Caterina Carboni

Peripheral Neural Activity Recording and Stimulation System

This paper presents a portable, embedded, microcontroller-based system for bidirectional communication (recording and stimulation) between an electrode, implanted in the peripheral nervous system, and a host computer. The device is able to record and digitize spontaneous and/or evoked neural activities and store them in data files on a PC. In addition, the system has the capability of providing electrical stimulation of peripheral nerves, injecting biphasic current pulses with programmable duration, intensity, and frequency. The recording system provides a highly selective band-pass filter from 800 Hz to 3 kHz, with a gain of 56 dB. The amplification range can be further extended to 96 dB with a variable gain amplifier. The proposed acquisition/stimulation circuitry has been successfully tested through in vivo measurements, implanting a tf-LIFE electrode in the sciatic nerve of a rat. Once implanted, the device showed an input referred noise of 0.83 μVrms, was capable of recording signals below 10 μ V, and generated muscle responses to injected stimuli. The results demonstrate the capability of processing and transmitting neural signals with very low distortion and with a power consumption lower than 1 W. A graphic, user-friendly interface has been developed to facilitate the configuration of the entire system, providing the possibility to activate stimulation and monitor recordings in real time.

An HV-CMOS Integrated Circuit for Neural Stimulation in Prosthetic Applications

An integrated neural stimulator for prosthetic applications, realized with a high-voltage CMOS 0.35-μm process, is presented. The device is able to provide biphasic current pulses to stimulate eight electrodes independently. A voltage booster generates a 17-V voltage supply in order to guarantee the programmed stimulation current even in case of high impedances at the electrode-tissue interface. Pulse parameters such as amplitude, frequency, and width can be programmed digitally. The device has been successfully tested by means of both electrical and in vivo tests, and the results show its capability to provide currents on the order of hundreds of microamperes with impedances on the order of tens of kiloohms.

An integrated interface for peripheral neural system recording and stimulation: system design, electrical tests and in-vivo results.

The prototype of an electronic bi-directional interface between the Peripheral Nervous System (PNS) and a neuro-controlled hand prosthesis is presented. The system is composed of 2 integrated circuits: a standard CMOS device for neural recording and a HVCMOS device for neural stimulation. The integrated circuits have been realized in 2 different 0.35μm CMOS processes available from ams. The complete system incorporates 8 channels each including the analog front-end, the A/D conversion, based on a sigma delta architecture and a programmable stimulation module implemented as a 5-bit current DAC; two voltage boosters supply the output stimulation stage with a programmable voltage scalable up to 17V. Successful in-vivo experiments with rats having a TIME electrode implanted in the sciatic nerve were carried out, showing the capability of recording neural signals in the tens of microvolts, with a global noise of 7μVrms, and to selectively elicit the tibial and plantar muscles using different active sites of the electrode.

Compact, Multi-Channel, Electronic Interface for PNS Recording and Stimulation

A multi-channel system for neural signal recording/stimulation is presented. The system is split on two devices: an implantable High Voltage (HV) CMOS integrated circuit (IC) hosting a sigma delta modulator, together with a low noise preamplifier/prefilter and a digital platform for sigma delta decimation/control implemented on a FPGA. This innovative approach guarantees a robust communication link while minimizing the blocks to be implanted, saving power and area. The recording unit exhibits an IRN = 2.12μVrms in 800Hz − 8kHz bandwidth, a programmable gain in the range 45.4dB − 58dB and a 14-bit A/D conversion. The IC hosts also a current-mode stimulator able to deliver currents in the range of hundreds of microampere to electrodes with impedances up to 100kΩ.

A Novel Embedded System for Direct, Programmable Stimulation of the Peripheral Neural System

A device aimed at restoring the sensory feedback in amputees is presented. Biphasic current pulses can be generated and delivered to the Peripheral Neural System (PNS) through neural electrodes. The current pulses can be controlled in terms of amplitude, width and frequency. Moreover, the system can be configured to generate customized waveforms. The device is based on an IC implemented on a 0.35um HV process and includes a voltage booster and a programmable current DAC, allowing to deliver the programmed current even in case of high impedance contact at the electrode-tissue interface. The system has been implemented and successfully tested by means of in-vivo experiments with rats.

Investigation on the hermeticity of an implantable package with 32 feedthroughs for neural prosthetic applications

This paper presents an implantable package aimed at hosting a bidirectional neural interface for neural prosthetic applications. The package has been conceived to minimize the invasivity for the patient, for this reason a cylindrical container with an outer diameter of 7 mm and a length of 21 mm has been designed. The package, realized in alumina (Al2O3), presents 32 hermetic feedthroughs located at the top and bottom base of the cylinder. The hermetic housing has been assembled using a low-temperature soldering method based on a previous platinum/gold (Pt/Au) metallization of the ceramic parts. The packages hermeticity has been successfully proved by means of in-vitro tests, exhibiting an increase in the inner relative humidity of 20 %RH over 75 days of observation.