2019
As said before , although relatively small or medium sized lattice structures can be obtained , one not only sacrifices the stiffness but also it may be more difficult to search for the original global optimal lightweight design solution .
 material: As; engineering feature: lattice structures; material: be; machanical property: stiffness; material: be; concept or principle: lightweight; engineering feature: design
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 material: As; engineering feature: lattice structures; material: be; machanical property: stiffness; material: be; concept or principle: lightweight; engineering feature: design