A future for digital public goods for monitoring SDG indicators.

Digital public goods (DPGs), if implemented with effective policies, can facilitate the realization of the United Nations Sustainable Development Goals (SDGs). However, there are ongoing deliberations on how to define DPGs and assure that society can extract the maximum benefit from the growing number of digital resources. The International Research Center of Big Data for Sustainable Development Goals (CBAS) sees DPGs as an important mechanism to facilitate information-driven policy and decision-making processes for the SDGs. This article presents the results of a CBAS survey of 51 respondents from around the world spanning multiple scientific fields, who shared their expert opinions on DPGs and their thoughts about challenges related to their practical implementation in supporting the SDGs. Based on the survey results, the paper presents core principles in a proposed strategy, including establishment of international standards, adherence to open science and open data principles, and scalability in monitoring SDG indicators. A community-driven strategy to develop DPGs is proposed to accelerate DPG production in service of the SDGs while adhering to the core principles identified in the survey.

Untethered unidirectionally crawling gels driven by asymmetry in contact forces.

Reversible thermoresponsive hydrogels, which swell and shrink (deswell) in the temperature range of 30° to 60°C, provide an attractive material class for operating untethered soft robots in human physiological and ambient conditions. Crawling has been demonstrated previously with thermoresponsive hydrogels but required patterned or constrained gels or substrates to break symmetry for unidirectional motion. Here, we demonstrate a locomotion mechanism for unidirectionally crawling gels driven by spontaneous asymmetries in contact forces during swelling and deswelling of segmented active thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) and passive polyacrylamide (pAAM) bilayers with suspended linkers. Actuation studies demonstrate the consistent unidirectional movement of these gel crawlers across multiple thermal cycles on flat, unpatterned substrates. We explain the mechanism using finite element simulations and by varying experimental parameters such as the linker stiffness and the number of bilayer segments. We elucidate design criteria and validate experiments using image analysis and finite element models. We anticipate that this mechanism could potentially be applied to other shape-changing locomotors.