Thermo Fisher Scientific Inc. of Waltham on Monday opened a 156,000-square-foot manufacturing plant in Tewksbury where it will make portable and handheld instruments, including devices used in pharmaceuticals, consumer products, and law enforcement.

Roughly 400 people work at the facility, which Thermo Fisher calls its Center of Excellence, and the company said it expects to add another 100 employees over the next five years.

“This new Center of Excellence creates a strong base for our continued growth,” Marc N. Casper, Thermo Fisher’s chief executive, said in a statement. “Our $20 million investment in this world-class facility reaffirms our commitment to Massachusetts and a growing economy that is fueled by new scientific discoveries.”

Governor Deval Patrick, who attended the facility’s ribbon cutting on Monday, said his administration will continue to work with Thermo Fisher to expand the company’s local presence. The company currently has more than 1,400 employees in the state.

“Massachusetts leads the world in life sciences thanks to our growth strategy of investing in education, innovation and infrastructure,” Patrick said.