Highly penetrant organic solvent-resistant layer-by-layer assembled ultra-thin barrier coating for confined microchannel devices

Recently, there has been an increasing demand for developing high performance barrier films for effectively suppressing the penetration of organic solvent. Particularly, in microfluidic systems for lab-on-a-chip devices or inkjet printing, the predominantly faced challenges are swelling deformation and channel blockage by the penetrated solvents, which significantly deteriorates the device performance and lifetime. To address this issue, here we present a robust method for the deposition of barrier layers inside microchannels using a surface chargeregulated layer-by-layer assembly of polyelectrolyte multilayers (PEM). Owing to the highly negative surface charge and additionally employed crosslinking reaction using glutaraldehyde (GA), the Donnan repulsion at the barrier film surface and size-narrowing effect in internal pores can be simultaneously intensified, which rendered excellent barrier performance against highly penetrating organic solvents only with a 14-nm-thick coating layer. Further, we employed a wrinkling-based metrology for precisely evaluating the barrier property of the multilayered films. As a result, highly negatively charged PEM surface (-64.2 mV) with small inner pores (<0.5 nm) resulted in excellent barrier performance to the penetration of various conventional organic solvents used for microelectronic processing. Finally, the practical applicability of the PEM barrier films coated in complexly structured microchannels was demonstrated by fully securing the devices intact even under continuous exposure to organic solvent flowing for 4 h. As such, this study provides a general guideline for the internal deposition of barrier films regardless of the form factor of target surfaces toward next generation organic and wearable electronic devices, along with microfluidic chemical reactor systems.