Accurate and objective determination of myalgic encephalomyelitis/chronic fatigue syndrome disease severity with a wearable sensor.

BACKGROUND: Approximately 2.5 million people in the U.S. suffer from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This disease negatively impacts patients' ability to function, often resulting in difficulty maintaining employment, sustaining financial independence, engaging socially with others, and in particularly severe cases, consistently and adequately performing activities of daily living. The focus of this research was to develop a sensor-based method to measure upright activity defined as time with feet on the floor and referred to as UpTime, as an indicator of ME/CFS disease severity. METHODS: A commercially available inertial measurement unit (IMU), the Shimmer, was selected for this research. A Kalman filter was used to convert IMU data collected by the Shimmer to angle estimates. Angle estimate accuracy was confirmed by comparison to a motion capture system. Leg angle estimates were then converted to personalized daily UpTime scores using a critical angle of 39º from vertical to differentiate between upright (feet on the floor) and not upright. A 6-day, case-control study with 15 subjects (five healthy controls, five moderate-level ME/CFS, and five severe-level ME/CFS) was conducted to determine the utility of UpTime for assessing disease severity. RESULTS: UpTime was found to be a significant measure of ME/CFS disease severity. Severely ill ME/CFS patients spend less than 20% of each day with feet on the floor. Moderately ill ME/CFS patients spend between 20-30% of each day with feet on the floor. Healthy controls have greater than 30% UpTime. IMU-measured UpTime was more precise than self-reported hours of upright activity which were over-estimated by patients. CONCLUSIONS: UpTime is an accurate and objective measure of upright activity, a measure that can be used to assess disease severity in ME/CFS patients. Due to its ability to accurately monitor upright activity, UpTime can also be used as a reliable endpoint for evaluating ME/CFS treatment efficacy. Future studies with larger samples and extended data collection periods are required to fully confirm the use of UpTime as a measure of disease severity in ME/CFS. With the added perspective of large-scale studies, this sensor-based platform could provide a recovery path for individuals struggling with ME/CFS.

A Multi-Beam Shared-Inductor Reconfigurable Voltage/SECE Mode Piezoelectric Energy Harvesting Interface Circuit.

This paper presents an autonomous multi-input (multi-beam) reconfigurable power-management chip for optimal energy harvesting from weak multi-axial human motion using a multi-beam piezoelectric energy harvester (PEH). The proposed chip adaptively operates in either voltage-mode or synchronous-electrical-charge-extraction-mode (VM-SECE) to improve overall efficiency, extract maximum energy regardless of the PEH beams' impedance/voltage/frequency variations, and protect the chip against large inputs, eliminating the need for high-voltage processes. It can simultaneously harvest energy from up to 6 beams using only one shared off-chip inductor. It uses an active negative voltage converter to extend the input-voltage range to as low as 35 mV. In addition, an active voltage doubler with a small footprint is implemented for faster cold start. A prototype VM-SECE chip was fabricated in a 0.35-µm 2P4M standard CMOS process occupying 1.9 mm2 active area. To fully characterize the chip performance, it was tested with both a commercial single-beam PEH and a custom-made PEH with five mechanically plucked thin-film beams. With the commercial PEH, compared to an on-chip full-wave active rectifier (FAR) with 95.6% efficiency, the VM-SECE chip harvested 3.28x more power for shock inputs at 1 Hz frequency and 4.39 g acceleration. With the custom 5-beam PEH for a pseudo-walking condition, compared to the on-chip FAR, the VM-SECE chip harvested 1.59x and 2.38x more power for 1-and 5-beam operations, respectively.

Magnetoelectric Transducer Designs for Use as Wireless Power Receivers in Wearable and Implantable Applications.

As the size of biomedical implants and wearable devices becomes smaller, the need for methods to deliver power at higher power densities is growing. The most common method to wirelessly deliver power, inductively coupled coils, suffers from poor power density for very small-sized receiving coils. An alternative strategy is to transmit power wirelessly to magnetoelectric (ME) or mechano-magnetoelectric (MME) receivers, which can operate efficiently at much smaller sizes for a given frequency. This work studies the effectiveness of ME and MME transducers as wireless power receivers for biomedical implants of very small (<2 mm³) size. The comparative study clearly demonstrates that under existing safety standards, the ME architecture is able to generate a significantly higher power density than the MME architecture. Analytical models for both types of transducers are developed and validated using centimeter scale devices. The Institute of Electrical and Electronics Engineers (IEEE) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) standards were applied to the lumped elements models which were then used to optimize device dimensions within a 2 mm³ volume. An optimized ME device can produce 21.3 mW/mm³ and 31.3 W/mm³ under the IEEE and ICNIRP standards, respectively, which are extremely attractive for a wide range of biomedical implants and wearable devices.

Characterization of load reduction while lifting drywall using an unpowered drywall lifting device.

BACKGROUND: Drywall installation has an injury rate four times that of the construction industry average. Workers are exposed to hazards related to slips, falls, and falling objects, in addition to the large and awkward loads they must carry. Drywall sheets can weigh more than 100 lb. and contribute to disabling musculoskeletal injuries of the shoulders and back. OBJECTIVE: In this study, an unpowered lift assist device was developed to manage the load of a drywall sheet during the installation process. METHODS: In order to measure the effect of the lift assist device, a laboratory study with 10 healthy male participants performing two lifts, lifting from ground to erect and lifting from erect to ceiling, with and without the help of the device, was performed. These lifts were chosen to simulate a drywall installer's frequent lifting motions. Participants were fitted with electromyography (EMG) on the erector spinae, latissimus dorsi, rectus abdominus, and external oblique muscles to measure activation. Mean, peak, and effort data for the lifting exercises were extracted and compared to the unassisted lift. RESULTS: The lift assist device resulted in a reduction in mean EMG signal of 69% average over both lifts and muscle groups. Peak EMG and effort (i.e., area under the curve) were reduced by 78% and 75%, respectively. CONCLUSIONS: These data demonstrate the effectiveness of the device in reducing compressive back loads during drywall installation, which warrants future development.