Nanoimprinting over topography and multilayer three-dimensional printing

Abstract

We have developed a simple imprinting technique that allows patterning over a nonflat substrate without the need for planarization. In this process, a polymer film is spin coated onto the mold and then transferred to a patterned substrate by imprinting. By selecting polymers with different mechanical properties, either suspended structures over wide gaps or supported patterns on raised features of the substrate can be obtained with high uniformity. It is found that imprinting at a temperature well above the glass transition temperature (Tg) of the polymer causes the thin residue film between features to dewet from the mold, which can greatly simplify the subsequent pattern transfer process. Multilayer three-dimensional polymer structures have also been successfully fabricated using this new imprinting method. The yield and dimensional stability in the multilayer structure can both be improved when polymers with progressively lower Tg are used for different layers. Compared to existing techniques for patterning on nonflat substrates, the current method has a number of advantages, including simplicity, versatility, high resolution, and low pattern distortion.

Nanopattern-induced changes in morphology and motility of smooth muscle cells

“…Nanoimprint lithography was used to generate gratings with 350 nm linewidth, 700 nm pitch, and 350 nm depth in a PMMA thin film that was spin-coated onto a Si substrate as previously described [30,32]. Briefly, a pre-patterned master SiO 2 grating-mold was pressed onto the PMMA polymer film at a temperature of 180 °C and a pressure of 6MPa.…”

“…We have recently developed nanoimprinting techniques that can produce a wide range of nanostructures, including multilayer three-dimensional structures made of flexible polymers [29,30]. In this study we examined the behavior SMC cultured on poly(methyl methacrylate) (PMMA) and poly(dimethlsiloxane) (PDMS) surfaces, consisting of nanopatterned gratings with 350 nm linewidth, 700 nm pitch, and 350 nm depth.…”

Hybrid 3D printing by bridging micro/nano processes

“…Because of difficulties in fabrication of the micro/nanoscale mold, it is difficult to apply these techniques with similar flexibility and scale to conventional manufacturing techniques [22]. For some limited cases, such as single-layer polymer materials, this kind of forming technique can be used to create the desired structures [23]; however, it is limited in terms of the geometric degree of freedom.…”

Alternative lithography strategies for flexible electronics

“…Nonflat surfaces can be patterned with rigiflex molds [125] and reverse NIL (rNIL). [147,148] Small and large features can be patterned by hybrid solutions combining NIL and conventional photolithography (combined nanoimprint-and photolithography; CNP). [149] Complex electronic devices demand a good registration and overlay control in the patterning process.…”

“…gate) to define the next layer, or a multilevel etch mask defining all following layers can be fabricated on the substrate. In self-aligned imprint lithography (SAIL), [145][146][147][148][149][150][151][152] the entire material stack is deposited on the flexible foil whereafter a single, three-dimensional imprint is made defining all layers of the electronic device. The individual layers and structures of the device are patterned by smartly switching etch processes, opening one layer after the other using the just opened layer as etch mask and the next layer as etch stop.…”