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We present a handheld skin printer that enables the in situ formation of biomaterial and skin tissue sheets of different homogeneous and architected compositions. When manually positioned above a target surface, the compact instrument (weight ＜0.8 kg) conformally deposits a biomaterial or tissue sheet from a microfluidic cartridge. Consistent sheet formation is achieved by coordinating the flow rates at which bioink and cross-linker solution are delivered, with the speed at which a pair of rollers actively translate the cartridge along the surface. We demonstrate compatibility with dermal and epidermal cells embedded in ionically cross-linkable biomaterials (e.g., alginate), and enzymatically cross-linkable proteins (e.g., fibrin), as well as their mixtures with collagen type I and hyaluronic acid. Upon rapid crosslinking, biomaterial and skin cell-laden sheets of consistent thickness, width and composition were obtained. Sheets deposited onto horizontal, agarose-coated surfaces were used for physical and in vitro characterization. Proof-of-principle demonstrations for the in situ formation of biomaterial sheets in murine and porcine excisional wound models illustrate the capacity of depositing onto inclined and compliant wound surfaces that are subject to respiratory motion. We expect the presented work will enable the in situ delivery of a wide range of different cells, biomaterials, and tissue adhesives, as well as the in situ fabrication of spatially organized biomaterials, tissues, and biohybrid structures. [ABSTRACT FROM AUTHOR]

A 8\,\times\,12 array of integrated potentiostats for on-CMOS neurotransmitter imaging is presented. Each potentiostat channel measures bidirectional redox currents proportional to the concentration of a neurochemical. By combining the current-to-frequency and the single-slope analog-to-digital converter (ADC) architectures a total linear dynamic range of 95 dB is achieved. A 3.8 mm\,\times\,3.1 mm prototype fabricated in a 0.35 \mu m standard CMOS technology was integrated with flat and 3D on-die gold microelectrodes and an on-chip microfluidic network. It is experimentally validated in in-situ recording of neurotransmitter dopamine. [ABSTRACT FROM PUBLISHER]

A hybrid CMOS-microfluidic microsystem for chemiluminescence and electrochemiluminescence-based biochemical sensing is presented. The microsystem integrates a two-layer soft polymer microfluidic network and a CMOS imager fabricated in a standard 0.35-\mum technology. The CMOS imager consists of a 64\,\times\,128-pixel array interdigitated with a 32\,\times\,64 electrolessly plated nickel–gold microelectrode array. A two-transistor reset path technique attenuates the subthreshold leakage current of the reset transistor which constitutes a significant portion of the dark current. An active reset technique, in-pixel flicker noise cancellation, and pixel binning contribute to noise reduction. The imager achieves a low dark current of 3.6 nA/cm^2 for photodiode reset voltages as high as 2.3 V, noise of 110 \muVrms with maximum time of photon integration of 90 s, and a dynamic range of 67.8 dB. The CMOS-microfluidic microsystem is validated in on-chip chemiluminescence and electrochemiluminescence detection of luminol. [ABSTRACT FROM PUBLISHER]

The effects of lithium chloride on the allylation of zirconacyclopentadienes with allylic halides in the presence of CuCl have been studied. It is found that mono-allylation products are formed predominantly in the absence of lithium chloride, while the presence of lithium chloride leads to the formation of di-allylation products. [Copyright &y& Elsevier]

Dialkylzirconocenes react with molybdenum or tungsten hexacarbonyl and iodine or NBS to form cyclopentadiene molybdenum or tungsten tricarbonyl iodine or bromide. [Copyright &y& Elsevier]

Fenpropathrin and fenvalerate are two widely used pyrethroid insecticides. Due to one and two asymmetrical centers, fenpropathrin and fenvalerate consist of two and four stereoisomers, respectively. In the present study, the degradation of fenpropathrin and fenvalerate in two soils, an alkaline soil and an acidic soil, was investigated using enantioselective high-performance liquid chromatography (HPLC) and the following results were obtained. (i) Degradation of fenpropathrin and fenvalerate in alkaline soil was slightly enantioselective with S-fenpropathrin and αS,2R-fenvalerate being faster degraded, respectively. (ii) Fenpropathrin and fenvalerate were found configurationally unstable in alkaline soil and significant racemization at the chiral α-C position took place along with the degradation process. The racemization is chemically induced since it occurred under both nonsterilized and sterilized conditions. (iii) No racemization was observed in acidic soil. The soil pH dependent effect of the racemization was further validated by incubating S-fenpropathrin and αS,2R-fenvalerate in methanol–buffer solutions with different pH values. (iv) Fenvaleric acid was identified as the main metabolite of fenvalerate, formed by cleavage of the ester bond, during fenvalerate degradation in alkaline soil. Formation of fenvaleric acid in alkaline soil was slightly enantioselective, resulting in an enrichment of S-fenvaleric acid in the soil. [Copyright &y& Elsevier]