Doojoon Jang

Monolayer nanoporous graphene represents an ideal membrane for molecular separations, but its practical realization is impeded by leakage through defects in the ultrathin graphene. Here, we report a multiscale leakage-sealing process that exploits the nonpolar nature and impermeability of pristine graphene to selectively block defects, resulting in a centimeter-scale membrane that can separate two fluid reservoirs by an atomically thin layer of graphene. After introducing subnanometer pores in g

Dialysis is a ubiquitous separation process in biochemical processing and biological research. State‐of‐the‐art dialysis membranes comprise a relatively thick polymer layer with tortuous pores, and suffer from low rates of diffusion leading to extremely long process times (often several days) and poor selectivity, especially in the 0–1000 Da molecular weight cut‐off range. Here, the fabrication of large‐area (cm 2 ) nanoporous atomically thin membranes (NATMs) is reported, by transferring graphe

Molecular sieving across atomically thin nanoporous graphene is predicted to enable superior gas separation performance compared to conventional membranes. Although molecular sieving has been demonstrated across a few pores in microscale graphene membranes, leakage through nonselective defects presents a major challenge toward realizing selective membranes with high densities of pores over macroscopic areas. Guided by multiscale gas transport modeling of nanoporous graphene membranes, we designe

Nanoporous graphene has the potential to advance membrane separations by offering high selectivity with minimal resistance to flow, but how mass transport depends on the structure of pores in this atomically thin membrane is poorly understood. Here, we investigate the relationship between tunable pore creation using ion bombardment and oxygen plasma etching, the resulting pore size distributions, and the consequent water and solute transport. Through tuning of the pore creation process, we demon

Abstract Flexible thermoelectrics that enable conformal contact with heat sources of arbitrary shape are indispensable for self‐powered wearable electronics. Scalable integration of flexible thermoelectric (TE) materials into functional devices has improved over the past few years, however, the practical applications of flexible TE materials are still hindered by low performance. Herein, highly aligned carbon‐nanotube yarns (CNTYs) are proposed, combined with selective doping via picoliter scale

Atomically thin single crystals, without grain boundaries and associated defect clusters, represent ideal systems to study and understand intrinsic defects in materials, but probing them collectively over large area remains nontrivial. In this study, the authors probe nanoscale mass transport across large‐area (≈0.2 cm 2 ) single‐crystalline graphene membranes. A novel, polymer‐free picture frame assisted technique, coupled with a stress‐inducing nickel layer is used to transfer single crystalli

Two-dimensional materials such as graphene offer fundamentally transformative opportunities in membrane separations and as impermeable barriers, but the lack of facile methods to assess and control its 'impermeability' critically limits progress. Here we show that a simple etch of the growth catalyst (Cu) through defects in monolayer graphene synthesized by chemical vapor deposition (CVD) can be used to effectively assess graphene quality for membrane/barrier applications. Using feedback from th

Abstract Compliant thermoelectric generators (TEGs) can fully exploit their energy conversion efficiency by establishing conformal interfaces on arbitrarily shaped 3D heat sources. Although additive manufacturing processes allow scalable fabrication with flexibility and customizability, most printable TEGs are fabricated as planar‐type devices that harvest heat only in the in‐plane direction. Herein, 3D‐compliant TEGs fabricated solely using direct ink writing, which enables thermal‐transfer opt

Atomically thin membranes comprising nanopores in a 2D material promise to surpass the performance of polymeric membranes in several critical applications, including water purification, chemical and gas separations, and energy harvesting. However, fabrication of membranes with precise pore size distributions that provide exceptionally high selectivity and permeance in a scalable framework remains an outstanding challenge. Circumventing these constraints, here, a platform technology is developed

We propose a novel design of thermoelectric (TE) effect-based soft temperature sensors for directly monitoring localized subtle temperature stimuli. This design integrates rheology-engineered three-dimensional (3D) printing of high-performance carbon-based TE materials and polymer-based viscoelastic materials with low thermal conductivity. Rheological engineering of carbon nanotube (CNT) TE inks ensures the 3D printing of highly sensitive TE sensing units on directly written 3D soft platforms. A

We strategically modify lignin as effective p- and n-dopants for nanocarbon materials, offering promising alternatives to chemical dopants from fossil-fuels.

We report a rationally designed stretchable conductive composite of low Ag percolation threshold concentration with the aid of boron nitride (BN) as a non-conductive auxiliary filler.

Wearable Electronics In article number 2200256, Seungjun Chung, Chong Rae Park, Heesuk Kim and co-workers fabricate a highly integrated, wearable carbon-nanotube-yarn (CNTY)-based thermoelectric generator (TEG) by precisely doping CNTY into p- and n-type segments via picoliter scale inkjet printing (depicted as splash of solution). The TEG can conformably wrap around bodies and harvest electric energy directly from body heat.