Fabrication of high-aspect-ratio neutron absorption gratings by microfluidic particle filling method based on all-aqueous process

The quality of neutron gratings critically determines the performance of neutron grating interferometers. However, conventional gadolinium-particle filling methods face significant challenges in the fabrication of small-period, high-aspect-ratio neutron absorption gratings. This study proposes a microfluidic particle filling method based on an all-aqueous process for the fabrication of high-aspect-ratio neutron absorption gratings. Liquid-phase pressurization combined with the all-aqueous process effectively addresses particle transport obstruction within high-aspect-ratio grating trenches, thus enhancing the particle filling ratio. The adaptive particle filling mechanism adaptively redistributes the flow rate of particle suspension in response to flow impedance differences caused by variations in geometric parameters and filling conditions in microchannels. This process progressively minimizes impedance differences, enabling uniform particle filling. The effects of pressure, particle suspension flow velocity, and concentration on particle filling were investigated, and the particle filling ratio and uniformity were evaluated using X-ray absorption imaging. Neutron absorption gratings with a period of 4 μm were successfully fabricated, demonstrating the applicability of this method to small-period, high-aspect-ratio gratings. This work offers a novel and effective strategy to address the challenges associated with fabricating neutron absorption gratings with small periods and high aspect ratios.