Although microfluidics has shown exciting potential, its broad applications are significantly limited by drawbacks of the materials used to make them. In this work, we present a convenient strategy for fabricating whole-Teflon microfluidic chips with integrated valves that show outstanding inertness to various chemicals and extreme resistance against all solvents. Compared with other microfluidic materials [e.g., poly(dimethylsiloxane) (PDMS)] the whole-Teflon chip has a few more advantages, such as no absorption of small molecules, little adsorption of biomolecules onto channel walls, and no leaching of residue molecules from the material bulk into the solution in the channel. Various biological cells have been cultured in the whole-Teflon channel. Adherent cells can attach to the channel bottom, spread, and proliferate well in the channels (with similar proliferation rate to the cells in PDMS channels with the same dimensions). The moderately good gas permeability of the Teflon materials makes it suitable to culture cells inside the microchannels for a long time.microchips | on-chip cell culture | solvent resistive chip T his report describes a convenient method for the fabrication of whole-Teflon microfluidic chips; we also integrate microvalves into the chips and demonstrate a few key applications of the whole-Teflon microfluidic chips with various organic solvents and biomolecules, and for culturing biological cells.Microfluidics (1) emerged during the early 1990s with channel networks in silicon or glass. Microprocessing of these materials is labor-intensive and time-consuming, it requires sophisticated equipment in a clean room, and often involves hazardous chemicals. The subsequent use of poly(dimethylsiloxane) (PDMS) greatly simplified the fabrication of microchips (2) and led to the rapid development of the field. PDMS has other attractive properties, such as being elastic (easy to make efficient microvalves), permeable to gases, and compatible with culturing biological cells. Despite these advantages, applications of PDMS chips are severely limited by a few drawbacks that are inherent to this material: (i) strong adsorption of molecules, particularly large biomolecules, onto its surface (3); (ii) absorption of nonpolar and weakly polar molecules into PDMS bulk; (iii) leaching of small molecules from PDMS bulk into solutions; and (iv) incompatibility with organic solvents. Therefore, special attention must be paid when quantitative analysis is needed (materials lost on channel walls and into the PDMS bulk) or organic solvents are involved. Because many drug molecules are small with relatively low polarity and cells can be very sensitive to their environment, data interpretation requires particular caution when cell-based drug screening and cell culturing are performed on PDMS microchips. Various techniques (4-8) have been proposed to modify PDMS bulk and surface properties, but they normally complicate the fabrication and still cannot effectively solve the problems. Most other plastics (9-11) have simi...

Along with the technology evolution for dense integration of high-power, high-frequency devices in electronics, the accompanying interfacial heat transfer problem leads to urgent demands for advanced thermal interface materials (TIMs) with both high through-plane thermal conductivity and good compressibility. Most metals have satisfactory thermal conductivity but relatively high compressive modulus, and soft silicones are typically thermal insulators (0.3 W m–1 K–1). Currently, it is a great challenge to develop a soft material with the thermal conductivity up to metal level for TIM application. This study solves this problem by constructing a graphene-based microstructure composed of mainly vertical graphene and a thin cap of horizontal graphene layers on both the top and bottom sides through a mechanical machining process to manipulate the stacked architecture of conventional graphene paper. The resultant graphene monolith has an ultrahigh through-plane thermal conductivity of 143 W m–1 K–1, exceeding that of many metals, and a low compressive modulus of 0.87 MPa, comparable to that of silicones. In the actual TIM performance measurement, the system cooling efficiency with our graphene monolith as TIM is 3 times as high as that of the state-of-the-art commercial TIM, demonstrating the superior ability to solve the interfacial heat transfer issues in electronic systems.