A high power CMOS class-D amplifier for inductive-link medical transmitters

Powering of medical implants by inductive coupling is an effective technique, which avoids the use of bulky implanted batteries or transcutaneous wires. On the external unit side, class-D and class-E power amplifiers (PAs) are conventionally used thanks to their high efficiency at high frequencies. The initial specifications driving this work require the use of multiple independent stimulators, which imposes serious constraints on the area and functionality of the external unit. An integrated circuit class-D PA has been designed to provide both small area and enhanced functionality, the latter achieved by the addition of an on-chip phased-locked loop (PLL), a dead-time generator and a phase detector. The PA has been designed in a 0.18μm CMOS high-voltage process technology and occupies an area of 9.86 mm2. It works at frequencies up to 14 MHz and 30 V supply and efficiencies higher than 80% are obtained at 14 MHz. The PA is intended for a closed-loop transmitter system that optimises power delivery to medical implants

An Implantable Wireless Multi-Channel Neural Prosthesis for Epidural Stimulation

This paper presents a fully implantable multi-channel neural prosthesis for epidural stimulation. The prosthesis features three telemetry-operated independent stimulators providing in total eighteen stimulation channels. The stimulator circuits were implemented in a 0.6-μm CMOS technology. The prosthesis is protected in a hermetically sealed ceramic enclosure and encapsulated in medical grade silicone rubber. In-vitro measured results with electrodes in saline are presented

A CMOS Smart Temperature and Humidity Sensor with Combined Readout.

A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating temperature and humidity on-chip. The smart sensor has two modes of operation, in which either the temperature or humidity is converted into a digital code representing a frequency ratio between two oscillators. This ratio is determined by the ratios of the timing capacitances and bias currents in both oscillators. The reference oscillator is biased by a current whose temperature dependency is complementary to the proportional to absolute temperature (PTAT) current. For the temperature measurement, this results in an exceptional normalized sensitivity of about 0.77%/°C at the accepted expense of reduced linearity. The humidity sensor is a capacitor, whose value varies linearly with relative humidity (RH) with a normalized sensitivity of 0.055%/% RH. For comparison, two versions of the humidity sensor with an area of either 0.2 mm2 or 1.2 mm2 were fabricated in a commercial 0.18 μm CMOS process. The on-chip readout electronics operate from a 5 V power supply and consume a current of approximately 85 µA

An Implantable Versatile Electrode-Driving ASIC for Chronic Epidural Stimulation in Rats

This paper presents the design and testing of an electrode driving application specific integrated circuit (ASIC) intended for epidural spinal cord electrical stimulation in rats. The ASIC can deliver up to 1 mA fully programmable monophasic or biphasic stimulus current pulses, to 13 electrodes selected in any possible configuration. It also supports interleaved stimulation. Communication is achieved via only 3 wires. The current source and the control of the stimulation timing were kept off-chip to reduce the heat dissipation close to the spinal cord. The ASIC was designed in a 0.18- \mu m high voltage CMOS process. Its output voltage compliance can be up to 25 V. It features a small core area ( {< } 0.36 mm ^{2} ) and consumes a maximum of 114 \mu W during a full stimulation cycle. The layout of the ASIC was developed to be suitable for integration on the epidural electrode array, and two different versions were fabricated and electrically tested. Results from both versions were almost indistinguishable. The performance of the system was verified for different loads and stimulation parameters. Its suitability to drive a passive epidural 12-electrode array in saline has also been demonstrated

Paleostrain stratigraphic analysis of calcite twins across the Cambrian-Ordovician unconformity in the Tethyan Himalaya, Spiti and Zanskar valley regions, India

Abstract Calcite strain analyses were conducted on low-grade Cambrian and Carboniferous limestone samples collected above and below the Cambrian-Ordovician unconformity in the Spiti and Zanskar valley regions of the NW Himalaya in order to compare strain patterns in rocks that bracket an enigmatic early Paleozoic tectonic episode. All samples record a layer-parallel shortening strain at a high angle to folds and faults in the Tethyan Himalayan fold-thrust belt. In the Carboniferous samples, we relate these layer-parallel strains to the onset of Cenozoic deformation within the Tethyan Himalayan fold-thrust belt. The Cambrian sample from the Spiti area contains a layer-parallel shortening strain even though the Cambrian-Ordovician unconformity is angular. This suggests that the twinning strains in the Cambrian sample may have formed at the onset of early Paleozoic folding and subsequent erosion, and that early phases of Cenozoic shortening were coaxial to early Paleozoic shortening. The maximum shortening axis in the Carboniferous samples, which is probably parallel to the early thrust transport direction in the Tethyan Himalayan fold-thrust belt, is parallel to the NE movement of India with respect to Eurasia in the Middle Eocene, suggesting that it might closely correspond to the India/Eurasian slip direction during this time period

A multi-channel stimulator with an active electrode array implant for vagal-cardiac neuromodulation studies.

Background: Implantable vagus nerve stimulation is a promising approach for restoring autonomic cardiovascular functions after heart transplantation. For successful treatment a system should have multiple electrodes to deliver precise stimulation and complex neuromodulation patterns. Methods: This paper presents an implantable multi-channel stimulation system for vagal-cardiac neuromodulation studies in swine species. The system comprises an active electrode array implant percutaneously connected to an external wearable controller. The active electrode array implant has an integrated stimulator ASIC mounted on a ceramic substrate connected to an intraneural electrode array via micro-rivet bonding. The implant is silicone encapsulated for biocompatibility and implanted lifetime. The stimulation parameters are remotely transmitted via a Bluetooth telemetry link. Results: The size of the encapsulated active electrode array implant is 8 mm × 10 mm × 3 mm. The stimulator ASIC has 10-bit current amplitude resolution and 16 independent output channels, each capable of delivering up to 550 μA stimulus current and a maximum voltage of 20 V. The active electrode array implant was subjected to in vitro accelerated lifetime testing at 70 °C for 7 days with no degradation in performance. After over 2 h continuous stimulation, the surface temperature change of the implant was less than 0.5 °C. In addition, in vivo testing on the sciatic nerve of a male Göttingen minipig demonstrated that the implant could effectively elicit an EMG response that grew progressively stronger on increasing the amplitude of the stimulation. Conclusions: The multi-channel stimulator is suitable for long term implantation. It shows potential as a useful tool in vagal-cardiac neuromodulation studies in animal models for restoring autonomic cardiovascular functions after heart transplantation

Neural Stimulation Hardware for the Selective Intrafascicular Modulation of the Vagus Nerve

The neural stimulation of the vagus nerve is able to modulate various functions of the parasympathetic response in different organs. The stimulation of the vagus nerve is a promising approach to treating inflammatory diseases, obesity, diabetes, heart failure, and hypertension. The complexity of the vagus nerve requires highly selective stimulation, allowing the modulation of target-specific organs without side effects. Here, we address this issue by adapting a neural stimulator and developing an intraneural electrode for the particular modulation of the vagus nerve. The neurostimulator parameters such as amplitude, pulse width, and pulse shape were modulated. Single-, and multi-channel stimulation was performed at different amplitudes. For the first time, a polyimide thin-film neural electrode was designed for the specific stimulation of the vagus nerve. In vivo experiments were performed in the adult minipig to validate to elicit electrically evoked action potentials and to modulate physiological functions, validating the spatial selectivity of intraneural stimulation. Electrochemical tests of the electrode and the neurostimulator showed that the stimulation hardware was working correctly. Stimulating the porcine vagus nerve resulted in spatially selective modulation of the vagus nerve. ECAP belonging to alpha and beta fibers could be distinguished during single- and multi-channel stimulation. We have shown that the here presented system is able to activate the vagus nerve and can therefore modulate the heart rate, diastolic pressure, and systolic pressure. The here presented system may be used to restore the cardiac loop after denervation by implementing biomimetic stimulation patterns. Presented methods may be used to develop intraneural electrodes adapted for various applications