Minimally invasive surgery is increasingly used in many medical operations because of the benefits for the patients. However, for the surgeons, accessing the situs through a small incision or natural orifice comes with a reduction of the degrees of freedom of the instrument. Due to friction of the mechanical coupling, the haptic feedback lacks sensitivity that could lead to damage of the tissue. The approach of this work to overcome these problems is to develop a control concept for position control and force estimation with shape memory alloys (SMA) which could offer haptic feedback in a novel handheld instrument. The concept aims to bridge the gap between manually actuated laparoscopic instruments and surgical robots. Nickel-titanium shape memory alloys are used for actuation because of their high specific energy density. The work includes the manufacturing of a functional model as a proof of concept comprising the development of a suitable forceps mechanism and electronic circuit for position control and gripping force measurement, as well as designing an ergonomic user interface with haptic force feedback.

Surgical VR-simulators including haptic and tactile feedback can severely improve the training of surgeons. However, so far only minimally invasive surgery benefited from the capabilities of VR. For non-minimally invasive surgery, only one prototype to simulate the reaming of the acetabula during hip joint replacement surgery exists, which is unable to simulate the vibrations of the surgical reamer. By integrating electronic components, a tactile reamer, able to simulate the vibrations, could be developed. A qualitative assessment with orthopedic surgeons revealed that the simulated sound of the vibrations is realistic but the intensity of the vibrations needs to be improved.

Ultrasound image velocimetry (UIV) allows noninvasive flow imaging of opaque media with high spatial and temporal resolution, which is especially relevant for experimental research in magnetohydrodynamics (MHD). To extract quantitative flow data from lab-scale experiments in low melting alloys and interpret the results, the measurement uncertainty of a specific experiment has to be determined. In this article, we describe a novel, generic method for estimating the uncertainty of a specific experimental setup according to the guide to the expression of uncertainty in measurement (GUM). It is based on an uncertainty model of the UIV processing, which is calibrated using a flow reference in liquid metal. The proposed model uses a priori knowledge of an expected velocity gradient, a static calibration of the focus distortion, and the peak ratio of the correlation from the measurement data itself to yield the optimal parameterization of UIV and the velocity uncertainty for a specific experiment. This enables the use of the UIV method for quantitative flow imaging with an explicit uncertainty estimate in experiments where no reference flow is available. Building on this, we derive generic guidelines for an optimal parameterization of UIV to a specific experiment. The approach is demonstrated on a magnetically driven flow of gallium-indium-tin (GaInSn) alloy in a cuboid container. In conclusion, this work is a blueprint to obtain quantified planar vector flow maps with UIV in diverse MHD experiments; practical guidelines are derived and an uncertainty estimation procedure is elaborated.

Flow batteries using suspension electrodes, e.g., zinc-air flow batteries (ZABs), have recently gained renewed interest as potential candidates for grid energy storage or mobile applications. The performance of ZABs depends on the local flow conditions of the suspension in the electrochemical cell, which acts as an electrode. Hence, it is crucial to measure and understand the complex flow characteristics of such solid-liquid suspensions. The investigated suspension electrode is an opaque slurry that consists of microscopic zinc particles and an aqueous potassium hydroxide electrolyte. Commonly, ultrasound Doppler velocimetry is used for flow imaging in opaque fluids. However, due to the high particle concentration in the suspension electrode, strong scattering and wavefront distortions of the ultrasound are introduced. In this paper, we show that this results in an increased measurement uncertainty for Doppler-based velocity estimation. Instead, ultrasound image velocimetry is applied to measure the 2-D and two-component flow field in the zinc-electrolyte suspension. This is possible by adapting the measurement system to the suspension with a calibration setup. The total measurement uncertainties of 4.1% and 2.5% for the axial and lateral flow components are derived from the calibration measurements. For the first time, the flow field of such a suspension could be measured in a scaled fluidic model of a ZAB. The comparison of the estimated flow rates from the velocity profiles showed good agreement to a gravimetric reference. A significant difference in the flow characteristics of a macroscopically homogeneous electrolyte and the same electrolyte loaded with 8 vol.-% zinc particles, i.e., the suspension electrode, was found. Along with the demonstration of the measurement technique for opaque, concentrated suspensions, the measurement data will be used to calibrate and validate numerical models for comparable multiphase fluids.

To date, the efficiencies of proton exchange membrane exchange fuel cells (PEMFCs) are limited by the water flooding issue. Water monitoring systems, which are a crucial step to overcoming these flooding-related problems, are mostly either invasive or compromise on the temporal resolution and field of view. Thus, we propose an ultrasonic-Lamb-waves-based, real-time, nondestructive water monitoring system. Briefly, ultrasonic transducers are mounted on the back side of bipolar plates (BPPs) exciting Lamb waves along flow channels incorporated in BPPs. Echo signals from water droplets in the channels are also received by the transducers. Thus, with the knowledge of Lamb wave propagation velocity, water droplets are spatially resolved by time-of-flight of each droplet echo. Meanwhile, the energy of each droplet induced echo wave packet is used to quantify the local flooding status. We have implemented a flexible and generic system adaptable to various flow field designs. The working principle was demonstrated for ex-situ conditions with a BPP with a 25 cm ² active area. A water sensitivity of at least 50 nL was realized, allowing for studying droplet and slug flows in PEMFCs. A 1.3 mm spatial resolution and a 2 kHz temporal resolution were simultaneously achieved. The high-performance water monitoring opens new horizons to study dynamic water evolution in channels of PEMFCs using cost-effective instrumentation, which may pave the way towards more efficient high-power PEMFCs with increased lifetimes.