Due to their excellent physical and chemical characteristics, multi-wall carbon nanotubes (MWCNT) have the potential to be used in structural composites, conductive materials, sensors, drug delivery and medical imaging. However, because of their small-size and light-weight, the applications of MWCNT also raise health concerns. In vivo animal studies have shown that MWCNT cause biomechanical and genetic alterations in the lung tissue which lead to lung fibrosis. To screen the fibrogenic risk factor of specific types of MWCNT, we developed a human lung microtissue array device that allows real-time and in-situ readout of the biomechanical properties of the engineered lung microtissue upon MWCNT insult. We showed that the higher the MWCNT concentration, the more severe cytotoxicity was observed. More importantly, short type MWCNT at low concentration of 50 ng/ml stimulated microtissue formation and contraction force generation, and caused substantial increase in the fibrogenic marker miR-21 expression, indicating the high fibrogenic potential of this specific carbon nanotube type and concentration. The presented microtissue array system provides a powerful tool for high-throughput examination of the therapeutic and toxicological effects of target compounds in realistic tissue environment.

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Investment molding is used to create hollow, in-plane, polymer microneedles. Sacrificial investment pieces (.32 µm-diameter aluminum bond wires) are bonded into silicon micromachined molds. Needles are formed by filling these molds with Cyclic Olefin Copolymer (Ticona Topas ® ) using an injection molding machine. These needles are immersed in etchant, dissolving the investment and leaving a hollow part. Two micromachining techniques are used to make molds, RIE and KOH. The RIE molds deliver microneedles 280 µm in length with rectangular (130 µm x 100 µm) crosssections and inner diameter of ~35 µm. The KOH molds are used to create 300 µm long microneedles with 150 µm wide triangular shafts with tapered tips.

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