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Penta-twinned nanowires, made of silver, gold, or copper, are envisioned to enable many applications, most notably stretchable and flexible electronics. In several instances of analysis of their behavior for device design, such as heat transfer due to current-induced heating, adhesion to substrates, or adhesion of nanowires to each other in conductive networks, knowledge of variables related to the mechanics of their contact is needed, for example the contact area (or radius). Due to the nanowires’ change in cross section, from circular to rounded- pentagonal as diameter increases, adhesive contact analysis is complex, and up to now has been simplified to assume either circular or perfect pentagonal cross sections. Here, we analyze the adhesive contact of the nanowires, fully considering the complexity of the cross section. We present equations to describe the geometry of the cross-section as it decreases in roundness with increasing diameter, finite element simulations that include elastic anisotropy and Lennard-Jones adhesive interactions, and observations on the adequacy of simplified contact models in describing the behavior. Calculations are presented for contact to typical stiff (silicon) and compliant (PDMS) substrates. The results reveal that, contrary to previous assumptions, the nanowires do not conform to the behavior of a perfect pentagon for the diameters typically encountered experimentally, and the roundness of the cross-section remains a factor that reduces the contact area. This reduction depends on the stiffness of the contact, being greater for stiff substrates.Penta-twinned nanowires, made of silver, gold, or copper, are envisioned to enable many applications, most notably stretchable and flexible electronics. In several instances of analysis of their behavior for device design, such as heat transfer due to current-induced heating, adhesion to substrates, or adhesion of nanowires to each other in conductive networks, knowledge of variables related to the mechanics of their contact is needed, for example the contact area (or radius). Due to the nanowires’ change in cross section, from circular to rounded- pentagonal as diameter increases, adhesive contact analysis is complex, and up to now has been simplified to assume either circular or perfect pentagonal cross sections. Here, we analyze the adhesive contact of the nanowires, fully considering the complexity of the cross section. We present equations to describe the geometry of the cross-section as it decreases in roundness with increasing diameter, finite element simulations that include elastic anisotropy and Lennard-Jones adhesive interactions, and observations on the adequacy of simplified contact models in describing the behavior. Calculations are presented for contact to typical stiff (silicon) and compliant (PDMS) substrates. The results reveal that, contrary to previous assumptions, the nanowires do not conform to the behavior of a perfect pentagon for the diameters typically encountered experimentally, and the roundness of the cross-section remains a factor that reduces the contact area. This reduction depends on the stiffness of the contact, being greater for stiff substrates. 

Abstract Silver nanowires have a wide range of potential applications in stretchable and transparent electronics due to their excellent electrical, mechanical, and optical properties. For a successful application in electronic devices, evaluating the electrical reliability of these nanowires is required. We have studied experimentally the behavior of current density at failure for penta-twinned silver nanowires with diameters between 53 and 173 nm, for 93 samples. The current densities at failure are widely scattered, have an average of 9.7 × 10 7 A cm −2 , and a standard deviation of 2.96 × 10 7 A cm −2 . Heat-transfer modeling is employed to explain the results, and Weibull statistics are used to quantify failure probabilities, thus offering guidelines for future designs based on these nanowires. The scatter observed in the measurements is attributed to surface-roughness variations among samples, which lead to local hot spots of high current density. These results quantify the Joule heating electrical reliability of silver nanowires and highlight the importance of heat transfer in increasing it. 

Needle-and-syringe-based delivery has been the commercial standard for vaccine administration to date. With worsening medical personnel availability, increasing biohazard waste production, and the possibility of cross-contamination, we explore the possibility of biolistic delivery as an alternate skin-based delivery route. Delicate formulations like liposomes are inherently unsuitable for this delivery model as they are fragile biomaterials incapable of withstanding shear stress and are exceedingly difficult to formulate as a lyophilized powder for room temperature storage. Here we have developed a approach to deliver liposomes into the skin biolistically—by encapsulating them in a nano-sized shell made of Zeolitic Imidazolate Framework-8 (ZIF-8). When encapsulated within a crystalline and rigid coating, the liposomes are not only protected from thermal stress, but also shear stress. This protection from stressors is crucial, especially for formulations with cargo encapsulated inside the lumen of the liposomes. Moreover, the coating provides the liposomes with a solid exterior that allows the particles to penetrate the skin effectively. In this work, we explored the mechanical protection ZIF-8 provides to liposomes as a preliminary investigation for using biolistic delivery as an alternative to syringe-and-needle–based delivery of vaccines. We demonstrated that liposomes with a variety of surface charges could be coated with ZIF-8 using the right conditions, and this coating can be just as easily removed—without causing any damage to the protected material. The protective coating prevented the liposomes from leaking cargo and helped in their effective penetration when delivered into the agarose tissue model and porcine skin tissue.