Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

3D printing of cementitious materials with superabsorbent polymers: a durable solution?

Nowadays, 3D printing of cementitious materials is a hot research topic in the construction industry. This construction method is capable of producing complex geometries and largescale components without the use of expensive formwork. However, due to the lack of molding, more shrinkage will be induced and the amount of cracks will increase. As this phenomenon introduces ingress paths for chemical substances, it will affect the durability of the printed element in a negative way. One potential way to tackle this disadvantage is to include superabsorbent polymers (SAPs) in the cementitious material. As these polymers are able to absorb part of the mixing water and to release it during hardening, they induce internal curing and can mitigate self-desiccation and autogenous shrinkage. Another positive effect of using SAPs is the increased moisture content of the printed surface, enhancing the bond between two subsequent layers. For the aim of this research, two different SAPs were used to fabricate printed elements and the microstructural changes are correlated with their influence on durability and sustainability. First results showed that in general, the addition of superabsorbent polymers decreases the shrinkage in printed materials. They also reduce the nanoporosity in the range of 100 nm to 500 nm and increase the amount of voids with a diameter above 700 nm, resulting in less microcracks and a decreased amount of preferential ingress paths for chemical substances. On the other hand, the total air content increases with the addition of SAPs, proportional to the amount of SAPs added

Effect of laparoscopic grasper force transmission ratio on grasp control

Background- Surgeons may cause tissue damage by incorrect laparoscopic pinch force control. Unpredictable tissue and grasper properties may cause slips or ruptures. This study investigated how different forms of haptic feedback influence the surgeon’s ability to generate a safe laparoscopic grasp while pulling tissues of variable stiffness using graspers with different force transmission ratios. The results will help define design requirements for training facilities and instruments. Methods- For this study, 10 participants lifted an object barehanded, with tweezers, or with one of two laparoscopic graspers until they where able to complete five consecutive safe lifts under different tissue stiffness conditions. The participants were presented with indirect visual feedback of pinch force, object location, and target location. Results- Lifting with instruments (tweezers or graspers) required 4.5 to 14.5 times as many practice trials as barehanded lifting, where no slips were recorded. Additionally, slips occurred more often with a decreasing force transmission ratio of the graspers and with increasing tissue stiffness. The maximal pinch force was higher in lifting with instruments than in barehanded lifting (26–60%) irrespective of the stiffness conditions. Using a grasper, the slip margin often was not high enough in the stiffest condition, resulting in slippage of up to 84%. Conclusions- Without the direct tactile feedback that occurs with normal skin–tissue contact, subjects using graspers have trouble anticipating slippage when lifting tissue with variable stiffness. Performance drops with a decreased force transmision ratio of the instrument and increased tissue stiffness. Furthermore, the pinch forces are not adapted to the variable stiffness conditions. The same pinch force is applied irrespective of tissue stiffness. It takes participants longer to learn a safe laparoscopic grasp than to learn barehanded lifts. Additionally, to perform safe laparoscopic surgery, care should be taken when graspers with a low force transmission ratio are used.Industrial DesignIndustrial Design Engineerin