Wavemark Inc., a healthcare RFID tech firm in Littleton, has raised $3.9 million in an equity financing, according to a filing with the U.S. Securities and Exchange Commission.

In addition to its executive team, the regulatory filing included in its list of related persons board member Michael Finney, a private investor; board member Victoria Hamilton, the research initiatives coordinator at Columbia University; and board member Benson Shapiro, the Malcolm P. McNair Professor of Marketing Emeritus at Harvard Business School.

Joe Impellizeri, vice president of finance and administration, was not immediately available for comment, but the filing noted that the almost $4 million will be used for working capital. The company was founded in 2003 with funding intially from friends and family and more recently from professional private investors, according to an earlier report from Wavemark founder Patrick Littlefield.

Wavemark adds RFID technology to expensive medical devices to help medical facilities track the devices and ensure that the hospitals have enough, but not too many. As of April, Littlefield noted that customers include 50 hospital departments nationwide and growing, including Boston-based Tufts Medical Center and Worcester-based UMass Memorial Health Care. Customers buy the system on a subscription basis, and the costs generally range from $50,000 to $100,000 per year, per department.