Author: dannyferreiradias

Talk @ MRS in Boston

Vasiliki Giagka recently returned to MRS in Boston, where she kicked off a session on neuroelectronic interfaces with a talk on robust and conformal hybrid electronics. In addition, the group’s work NanoBlooms was selected among the 50 finalists of the Science as Art competition.

These beautiful blooms were created during a Friday afternoon experiment of Maria Camarena Perez while experimenting with the graphene growth on molybdenum catalysts and are planted on a SiO2 “soil”.

IZM @ COMPAMED2025

Andrada Velea will be attending COMPAMED in Düsseldorf, representing the Technologies for Bioelectronics Group together with colleagues from Fraunhofer IZM. Visitors working in the field of neural interfaces are invited to stop by and connect.

The team will be available at Hall 8a / H29-2 to discuss topics including flexible electrodes, soft and conformal encapsulation for active implants, and the use of ultrasound in next-generation neural interfaces.

We look forward to engaging with the community and exchanging ideas at COMPAMED.

Beyond Acoustic Transparency: The Role of Polymer Encapsulation

Ultrasound is a powerful modality for wireless powering of implantable devices. But packaging remains a major challenge: hermetic cases often block acoustic transmission, while soft polymer encapsulation may alter device performance.

Schematic illustration of the implantable MUT receiver and its layered structure

In our recent work at IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (UFFC), we investigated how implant-grade polymer coatings such as thermoplastic polyurethane, parylene-C, and medical-grade silicones affect the receive performance of piezoelectric micromachined ultrasonic transducers (PMUTs).

Key findings:
  • All tested coatings were highly acoustically transparent (>94% transmission).
  • But performance depends not only on acoustic transparency, but also on mechanical effects: stiffness, residual stress and fleixural rigidity of the coating.
  • Softer materials (e.g. silicones) preserve sensitivty even at larger thicknesses.
  • Stiffer coatings (e.g., parylene-C) can reduce sensitivity, unless applied in very thin layers.
Test structures and encapsulation methods. (a) Top-view of the PMUT array layout. (b) Description
of the encapsulation processes.
Acoustic characterisation of materials. (a) Simulated transmission coefficients through several polymer thicknesses
(b) Measured transmission coefficients juxtaposed against simulations.

Our results provide a framework for selecting encapsulation strategies that balance long-term stability and ultrasonic performance, enabling more reliable and miniaturized implantable devices.

Get the full paperDownload

Cite this paper: A. I. Velea, R. Panskus, B. Szabo, V. A. -L. Oppelt, L. Holzapfel, C. B. Karuthedath, A. T. Sebastian, T. Stieglitz, A. S. Savoia, and V. Giagka, “Effects of Soft Encapsulation on the Receive Performance of PMUTs for Implantable Devices,” IEEE Trans. Ultrasonics, Ferroelectrics, and Frequency Control (UFFC), vol. 72, no. 9, pp. 1282-1292, Sept. 2025, doi: 10.1109/TUFFC.2025.3592740.

Project Kickoff: DUSTIN

This project explores a new approach to the treatment of autoimmune diseases through a miniaturized, wireless, and battery-free implant. Developed in collaboration with the Fraunhofer Institutes IMS, ENAS, IZM, and ITEM, the system is designed to stimulate small nerve branches deep inside the body, directly at the target site and without systemic side effects.

By enabling precise stimulation of even the smallest nerve branches, this technology opens up new therapeutic possibilities beyond conventional drug-based treatments. It also highlights the potential of interdisciplinary research at the intersection of microelectronics, ultrasound technology, and biomedical engineering.

Project members from left:  Tatjana Fedtschenko, Andrada Velea, Stefan Bol, Kira Heinrich, Dr. Ulrich Froriep, Dr. Nooshin Saeidi, Prof. Karsten Seidl, Lukas Holzapfel, Karman Selvam

Within the project, Fraunhofer IMS develops the microchip for control, stimulation and wireless communication, Fraunhofer ENAS contributes micro-electromechanical ultrasound transducers for energy and data transfer, Fraunhofer IZM develops biocompatible and flexible housings and electrodes, and Fraunhofer ITEM evaluates the system under realistic testing conditions.

The project is funded by the PREPARE program of the Fraunhofer-Gesellschaft.

More information is available here.

IEEE EMBS 2025 in Copenhagen

At IEEE Engineering Medicine and Biology Society 2025 in Copenhagen, the session on Conformal Neural Interfaces: Technologies and Applications led to thoughtful discussions on the future of neuroelectronics. Vasso Giagka showcased the promise of long-lasting, high-density conformal neural interfaces built with medical-grade polymers. An approach that closely alignes with the vision of the SPARCLE Consortium.

SPARCLE is proud to contribute to this evolving field, where bioelectronic medicine is becoming softer, smarter, and more seamlessly integrated into the body.

This project has received funding through the Xecs research and innovation program, supported by national funding authorities under the coordination of Eureka.

More information is available here.

AIMD Workshop 2025 in Barcelona

At the Active Implantable Medical Devices (AIMD) Workshop 2025 in Barcelona, Vasso Giagka presented recent advances in soft and active neuroelectronics, with a focus on conformal coating technologies, long-term biobarrier studies, and novel, medical-grade polymer substrates for next-generation neural implants.

The presentation emphasized the importance of integrating materials science, electronics, and biology in the development of reliable neural interfaces. Key topics included the move toward miniaturized, high-density, and battery-free implants and the critical role of encapsulation in protecting devices from the body’s ionic environment.

Discussions also highlighted how electrical signaling strategies influence device lifetime, with alternating (biphasic) stimulation shown to improve longevity compared to direct current biasing, and reinforced the need for in vivo validation to assess long-term performance.

Overall, the session underscored the value of interdisciplinary collaboration in advancing safe, effective, and durable implantable neurotechnologies.

Optogen 2025 in Copenhagen

Vasso Giagka is attending and speaking at the 10th international workshop on Technologies for Optogenetics and Neurophotonics in Copenhagen, Denmark. The OPTOGEN conference brings together the most active scientists and technologists to discuss recent progresses and future challenges in technologies for in vivo optogenetics and optical neural interfaces: from new implantable devices to latest molecular tools developments.

How Soft Encapsulation Enables Long-Term Reliability of Silicon IC Implants

Our latest paper, “On the longevity and inherent hermeticity of silicon-ICs: evaluation of bare-die and PDMS-coated ICs after accelerated aging and implantation studies,” is now published in Nature Communications Portfolio.

Silicon integrated circuits (ICs) are at the heart of next-generation brain-computer interfaces BCIs and active neural implants. A key question driving our work: How do we ensure these tiny, powerful chips remain reliable in the body’s corrosive environment for decades?

In our study, we evaluated the inherent hermeticity of CMOS ICs and explored PDMS as a lightweight, accessible encapsulation material to enhance their longevity in vivo.

Schematic illustrations of silicon-IC test structures (dimensions not to scale). (a) A wire-bonded IC partially coated with PDMS. (b) A cross-sectional schematic demonstrating the multilayer stack of a representative 6-metal CMOS process. (c-e) Schematic of implemented test structures in silicion-IC, from simple to more advanced.
Key findings:
  • Foundry-fabricated CMOS exhibit inherent hermeticity, and can maintain their functionality in the body for at least 12 months unprotected. However, the outer nitride layers gradually degrade over time.
  • PDMS encapsulation acts as a soft moisture-permeable coating, preventing nitride dissolution, inhibiting ion ingress, and extending implantable IC lifetimes to decades.
  • Accelerated aging models in PBS alone are insufficient for bare die ICs but remain valid for PDMS-encapsulated chips, thanks to the material’s protective properties.
Positive mode ToF-SIMS depth profiles analyzing the ionic barrier performance of the exposed passivation layers after 7 and 12 months implantation in rat.

This publication represents 4+ years of interdisciplinary effort, including in vitro and in vivo studies, to bring CMOS technology closer to its full potential in bioelectronics. There is a wealth of information in the paper, including guidelines for designing state-of-the-art polymer-packaged neurotechnologies.

We believe these findings will contribute to advancing the clinical relevance of neurotechnologies, paving the way for minimally invasive, reliable brain-machine interfaces and active neuroelectronic implants.

Get the full paper Download

Cite this paper: K. Nanbakhsh, A. Shah Idil, C. Lamont, C. Dusco, O. C. Akgun, D. Horvath, K. Toth, D. Meszena, I. Ulbert, F. Mazza, T. G. Constandinou, W. A. Serdijn, A. Vanhoestenberghe, N. Donaldson, and V. Giagka, “On the Longevity and Inherent Hermeticity of Silicon-ICs: Evaluation of Bare-Die and PDMS-Coated ICs After Accelerated Aging and Implantation Studies,” Nat. Commun., vol. 16, no. 12, Jan. 2025. doi: 10.1038/s41467-024-55298-4.