AMP_06_September_2021

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 1 3 0 SUSTAINABILITY Due to the robustness of the foams, they can be easily cleaned, e.g., by rinsing MASK INNOVATION AWARD WINNER A recent entry to the U.S. BARDA-NIOSH Mask Innova- tion Challenge by members of this Georgetown team, based on the nanoporous foams, was selected as one of the 10 Phase 1 Winners, out of over 1400 designs submitted nationally [15] . Us- ing their innovative, reusable nanoporous metal foams as an ac- tive filter media that are as light as a feather, the Georgetown smart mask is designed to provide efficient filtration of partic- ulate matter. TABLE 1 — SUMMARY OF 2ED-Cu FOAM SPECIFICATIONS AND MASS-BASED FILTRATION EFFICIENCIES* Foam density, % Thickness, mm Particle size, μm Pressure drop coefficient, mmH 2 O ⋅ s/cm Mass capture efficiency E m , % 5 0.8 0.1-0.4 0.59 ± 0.03 85.5 ± 3.1 9 1.0 0.1-0.4 0.74 ± 0.03 82.5 ± 0.5 15 1.0 0.8-1.6 0.99 ± 0.11 99.4 ± 0.1 15 1.0 0.5-0.8 0.99 ± 0.11 96.1 ± 0.1 15 1.0 0.1-0.4 0.99 ± 0.11 78.3 ± 1.3 15 2.5 0.1-0.4 2.81 ± 0.21 97.0 ± 2.1 30 2.0 0.2-0.4 4.77 ± 0.24 54.2 ± 0.5 *Adapted with permission from Malloy et al. [4] . Fig. 4 — Comparison of quality factor Q 0.3 for the synthesized 2ED-Cu foams and other types of filters, adapted with permission fromMalloy et al. [4] . Lightweight copper foam sample sits on the bristles of a plant. in water or sonication. The foams are also resistant to oils and various other polymer deteriorating chemicals, and can survive high temperatures and large pressures without breaking or deform- ing. These features enable convenient decontamination and reuse, significant- ly prolonging their useful lifetime. At the eventual end of their use, the foams can be easily reclaimed and recycled. OUTLOOK These metal foams are “smart” because they can accommodate multi- ple filtration mechanisms. For example, copper has antimicrobial properties that help kill trapped bacteria and vi- ruses. It is also a known catalyst to trig- ger chemical reactions to break down toxic gases such as CO [14] . Electrostatics may be integrated into the foams to fur- ther enhance the filtration efficiency. The foams are economically via- ble. The materials cost of the foams is estimated to be around $2 for a full-size mask, and a fraction of that for smaller cartridges. These costs will be substan- tially reduced if the foams are produced on industrial scales. Furthermore, the foams can be readily integrated with other mask designs, either as the filtra- tion media themselves, or as inserts or cartridges into other masks. They may also find applications in household and vehicle air cleaners. Acknowledgments This work was initiated by a gener- ous gift from the Tom and Ginny Cahill Fund for Environmental Physics at U.C. Davis. Work at Georgetown University was supported by the Georgetown En- vironment Initiative - Impact Program Award and the McDevitt bequest. This article is adapted from Nano Lett., Vol 21, p 2968-2974, 202 1, https:// pubs.acs.org/doi/10.1021/acs .nanolett. 1c00050. ~AM&P