Abstract
The porosity of filters is typically fixed; thus, complex purification processes require application of multiple specialized filters. In contrast, smart filters with controllable and tunable properties enable dynamic separation in a single setup. Herein, an electroactive filter with controllable pore size is demonstrated. The electroactive filter is based on a metal mesh coated with a polythiophene polymer with ethylene glycol sidechains (p(g3T2)) that exhibit unprecedented voltage‐driven volume changes. By optimizing the polymer coating on the mesh, controllable porosity during electrochemical addressing is achieved. The pores reversibly open and close, with a dynamic range of more than 95%, corresponding to over 30 μm change of pores’ widths. Furthermore, the pores’ widths could be defined by applied potential with a 10 μm resolution. From among hundreds of pores from different samples, about 90% of the pores could be closed completely, while only less than 1% are inactive. Finally, the electroactive filter is used to control the flow of a dye, highlighting the potential for flow control and smart filtration applications.
Highlights
We demonstrated an electroactive filter with tunable porosity in the micrometer range
By optimizing the polymer coating, we achieved a dynamic range between 0 and 32 μm on the pores’ width, demonstrating the first tunable mesh in the micrometer scale. 87% of the pores could be closed completely, while less than 1% of the pores were inactive
The p(g3T2)-based filters have high control on the closed state, while the open state requires further optimization as there is variability on the pores width (79% between 25 and 50 μm), which is a result of irreversible volume change and the increase in the absolute polymer volume during electrochemical cycling
Summary
To fabricate the electroactive filter, metal meshes with squareshaped pores of 73.7 Â 73.7 (Æ2.7) μm were coated with p(g3T2) (see Figure 1a). P(g3T2), as other CPs, exhibits an irreversible volume change during the first cycle that is a result of molecular rearrangements and water retention during electrochemical switching.[10] As the volume change magnitude depends on the initial polymer volume, from one side, we can achieve larger volume change, but on the other side, we observed larger irreversibility for meshes coated with 15 and 20 mg mLÀ1. P(g3T2)’s absolute volume and irreversible change increase over cycling, resulting in smaller pore widths both in the closed and in the open state.[22]. A mesh coated with a polymer concentration of 15 mg mLÀ1 was switched between open and closed states for 20 cycles (Figure S8, Supporting Information). The polymer volume after drying decreased and became comparable with the pristine state (Figure S9, Supporting Information), demonstrating that the volume change during electrochemical addressing is mostly due to retention of water. The experiment was repeated for three electroactive filters, all showing consistent results, not just in terms of general flow control and in terms of the kinetics of the release and flow control (Figure S10, Supporting Information)
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