Andreas Brose

Pre-tuned resonant marker for iMRI using aerosol deposition on polymer catheters

New advances in MRI technology enable fast acquisition of high-resolution images. In combination with the new open architecture this scanners are entering the surgical suite being used as intra-operative imaging modality for minimally invasive interventions. However, for a usage on a large scale the major issue of availability of appropriate surgical tools is still unsolved. Such instruments, i.e. needles and catheters have to be MR-safe and -compatible but in contrast still have to be visible within the MRI image. This usually is solved by integration of markers onto non-magnetic devices. For reasons of MR-safety, work-flow and cost effectiveness semi-active markers without any connection to the outside are preferable. The challenge in development and integration of such resonant markers is to precisely meet the MRI frequency by keeping the geometrical dimensions of the interventional tool constant. This paper focuses on the reliable integration and easy fabrication of such resonant markers on the tip of an interventional instrument. Starting with a theoretical background for resonant labels a self-sufficient pre-tuned marker consisting of a standard capacitor and a thin-film inductor is presented. A prototype is built using aerosol deposition for the inductor on a 6-F polymer catheter and by integration of an off-the-shelf capacitor into the lumen of the catheter. Due to the fact that the dielectric materials of some capacitors lead to artifacts in the MRI image different capacitor technologies are investigated. The prototypes are scanned by an interventional MRI device proving the proper functionality of the tools.

Technology Roadmap for Integration of Resonant Markers in MRI Compatible Instruments

Open MR scanners with an improved patient access are well-suited for minimal-invasive interventions. Considering that instruments like catheters appear hypointense in the MR image due to their signal-loss artefact, suitable visualization techniques like passive resonant circuits tuned to the Larmor frequency are required for generating a hyperintense change of the signal intensity. Within this paper various microsystems technologies for fabricating resonant markers will be compared in order to estimate their potential for a subsequent application.

Aerosol deposition of catalytic ink to fabricate fine pitch metallizations for moulded interconnect devices (MID)

The permanent miniaturization of automotive, medical and consumer products requires alternative packaging solutions. So far most electronic products are circuit boards mounted in a separate body. An upcoming alternative are moulded interconnect devices (3D-MID). They combine the substrate function for interconnects and the housing function. To ensure a high integration density it is necessary to apply fine pitch metallizations to the polymer devices.

Characterization of Ultrasonic Wire Bonding for LDS MID Prototyping

Functional prototyping during development of new molded interconnect device (MID) products offers benefits such as evaluation of design specifications, validation of manufacturing technologies, and functional testing of the entire product. Introduction of ProtoPaint laser direct structuring (LDS) by LPKF Laser and Electronics AG has opened new possibilities to develop MID prototypes using LDS of additive manufactured plastic parts. In this experimental work, selective laser sintered (SLS) substrates of three different plastic materials-polyether ether ketone, PA12, and Duraform HST-are used to manufacture MID prototypes. These SLS substrates are functionalized by coating with ProtoPaint LDS lacquer, to produce laser-activable surface, followed by subsequent laser activation and electroless chemical plating processes to metallize conductive patterns. The compatibility of this LDS metallization on the MID prototypes toward aluminum wire bonding as a common contacting technology is evaluated. Pretreatment procedures-namely, ultrasonic cleaning in isopropanol solution, ultrasonic cleaning in ethanol solution, plasma treatment using H2 and N2, and coating with 1k plastic primer, 1k plastic filler, and 2k primer filler-are adopted for the blank SLS plastic substrates to further study and improve the coating of ProtoPaint functional layer, which attributes to better metallization of substrates.

Fabrication of MEMS-based 3D-μECoG-MEAs

Abstract The microfabrication and packaging of novel, three-dimensional, polyimide-based, highly flexible, microscale electrocorticography multi-electrode arrays for enhanced epicortical recording of local field potentials is presented. A polyimide foil embeds metallic structures relating to 32 taper-type electrode sites, contact pads as well as interconnecting conductor paths which are integrated in the planar portion of the electrode substrate material. Circular exposed and, thus, active electrode sites are 50 μm in diameter and employed center-to-center pitches range from 250 μm to 1 mm, respectively. As-fabricated 3D-μECoG-MEAs provide taper heights of approximately 4 μm as well as 59 μm being distinguished by characteristic impedances of about 368.9 kΩ at 1 kHz measured in saline electrolyte. The applied packaging strategies favor flip-chip bonding and vapor phase soldering of the polymer substrates to customized printed circuit boards.

Investigation of adhesion strength of metallization on thermoplastic and ceramic substrates

One essential reliability criteria for Laser Direct Structured Molded Interconnect Devices is the adhesion between substrate and metallization. Low adhesion values are indicative of premature failure of the metallization and are often due to inadequate laser activation of the substrate. A measure of the adhesion is the force at which the metallization fails. Pull-off adhesion testing according to DIN EN ISO 4624 is used to assess the adhesive force between MID-substrate and metal layer. Besides thermoplastic LDS materials (LCP Vectra 840i LDS, TECACOMP® LCP LDS black 4107V, PEEK LDS black 3980, PPA LDS black 4108V), aluminum-nitride ceramic (Alunit®) plates were also laser-activated and metallized according to LPKF-LDS process. Furthermore 3D-printed plastic parts (PA2200 and PEEK), manufactured by Selective Laser Sintering (SLS) have been used. These SLS substrates are functionalized by coating with LPKF ProtoPaint LDS paint, which makes the plastic parts compatible to the LDS process. After IR-laser activation with LPKF MicroLine3D 165i system, the metallization is formed on the activated surface by electroless plating of copper, nickel and immersion gold consecutively. The adhesion strength of metallization was investigated by performing pull-off test of dollies with a shaft diameter of 2 mm. The pull tool for the 4 mm wide dolly head can easily be adapted to different bond testers. The copper dollies are lead-free soldered to the metallization. Due to the lower melting point of PA 2200, adhesive bonding was adopted to bond the dollies to the substrate metallization to reduce the bonding process temperature. This paper will investigate the influence of laser parameters such as laser power and scanning velocity on adhesion between metallization and LDS substrate.

Neurovascular intervention with an electromagnetic navigated guidewire

Electromagnetic Tracking Systems (EMTS) enable navigation without a line-of-sight. Therefore, those systems are widely used in military and medical applications as well as in kinematic studies. In the medical domain, EMTS are often integrated into flexible surgery devices, e.g. endoscopes or catheters, enabling the tracking of those devices without an additional imaging modality. In this paper we present an experimental setup for tracking a guidewire with a diameter of 0.46 mm in a neurovascular intervention.

An in situ measurement system for the mechanical impact of the PCB processing chain on stress sensitive devices

In the past, silicon based measurement system were used to characterize packaging induced stresses of electronic devices [1]. In this paper a new approach for qualifying mechanical PCB manufacturing processes is presented. Silicon based package equivalents (S3MD; Stress Sensitive Surface Mounted Devices) are used instead of real devices at locations of expected dangerous mechanical impact. The silicon based package equivalents have strain sensitive structures implemented. These structures are formed by thin film processes and are designed as strain sensitive metal resistors. Therefore, the mechanical impact of the following steps in the PCB process chain can be monitored. The sensor devices are qualified in the AEC Q200 “board flex” test to get the limiting strain values. In the result, we show a new method to get in situ measured data of the mechanical impact of PCB manufacturing processes.

Fabrication and test of arrays of langasite microbalances

The design of piezoelectricaly actuated plano-convex shaped resonators has been studied to optimize their Q-factor and signal spectrum at high temperatures. The investigated arrays of thickness-shear-mode (TSM) resonators consist of langasite, a high temperature stable material. As viscoelastic damping and an increasing conductivity decreases the Q-factor at elevated temperatures, design optimizations have to counteract these effects. Two and three dimensional finite element (FE) models have been solved to analyze the resonant behavior and the effects of energy confinement at different temperatures depending on geometry. The separation and suppression of spurious modes, the improvement of the Q-factor and the confinement of the TSM could be shown. The simulated effects of energy confinement could be proofed by impedance measurements.