Significance: Strategies to improve efficacy and reduce side effects of immune checkpoint blockade (ICB) therapy are clinically relevant. Here, we described a transdermal cold atmospheric plasma (CAP)-mediated ICB therapy. Local delivery of CAP through hollow-structured microneedles as microchannels promote the release of tumor-associated antigens by CAP. The subsequent T cell-mediated immune response can be augmented by the immune checkpoint inhibitors delivered via microneedles, resulting in enhanced local and systemic anticancer immunity. The synergism between CAP and ICB integrated with microneedles provides a platform technique for cancer treatment and other diseases in a minimally invasive manner.

Syndrome coronavirus 2 (SARS-CoV-2) infectious virions are viable on various surfaces (e.g., plastic, metals, and cardboard) for several hours. This presents a transmission cycle for human infection that can be broken by developing new inactivation approaches. We employed an efficient cold atmospheric plasma (CAP) with argon feed gas to inactivate SARS-CoV-2 on various surfaces including plastic, metal, cardboard, basketball composite leather, football leather, and baseball leather. These results demonstrate the great potential of CAP as a safe and effective means to prevent virus transmission and infections for a wide range of surfaces that experience frequent human contact. Since this is the first-ever demonstration of cold plasma inactivation of SARS-CoV-2, it is a significant milestone in the prevention and treatment of coronavirus disease 2019 (COVID-19) and presents a new opportunity for the scientific, engineering, and medical communities.

A portable air-fed cold atmospheric plasma device was invented for postsurgical cancer immunotherapy to inhibit tumor relapse.

Ionic liquid electrospray thrusters are capable of producing microNewton precision thrust at a high thrust–power ratio but have yet to demonstrate lifetimes that are suitable for most missions. Accumulation of propellant on the extractor and accelerator grids is thought to be the most significant life-limiting mechanism. In this study, we developed a life model to examine the effects of design features, operating conditions, and emission properties on the porous accelerator grid saturation time of a thruster operating in droplet emission mode. Characterizing a range of geometries and operating conditions revealed that modifying grid aperture radius and grid spacing by 3–7% can significantly improve thruster lifetime by 200–400%, though a need for explicit mass flux measurement was highlighted. Tolerance analysis showed that misalignment can result in 20–50% lifetime reduction. In addition, examining the impact of electron backstreaming showed that increasing aperture radius produces a significant increase in backstreaming current compared to changing grid spacing. A study of accelerator grid bias voltages revealed that applying a reasonably strong accelerator grid potential (in the order of a kV) can minimize backstreaming current to negligible levels for a range of geometries.

Recently, several researchers [e.g., Yang et al., Sci. Rep. 5, 10959 (2015)] have shown that tungsten fuzz can grow on a hot tungsten surface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facing tungsten components. This work reports the direct measurements of the total effective secondary electron emission (SEE) from tungsten fuzz. Using dedicated material surface diagnostics and in-situ characterization, we find two important results: (1) SEE values for tungsten fuzz are 40%–63% lower than for smooth tungsten and (2) the SEE values for tungsten fuzz are independent of the angle of the incident electron. The reduction in SEE from tungsten fuzz is most pronounced at high incident angles, which has important implications for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively higher sheath potential difference that reduces plasma electron energy loss to the confining wall. Thus, the presence or self-generation in a plasma of a low SEE surface such as tungsten fuzz can be desirable for improved performance of many plasma devices.

Theoretical, analytical, and experimental investigations of electrospray operation in vacuum facilities show that secondary species emission (SSE) plays a significant role in the behavior of electrospray thrusters during ground testing. A review of SSE mechanisms, along with an analysis of onset thresholds for electrospray thruster conditions, indicates that secondary species (e.g., electrons, anions, cations, etc.) must be carefully considered for accurate measurements and determination of performance and life. Presented models and experiments show that SSE-induced thruster-to-facility coupling can lead to considerable measurement uncertainty but can be effectively mitigated with an appropriate beam target design. The Electrospray SSE Control-volume Analysis for Resolving Ground Operation of Thrusters model is applied to experimental data to analyze SSE behavior. A heat and mass flux analysis of the Air Force Electrospray Thruster Series 2 (AFET-2) shows that SSE-induced Ohmic dissipation can cause performance limitations in ionic liquid ion source thrusters. The presented analytical models show that backstreaming current density contributing to less than 0.1% of measured emitter current density can cause substantial variation in propellant properties. Additionally, backstreaming current density contributing to less than 3% of emitted current can cause the 0.86 $\mu$ g s${}^{-1}$ neutral loss rate estimated during AFET-2 testing. Arguments are presented to support the notion that glow discharges observed in electrospray thrusters during vacuum operation are a consequence of secondary species backstreaming to the emission site, rather than a process intrinsically caused by ion evaporation. Recommendations for general best practices to minimize the effects of SSE on electrospray thruster operation are provided.