Cedric W. L. Lee

Fabrication of Textile Antennas and Circuits With 0.1 mm Precision

We present a new selection of E-fibers (also referred to as E-threads) and associated embroidery process. The new E-threads and process achieve a geometrical precision down to 0.1 mm. Thus, for the first time, accuracy of typical printed circuit board (PCB) prototypes can be achieved directly on textiles. Compared to our latest embroidery approach, the proposed process achieves: 1) 3 × higher geometrical precision; 2) 24 × lower fabrication cost; 3) 50% less fabrication time; and 4) equally good RF performance. This improvement was achieved by employing a new class of very thin, 7-filament, Elektrisola E-threads ( diameter ≈ 0.12 mm, almost 2 × thinner than before). To validate our approach, we “printed” and tested a textile spiral antenna operating between 1-5 GHz. Measurement results were in good agreement with simulations. We envision this textile spiral to be integrated within a cap and unobtrusively acquire neuropotentials from wireless fully-passive brain implants. Overall, the proposed embroidery approach brings forward new possibilities for a wide range of applications.

A Wireless Fully Passive Neural Recording Device for Unobtrusive Neuropotential Monitoring

Goal: We propose a novel wireless fully passive neural recording device for unobtrusive neuropotential monitoring. Previous work demonstrated the feasibility of monitoring emulated brain signals in a wireless fully passive manner. In this paper, we propose a novel realistic recorder that is significantly smaller and much more sensitive. Methods: The proposed recorder utilizes a highly efficient microwave backscattering method and operates without any formal power supply or regulating elements. Also, no intracranial wires or cables are required. In-vitro testing is performed inside a four-layer head phantom (skin, bone, gray matter, and white matter). Results: Compared to our former implementation, the neural recorder proposed in this study has the following improved features: 1) 59% smaller footprint, 2) up to 20-dB improvement in neuropotential detection sensitivity, and 3) encapsulation in biocompatible polymer. Conclusion : For the first time, temporal emulated neuropotentials as low as 63 μVpp can be detected in a wireless fully passive manner. Remarkably, the high-sensitivity achieved in this study implies reading of most neural signals generated by the human brain. Significance: The proposed recorder brings forward transformational possibilities in wireless fully passive neural detection for a very wide range of applications (e.g., epilepsy, Alzheimers, mental disorders, etc.).

A High-Sensitivity Fully Passive Neurosensing System for Wireless Brain Signal Monitoring

A high-sensitivity, fully passive neurosensing system is presented for wireless brain signal monitoring. The proposed system is able to detect very low-power brain-like signals, viz. as low as -82 dBm (50 μVpp) at fneuro > 1 kHz. It is also able to read emulated neural signals as low as -70 dBm (200 μVpp) at fneuro > 100 Hz. This is an improvement of up to 22 dB in sensitivity as compared with previously reported neural signals. The system is comprised of an implanted neurosensor and an exterior interrogator. The neurosensor receives an external carrier signal and mixes it with the neural signals prior to retransmitting to the interrogator. Of importance is that the implanted neurosensor is fully passive and does not require a battery nor rectifier/regulator but is concurrently wireless for unobtrusive neurosensing with minimal impact to the individuals activity. To achieve this remarkable high sensitivity, the sensing system employed: 1) a subharmonic mixer using an anti-parallel diode pair; 2) a pair of implanted/interrogator antennas with high transmission coefficient |S21|;and 3) a matching circuit between the implanted antenna and the mixer. This neurosensing system brings forward a new possibility of wireless neural signal detection using passive brain implants.

Fully-passive and wireless detection of very-low-power brain signals

A fully-passive and wireless neurosensing system is presented for acquisition of very-low-power brain signals. The system can detect neuropotentials as low as 50μVpp in frequency-domain. This is an improvement of up to 22dB in sensitivity compared to previously reported neuropotentials. Importantly, it implies reading of most known and useful brain signals. Currently, the system can also recover neuropotentials down to 200μVpp in time-domain. This remarkable sensitivity is enabled by: (a) an anti-parallel diode pair (APDP) implanted mixer that performs harmonic mixing with high conversion efficiency, and (b) a pair of highly-coupled interrogator and implanted antennas. The proposed neurosensing system creates transformational health-status monitoring possibilities for a very wide range of applications.

Passive, on chip and in situ detection of neuropotentials

A fully-passive, on chip wireless system is proposed for in situ detection of neuropotentials. The system aims to replace conventional wired brain-sensing technologies, thus enhancing patient mobility and preserving safety. It consists of an implanted neurosensor that comprises an implanted antenna and mixer, and an exterior RF interrogator. Link budget issues are discussed, highlighting the challenges of detecting human brain neuropotentials as small as 10s of μVpp.

A high-sensitivity fully-passive wireless neurosensing system for unobtrusive brain signal monitoring

A high-sensitivity, fully-passive and wireless neurosensing system is presented for unobtrusive brain signal monitoring. The system is able to wirelessly detect neuropotentials down to 28 μVpp in the frequency band of 100 Hz to 5 kHz. This is a 90-fold sensitivity improvement as compared to previous fully-passive implementations. Importantly, it implies detection of most neural signals generated by the human brain. The system consists of an implanted neurosensor and an exterior interrogator, and utilizes a highly-efficient microwave backscattering method for signal detection. High sensitivity is achieved via: (a) a sub-harmonic implanted mixer with high conversion efficiency, (b) a pair of highly-coupled implanted/interrogator antennas, and (c) a carefully matched interface between the implant antenna and mixer circuit. The proposed neurosensing system brings forward a new possibility of wireless neural signal detection using fully-passive technology.

Miniature fully-passive brain implant for wireless real-time neuropotential monitoring

We present a 8.7 mm × 10 mm fully-passive brain implant transceiver, capable of neuropotential acquisition as low as 20 μVpp. This high sensitivity wireless implant implies that, for the first time, most neuropotentials generated by the human brain can be read in a wireless and fully-passive manner. Concurrently, the proposed implant is 63% smaller than previously reported fully-passive neurorecorders. The neuropotential recording system consists of the brain implant and an exterior interrogator. Unique aspects of our design include: a) an Anti-Parallel Diode Pair (APDP) mixer within the implant for efficient harmonic mixing, and b) a set of highly-coupled miniature implanted and exterior antennas. This leads to >30 dB sensitivity improvement over previous implants. Overall, this is a game-changing capability for studying several conditions (epilepsy, tremor, addictions, etc.).

Wireless biomedical telemetry using a fully-passive brain implant

Wireless biomedical telemetry between a fully-passive brain implant and an exterior interrogator is presented. A key aspect of the proposed implant is minimization of losses to wirelessly record neurological signals as low as 50 μVpp for the first time. To achieve this, we employed an implanted patch with a novel mixed architecture, and an interrogator spiral antenna. All components were integrated and optimized to achieve |S21| ≈ -26 dB and -19 dB at 2.4 GHz and 4.8 GHz, respectively. Measurement results are presented in good agreement with simulations.