Artificial Muscles (AMs) are often used as the actuation source for soft robots. AMs demonstrate great power-to-weight ratios, are generally compliant and therefore a safe mode of actuation in human-machine interfaces. Flat Pneumatic Artificial Muscles (FPAMs) are a subgroup of AMs and are designed to contract once pressurized. They are low-volume silicone bladders that An analysis of the current research on FPAMs provides knowledge about the benefits and improvements that can be made. The design of a novel FPAM is presented to reduce the normal expansion during actuation. The novelty that this paper brings includes: 1) a new production method with embedded mesh as the reinforcement of the silicone bladder 2) intricate zero-volume air chamber (ZAC) designs formed by dissolving 3D-printed Polyvinyl alcohol (PVA) masks 3) normal expansion measurements aimed to find the relation between internal pressure, air chamber design and normal expansion of the novel FPAM. Three different ZAC designs will be examined: a rectangular, a hexagonal and a diamond pattern. They are characterized with isometric contraction - and active force control tests at 60 kPa. During these tests the normal expansion of the FPAMs will be measured with a laser sensor. The rectangular ZAC design proved to outperform the other patterns by a wide margin. It produces 200\% more isometric force (13.3 N) and 400\% more contraction (7.7 mm / 9.7\%). However, the diamond ZAC showed a reduced normal expansion of 54 \%, thereby achieving the goal of reducing the normal expansion by redesigning the ZAC.