Mattress-based sweat sensing systems can provide nonintrusive, continuous health monitoring. Commercialization of physical sensors in beds has already been achieved, while chemical sensing within the same platform is still in its infancy. We describe our approach towards the development of flexible potentiometric sensors and demonstrate low-temperature fabrication of these devices. Three commonly used mattress fabrics have been contrasted as sweat capture layers, leading to pH sensing with a sensor embedded within the hydrophilic fabric. It is found that noise, sensitivity and linearity can be affected by the rate of liquid flow, temperature of the Al2O3 deposition and stability of the thin film Ag/AgCl reference electrode realized on-chip.