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Hollow microneedles are extremely attractive to drug delivery domains with high demands from clinics and industry. However, its complicated fabrication processes have impeded its wide adoption. This paper presents a simple one-step fabrication method for hollow microneedles based on diffraction UV lithography and solid-liquid light propagation. The fabrication process utilizes bottom-up exposure of a liquid photosensitive resin through photomask patterns comprising a plurality of apertures. Hollow microneedles with various heights were fabricated in a range of 400 µm to 600 µm from a few minutes of UV exposure. The fabricated hollow microneedles were characterized with force-displacement tests showing a good tip strength of 0.35 N per single unit. A hollow fluidic test on a pig cadaver skin showed great potential for drug delivery. Also, batch fabrication with multiple height microneedles on a single substrate has demonstrated compatibility with the manufacturing process.

This paper presents a simple in-house fabrication of a solenoid inductor using 3D printing, selective electroless plating, and electroplating for the inductor, and pressing for a highly laminated metal core. The frame of the solenoid inductor was 3D printed, where the design of the frame has a solenoid trench and ridge for wiring and insulator, respectively. The ridge of the frame was selectively coated with a novolac resin by dipping and rolling. The unique selective electroless plating showed the direct patterning to form a solenoid conductive path that came from the different surface activation. Electroplating to thicken the solenoid wire completes the inductor fabrication. A pressing and stacking of a nickel film form the highly laminated magnetic core for the inductor. A 10-turn solenoid inductor with a wire thickness of was successfully fabricated. An average inductance of 133 nH was measured in air-core condition. A 120 nickel layer cores were integrated into the inductor and showed the boosted inductance of 252 nH. The proposed simple fabrication has a great potential for various RF passive 3D devices including antennas, filters, and waveguides.

This paper presents frequency-selective 3D vertical pillars arrays that have been tuned to 15 GHz as a center frequency of the Ku-Band (12-18 GHz) for satellite applications. The vertical pillars were designed with a quarter wavelength height and a half lambda period at 15 GHz. Simple in-house fabrication methods including electroless and electro platings were introduced to fabricate the frequency-selective 3D vertical pillars arrays. An array of pillars was 3D printed together on the substrate. The electroless plating was introduced to deposit a seed copper layer over the device, where the pillar and the substrate were metalized simultaneously. An additional copper layer was electroplated over the sample to thicken the copper layer considering the skin depth at 15 GHz. The completed sample was electrically characterized using a network analyzer with two horn antennas operating at 15 GHz. Various 3D structures were successfully fabricated and showed great potentials for frequency selective surface applications.

This paper presents a tiltable UV-LED lithography system for 3D microfabrication. Collimated light with adjustable intensity from 7-by-7 405-nm UV-LEDs was used as a light source. An orbital rotation of the UV-LED array provided the uniform light intensity. The key advantages of the proposed system create 3D light traces without the sample's tilt-rotational movement, which is used to cause non-uniform light exposure and sample instability. Also, the tiltable UV-LED lithography can directly pattern on a liquid photosensitive state resin that provides a rapid process without soft baking and post-exposure baking. Several 3D microstructures in hundreds-microns to millimeter heights were successfully fabricated including vertical pillars, inclined pillars, triangular slabs, single and dual microneedle, and multi-angled petals. The tiltable UV-LED lithography has a great potential for a 3D micromanufacturing area with various 3D MEMS applications.