Optical gratings fabricated using the capillary-assisted self-assembly of nanoparticles on a flexible substrate.

We demonstrate a cost-effective and high-throughput fabrication technique to deposit colloidal nanoparticles on a patterned polymer substrate using a capillary-assisted self-assembly method over a large area. In particular, we fabricate optical gratings using gold nanoparticles and a polymer substrate. We show the versatility of the technique over different nanoparticle diameters and grating periodicities. Through both experiments and simulations, we show enhanced transmission in the first-order diffraction of the gold-polymer grating as compared to the air-polymer grating. Our fabrication technique also enables the transfer of the nanoparticle pattern from the polymer substrate to any desired surface. Here we demonstrate the transfer of the nanoparticle grating structure to the tip of optical fibers.

Volunteer geographic information in the Global South: barriers to local implementation of mapping projects across Africa.

The world is awash in data-by 2020 it is expected that there will be approximately 40 trillion gigabytes of data in existence, with that number doubling every 2 to 3 years. However, data production is not equal in all places-the global data landscape remains heavily concentrated on English-speaking, urban, and relatively affluent locations within the Global North. This inequality can contribute to new forms of digital and data colonialism. One partial solution to these issues may come in the form of crowdsourcing and volunteer geographic information (VGI), which allow Global South populations to produce their own data. Despite initial optimism about these approaches, many challenges and research gaps remain in understanding the opportunities and barriers that organizations endemic to the Global South face in carrying out their own sustainable crowdsourcing projects. What opportunities and barriers do these endemic organizations face when trying to carry out mapping projects driven by their own goals and desires? This paper contributes answers to this question by examining a VGI project that is currently mapping public libraries across the African continent. Our findings highlight how dramatically digital divides can bias crowdsourcing results; the importance of local cultural views in influencing participation in crowdsourcing; and the continued importance of traditional, authoritative organizations for crowdsourcing. These findings offer important lessons for researchers and organizations attempting to develop their own VGI projects in the Global South.