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. 2013 Apr;7(2):115-28.
doi: 10.1109/TBCAS.2013.2255874.

A 100-channel Hermetically Sealed Implantable Device for Chronic Wireless Neurosensing Applications

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Free PMC article

A 100-channel Hermetically Sealed Implantable Device for Chronic Wireless Neurosensing Applications

Ming Yin et al. IEEE Trans Biomed Circuits Syst. .
Free PMC article

Abstract

A 100-channel fully implantable wireless broadband neural recording system was developed. It features 100 parallel broadband (0.1 Hz-7.8 kHz) neural recording channels, a medical grade 200 mAh Li-ion battery recharged inductively at 150 kHz , and data telemetry using 3.2 GHz to 3.8 GHz FSK modulated wireless link for 48 Mbps Manchester encoded data. All active electronics are hermetically sealed in a titanium enclosure with a sapphire window for electromagnetic transparency. A custom, high-density configuration of 100 individual hermetic feedthrough pins enable connection to an intracortical neural recording microelectrode array. A 100 MHz bandwidth custom receiver was built to remotely receive the FSK signal and achieved -77.7 dBm sensitivity with 10(-8) BER at 48 Mbps data rate. ESD testing on all the electronic inputs and outputs has proven that the implantable device satisfies the HBM Class-1B ESD Standard. In addition, the evaluation of the worst-case charge density delivered to the tissue from each I/O pin verifies the patient safety of the device in the event of failure. Finally, the functionality and reliability of the complete device has been tested on-bench and further validated chronically in ongoing freely moving swine and monkey animal trials for more than one year to date.

Figures

Fig. 1
Fig. 1
Photographs of the hermetically packaged 100-Ch fully implantable wireless neurosensing device.
Fig. 2
Fig. 2
SolidWorks (Waltham, MA, USA) model exploded view of the hermetically packaged 100-Ch fully implantable wireless neurosensing device.
Fig. 3
Fig. 3
(a) Circuit block diagram and (b) photographs of PCB-A and PCB-B for the hermetically packaged 100-Ch fully implantable wireless neurosensing device. The highlighted blocks in (a) are the custom designed ASICs and the rest are off-the-shelf components.
Fig. 4
Fig. 4
(a) Schematic of the preamplifier design implemented within both versions of the 100-channel preamplifier ASIC. Note: the bias resistor R in the latest version has been pulled off-chip for post-fabrication high-pass adjustment. (b) Schematic of the OTA. (c) Noise spectrum density of the preamplifier shows an input referred noise of 2.83 μ Vrms over a frequency range of 1 Hz to 10 kHz, and an noise efficiency factor (NEF) of 3.3.
Fig. 5
Fig. 5
Circuit block diagram of the 100-Ch preamplifier ASIC.
Fig. 6
Fig. 6
Microphotographs of the 100-ch preamplifier ASIC and the controller ASIC.
Fig. 7
Fig. 7
Measured charging efficiency of the implantable neurosensing device at different charging distances. The forward power is 800 mW at 150 kHz frequency. The charging efficiency is calculated by using the product of the charging current and the charging voltage (5 V) divided by the forward power.
Fig. 8
Fig. 8
ESD protection circuits for the preamplifier input on the 100-channel preamplifier ASIC using the two stage diode connected NMOS structure.
Fig. 9
Fig. 9
(a) The preamplifier input ESD protection circuit I-V before and (b) after Class 1A, (c) Class 1B, and (d) Class 1C ESD Testing. Results show that when the ESD protection circuit is intact, the forward and reverse biased conducting resistances are small with values around 7Ω and 50Ω at large bias voltages respectively.
Fig. 10
Fig. 10
(a) Photograph and (b) block diagram of the RF superheterodyne receiver for the 100-ch wireless neural recording system.
Fig. 11
Fig. 11
Bit error rate measurement setup for the custom RF receiver.
Fig. 12
Fig. 12
(a) Measured line-of-sight (LOS) received signal strength vs. distance using a 10 dBi planar antenna. (b) Measured BER for the receiver with different input signal strength using a 48 Mbps pseudorandom test pattern. The result is compared with the theoretical BER of a non-coherent FSK receiver.
Fig. 13
Fig. 13
Measured eye diagram of the received baseband signal with different input signal strengths using a 33 Mbps pseudorandom test pattern. (a)–41.1 dBm input power. (b) –47.6 dBm input power. (c) –57.8 Bm input power. (d) –78.1 dBm input power. (e) Based band data pulse width and amplitude deviation summary.
Fig. 14
Fig. 14
1 mVpp 100 Hz artificial spike signals recorded wirelessly using the 100-channel implantable neurosensing device at a 1 m distance.
Fig. 15
Fig. 15
(a) A cartoon of the device implantation and array placement. (b) X-ray images of the implantable device in a swine and a rhesus macaque.
Fig. 16
Fig. 16
(a) Simultaneously recorded in vivo neural spikes from an awake Yorkshire swine and (b) a rhesus macaque monkey using the 100-Channel fully implanted wireless neurosensing device. The 100-channel sorted neural spikes are displayed in a 10 × 10 grid showing in the top column of the figure. The insets at the top left corner of each grid show examples of the channel that has multiple units. The bottom column of the figure shows the spike signal and LFP signal extracted from a signal channel. The insets on the left of each LFP trace show the zoom-in view of the spikes.
Fig. 17
Fig. 17
Wirelessly recorded data from the neurosensing device implanted in a rhesus macaque monkey. (a) and (b) Threshold crossings across all channels can be reduced to a low-dimensional state space through principal component analysis (among other methods). We present such neural trajectories produced during free movement of monkey JV: scratching eye (blue), touching an apple (green) and turning head (purple). Circles represent centroids of trajectory during each movement. (c) A selection of 15/100 broadband recording channels demonstrating heterogeneity of the neural signals and the richness of high-sample rate data collection (20 kSps). (d) A raster plot (12 s) marking threshold-crossing timestamps for all input channels and behavior is indicated by color: scratching eye (blue), touching an apple (green) and turning head (purple).

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