Paper-based sensors and assays have evolved rapidly due to the conversion of paper-based microfluidics, functional paper coatings, as well as new electrical and optical readout techniques. Nanomaterials have gained substantial traction as key components in paper-based sensors, as they can be coated or printed relatively easily on paper to locally control the device functionality. Here we report a new combination of methods to fabricate carbon nanotube based (CNT) electrodes for paperbased electrochemical sensors using a combination of laser cutting, drop-casting and origami. We applied this process to a range of filter papers with different porosities, and used their differences in three-dimensional cellulose networks to study the influence of the cellulose scaffold on the final CNT network and the resulting electrochemical detection of glucose. We found that an optimal porosity exists which balances the benefits of surface enhancement and electrical connectivity within the cellulose scaffold of the paper-based device and demonstrate a cost-effective process for fabrication of device arrays.

The three-dimensional imaging of mesoscopic samples with Optical Projection Tomography (OPT) has become a powerful tool for biomedical phenotyping studies. OPT uses visible light to visualize the 3D morphology of large transparent samples. To enable a wider application of OPT, we present OptiJ, a low-cost, fully open-source OPT system capable of imaging large transparent specimens up to 13 mm tall and 8 mm deep with 50 µm resolution. OptiJ is based on off-the-shelf, easy-to-assemble optical components and an ImageJ plugin library for OPT data reconstruction. The software includes novel correction routines for uneven illumination and sample jitter in addition to CPU/GPU accelerated reconstruction for large datasets. We demonstrate the use of OptiJ to image and reconstruct cleared lung lobes from adult mice. We provide a detailed set of instructions to set up and use the OptiJ framework. Our hardware and software design are modular and easy to implement, allowing for further open microscopy developments for imaging large organ samples.

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