Developments of flexible detection arrays suggest that portable robust detectors are indeed possible. A large area flexible array promises a large capture cross section in a light weight rugged format suitable for deployment at ports of entry. The approach for this detector uses a high neutron-capture cross-section layer, such as 10B, which captures incident thermal neutrons, and emits energetic ionizing charged particles. These ionizing particles are sensed using an integrated diode. The resulting charge is then amplified via a low-noise thin film transistor amplifier. We present a low-noise optimized active pixel sensor (APS) design which can be implemented in either a low temperature InGaZnO or an a-Si:H thin film transistor (TFT) process compatible with plastic substrates. Here, we also present a detectable alpha particle response with our dual stage APS design in combination with an externally connected commercial PIN diode. Furthermore, we discuss detector and array modeling which will further aid in future designs.