Biology subjects

Solzbacher, F.

Publications and source records attributed to Solzbacher, F..

4 recordsLinked to original sources

bioRxiv2026

Thermoplastic polyurethane as a base material for soft, high-density neural interfaces

Polymers used as substrate and encapsulation for implantable devices are typically deposited layer-by-layer, leaving polymer-polymer interfaces that adhere poorly and become a critical failure point. Thermoplastic polyurethane (TPU) elastomers combine four properties not found together in any other candidate: decades of clinical use in long-term implants and availability in medical grade, a stiffness well below that of polyimide and parylene C, compatibility with microfabrication, and thermoplastic self-fusion, which removes the polymer-polymer interface entirely. This work introduces TPU as a base material for soft, high-density neural interfaces and demonstrates one route to realizing them. Gold is patterned on a sacrificial copper sheet by maskless lithography and transferred into TPU by vacuum lamination, giving conformally coated tracks down to 15 um at 30 um pitch within a single, merged polymer body. An additional electroplating step produces a nanostructured pinecone gold surface that increases the electrochemically active area of the electrodes, approximately doubling the charge injection capacity. Daisy-chain silicon chips were also embedded within the soft polymer body. The films transmit up to 88% at 470 nm, a wavelength commonly used for optogenetics. TPU showed no cytotoxicity towards differentiated SH-SY5Y cells and only a mild tissue response after 9.5 months of subcutaneous implantation in rats.

bioengineering↗

bioRxiv2025

Neuralace: Manufacture, Parylene-C Coating, and Mechanical Properties

Subdural electrode arrays have traditionally been used for epilepsy monitoring and surgical planning. With the emergence of brain-computer interface (BCI) applications, these arrays are now being explored for chronic use, leveraging their ability to record subdural signals for neural decoding. Transitioning from short-term implantation in epilepsy monitoring to long-term use in BCIs requires advancements through consideration of the foreign body response to ensure long-term durability and functionality. Biocompatibility challenges, such as fibrotic encapsulation and reactive astrogliosis, highlight the need for conformal subdural implant designs that minimize mechanical stress on neural tissue. This study investigates the mechanical properties of the Neuralace, a novel ultra-thin, high-channel-count mesh-type surface grid. We characterized the stiffness of the silicon-based interposer electrode meshes and evaluated the effects of various geometric configurations and polymeric encapsulation layers on the mechanical performance. Using a full factorial design of experiments framework and a custom low-force four-point bending setup, we identified the design factors that impact the stiffness of Neuralace structures. The results showed highly consistent stiffness measurements. The stiffness values of Neuralace structures ranged from 2.99 N/m to 7.21 N/m, depending on the cell-wall thickness (CWT) of the lace, the orientation angle, and whether the structures were encapsulated with parylene-C (PPXC). Orientation and CWT had the largest impact on the stiffness of the structures, while the effects of PPXC encapsulation were statistically significant but more subtle. The stiffest Neuralace configuration is expected to exert forces approximately 10 to 100 times lower than commercially available subdural implants would when conforming to radius of the smallest anatomical gyrus. This work demonstrates the feasibility of tailoring the mechanical properties of Neuralace to improve its suitability for chronic neural implantation, providing insights for future design iterations and conformable implant development.

neuroscience↗

bioRxiv2023

Implementation and testing of a biohybrid transitionmicroelectrode array for neural recording and modulation

Recent advances in microtissue engineered neural networks have opened avenues for the fabrication of biohybrid intracortical brain implants. To date, however, the experimental validation of these biohybrid implants has been restricted to singularly positioned electrodes, with the functionality confined to optical neuromodulation and neural recording. We present for the first time a biohybrid transition microelectrode array (TMEA) comprising a 4x4 matrix of biohybrid electrodes. These electrodes are expected to project axons into the brain, thereby establishing synaptic connections for electrical readout and excitation. Our device thus offers a promising pathway to leverage organic, endogenous materials in intracortical implants to enhance their biocompatibility as well as their functionality. In particular with respect to functionality, we assume that the spatiotemporal resolution of recorded neural signals may be significantly increased using this technology owing to the size ratios of these biohybrid microelectrodes compared to abiotic ones. Future investigations will therefore focus on the exploitation of the electrode density to further advance brain-computer interface technology.

neuroscience↗

bioRxiv2021

In vivo Monitoring of Glucose using Ultrasound-induced Resonance in Implantable Smart Hydrogel Microstructures

A novel glucose sensor is presented that uses smart hydrogels as a biocompatible implantable sensing element, which completely eliminates the need for any implanted electronics and uses an external conventional medical-grade ultrasound transducer for readout. The readout mechanism makes use of resonance absorption of ultrasound waves in glucose-sensitive hydrogels. Changes in in vivo glucose concentration in the interstitial tissue lead to swelling and de-swelling of the gels which in turn lead to changes in resonance behavior. The hydrogels are designed and shaped such as to exhibit specific mechanical resonance frequencies while remaining sonolucent to other frequencies. Thus, they allow conventional and continued ultrasound imaging, while yielding a sensing signal at specific frequencies that is correlated with glucose concentration. The resonance frequencies can be tuned by changing the shape and mechanical properties of the gel structures, such as to allow for multiple, co-located implanted hydrogels with different sensing characteristics or targets to be employed and read out, without interference, using the same ultrasound transducer, by simply toggling frequencies. The fact that there is no need for any implantable electronics, also opens the path towards future use of biodegradable hydrogels, thus creating a platform that allows injection of sensors that do not need to be retrieved when they reach the end of their useful lifespan.

bioengineering↗