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  1. Abstract

    3D printing using conventional stereolithography is challenging because the polymerized layers adhere to the solid constraining interface. The mechanical separation forces lead to poor process reliability and limit the geometrical design space of the printed parts. Here, these challenges are overcome by utilizing a static inert immiscible liquid below the resin as the constraining interface. We elucidate the mechanisms that enable the static liquid to mitigate stiction in both discrete layer-by-layer and continuous layerless growth modes. The inert liquid functions as a dewetting interface during the discrete growth and as a carrier of oxygen to inhibit polymerization during the continuous growth. This method enables a wide range of process conditions, such as exposure and resin properties, which facilitates micrometer scale resolutions and dimensional accuracies above 95%. We demonstrate multi-scale microstructures with feature sizes ranging from 16 μm to thousands of micrometers and functional devices with aspect ratios greater than 50:1 without using sacrificial supports. This process can enable additive 3D microfabrication of functional devices for a variety of applications.

  2. We report the design, fabrication, and experimental characterization of a chip-sized electromechanical micro-receiver for low-frequency, near-field wireless power transmission that employs both electrodynamic and piezoelectric transductions to achieve a high power density and high output voltage while maintaining a low profile. The 0.09 cm 3 device comprises a laser-micro-machined titanium suspension, one NdFeB magnet, two PZT-5A piezo-ceramic patches, and a precision-manufactured micro-coil with a thickness of only 1.65 mm. The device generates 520 μW average power (5.5 mW•cm -3 ) at 4 cm distance from a transmitter coil operating at 734.6 Hz and within safe human exposure limits. Compared to a previously reported piezoelectric-only prototype, this device generates ~2.5x higher power and offers 18% increased normalized power density (6.5 mW•cm -3 •mT -2 ) for potential improvement in wirelessly charging wearables and bio-implants.
  3. This paper presents the design, fabrication and experimental characterization of a chip-sized wireless power receiver for low-frequency electrodynamic wireless power transmission (EWPT). Utilizing a laser micro-machined meandering suspension, one NdFeB magnet, and two PZT-SA piezoelectric patches, this 0.08 cm 3 micro-receiver operates at its torsion mode mechanical resonance of 724 Hz. The device generates 360 μW average power (4.2 mWcm -3 power density) at 1 cm distance from a transmitter coil operating at 724 Hz and safely within allowable human exposure limits of 2 mTrms field. Compared to a previously reported macro-scale prototype, this volume-efficient micro-receiver is 31x smaller and offers 3.2x higher power density within a low-profile, compact footprint for wirelessly charging wearable and bio-implantable devices.