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The purpose of this study was to evaluate the reliability and validity of the raw accelerometry output from research-grade and consumer wearable devices compared to accelerations produced by a mechanical shaker table. Raw accelerometry data from a total of 40 devices (i.e., n = 10 ActiGraph wGT3X-BT, n = 10 Apple Watch Series 7, n = 10 Garmin Vivoactive 4S, and n = 10 Fitbit Sense) were compared to reference accelerations produced by an orbital shaker table at speeds ranging from 0.6 Hz (4.4 milligravity-mg) to 3.2 Hz (124.7mg). Two-way random effects absolute intraclass correlation coefficients (ICC) tested inter-device reliability. Pearson product moment, Lin’s concordance correlation coefficient (CCC), absolute error, mean bias, and equivalence testing were calculated to assess the validity between the raw estimates from the devices and the reference metric. Estimates from Apple, ActiGraph, Garmin, and Fitbit were reliable, with ICCs = 0.99, 0.97, 0.88, and 0.88, respectively. Estimates from ActiGraph, Apple, and Fitbit devices exhibited excellent concordance with the reference CCCs = 0.88, 0.83, and 0.85, respectively, while estimates from Garmin exhibited moderate concordance CCC = 0.59 based on the mean aggregation method. ActiGraph, Apple, and Fitbit produced similar absolute errors = 16.9mg, 21.6mg, and 22.0mg, respectively, while Garmin produced higher absolute error = 32.5mg compared to the reference. ActiGraph produced the lowest mean bias 0.0mg (95%CI = -40.0, 41.0). Equivalence testing revealed raw accelerometry data from all devices were not statistically significantly within the equivalence bounds of the shaker speed. Findings from this study provide evidence that raw accelerometry data from Apple, Garmin, and Fitbit devices can be used to reliably estimate movement; however, no estimates were statistically significantly equivalent to the reference. Future studies could explore device-agnostic and harmonization methods for estimating physical activity using the raw accelerometry signals from the consumer wearables studied herein. 

Abstract We report threshold voltage (V_TH) control in ultrawide bandgap Al_0.4Ga_0.6N-channel metal oxide semiconductor heterostructure field-effect transistors using a high-temperature (300 °C) anneal of the high-kZrO₂gate-insulator. Annealing switched the polarity of the fixed charges at the ZrO₂/AlGaN interface from +5.5 × 10¹³cm⁻²to −4.2 × 10¹³cm⁻², pinningV_THat ∼ (−12 V), reducing gate leakage by ∼10³, and improving subthreshold swing 2× (116 mV decade⁻¹). It also enabled the gate to repeatedly withstand voltages from −40 to +18 V, allowing the channel to be overdriven doubling the peak currents to ∼0.5 A mm⁻¹. 

Abstract We demonstrate fully fabricated AlGaN/GaN high electron mobility transistors (HEMTs) transferred from sapphire to copper tape on flexible polyethylene terephthalate using 193 nm excimer laser liftoff (LLO). The heterojunction is structurally intact after LLO, leading to preserved electron mobility μ n ∼1630 cm 2 V −1 s −1 and carrier concentration n s ∼10 13 cm −2 . The maximum drain saturation current decreased by ∼18% after transfer, which is a lower reduction than other reported transfer methods. The drain current of this flexible HEMT increased monotonically under tensile stress applied using a convex-shaped plate, while the threshold voltage shifted more negative in quantitative agreement with the expected piezoelectric charge for an intact heterojunction.