The phrase 'serving as a substitute' is correct and commonly used in written English.
It is usually used to indicate that something is being used to fill the role or take the place of something else. For example, "John, who was serving as a substitute teacher, was popular with all the students."
The device follows the same principle, with an arrangement of three microphones serving as a substitute for the ears.
One could say that there's nothing at stake in this play except the future of humanity; when it comes to actual human beings, Shaw here is perhaps too clever by half, the extra half-portion of cleverness serving as a substitute for emotional depth.
School of Rock starred Jack Black as a failed rock musician who rekindles his love for music while serving as a substitute teacher at a primary school, forming a band with his students and taking them to a battle of the bands competition.
But anthrax may be serving as a substitute for larger anxieties stirred up by the first terrorist attacks, he said, adding, "And it's safe to say that it's only a matter of time that we're going to stop talking about anthrax as well".
The main goal is to predict the best refrigerant capable of serving as a substitute for R22.
Our data suggests that DNA extraction by pressure was capable of serving as a substitute for the centrifuge method, and the compact and automatic nature of the pressure system device provided rapid and valuable information for clinical practice.
The première would serve as a substitute for a traditional runway show.
The development aid that served as a substitute for compensation is now drying up.
Lower fishing quotas cannot serve as a substitute for habitat protection, he said.
There are sacrifices, however, in which the victim does serve as a substitute for the guilty.
On Nov. 24, 2000 Marianne Marshall, a Nassau County commissioner, served as a substitute board member in place of David Howard.
