Metal Infiltration into Biomaterials by ALD and CVD: A Comparative Study

Abstract

Atomic layer deposition (ALD) is a subset of chemical vapor deposition (CVD) and both use very similar chemistry. Recently, it has been reported that ALD has the potential to realize a new design paradigm of bioinorganic materials through metal infiltration, which in nature has been employed as a hardening strategy for many tissues in diverse biological organisms. Herein, using a spider dragline silk and a collagen membrane as targets, we have performed a comparative study to elucidate the difference of the metal infiltration effect by ALD and CVD. From the comparison of mechanical properties, concentration of the infiltrated metal, and structural changes induced by the infiltrated metal, it has been proven that the metal can effectively infiltrate biomaterials by ALD and the infiltrated metal leads to highly improved mechanical properties accompanied by substantial changes in the protein structures, whereas CVD is less effective.

Progress and future directions for atomic layer deposition and ALD-based chemistry

“…45 Many vapor infi ltration reaction schemes are possible and can produce a new class of "vaporsource" hybrids, with unique chemical structure, controlled physical response, and wide-ranging functional capability. These materials and processes have signifi cant potential for continued exploration.…”

Systematic study of trimethyl aluminum infiltration in polyethylene terephthalate and its effect on the mechanical properties of polyethylene terephthalate fibers

“…[9][10][11][12] The formation of a hybrid organic-inorganic coating is predominantly observed in polymers with carbonyl groups, such as polyamides and polyesters. 18,19 The key to infiltration of precursors by these techniques is to increase the exposure conditions using either hold steps or longer precursor doses. 14 Further studies have revealed that precursors can infiltrate the bulk of fiber forming polymers resulting in a hybrid modification that templates the porous internal structure of the polymer fiber.…”

Hybrid nanomaterials through molecular and atomic layer deposition: Top down, bottom up, and in-between approaches to new materials

“…The initial work describing the infiltration mechanism as possible means to alter materials showed significant changes in mechanical properties of spider silk 37,55 , as seen in Figure 16. The chemical interaction of precursors with substrates was further shown with chemically simpler and better defined substrates, namely the so-called J-aggregates that are self-assembled fibers consisting of porphyrin rings 161 .…”

“…(B) The alternating exposure (E) and purge steps (P) create a nearly step-wise-like pressure profile as a function of time, which, when compared to a CVD process (C) that has a nearly constant pressure profile. Reproduced with permission, Wiley-VCH [37]. The insulator is polypropylene with the complete structure shown in c).…”

“…ALD and MLD, focused on their combination for synthesizing hybrid materials. ALD can be considered a similar, though chemically distinct, case of chemical vapor deposition (CVD), where the reaction is separated into two self-limiting halfreactions, an illustration of which can be found in Figure 1 37 . Between each halfreaction is an essential purge step, step 3 and 6 in Figure 1, that prevents any parasitic gas phase reactions (i.e.…”