The self-cleaning function of superhydrophobic surfaces is conventionally attributed to the removal of contaminating particles by impacting or rolling water droplets, which implies the action of external forces such as gravity. Here, we demonstrate a unique self-cleaning mechanism whereby the contaminated superhydrophobic surface is exposed to condensing water vapor, and the contaminants are autonomously removed by the self-propelled jumping motion of the resulting liquid condensate, which partially covers or fully encloses the contaminating particles. The jumping motion off the superhydrophobic surface is powered by the surface energy released upon coalescence of the condensed water phase around the contaminants. The jumping-condensate mechanism is shown to spontaneously clean superhydrophobic cicada wings, where the contaminating particles cannot be removed by gravity, wing vibration, or wind flow. Our findings offer insights for the development of self-cleaning materials.particle adhesion and removal | water-repellant insect wings | nanostructured interfaces | capillary forces B oth natural and synthetic superhydrophobic surfaces are believed to achieve self-cleaning by the so-called "lotus effect" (1, 2). The lotus effect typically refers to the removal of the contaminating particles by impacting and/or rolling water droplets (1, 3). The superhydrophobicity is important because of the associated large contact angle and small hysteresis (4), which promotes the rolling motion carrying away contaminants. According to the conventional wisdom of the lotus effect, the self-cleaning function will cease without incoming droplets or favorable external forces, posing severe restrictions for practical applications of superhydrophobic materials.Here, we demonstrate an autonomous mechanism to achieve self-cleaning on superhydrophobic surfaces, where the contaminants are removed by self-propelled jumping condensate powered by surface energy. When exposed to condensing water vapor, the contaminating particles are either fully enclosed or partially covered with the resulting liquid condensate. Building upon our previous publications showing self-propelled jumping upon drop coalescence (5, 6), we show particle removal by the merged condensate drop with a size comparable to or larger than that of the contaminating particle(s). Further, we report a distinct jumping mechanism upon particle aggregation, without a condensate drop of comparable size to that of the particles, where a group of particles exposed to water condensate clusters together by capillarity and self-propels away from the superhydrophobic surface.The jumping-condensate mechanism reported here offers a unique route toward self-cleaning, with potential applications ranging from microelectronic wafer cleaning to heat exchanger maintenance (7). Particle removal is often accomplished in a gas flow or a liquid stream by hydrodynamic shear stresses, which are parallel to the surface. The parallel hydrodynamic forces are not ideal in competing against the adhesive mech...

Fiber-based coalescers are widely used to accumulate droplets from aerosols and emulsions, where the accumulated droplets are typically removed by gravity or shear. This Letter reports self-propelled removal of drops from a hydrophobic fiber, where the surface energy released upon drop coalescence overcomes the drop-fiber adhesion, producing spontaneous departure that would not occur on a flat substrate of the same contact angle. The self-removal takes place above a threshold drop-to-fiber radius ratio, and the departure speed is close to the capillary-inertial velocity at large radius ratios.

Phase engineering of nanomaterials provides a promising way to explore the phase-dependent physicochemical properties and various applications of nanomaterials. A general bottom-up synthesis method under mild conditions has always been challenging globally for the preparation of the semimetallic phasetransition-metal dichalcogenide (1T′-TMD) monolayers, which are pursued owing to their unique electrochemical property, unavailable in their semiconducting 2H phases. Here, we report the general scalable colloidal synthesis of nanosized 1T′-TMD monolayers, including 1T′-MoS 2 , 1T′-MoSe 2 , 1T′-WS 2 , and 1T′-WSe 2 , which are revealed to be of high phase purity. Moreover, the surfactantreliant stacking-hinderable growth mechanism of 1T′-TMD nano-monolayers was unveiled through systematic experiments and theoretical calculations. As a proof-of-concept application, the 1T′-TMD nano-monolayers are used for electrocatalytic hydrogen production in an acidic medium. The 1T′-MoS 2 nano-monolayers possess abundant in-plane electrocatalytic active sites and high conductivity, coupled with the contribution of the lattice strain, thus exhibiting excellent performance. Importantly, the catalyst shows impressive endurability in electroactivity. Our developed general scalable strategy could pave the way to extend the synthesis of other broad metastable semimetallic-phase TMDs, which offer great potential to explore novel crystal phase-dependent properties with wide application development for catalysis and beyond.

Dropwise condensation can be enhanced by superhydrophobic surfaces on which the condensate drops spontaneously jump upon coalescence. However, the self-propelled jumping in prior reports is mostly perpendicular to the substrate. Here, we propose a substrate design with regularly spaced micropillars. Coalescence on the sidewalls of the micropillars leads to self-propelled jumping in a direction nearly orthogonal to the pillars and therefore parallel to the substrate. This in-plane motion in turn produces sweeping removal of multiple neighboring drops. The spontaneous sweeping mechanism may greatly enhance dropwise condensation in a self-sustained manner.

Self-collected vaginal specimens tested for high-risk human papillomavirus (HR-HPV) have been shown to be less sensitive for the detection of cervical intraepithelial neoplasia or cancer ( CIN 3) than physician-collected endocervical specimens. To increase the sensitivity of self-collected specimens, we studied a self-sampling device designed to obtain a larger specimen from the upper vagina (POI/NIH self-sampler) and a more sensitive polymerase chain reaction (PCR)-based HR-HPV assay. Women (10,000) were screened with cervical cytology and HR-HPV testing of vaginal self-collected and endocervical physiciancollected specimens. Women were randomly assigned to use either a novel self-collection device (POI/NIH self-sampler) or conical-shaped brush (Qiagen). The self-collected and clinician-collected specimens were assayed by Cervista (Hologic) and the research only PCR-based matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF). Women with any abnormal screening test underwent colposcopy and biopsy. Women (8,556), mean age of 38.9, had complete data; 1.6% had CIN 3. For either HR-HPV assay, the sensitivity was similar for the two self-collection devices. Tested with Cervista, the sensitivity for CIN 3 of self-collected specimens was 70.9% and for endocervical specimens was 95.0% (p 5 0.0001). Tested with MALDI-TOF, the sensitivity for CIN 3 of self-collected specimens was 94.3% and for endocervical specimens was also 94.3% (p 5 1.0). A self-collected sample using a PCR-based assay with the capability of very high throughput has similar sensitivity as a direct endocervical specimen obtained by a physician. Large population-based screening ''events'' in low-resource settings could be achieved by promoting self-collection and centralized high-throughput, low-cost testing by PCR-based MALDI-TOF.The ideal cervical cancer-screening test would be both sensitive and specific for cervical intraepithelial neoplasia (CIN) Grade 3 or early cancer ( CIN 3). As 85% of the global burden of cervical cancer resides in developing countries, 1 this ideal screening test would not require a pelvic examination, which is time consuming and increases the costs by using speculums, or extensive clinical infrastructure and would be inexpensive. A vaginal self-collected specimen tested for high-risk human papillomavirus (HR-HPV) meets some of these criteria as it does not require a pelvic examination, requires fewer resources, and is less dependent on a complex healthcare infrastructure. Therefore, it is probably less expensive and easier to implement than testing using clinician-collected specimens. Still, of course, programmatic models will need to be developed to manage the call-back and tracking necessary for positive cases. Also when compared to endocervical clinician-collected specimens tested for HR-HPV, the vaginal self-collected specimens have lower sensitivity and specificity for high-grade precancers and cancer. [2][3][4][5][6][7][8][9] There are several possible explanations for this lower sensitivity and specifi...