ORONO, Maine — Jack Lander, 10, built a structure out of marshmallows and dried spaghetti that reached 35 inches tall and was set to win a prize at Saturday’s 2012 Engineering EXPO when his sister, 12-year-old Meg, started to build.

“She saw his and said, ‘That’s not happening,’” the rival siblings’ mother, Beth Lander, said while watching youngsters from all over the region at the University of Maine’s field house constructing towers from the edible building materials. “There was war going on.”

“My sister got 39 inches,” Jack Lander said, sucking on a lollipop and watching the other young construction engineers at work.

“It doesn’t matter that she won — she beat her brother,” the youngsters’ mother said.

The Orrington family has been attending the annual engineering expo for years because there is no better way to open a child’s mind, Beth Lander said.

“This is the best way to learn — hands on,” she said. “It makes sense. I think it makes things suddenly click. And it’s fun.”

The expo is organized by the Maine Engineering Promotional Council and has more than a dozen sponsors, including Time Warner Cable, General Dynamics, the University of Southern Maine and UMaine’s College of Engineering.

In addition to the activities at the field house, attendees also could tour the Advanced Structures and Composites facility where offshore wind turbines are being developed and the Process Development Center where UMaine researchers are working with gold nanoparticles and model cellular membranes.

A lunar habitat tour also was set up so folks of all ages could explore the inside of a lunar module.

“It’s stuff like this that opens kids’ minds,” Stacy White, of Franklin, said as her 6-year-old son, Colton, finished making yellow slime from a mixture of several simple household ingredients.

She and her husband, Eric, brought their son to the engineering expo because, she said, “He loves to take things apart and put them back together.”

Caitlin Peary, 11, a student at Bangor Christian School, made slime that matched her sweater perfectly and also earned 15 points of extra credit in science by attending the expo.

The slime is made from Elmer’s glue, water, food coloring and borax, a laundry and cleaning agent that has been used in homes for more than a century, explained UMaine junior bioengineering student Jeffrey King, of Portland.

“The borax causes cross-links between the glue and it forms a polymer,” he said. “Polymers can be used in things like plastic. Another application is skin graphs for burns patients.”

The slime is “simple science that gets them thinking about what can be done with the technology,” King said of the younger students in attendance.

This week marks Maine Engineers Week, and is a time to celebrate how engineers make life easier, Victoria Blanchette, Maine Engineering Promotional Council executive director and spokeswoman for UMaine’s College of Engineering, said in a statement.

The expo was filled with Maine’s top engineering firms, engineering schools, educators, government agencies and engineering societies who provided hands-on activities and exhibits to encourage youngsters in Maine to pursue careers in engineering. The expo showed young people “all the exciting places that their math and science skills can take them,” Blanchette said.

Philip Dunn, UMaine construction management technology faculty member, said his and other engineering departments are looking for more woman to learn the trade.

“We don’t have a high percentage of women in our program but the ones we have are being successful,” he said.

Dunn used the marshmallow and spaghetti building as an example as to the difference between how boys and girls approach a project. Most boys building the structures typically start fast and keep adding on layers of marshmallows and spaghetti until it falls, he said.

“I feel the girls are more intent” and “they are more methodical with how they do things,” Dunn said. “We need more women in engineering.”

Meg Lander — one winner of the hourly marshmallow and spaghetti building contest — said she plans to go into engineering as an architect.