Customized microneedle arrays (CMNAs) hold great promise for precise transdermal delivery in a minimally invasive manner. Currently, the fast customization of microneedle arrays remains a great challenge. Here, we show a static optical projection lithography (SOPL) technology for fast 3D printing CMNAs. In this technology, the digital light is statically projected to induce the spatial polymerization of monomer solutions, and therefore microneedle formation can be precisely controlled by the intensity distribution of the projected light. The obtained CMNAs do not have the stair-like surface and layer-by-layer structure that are associated with the common 3D-printing technologies. This method enables fast fabrication of CMNAs with designed shape, size, and distribution in seconds without mechanical motion system. Upconversion nanoparticles (UCNPs) were delivered into skin by the CMNAs, to form a personalized dot matrix for in vivo information storage. Under the irradiation of near-infrared (NIR) light, the UCNPs in skin displayed a visible dot matrix, presenting information encoded in the structure of CMNAs. This work demonstrates a SOPL technology for rapidly customizing high-quality microneedle arrays and a CMNA-mediated in vivo information storage strategy.

Hollow microneedle patches (HMNPs) have great promise for efficient and precise transdermal drug delivery in a painless manner. Currently, the clinical application of HMNPs is restricted by its complex manufacturing processes. Here, we use a new three-dimensional (3D) printing technology, static optical projection lithography (SOPL), for the fast fabrication of HMNPs. In this technology, a light beam is modulated into a customized pattern by a digital micromirror device (DMD) and projected to induce the spatial polymerization of monomer solutions which is controlled by the distribution of the light intensity in the monomer solutions. After an annulus picture is inputted into the DMD via the computer, the microneedles with hollow-cone structure can be precisely printed in seconds. By designing the printing pictures, the personalized HMNPs can be fast customized, which can afford the scale-up preparation of personalized HMNPs. Meanwhile, the obtained hollow microneedles (HMNs) have smooth surface without layer-by-layer structure in the commonly 3D-printed products. After being equipped with a micro-syringe, the HMNPs can efficiently deliver insulin into the skin by injection, resulting in effective control of the blood glucose level in diabetic mice. This work demonstrates a SOPL-based 3D printing technology for fast customization of HMNPs with promising medical applications.

Meander lines (MLs) in two configurations are presented to reduce the mutual coupling (MC) between two microstrip patch antenna elements. Inserting a slot in the ground plane between the antenna elements is a simple method to reduce the MC, while adding the MLs in the slot of the ground can further reduce the MC. In the first configuration, one ML is inserted in the slot of the ground and a maximum MC reduction of 39 dB throughout the −10 dB bandwidth is achieved. What’s more, the radiation patterns are not changed compared with the dual-element microstrip antenna array with a slotted ground. For the second configuration, two MLs are added in the slot of the ground. It is found that a maximum isolation of 53 dB can be obtained. However, the radiation patterns are slightly changed compared with the dual-element microstrip antenna array with a slot in the ground. Meanwhile, the measured peak gain and efficiency of the dual-element microstrip antenna array in the two configurations are given. Along with this paper, several prototypes have been fabricated and measured. The simulated results are in good accordance with the measurements, which are presented to verify that MC reduction can be achieved between microstrip antenna elements by adding the MLs in the slotted ground.

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