A non-invasive, cuff-less, capable of continuous detection and low cost blood pressure sensor is proposed in this study. The proposed blood pressure sensor has a specially-designed strain sensor attached to a flexible plate and encapsulated by a gel module. The sensor is able to detect pulse signals of the artery vibration under the skin of a human wrist by a simple, flexible attachment pad. The strain sensor is expected to vibrate in a synchronized fashion with artery pulsation. The pulse vibration is expected to be transmitted to the strain sensor through the gel module. This module is made of highly bio-compatible materials like polyethylene (PE), polyurethane (PU), polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), or polymethylmethacrylate (PMMA). The gel module supports the strain sensor to a stability condition with top surface contacting tightly with the human skin while the bottom surface is under a low pressure exerted by a pressurizing wrist belt.