In this experimental study, flow boiling in mini/microtubes was investigated with surface enhancements provided by polyhydroxyethylmethacrylate (pHEMA) coatings (of ∼30 nm thickness) on inner microtube walls. Flow boiling heat transfer experiments were conducted on microtubes (with inner diameters of 249, 507 and 998 µm) having inner surfaces of pHEMA coatings, which increase heat transfer surface area, enable liquid replenishment upon bubble departure, provide additional nucleation sites, and serve for extending critical heat flux (CHF) enhancing boiling heat transfer. The de-ionized water was utilized as the working fluid in this study. pHEMA nanofilms of thickness ∼30 nm on the microtube walls were coated through an initiated chemical vapor deposition technique. Experimental results obtained from the coated microtubes were compared to their plain surface counterparts at two mass flux values (10 000 and 13 000 kg m−2 s−1). In comparison to the plain surface microtubes, the coated surfaces demonstrated an increase up to 24% and 109% in CHF and heat transfer coefficients, respectively. These promising results support the use of pHEMA coated microtubes/channels as a surface enhancement technique for microscale cooling applications.

Responsive micropatterned surfaces are fabricated using a facile, one-step method that allows for the separate control of topography and surface chemistry. Temperature responsive poly(N-isopropylacrylamide) (pNIPAAm), and amphiphilic poly(hydroxyethyl methacrylate-co-perfluorodecylacrylate) (p(HEMA-co-PFA)) polymer thin films are deposited on prestrained polydimethylsiloxane (PDMS) substrates using the initiated chemical vapor deposition (iCVD) technique. Subsequent release of the strain results in the formation of periodic wrinkle structures on the surface of polymer thin films. The iCVD technique allows control of the chemical composition while preserving the functional groups of the polymers intact. Surface topography is controlled separately by tuning elastic modulus of the polymer coatings and substrates. Highly ordered, well-defined wrinkle structures are obtained on pNIPAAm surfaces whereas wrinkles on the amphiphilic surfaces are less ordered due to the difference in elastic moduli of the polymers. Furthermore, process temperature is observed to have detrimental effects on the ordering of the wrinkles.

Aqueous-based slurry media for cathode electrode production offers a cleaner and safer environment during the electrode manufacturing step compared with the conventional organic solvent-based method used in the lithium-ion battery industry. In this work, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and poly(ethylene oxide) (PEO) water-based binders are used to prepare LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC) cathode electrode. Detail electrochemical analysis reveals that the optimum mass ratio of CMC:SBR mixture is 1:2 when preparing an aqueous slurry for the NMC electrode. To mitigate particle cracking phenomenon during electrode drying step and obtain higher mass loading, a multi-layer coating technique is implemented. CMC-PEO binder mixture in aqueous media is also studied as an alternative aqueous processing method for NMC electrodes. The electrodes prepared with CMC-PEO mixture are demonstrated to be all crack-free, and electrochemical results indicate that the optimum mass loading of NMC electrode is between 15 and 18 mg cm À2 . This method is further tested in pouch cell format using a roll-to-roll pilot-scale production line to show the feasibility for commercial applications. Remarkably, pouch cell results manifest that aqueous-processed NMC cathode against graphite anode maintains its 89% capacity at 1C even after 1000 cycles. Highlights• Water-based binders of carboxymethyl cellulose-poly(ethylene oxide) provide excellent cycling stability for LiNi 0.5 Mn 0.3 Co 0.2 O 2 electrode.• Multilayer coating allows electrodes for higher loadings without any crack formation.• The water-based electrode preparation method is validated by pilot scale roll-to-roll electrode production line.

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