation in this EEH compared to a reference EEH. The EEH design shows peak power generation improvement of up to a relative factor 3.2 at low frequencies due to the occurrence of superharmonic resonances.

In high-dose-rate brachytherapy (HDR-BT) for prostate cancer treatment, interstitial hyperthermia (IHT) is applied to sensitize the tumor to the radiation (RT) dose, aiming at a more efficient treatment. Simultaneous application of HDR-BT and IHT is anticipated to provide maximum radiosensitization of the tumor. With this rationale, the ThermoBrachyTherapy applicators have been designed and developed, enabling simultaneous irradiation and heating. In this research, we present a method to optimize the three-dimensional temperature distribution for simultaneous HDR-BT and IHT based on the resulting equivalent physical dose (EQD_phys) of the combined treatment. First, the temperature resulting from each electrode is precomputed. Then, for a given set of electrode settings and a precomputed radiation dose, the EQD_phys is calculated based on the temperature-dependent linear-quadratic model. Finally, the optimum set of electrode settings is found through an optimization algorithm. The method is applied on implant geometries and anatomical data of 10 previously irradiated patients, using reported thermoradiobiological parameters and physical doses. We found that an equal equivalent dose coverage of the target can be achieved with a physical RT dose reduction of 20% together with a significantly lower EQD_phys to the organs at risk (p-value < 0.001), even in the least favorable scenarios. As a result, simultaneous ThermoBrachyTherapy could lead to a relevant therapeutic benefit for patients with prostate cancer.