Nanoimprinting

Nanoimprinting is a high-resolution lithography technique in which nanoscale patterns are transferred into a substrate by pressing a mold bearing the desired features into a deformable resist. The method can produce patterns with dimensions down to tens of nanometers over relatively large areas and often at lower cost and higher throughput than some alternative lithographies.

Two main variants are thermal nanoimprint lithography (T-NIL) and UV nanoimprint lithography (UV-NIL). In T-NIL, a rigid mold and a thermoplastic resist are heated above the resist’s glass transition temperature, pressed into contact under controlled pressure, then cooled and separated, leaving the pattern imprinted in the resist. In UV-NIL, a UV-curable resist is used; the mold is pressed into the uncured resist at or near room temperature, the resist is exposed to ultraviolet light through the mold to cure, and then the mold is released to reveal the pattern.

Molds are typically fabricated from durable materials such as silicon, quartz, or nickel and can be reused many times. Resists include thermoplastics (for T-NIL) and UV-curable polymers (for UV-NIL). A residual layer of resist often remains on the substrate and may require etching or planarization. Roll-to-roll implementations enable large-area and flexible-substrate replication.

Applications span electronics, photonics, microfluidics, and biosensing, where high-resolution patterning and compatibility with various substrates are advantageous. Advantages of nanoimprinting include simple process flow, high resolution, and potential for low-cost, high-throughput manufacturing; limitations involve mold replication fidelity, defect control, demolding-induced damage, residual layers, and alignment challenges for multilayer structures. The technique was introduced in the mid-1990s by researchers including Stephen D. Chou and colleagues and has since evolved with commercial and research developments.