Introduction:

A bubble collapsing near an interface may result in the formation of a liquid jet protruding from the distal bubble side, through the bubble, towards the interface. Ultrasound-assisted jetting has been observed when subjecting fluids to acoustic amplitudes above the inertial cavitation threshold, limiting its application in medicine. The purpose of this study was to investigate the feasibility of low-amplitude jetting for fluid containing biocompatible cavitation nuclei, by placing the region of interest in a confined space to ensure a standing wave field.

Methods:

Droplets of QuantisonTM ultrasound contrast agent were pipetted into a Perspex cylindrical compartment of 8-mm diameter and 2-mm height, which was part of an imaging system. The contrast agent was subjected to 3-cycle ultrasound pulses with a centre frequency of 1 MHz whilst being observed with high-speed photography. The high-speed camera was operating at a frame rate of ten million frames per second.

Results:

Jetting was observed in an acoustic regime whose free-field mechanical index was 0.6. Empirical curve matching showed a pulse amplification by a factor of six owing to the chosen geometry.

Conclusion:

In conclusion, jetting was observed to occur with microbubbles nucleated from ultrasound contrast agent mi-crobubbles. Visible jet lengths of twice the bubble radius on the verge of collapse were measured. Owing to the confined space, the local acoustic amplitude was amplified to surpass the cavitation threshold. This finding is of interest for medical ultrasonic applications where the local environment comprises strong reflectors.

Drug-loaded magnetic nanoparticles accumulated by an external magnetic field already showed their efficacy in localized tumor treatment in animal studies. Furthermore, specific magnetic nanoparticles are sonosensitive, enabling them to generate inertial cavitation when exposed to a focused ultrasound field. This can be used for controlling drug release, as well as for particle detection and mapping. In addition to inertial cavitation, stable cavitation is also a part of the cavitation process. While stable cavitation is less harmful to surrounding tissue compared to inertial cavitation, it also contributes to enhanced tumor perfusion. Hence, an optimal strategy could involve inducing inertial cavitation only within the tumor region for drug release and mapping, while employing stable cavitation outside the tumor to enhance perfusion. This study aims to investigate stable cavitation mediated by magnetic nanoparticles while examining their overall cavitation behavior.

Specialised cells in the blood play an important role in controlling the immune responses. Thus, these cells are also valuable for the diagnosis and treatment of diseases such as autoimmune disorders and cancer. Trace-less Affinity Cell Selection technology, also known as Fab-TACS technology, is a new approach to precisely isolate specific immune cells from blood samples. Currently, this technology is used in a device called Fabian, which resembles a cassette with a capacity of 60 ml. For diagnostic purposes, however, the sample size must be reduced to a few microliters. For this purpose, a stand-alone setup for the control of a microfluidic cartridge was developed and a sequence for the implementation of the TACS technology was designed and characterized. As the combination of cell purification and subsequent cell counting in a single device can streamline workflows and save time, we also integrated an analysis platform for cell counting into the setup. Instead of using two separate devices, isolated samples can be counted immediately after isolation without interruption. This platform was initially tested with latex particles that were passed through the detection channel of the microfluidic cartridge. The functionality of the developed program sequence and cell counting was successfully demonstrated in verification experiments .

Numerous ultrafine membranes produced via electrospinning technique exhibit multidirectional strength and elasticity. In contrast to compact polymer film coatings or foils, they also have an exceptional surface-to-volume ratio, which makes them attractive carrier structures for many biomedical applications, also with regard to the release of bioactive substances. Within the scope of an orientation study we investigate the mechanical properties of biodegradable nanofibrous carrier materials using tensile bars made of nanoparticle (un-)loaded polydioxanone (PDX), polylactide (PLA), polyglycolide (PGA) or polybutylene succinate (PBS). Mass loss and tensile strength as well as pH changes of the unbuffered medium under physiological conditions were examined within defined time periods up to one month. Initial tests with various antibacterial additives, especially TiO2 or Ag nanoparticles and octenidine were performed.

Introduction

In today's medicine, electroencephalography (EEG) is used to measure and record the electrical activities of the brain. The use of EEG in everyday life over a longer period of time would enable improved patient care for those affected by epilepsy, as the diagnosis could be more specific and the therapy more individualized. Applications of EEG within consumer and industrial technology are also conceivable, for example in monitoring attention in driver assistance systems in semi-autonomous and autonomous driving. However, there are currently only adhesive or dry electrode systems, both of which have disadvantages and are therefore not suitable.

Methods

We developed modular tools from micro system technology (MST) applying PVD sputtering, galvanic, laser, thin-film, lamination and micro printing processes to build a versatile bioelectronic platform for high-fidelity, highly flexible, transcutaneous, long-term bioelectrodes. This platform can be used for InEar-EEG recording. Bare Au and Au with PEDOT:PSS coated micro electrodes have been characterized in terms of functionality, biocompatibility, signal quality, SNR, interface impedance, design flexibility and costs with dedicated testing procedures and standards. We compared these results against gold standard Ag/AgCl electrodes.

Results

We present capabilities of today`s advanced MST platforms and tools for high-fidelity, flexible bioelectronics. Our end point (a functional bioelectronic platform to be integrated on an otoplastic for InEar recording) will be discussed. Design concepts and data from bench tests for long-term transcutaneous use will be disclosed (mechanical, electrical, physico-chemical and functional tests).

Conclusion

Micro system technology platforms are very versatile for biomedical engineering. They are suitable for next-generation long-term micro electrodes. The signal quality is similar as today’s gold standard surface electrodes. New advanced manufacturing processes from MST can be therefore used for a number of new consumer-type bioelectronic devices. However, to realize the full potential of these modern technologies also smart design concepts should be applied.

Optogenetics enables insights into the development of neural diseases. Custom-designed neural probes are necessary to access targeted brain regions. Multifunctional and mechanically flexible probes with minimal footprint, comprising fluidic channels for drug delivery, light sources for optical stimulation, and micro electrodes for electro¬physiological readout are beneficial due to reduced tissue trauma and consequently increased long-term stability. This study introduces a mechanically compliant neural probe that provides microfluidic channels and electrodes arranged close to fluidic outlet ports. The key challenge is to open the fluidic inlet and outlet ports avoiding potential channel clogging. A novel laser-based patterning process is demonstrated using a 248 nm KrF excimer laser. It offers high design flexibility in positioning the fluidic ports along the fluidic channels, as well their contamination-free opening under dry conditions. The laser patterning process applies reflective metal layers inside the fluidic channels, confining the laser ablation to the channel cover, thus minimizing potential damage of the channel substrate. Based on its high reflectivity and correspondingly low absorption and transmission at the applied laser wavelength, aluminium is determined to be the best choice for this protective layer.