In optical lithography tools, thermal aberration of a projection lens, which is caused by lens heating effect, leads to degradation of imaging quality. In addition to in-line feedforward compensation technology, thermal aberration can be reduced by optimizing optical design of a projector. Thermal aberration analysis of a projection lens benefits the optimization of optical design. A model of lens heating effect for a lithographic projector is introduced, which is capable of evaluating the synthetical thermal aberration of a projector as well as analyzing the contribution of an individual optical element. Simulation results by the introduced model show that not only the deformation of lens surface, the variance of refractive index but also the change of optical path, which depends on optical design, should be considered in thermal aberration analysis. The contributions of optical elements at different locations of the projector are also analyzed. Based on the model and the simulation results, an optimization method is proposed. A projector for i-line lithography is optimized by the proposed method. Main aberrations Z5, Z9, and Z17 are reduced by about 40%. The image quality of the lithographic projector in steady state is also improved.

Thermal interface material (TIM) is a key component to dissipate the accumulated heat in the majority of power electronic systems. In this work, a facile and solid-state ball-milling method is adopted for the solvent-free reduction of exfoliated graphite nanoplatelets (EGNs) into high-quality ball-milled exfoliated graphite nanoplatelet (BMEGN) fillers. In addition, BMEGN fillers are embedded and uniformly dispersed with polydimethylsiloxane (PDMS) matrix to make a highly stretchable BMEGN-embedded PDMS-TIMs (BMEGN/PDMS) with strongly enhanced thermal conductivity. Furthermore, material characterizations were thoroughly investigated using scanning electron microscopy, transmission electron microscope, Raman spectroscopy, thermogravimetric analysis, and x-ray diffraction. Improvements in the thermal conductivity of TIMs by adding BMEGN were compared, the thermal conductivity was observed for BMEGN fillers with 0- to 48-h ball-milling time, and an enhanced in-plane thermal conductivity of 15.04 to 16.91 W/mK and through-plane thermal conductivity of 1.03 to 1.19 W/mK can be experimentally measured. A strong anisotropy was observed in the range of 14.60 (BMEGN12h/PDMS) to 14.21 (BMEGN48h/PDMS). The results reveal that the ball-milled graphene filler network with branched morphology can effectively provide the synergetic effect of a thermally conductive pathway via diffusion of phonon vibration in flexible composites. The combination of thermal conductivity and thermal stability may facilitate the applications in thermal management.

A concept using a glass-based microchip with finger electrodes, under a two-step voltage-controlled manner, to accomplish the formation and collection of liposomes is presented. By the actions of electro-osmotic and electrolytic bubbles in low and high applied voltages, respectively, the liposomes were first formed in an electrolyte reservoir; then, they were successfully moved to a collected reservoir, which is helpful for subsequent on-chip processing. This study evaluated the distribution of an electric field for different couple-finger distances using finite-element analysis software. The simulation result shows that the electric field density increases rapidly with the decrease of finger distance, with a quadratic relationship. Experiment results show that, when the applied AC voltage is 1 Vp-p, at a driving frequency of 10 Hz, the liposomes are first formed near the boundary of the electrolyte reservoir, and when the voltage is higher, the mass production of liposomes is achieved. When the voltage is higher than 4 Vp-p, the electrolytic bubbles grow cyclically to separate the liposomes from the electrolyte reservoir and therefore collect in a specific reservoir. Liposomes encapsulate doxorubicin, and their drug release to the lung cancer cell line H1299 was also implemented to verify their biointeraction characteristics. These experimental results were all identified using an inverted fluorescence microscope.