Ultrasound therapy has a long history of novel applications in medicine. Compared to high-intensity ultrasound used for tissue heating, low-intensity ultrasound has drawn in-creasing attention recently due to its ability to induce therapeutic changes without biologically significant temperature increase. Low-intensity pulsed ultrasound (LIPUS) is a specific type of ultrasound that delivers at a low intensity and outputs in the mode of pulsed waves. It has minimal thermal effects while maintaining the transmission of acoustic energy to the target tissue, which is able to provide non-invasive physical stimulation for therapeutic applications. LIPUS has been demonstrated to accelerate the healing of fresh fracture, nonunion and delayed union in both animal and clinical studies. The effectiveness of LIPUS for the applications of soft-tissue regeneration and inhibiting inflammatory responses has also been investigated experimentally. Additionally, research has shown that LIPUS is a promising modality for neuromodulation. The purpose of this review is to provide an overview of the recent developments of LIPUS for therapeutic applications, based on the papers that report positive effects, and to present the findings on the understanding of its mechanism. Currently available LIPUS devices are also briefly described in this paper.

This paper proposes charge pumps with improved power efficiency suitable for low-power on-chip applications. Undesired charge transfer, which has a direction opposite to that of the intended current flow, presents a significant source of power loss in charge pumps. The proposed charge pump circuit utilizes charge transfer switches with a complementary branch scheme to significantly reduce undesired charge transfer, thereby improving power efficiency and increasing output voltage effectively. An optimized gate control strategy is applied to further decrease the power loss caused by undesired charge transfer. Simulations of 8-stage charge pumps in a 0.13 μm standard CMOS technology show that for an input supply voltage of 1.2 V, the proposed charge pump circuit reaches a power efficiency of 58.72% with an output voltage of 7.45 V, when delivering 5-mA load current, and is able to maintain a power efficiency of around 50% and an output voltage of over 5 V as the load current increases to 10 mA. Compared with the other charge pump circuits, the simulation results demonstrate better performance of proposed charge pump circuits in terms of both voltage pumping gain and power efficiency.

Low-intensity ultrasound has drawn increasing attention recently as a non-invasive modality for medical therapeutic applications. Current commercially available low-intensity ultrasound devices are bulky and expensive. In this paper, a battery-powered miniaturized device is proposed to generate low-intensity therapeutic ultrasound. The proposed device consists of a custom Application-Specific Integrated Circuit (ASIC), an off-chip digital control block, and a piezoelectric transducer. The ASIC, which integrates a DC-DC boost converter and a transducer driver, is implemented in TSMC's 0.18 μm BCD Gen2 process. Measurement results show that a maximum output voltage of 14 V is achieved by the proposed fully-integrated DC-DC boost converter with a battery supply voltage of 3.7 V. The peak power conversion efficiency is 29% and the output power at the peak power conversion efficiency is 105 mW. The on-chip transducer driver employs a half-bridge circuit with two n-type devices at the output stage. A high-voltage level shifter with low power consumption and short propagation delay is proposed in this paper for the high-performance operation of the half-bridge transducer driver. The piezoelectric transducer is a customized transducer with a resonance frequency of 1.5 MHz. At this frequency, the proposed low-intensity ultrasound device is able to generate continuous-wave ultrasound with a therapeutic power intensity of 32 [Formula: see text]. The proposed low-intensity ultrasound device is low-cost, compact, and light-weight, which enables affordable, and wearable applications.

Reliability is one of the major concerns for ultralow power circuit designs. Markov random field (MRF) techniques have been applied to logic circuits to resist random noise when operating under ultralow supply voltage or sub-threshold voltage. Although conventional MRF networks can be easily mapped onto simple logic circuits, it becomes difficult when the circuits are large and complex. In this paper, we present a general coding-based partial MRF (CPMRF) method for multi-logic operations in one basic unit, which is referred to as a CPMRF pair. A CPMRF pair saves circuit area by sharing a common MRF network. It also inherits noise immunity from the MRF theory while obtaining noise immunity from the coding structure as a combination of robust ``1s'' and ``0s.'' The resulting architectures become more cost effective than conventional ones. To validate the performance of our proof-of-concept design, we fabricated a carry-lookahead adder implemented by the proposed CPMRF pairs using IBM 130-nm CMOS technology. Measurement results indicate that the CPMRF CLA can achieve high noise tolerance with 20% improvement while occupying 37.7% less area and reducing power consumption by 93% compared with the master-and-slave MRF CLA design.

Low-intensity pulsed ultrasound (LIPUS) is a non-invasive medical therapy that has attracted recent research interest due to its therapeutic effects. However, most LIPUS driver systems currently available are large and expensive. We have proposed a LIPUS interface application-specific integrated circuit (ASIC) for use in wearable medical devices to address some of the challenges related to the size and cost of the current technologies. The proposed ASIC is a highly integrated system, incorporating a DCDC module based on a charge pump architecture, a high voltage level shifter, a half-bridge driver, a voltage-controlled oscillator, and a corresponding digital circuit module. Consequently, the functional realization of this ASIC as a LIPUS driver system requires only a few passive components. Experimental tests indicated that the chip is capable of an output of 184.2 mW or 107.2 mW with a power supply of 5 V or 3.7 V, respectively, and its power conversion efficiency is approximately 30%. This power output capacity allows the LIPUS driver system to deliver a spatial average temporal average (SATA) of 29.5 mW/cm² or 51.6 mW/cm² with a power supply of 3.7 V or 5 V, respectively. The total die area, including pads, is 4 mm². The ASIC does not require inductors, improving its magnetic resonance imaging (MRI) compatibility. In summary, the proposed LIPUS interface chip presents a promising solution for the development of MRI-compatible and cost-effective wearable medical therapy devices.

Accurate time-domain simulation is crucial for designing large and complex photonic integrated circuits (PICs). Passive devices and circuits, such as Mach-Zehnder interferometers and all kinds of wavelength filters, play important roles in PICs, with their input and output characteristics typically described using S-parameters. However, their practical application in the time domain is limited by the fact that they are usually band-limited. Applying the inverse fast Fourier transform (IFFT) directly to these band-limited S-parameters can result in impulse responses that violate causality significantly. To address this issue, this paper proposes a novel method for extrapolating S-parameters of photonic circuits in order to obtain causal and accurate impulse responses.