Design of a semi-implantable hearing device for direct acoustic cochlear stimulation

A new hearing therapy based on direct acoustic cochlear stimulation was developed for the treatment of severe to profound mixed hearing loss. The device efficacy was validated in an initial clinical trial with four patients. This semi-implantable investigational device consists of an externally worn audio processor, a percutaneous connector, and an implantable microactuator. The actuator is placed in the mastoid bone, right behind the external auditory canal. It generates vibrations that are directly coupled to the inner ear fluids and that, therefore, bypass the external and the middle ear. The system is able to provide an equivalent sound pressure level of 125 dB over the frequency range between 125 and 8000 Hz. The hermetically sealed actuator is designed to provide maximal output power by keeping its dimensions small enough to enable implantation. A network model is used to simulate the dynamic characteristics of the actuator to adjust its transfer function to the characteristics of the middle ear. The geometry of the different actuator components is optimized using finite-element modeling.

Multi-stage ytterbium fiber-amplifier seeded by a gain-switched laser diode

We demonstrated all-fiber amplification of 11 ps pulses from a gain-switched laser diode at 1064 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 µW of fiber-coupled average output power. For the low output pulse energy of 325 fJ we have designed a multi-stage core pumped pre-amplifier in order to keep the contribution of undesired amplified spontaneous emission as low as possible. By using a novel time-domain approach for determining the power spectral density ratio (PSD) of signal to noise, we identified the optimal working point for our pre-amplifier. After the pre-amplifier we reduced the 40 MHz repetition rate to 1 MHz using a fiber coupled pulse-picker. The final amplification was done with a cladding pumped Yb-doped large mode area fiber and a subsequent Yb-doped rod-type fiber. With our setup we reached a total gain of 73 dB, resulting in pulse energies of >5.6 µJ and peak powers of >0.5 MW. The average PSD-ratio of signal to noise we determined to be 18/1 at the output of the final amplification stage.

Investigation on colloidal Te doped CdSe (CdSe:Te) quantum dots suspension in a liquid-core fiber

Here, we demonstrate the use of a colloidal CdSe:Te quantum dots suspension as active liquid-core in a specially designed optical element, based on a double-clad optical fiber structure. The liquid-core fiber was realized by filling the hollow core of a capillary and waveguiding of the core was ensured by using a liquid host that exhibits a larger refractive index than the cladding material of the capillary. Since the used capillary possessed a cladding waveguide structure, we obtained a liquid-core double-clad structure. To seal the liquid-core fiber and e.g. prevent the formation of bubbles, we developed a technique based on SMA connectors. The colloidal CdSe:Te quantum dots were excited by cladding-pumping using a pump laser at 532nm operating in the continuous-wave regime. We investigated the photoluminescence emitted from the colloidal CdSe:Te quantum dots suspension liquid-core and guided by the double-clad fiber structure. We observed a red shift of the (core) emission, that depends on the liquid-core fiber length and the pump power. This shift is due to the absorption of unexcited colloidal quantum dots and due to the waveguiding properties of the core. Here we report a core photoluminescence output power of 79.2μW (with an integrated brightness of ≈ 215.5 W/cm2sr ). Finally, we give an explanation, why lasing could not be observed in our experiments when setup as a liquid-core fiber cavity.

Mode-locked diode-pumped vanadate lasers operated with PbS quantum dots

The use of glasses doped with PbS nanocrystals as intracavity saturable absorbers for passive Q-switching and mode locking of c-cut Nd:Gd0.7Y0.3VO4, Nd:YVO4, and Nd:GdVO4 lasers is investigated. Q-switching yields pulses as short as 35 ns with an average output power of 435 mW at a repetition rate of 6–12 kHz at a pump power of 5–6 W. Mode locking through a combination of PbS nanocrystals and a Kerr lens results in 1.4 ps long pulses with an average output power of 255 mW at a repetition rate of 100 MHz.

Energy harvesting through arterial wall deformation: design considerations for a magneto-hydrodynamic generator

As the complexity of active medical implants increases, the task of embedding a life-long power supply at the time of implantation becomes more challenging. A periodic renewal of the energy source is often required. Human energy harvesting is, therefore, seen as a possible remedy. In this paper, we present a novel idea to harvest energy from the pressure-driven deformation of an artery by the principle of magneto-hydrodynamics. The generator relies on a highly electrically conductive fluid accelerated perpendicularly to a magnetic field by means of an efficient lever arm mechanism. An artery with 10 mm inner diameter is chosen as a potential implantation site and its ability to drive the generator is established. Three analytical models are proposed to investigate the relevant design parameters and to determine the existence of an optimal configuration. The predicted output power reaches 65 μW according to the first two models and 135 μW according to the third model. It is found that the generator, designed as a circular structure encompassing the artery, should not exceed a total volume of 3 cm3.

Energy harvesting through arterial wall deformation: A FEM approach to fluid–structure interactions and magneto-hydrodynamics

Engineers are confronted with the energy demand of active medical implants in patients with increasing life expectancy. Scavenging energy from the patient’s body is envisioned as an alternative to conventional power sources. Joining in this effort towards human-powered implants, we propose an innovative concept that combines the deformation of an artery resulting from the arterial pressure pulse with a transduction mechanism based on magneto-hydrodynamics. To overcome certain limitations of a preliminary analytical study on this topic, we demonstrate here a more accurate model of our generator by implementing a three-dimensional multiphysics finite element method (FEM) simulation combining solid mechanics, fluid mechanics, electric and magnetic fields as well as the corresponding couplings. This simulation is used to optimize the generator with respect to several design parameters. A first validation is obtained by comparing the results of the FEM simulation with those of the analytical approach adopted in our previous study. With an expected overall conversion efficiency of 20% and an average output power of 30 μW, our generator outperforms previous devices based on arterial wall deformation by more than two orders of magnitude. Most importantly, our generator provides sufficient power to supply a cardiac pacemaker.

Vascular turbine powering a cardiac pacemaker: an in-vivo case study

Background: Today’s medical devices are powered by batteries with a limited energy storage capacity. Depleted batteries have to be replaced, exposing the patients to the risk of adverse events. Thus, a method for harvesting energy inside the body is desirable since it would allow building devices without batteries. Methods: A miniaturized intravascular Tesla turbine was implanted as an arteriovenous shunt between the common carotid artery and external jugular vein of a pig. The harvested energy was used to power a custom-built temporary cardiac pacemaker. Results: At a flow rate of ~150 ml/min, an output power of 0.4 mW was measured. Successful ventricular pacing was performed. Conclusion: Harvesting energy from the circulation using an intravascular turbine is technically feasible and provides enough energy to power a cardiac pacemaker.

Effect of electromagnetic fields on highly diluted remedies measured by ultraviolet spectroscopy

Purpose: In homeopathy or anthroposophically extended medicine high dilutions are used. They showed significant differences in ultraviolet light (UV) transmission between controls and different dilution levels. Exposing such dilutions to physical factors such as UV light or elevated temperature (37�C) yielded significantly different UV transmissions values compared to unexposed dilutions. The aim was to test whether electromagnetic fields (EMF) of a mobile phone affect the UV absorbance of dilutions of Atropa belladonna (Ab) and quartz. Methods: Commercially available dilutions of Ab 4x, 6x, 12x, 15x, 30x and of quartz 6x, 12x, 15x, 30x were investigated. On 5 days, 4 samples of each dilution were exposed to the EMF by a mobile phone at 900MHz (GSM) with an output power of 2W for 3 h. Control samples were kept in a separate room. UV-absorbance of the samples in the range from 190 to 340 nm was measured in randomized order. The average absorbance from 200 to 340 nm and from 200 to 240 nm was compared between exposed and unexposed samples by a dependent t-test. Results: Between unexposed and exposed dilutions of Ab and quartz no significant differences were detected, except for quartz 12x over the range from 200 to 340 nm. Conclusion: Exposure of high dilutions of Ab and quartz to GSM EMF of a mobile phone did not alter UV absorbance of these dilutions.

Successful pacing using a batteryless sunlight-powered pacemaker.

AIMS Today's cardiac pacemakers are powered by batteries with limited energy capacity. As the battery's lifetime ends, the pacemaker needs to be replaced. This surgical re-intervention is costly and bears the risk of complications. Thus, a pacemaker without primary batteries is desirable. The goal of this study was to test whether transcutaneous solar light could power a pacemaker. METHODS AND RESULTS We used a three-step approach to investigate the feasibility of sunlight-powered cardiac pacing. First, the harvestable power was estimated. Theoretically, a subcutaneously implanted 1 cm(2) solar module may harvest ∼2500 µW from sunlight (3 mm implantation depth). Secondly, ex vivo measurements were performed with solar cells placed under pig skin flaps exposed to a solar simulator and real sunlight. Ex vivo measurements under real sunlight resulted in a median output power of 4941 µW/cm(2) [interquartile range (IQR) 3767-5598 µW/cm(2), median skin flap thickness 3.0 mm (IQR 2.7-3.3 mm)]. The output power strongly depended on implantation depth (ρSpearman = -0.86, P < 0.001). Finally, a batteryless single-chamber pacemaker powered by a 3.24 cm(2) solar module was implanted in vivo in a pig to measure output power and to pace. In vivo measurements showed a median output power of >3500 µW/cm(2) (skin flap thickness 2.8-3.84 mm). Successful batteryless VVI pacing using a subcutaneously implanted solar module was performed. CONCLUSION Based on our results, we estimate that a few minutes of direct sunlight (irradiating an implanted solar module) allow powering a pacemaker for 24 h using a suitable energy storage. Thus, powering a pacemaker by sunlight is feasible and may be an alternative energy supply for tomorrow's pacemakers.

The first batteryless, solar-powered cardiac pacemaker

BACKGROUND: Contemporary pacemakers (PMs) are powered by primary batteries with a limited energy-storing capacity. PM replacements because of battery depletion are common and unpleasant and bear the risk of complications. Batteryless PMs that harvest energy inside the body may overcome these limitations. OBJECTIVE: The goal of this study was to develop a batteryless PM powered by a solar module that converts transcutaneous light into electrical energy. METHODS: Ex vivo measurements were performed with solar modules placed under pig skin flaps exposed to different irradiation scenarios (direct sunlight, shade outdoors, and indoors). Subsequently, 2 sunlight-powered PMs featuring a 4.6-cm2 solar module were implanted in vivo in a pig. One prototype, equipped with an energy buffer, was run in darkness for several weeks to simulate a worst-case scenario. RESULTS: Ex vivo, median output power of the solar module was 1963 μW/cm2 (interquartile range [IQR] 1940-2107 μW/cm2) under direct sunlight exposure outdoors, 206 μW/cm2 (IQR 194-233 μW/cm2) in shade outdoors, and 4 μW/cm2 (IQR 3.6-4.3 μW/cm2) indoors (current PMs use approximately 10-20 μW). Median skin flap thickness was 4.8 mm. In vivo, prolonged SOO pacing was performed even with short irradiation periods. Our PM was able to pace continuously at a rate of 125 bpm (3.7 V at 0.6 ms) for 1½ months in darkness. CONCLUSION: Tomorrow's PMs might be batteryless and powered by sunlight. Because of the good skin penetrance of infrared light, a significant amount of energy can be harvested by a subcutaneous solar module even indoors. The use of an energy buffer allows periods of darkness to be overcome.

Influence of directionality and maximal power output on speech understanding with bone anchored hearing implants in single sided deafness

Bone-anchored hearing implants (BAHI) are routinely used to alleviate the effects of the acoustic head shadow in single-sided sensorineural deafness (SSD). In this study, the influence of the directional microphone setting and the maximum power output of the BAHI sound processor on speech understanding in noise in a laboratory setting were investigated. Eight adult BAHI users with SSD participated in this pilot study. Speech understanding in noise was measured using a new Slovak speech-in-noise test in two different spatial settings, either with noise coming from the front and noise from the side of the BAHI (S90N0) or vice versa (S0N90). In both spatial settings, speech understanding was measured without a BAHI, with a Baha BP100 in omnidirectional mode, with a BP100 in directional mode, with a BP110 power in omnidirectional and with a BP110 power in directional mode. In spatial setting S90N0, speech understanding in noise with either sound processor and in either directional mode was improved by 2.2-2.8 dB (p = 0.004-0.016). In spatial setting S0N90, speech understanding in noise was reduced by either BAHI, but was significantly better by 1.0-1.8 dB, if the directional microphone system was activated (p = 0.046), when compared to the omnidirectional setting. With the limited number of subjects in this study, no statistically significant differences were found between the two sound processors.

Yellow laser light generation by frequency doubling of the output from a master oscillator fiber power amplifier system

We present a power-scalable approach for yellow laser-light generation based on standard Ytterbium (Yb) doped fibers. To force the cavity to lase at 1154 nm, far above the gain-maximum, measures must be taken to fulfill lasing condition and to suppress competing amplified spontaneous emission (ASE) in the high-gain region. To prove the principle we built a fiber-laser cavity and a fiber-amplifier both at 1154 nm. In between cavity and amplifier we suppressed the ASE by 70 dB using a fiber Bragg grating (FBG) based filter. Finally we demonstrated efficient single pass frequency doubling to 577 nm with a periodically poled lithium niobate crystal (PPLN). With our linearly polarized 1154 nm master oscillator power fiber amplifier (MOFA) system we achieved slope efficiencies of more than 15 % inside the cavity and 24 % with the fiber-amplifier. The frequency doubling followed the predicted optimal efficiency achievable with a PPLN crystal. So far we generated 1.5 W at 1154nm and 90 mW at 577 nm. Our MOFA approach for generation of 1154 nm laser radiation is power-scalable by using multi-stage amplifiers and large mode-area fibers and is therefore very promising for building a high power yellow laser-light source of several tens of Watt.