A CMOS bone-guided cochlear implant (BGCI) microsystem is proposed and verified. In the implanted System on Chip (SoC) of the proposed BGCI, the evoked compound action potential (ECAP) acquisition and electrode–tissue impedance measurement (EAEIM) circuit is integrated to measure both ECAP and electrode–tissue impedance for clinical diagnoses. Both positive-/negative-voltage charge pumps and monopolar biphasic constant-current stimulation (CCS) stimulator are designed on-chip to realize monopolar biphasic CCS or double-electrode multiple stimulations with a maximum stimulation current of 1.2 mA and a step of 10 $\mu \text{A}$ . With the double-electrode multiple stimulations, the electric field can be shifted and localized under the stimulating electrode to stimulate the auditory nerves. The wireless bilateral data telemetry circuits with a full-wave active rectifier and the pulsed load-shift keying (PLSK) modulators/demodulators are designed for power and data transmission. In vivo animal tests on guinea pigs have shown that the Wave III of electrically evoked auditory brainstem responses (EABRs) can be evoked successfully by electrical stimulation. Moreover, the decreasing latency gradient of evoked Wave III has been measured under the double-electrode multiple stimulations where the location of peak electric field can be shifted to the stimulating electrode in the apical site to stimulate the auditory nerves. Thus, the desired frequency resolution and spatial specificity of stimulation can be achieved. Both electrical measurement and in vivo animal tests have verified that the proposed BGCI microsystem is a feasible solution to eliminate the symptoms for patients with high-frequency hearing loss.

In this paper, we experimentally investigate the phenomenon of electromagnetic wave tunneling through ϵ-negative (ENG) metamaterial layers surrounded by double-positive layers. Initial experiments are conducted by using a rectangular waveguide, which operates below its cutoff frequency to emulate an ENG layer. This ENG layer is then sandwiched by two dielectric substrates with relatively high dielectric constants and it is shown that the entire setup acts as a classical microwave filter with a second-order bandpass response. The power handling capability of this filter is examined experimentally using a high-power magnetron source with a frequency of 9.382 GHz, a pulse duration of 1 μs, and a peak power of 25 kW. Based on the results of this experiment, two methods for improving the power handling capability of these multi-layer structures are proposed. In particular, it is demonstrated that emulating the ENG layers with thin perforated metallic sheets with sub-wavelength holes significantly enhances their peak power handling capability. A prototype of such a device is designed, fabricated, and experimentally characterized and it is demonstrated that it can handle extremely high peak power levels. The results presented in this work are expected to be useful in designing microwave filters and frequency selective surfaces that can handle extremely high peak power levels.

Combining low-dimensional layers of dissimilar metal oxide materials to form a heterojunction structure offers a potent strategy to improve the performance and stability of thin-film transistors (TFTs). Here, we study the impact of channel layer thicknesses on the operating characteristics of In₂O₃/ZnO heterojunction TFTs prepared via sputtering. The conduction band offset present at the In₂O₃/ZnO heterointerface affects the device's operating characteristics, as is the thickness of the individual oxide layers. The latter is investigated using a variety of experimental and computational modeling techniques. An average field-effect mobility (μ_FE) of >50 cm² V⁻¹ s⁻¹, accompanied by a low threshold voltage and a high on/off ratio (∼10⁸), is achieved using an optimal channel configuration. The high μ_FE in these TFTs is found to correlate with the presence of a quasi-two-dimensional electron gas at the In₂O₃/ZnO interface. This work provides important insight into the operating principles of heterojunction metal oxide TFTs, which can aid further developments.

Objective: To develop and verify a CMOS bone-guided cochlear implant (BGCI) microsystem with electrodes placed on the bone surface of the cochlea and the outside of round window for treating high-frequency hearing loss. Methods: The BGCI microsystem consists of an external unit and an implanted unit. The external system-on-chip (SOC) is designed to process acoustic signals through an acquisition circuit and an acoustic DSP processor to generate stimulation patterns and commands that are transmitted to the implanted unit through a 13.56 MHz wireless power and bidirectional data telemetry. In the wireless power te-lemetry, a voltage doubler/tripler (2X/3X) active rectifier is used to enhance the power conversion efficiency and generate 2 V and 3 V output voltages. In the wireless data telemetry, phase-locked loop (PLL) based binary phase-shift keying (BPSK) and load-shift keying (LSK) modulators/demodulators are adopted for the down-link and uplink data through high-Q coils, respectively. The im-planted chip with 4-channel high-voltage-tolerant stimulator gen-erates biphasic stimulation currents up to 800 μA. Results: Electri-cal tests on the fabricated BGCI microsystem has been performed to verify the chip functions. The in-vivo animal tests in guinea pigs have shown the evoked third wave (Wave eIII) of electrically evoked auditory brainstem response (EABR) waveforms. It is ver-ified that auditory nerves can be successfully stimulated and acoustic hearing can be partially preserved. Conclusion and Significance: Different from traditional cochlear implants, the pro-posed BGCI microsystem is less invasive, preserves partially acoustic hearing, and provides an effective alternative to treating high-frequency hearing loss.