Description
Functionally graded materials offer a powerful conceptual framework for designing compositionally graded mechanical responses from a single material. Such a material will enable the tailoring and tuning of physico-mechanical properties across the structure. However, the existing manufacturing techniques for developing functionally graded polymer foams face challenges in integrating the compositional control and monodispersity with architectural precision. This work introduces a protocol for the digital manufacturing of functionally graded polymer foams using a scalable manufacturing method. We introduce a Microfluidics-based 3D printing platform to produce high internal phase emulsions (HIPEs) that can be photo-crosslinked via emulsion templating. Two monomer foams with distinct mechanical responses were selected and dynamically mixed using a micro-mixer coupled to a microfluidic chip. A hydrophobic, shear-thinning support bath solution was optimized to ensure rheological compatibility and structural stability with the HIPEs. Depending on the defined geometry, different flow profiles were generated to 3D print HIPEs in the bath solution with a composition gradient and a fixed porosity of 85%. The printed foams were photo-cured, and the excess bath solution was washed off. Mechanical properties of the foams were evaluated, and a programmable mechanical response of Young's modulus (0.02- 10 MPa) and energy absorption capacities of up to 0.15 J/Cm3 was obtained. This work establishes microfluidics-assisted 3D printing as a stable, scalable platform for the programmable fabrication of functionally graded polymer foams and thereby broadens the scope of producing mechanically heterogeneous materials.