Atomic Layer Deposition for Improving Surface Roughness of Microfluidic Injectors for XFEL and Synchrotron Sample Delivery*

Recent advances in additive manufacturing, such as two-photon polymerization (3D-2PP) and projection microstereolithography (PµSL) rely on a range of polymeric materials^1,2. However, it can be difficult to control the surface roughness and chemistry of the complex, micro-/nano-structured  devices. We use Atomic Layer Deposition (ALD), a technique compatible with many different substrates, to coat different polymers, exploring its potential to improve micro-device operation stability. The ALD process is integrated with particle-in-cell (PIC) and finite volume based (FVM) computational fluid dynamics (CFD) to determine the boundary layer thickness and optimal ALD parameters. This allows us to determine the coating properties on complex 3D structures, such as Gas Dynamic Virtual Nozzles (GDVN), used for sample delivery at X-ray free electron lasers (XFEL) and synchrotrons. The ALD coating can reduce the surface roughness, improve temperature resistance, and modify the surface chemistry. In combination with 3D-microprinting and CFD modeling, ALD offers a versatile approach to fabricate advanced, reliable microdevices for X-ray applications.

1: Trebbin et al., Lab Chip 2014, 14, 1733-1745

2: Nelson et al., Opt.Exp 2016, 11, 11515-11530