Femtosecond and nanosecond laser micromachining of oxidized multi- wall carbon nanotube doped morthane Kenneth E. Hix a , Mingwei Li b , Jacek Gosciniak b , Kevin Hartke a , Matt Rendina a , Larry R. Dosser a , Max Alexander c a Mound Laser & Photonics Center, Inc., P.O. Box 223, Miamisburg, OH 45343; b Spectra-Physics Lasers, Newport Corporation, 1335 Terra Bella Ave., Mountain View, CA 94043; c Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433 ABSTRACT Carbon nanocomposites consist of thermoset and thermoplastic materials filled with carbon nano-particles (nanotubes, bucky balls, etc.). This innovative group of materials offers many advantages over standard polymers such as electrical/thermal conductivity and improved structural properties. In the current study, an Yb:KGW solid-state femtosecond laser and an Nd:YVO 4 solid-state nanosecond laser were used to micromachine oxidized multi-wall carbon nanotube (MWCNT) doped morthane. The experimentation studied the relationship between various laser-processing parameters including laser pulse duration, pulse energy, beam scanning speed, and average power. The processing consisted of cutting channels into the materials using 1048 nm wavelength at 400 fs pulse duration, 1064 nm wavelength at 40 ns pulse duration, and 355 nm wavelength at 35 ns pulse duration. Additionally, the effects of oxidized MWCNT fill percentage were considered. The material removal rate was quantified for each experimental condition. The experimental results are discussed in terms of material removal rates, machining quality, and achievable feature size. Keywords : carbon nanocomposites, femtosecond, Yb:KGW, Nd:YVO 4 , micromachining 1. INTRODUCTION New and innovative polymer composite materials are being developed to meet the increasing mechanical, thermal, and electrical properties of materials within industries ranging from automotive to medical. As weight reduction, miniaturization, and further integration of structural, electrical, and aesthetic properties become prevalent, carbon nanocomposites have arrived to meet the requirements of the changing markets. A new set of polymer composite materials, based on the addition of carbon nanomaterials (nanotubes, nanofibers, bucky balls, etc.), is being developed. Carbon nanocomposites offer better thermal conductivity and structural strength over virgin polymer material 1 . Carbon doping of polymers has been a common engineering practice for many years. Carbon black enhances electrical and aesthetic properties and carbon fiber improves the mechanical properties of various polymers. However, there are still many engineering challenges associated with these materials, including particle dispersion and the large weight percent required for electrical conductivity 2 . The carbon nanotube is one of the first functional additives for polymers. It is small enough to integrate into the polymer matrix and contribute to the physical properties of the material. The functional advantages of carbon nanotubes have only been realized in a small set of polymer base materials. This set is continually growing as research and development continues. As the material systems become more mature there becomes a need for the ability to fabricate devices using these materials. Various methods for machining polymers exist including mechanical, chemical, and photonic machining. The most common form of photonic based machining employs the use of a focused laser beam, either by imaging or using direct- focus technique. Traditionally laser cutting of macro parts has been completed using a CO 2 laser. The far infra-red (10,600 nm) wavelength of the CO 2 is absorbed by most polymers and the resulting material removal mechanism is photothermal in nature 3 . The laser irradiation is absorbed into the thermal modes of the material and a very efficient melting and evaporation of the polymer occurs. Although the wavelength is efficiently absorbed into the polymer substrate, there is also a significant amount of heat generated that can result in melting and modification of peripheral material. This “heat affected zone” (HAZ) is generally undesirable for many applications. Another limitation of CO 2