We study pore nucleation in a model membrane system, a freestanding polymer film. Nucleated pores smaller than a critical size close, while pores larger than the critical size grow. Holes of varying size were purposefully prepared in liquid polymer films, and their evolution in time was monitored using optical and atomic force microscopy to extract a critical radius. The critical radius scales linearly with film thickness for a homopolymer film. The results agree with a simple model which takes into account the energy cost due to surface area at the edge of the pore. The energy cost at the edge of the pore is experimentally varied by using a lamellar-forming diblock copolymer membrane. The underlying molecular architecture causes increased frustration at the pore edge resulting in an enhanced cost of pore formation.Nucleation and growth occurs in a variety of physical systems where there is a phase transition. Crystallization of ice, the formation of micelles in solution, and the growth of diamonds from vitreous carbon are all systems where a nucleus can form and then either grow or shrink depending on its size [1]. In crystallization, for example, there is a trade-off between the volumetric free energy contribution which favors the crystalline phase, and the surface area dependent cost of the interfacial tension between the two phases which favors a single liquid phase [2]. By examining the free energy cost of creating a nucleated phase with radius r, the critical radius r c can be derived from classical nucleation theory. For a nucleus with r < r c , the nucleated phase is unstable to fluctuations, while for r > r c the nucleated phase is energetically favorable and the nucleus can grow. The same physics governs diverse phenomena including bubble nucleation of false vacuum states in inflationary cosmology [3], as well as many biologically important processes such as amyloid-beta protein aggregation [4,5], microtubule growth [6], and pore formation in cell membranes [7]. Membrane pores can be created by pathogenic bacteria to invade target cells [8], and play an important role in many biological processes such as mechanical force transduction [9] and water permeability of biological membranes [10]. In this letter we focus on pore formation in a membrane.For the nucleation of a pore in a membrane, there is a balance between two competing effects. First, there is an energy cost of having an interface between the membrane and its surrounding phase. Because the presence of a pore removes interface, this reduces the interfacial energy cost. Opposing this effect is the energetic cost of creating an edge around the perimeter of the pore. The stability and growth of pores depends on the relative contribution of interface reduction compared to the edge cost. The free energy cost of creating a pore in a membrane which has two surfaces with interfacial tension γ is given by [11] ∆G(r) = 2πrΓ − 2πr 2 γ,where Γ is the edge tension (or line tension) of the pore: the free energy cost per unit length of creating interface at t...

We study the dewetting of liquid films capped by a thin elastomeric layer. When the tension in the elastomer is isotropic, circular holes grow at a rate which decreases with increasing tension. The morphology of holes and rim stability can be controlled by changing the boundary conditions and tension in the capping film. When the capping film is prepared with a biaxial tension, holes form with a non-circular shape elongated along the high tension axis. With suitable choice of elastic boundary conditions, samples can even be designed such that square holes appear.

Isoprene is a reactive volatile organic compound (VOC) emitted by terrestrial vegetation, possibly contributing to abiotic stress tolerance (Monson et al., 2021). Annual isoprene emissions exceed all other non-methane VOCs,

Isoprene is a reactive volatile organic compound (VOC) emitted by terrestrial vegetation, possibly contributing to abiotic stress tolerance (Monson et al., 2021). Annual isoprene emissions exceed all other non-methane VOCs,

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