Sign-changing solutions for the sinh-Poisson equation with Robin Boundary condition

Given $\epsilon \in (0,1)$ and $\lambda > 1$, we address the existence of solutions for the Sinh-Poisson equation with Robin boundary value condition $$\begin{cases} \Delta u+\epsilon^2 (e^{u} - e^{-u})=0 &\mbox{in }\Omega\\ \frac{\partial u}{\partial\nu}+\lambda u=0 &\mbox{on }\partial\Omega, \end{cases}$$ where $\Omega\subset\mathbb{R}^2$ is a bounded smooth domain. We prove two existence results under a suitable relation between $\epsilon$ small and $\lambda$ large. When $\Omega$ is symmetric with respect to an axis, we prove the existence of a family of solutions $u_{\epsilon,\lambda}$ concentrating at two points with different spin, both located on the symmetry line and close to the boundary. In the second result, we assume $\Omega$ is not simply connected and we construct sign-changing solutions concentrating at points located close to the boundary, each of them on a different connected component of the boundary.