4D-Printed Temperature-Controlled Flow-Actuated Solid-Phase Extraction Devices.

Four-dimensional printing (4DP) technologies can extend the functionality and applicability of manufactured analytical devices through employing stimuli-responsive materials. In this study, we used a photocurable resin of stimuli-responsive shape-memory polymers and digital light processing three-dimensional printing (3DP) to fabricate a smart sample pretreatment device featuring a solid-phase extraction (SPE) column and a temperature-controlled flow-actuated valve. Through manipulation of the temperatures and flow rates of the sample, eluent, and rinsing streams, we used this 4D-printed SPE device to extract Mn, Co, Ni, Cu, Zn, Cd, and Pb ions from high-salt content samples and remove the sample matrix prior to their determination by inductively coupled plasma mass spectrometry. After optimizing the valve design and operation and the analytical scheme, this device displayed competitive analytical performance-the method detection limits (MDLs) ranged from 0.7 to 22.1 ng L-1 for these metal ions (the MDLs ranged from 0.5 to 18.8 ng L-1 when validating the same printed SPE column using an online automatic system equipped with electric switching valves). Furthermore, we performed analyses of these metal ions in three reference materials (CASS-4, 1643f, and 2670a) and spike analyses of collected samples (seawater, ground water, river water, and human urine) to confirm the reliability and applicability of this analytical method. For the first time, 4DP has been used to fabricate a multi-functional, stimuli-responsive sample pretreatment device displaying analytical performance equal to that of a commercial apparatus. This novel approach builds upon the functionality and diversity of 3DP-enabling devices with the goal of developing more efficient analytical schemes.