3D-Printed Autonomous Capillaric Circuits^†

Abstract

Capillaric circuits (CCs) are advanced capillary microfluidic devices that move liquids in complex pre-programmed sequences without external pumps and valves -relying instead on microfluidic control elements powered by capillary forces. CCs were thought to require high-precision micro-scale features manufactured by photolithography in a cleanroom, which is slow and expensive. Here we present rapidly and inexpensively 3D-printed autonomous CCs. Molds for CCs were fabricated with a benchtop 3D-printer, Poly(dimethylsiloxane) replicas were made, and fluidic functionality was verified with aqueous solutions. We established design rules for 3D-printed CCs by a combination of modelling and experimentation. The functionality and reliability of 3D-printed trigger valves -an essential fluidic element that stops one liquid until flow is triggered by a second liquid -was tested for different geometries and different solutions. Trigger valves with geometries up to 80-fold larger than cleanroom-fabricated ones were found to function reliably. We designed 3D-printed retention burst valves that encode sequential liquid drainage and delivery using capillary pressure differences encoded by varying valve height and width. Using an electrical circuit analogue of the CC, we established circuit design rules for ensuring strictly sequential liquid delivery. We realized a 3D-printed CC with reservoir volumes 60 times larger than cleanroom-fabricated circuits and autonomously delivered eight liquids in a pre-determined sequence in < 7 min, exceeding the number of sequentially-encoded, self-regulated fluidic delivery events previously reported. Taken together, our results demonstrate that 3D-printing enables rapid prototyping of reliable CCs with improved functionality and potential applications in diagnostics, research and education.

Tubing-Free Microfluidic Microtissue Culture System Featuring Gradual, in vivo-Like Substance Exposure Profiles

“…We could produce a concentration profile that features the characteristics of a typical plasma concentration over time upon oral administration of a substance (Kwon, 2001), as we have demonstrated by using amaranth red dye as drug-surrogate (Figure 7). A sequence of precisely timed medium exchanges, or the implementation of capillary stop valves that burst when sufficient pressure is built up at high tilting angles (Olanrewaju et al, 2016, 2018) can be used over longer culturing periods to reproduce long-term substance fluctuations, e.g., repeated drug dosing or circadian hormone profiles. Alternating filling of the reservoir connected to the narrow channel with hormone-containing and plain medium could be used to gradually increase and decrease hormone concentrations in the MT compartments.…”

Micro/nanofabrication of brittle hydrogels using 3D printed soft ultrafine fiber molds for damage-free demolding

“…As a result, surface treatment must be conducted to acquire a wettable surface in advance. [56] Whereas the hydrogel-based chips do not have this problem, the hydrophilicity of hydrogels is relatively good and the contact angle of GelMA used here is below 30° (Figure 7A). Along with the superfine channels, hydrogel-based chips can provide sufficient capillary pressure for autonomous liquid delivery.…”