Mobility impairment is a major problem that affects the quality of life of numerous older adults. With impaired mobility, such individuals usually have significant difficulty in standing up from a seated position, and thus often suffer from the lack of physical activities in their daily life. To address this problem, the authors present a new assistive device, namely, Semi-Wearable Sit-to-Stand Assist Generation-2 (SW-SiStA2), in this paper. Similar to the original (first generation) SW-SiStA, this novel semiwearable device can be easily attached to the user to provide sit-to-stand assistance, and can also be easily detached after reaching the standing posture to facilitate the subsequent ambulation. The new SW-SiStA2 is powered with a remote-release gas spring, which serves the dual purpose of actuation and energy storage (i.e.,, storing the energy accumulated during compression and powering the sit-to-stand assistance through extension). The remote release feature enables a user to easily control the SW-SiStA2 assistance through the locking and unlocking of the gas spring. The SW-SiStA2 was experimentally tested with human participants. Under the device's assistance, the participants were able to stand up much more easily, with significant reduction (up to 28% compared with the unassisted condition) of the muscle efforts in the process.