In an aspect, the present disclosure discloses a medical sensor to be connected to a monitoring device for vital sign monitoring. The medical sensor includes a flexible circuit layer having an electrode pattern, a foam layer laminated on the flexible circuit layer, a bonding layer sandwiched between the flexible circuit layer and the foam layer to bond the foam layer with the flexible circuit layer, and a gel sponge disposed on and electrically connected to the electrode pattern through the foam layer and the bonding layer. The area of the bonding layer is smaller than the area of the foam layer. A part of the foam layer adjacent the perimeter is not covered by the bonding layer, and not bonded to the flexible circuit layer by the bonding layer to provide the medical sensor enough conformability to a body.
