Miniature, battery-free implants promise transformative bio-electronic therapies by enabling minimally invasive implantation procedures, reducing risk, and extending device lifetime. Among all wireless power and data transfer (WPDT) modalities, magnetoelectrics (ME) has emerged as a particularly promising solution for millimeter-scale implants, boasting lower tissue attenuation and higher power transfer efficiency over conventional inductive and ultrasonic methods. However, as an acoustic resonator, ME devices face an inherent tradeoff between Q-factor and bandwidth, limiting their ability to simultaneously achieve high-speed communication and efficient wireless power transfer (WPT). To fundamentally circumvent the challenge, this paper presents dual-resonance ME WPDT that exploits the unique multimode resonances of ME transducers to realize WPT and communication at distinct frequencies. Based on this dual-resonance principle, we demonstrate reconfigurable active and passive schemes for different biomedical applications, with a proof-of-concept system including a miniature implant and an external transceiver. The active scheme achieves 60 kbps at operational distances of 6 cm with 2.5 mW implant power, while the passive backscatter offers 20 kbps continuous streaming at 4 cm with negligible power, demonstrating the first reported non-interrupted ME WPDT system and more than twice the data rate of previous ME backscatter methods. Both schemes further support on-off keying (OOK) and binary phase shift keying (BPSK) modulations, providing additional flexibility to tailor communication needs between power efficiency and robustness. The complete prototype system was validated through comprehensive in-vitro experiments and in-vivo EMG streaming in a rodent model.

Ultrasonic wireless power transfer (WPT) has been proved to be a promising approach to power biomedical implants. To extract the energy generated from the transducer, a rectifier is typically required. Previous inductor-based rectifiers (SSHI and SECE) require a large off-chip inductor to achieve good performance, which is not desired for miniaturization and safety reasons. Synchronized switch harvesting on capacitors (SSHC) rectifiers have been proved to achieve high performance without inductors; however, they are mainly designed for low-frequency kinetic energy harvesting. In this paper, an improved SSHC rectifier is designed to achieve a fully integrated design with all flying capacitors implemented on-chip. The proposed SSHC rectifier can properly operate at ultrasonic excitation frequency (100 KHz) with precise switching time control and ultrafast voltage flipping techniques. In addition, an on-chip ultralow-power LDO allows the system to be self-sustained. The system is designed in a TSMC 180nm BCD technology and post-layout simulation results are presented.

Synchronized switch harvesting on inductor (SSHI) is an efficient active rectifier to extract energy generated from piezoelectric transducer in piezoelectric energy harvesting system. Unlike passive rectifiers, SSHI rectifiers require a power supply to drive synchronized switches. Unfortunately, there is no stable supply when the system starts from the cold state. Most designs let the system work as a passive full bridge rectifier (FBR) to charge power capacitor until a supply is available. However, a FBR requires high open-circuit voltage (VOC) and the FBR’s output voltage cannot go over VOC. This prevents the system from starting the SSHI rectifier if VOCis low. This paper proposes a new transducer reconfiguration design to lower the required VOCby 4 $\times$ to start up the SSHI system from the cold state. The proposed system is designed in a 0.18$-\mu$m BCD process and post-layout simulations show that the successful cold-startup under low VOCvoltage.

Piezoelectric energy harvesting (PEH) has attracted much attention as an approach to exploit ambient vibrational energy to power self-sustained devices. Among the proposed interface circuits for PEH, Synchronized Switch Harvesting on Capacitor (SSHC) rectifier distinguishes itself since it achieves high power efficiency while requires no inductor. The power SSHC can extract is a function of the voltage flip efficiency. In previous studies the flip efficiency is given only under particular condition, which limits the analysis and design of SSHC circuits. This paper presents the derivation of a generic flip efficiency expression. From the result, a novel capacitor-scaling design is proposed which can reduce the total switched capacitance by up to 50% while achieving the same performance (or to enhance performance while maintaining the total capacitance). This is particularly preferred for a fully integrated design and can validated by simulations implemented in a 0.18 m. CMOS BCD technology.

A nanopower highly efficient low-dropout (LDO) regulator for energy harvesting (EH) applications is presented in this paper. The LDO is fully autonomous with a bandgap reference (BGR) featuring a novel bandgap supply-switching (SS) topology, an over-voltage protection (OVP), a under-voltage lockout (UVLO) and control block to obtain stable output and robust cold-start. The system provides configurable voltage supply (1.1 $\sim$2V) for potential loads, while consuming as low as 66 nW power. The entire system achieves a peak power efficiency of 95.6% at Vout=2V and $I_{\iota_{oad}}$=100$\mu$A.