A nanophotonic trapping platform based on on-chip tunable optical interference allows parallel processing of biomolecules and holds promise to make single molecule manipulation and precision measurements more easily and broadly available. The nanophotonic standing wave array trap (nSWAT) device [Nat. Nanotechnol. 9, 448 (2014); Nano Lett. 16, 6661 (2016)] represents such a platform and can trap a large array of beads by the evanescent field of the standing wave of a nanophotonic waveguide and reposition them using an integrated microheater. In this paper, by taking a systematic design approach, we present a new generation of nSWAT devices with significant enhancement of the optical trapping force, stiffness, and stability, while the quality of the standing wave trap is resistant to fabrication imperfections. The device is implemented on a silicon nitride photonic platform and operates at 1064 nm wavelength which permits low optical absorption by the aqueous solution. Such performance improvements open a broader range of applications based on these on-chip optical traps. © 2017 Optical Society of America.