The present application relates to a hand-held injection device for soft tissue comprising internal components which allows for mixing of materials prior to injection； a cartridge suitable for containing a first injectable material and couplable to a needle； a shell structured to contain the cartridge； a plunger which can be driven through the cartridge； a power source for activating one of the internal components； and a user-programmable controller coupled to the drive mechanism, where a user-defined injection rate can be set； a vial for a second material attached to a pump； the pump being configured to direct the second material through a one way valve into the cartridge for mixing the first material and the second material in the cartridge； a plunger configured to be driven through the cartridge to force the first material mixed with the second material out of the needle.
