  Recently, simultaneously transmitting and reflecting reconfigurable
intelligent surfaces (STAR-RISs) have emerged as a novel technology that
provides 360 coverage and new degrees-of-freedom (DoFs). They are also capable
of manipulating signal propagation and simultaneous wireless information and
power transfer (SWIPT). This paper introduces a novel STAR-RIS-aided secure
SWIPT system for downlink multiple input single output rate-splitting multiple
access (RSMA) networks. The transmitter concurrently communicates with the
information receivers (IRs) and sends energy to untrusted energy receivers
(UERs). The UERs are also capable of wiretapping the IR streams. We assume that
the channel state information (CSI) of the IRs is known at the information
transmitter, but only imperfect CSI for the UERs is available at the energy
transmitter. By exploiting RSMA, the base station splits the messages of the
IRs into common and private parts. The former is encoded into a common stream
that can be decoded by all IRs, while the private messages are individually
decoded by their respective IRs. We find the precoders and STAR-RIS
configuration that maximizes the achievable worst-case sum secrecy rate of the
IRs under a total transmit power constraint, a sum energy constraint for the
UERs, and subject to constraints on the transmission and reflection
coefficients. The formulated problem is non-convex and has intricately coupled
variables. To tackle this challenge, a suboptimal two-step iterative algorithm
based on the sequential parametric convex approximation method is proposed.
Simulations demonstrate that the RSMA-based algorithm implemented with a
STAR-RIS enhances both the rate of confidential information transmission and
the total spectral efficiency. Furthermore, our method surpasses the
performance of both orthogonal multiple access (OMA) and non-OMA (NOMA).
