Medical grade polyethylene-based skeletal implants exhibit osteo-disintegration, erosion, and modest hemocompatibility. Herein, we report on the fabrication of highly adherent undoped and Si-containing DLC (Si-DLC) coatings for biomedical implant applications by utilizing plasma and laser-based processing techniques on thermally sensitive polyethylene (PE) substrates. Scratch testing reveals a strong interfacial shear strength of 620 MPa for DLC coatings deposited on PE. A contact stress of ∼32 MPa induced cracking of the DLC thin film. The Si-DLC films demonstrated a higher critical failure load and less cracking compared to undoped DLC films. The contact angle for PE increased from 90° to 110° when it was coated with the Si-DLC thin film. A high optical bandgap of 2.5 eV was calculated for the 21 at% Si-DLC thin films. Pulsed laser annealing (PLA) of Si-DLC films at 0.3 J cm⁻² increased the amount of sp² bonded carbon, resulting in an improvement in lubricity, hydrophobicity, and electrical conductivity properties. In addition, the laser patterned pristine DLC films showed the formation of reduced graphene oxide, which possessed sizeable properties for wearable electronics and biosensing applications (R_s = 0.6 kΩ □⁻¹). This study indicates that PLA is a useful technique for modifying the properties of DLC thin films on flexible polymeric substrates for state-of-the-art biomedical and electronic sensing applications.

We report the formation of Q-carbon nanolayers, Q-carbon nanoballs, nanodiamonds, microdiamonds, and their composites by controlling laser and substrate variables. The choice of these parameters is guided by the SLIM (simulation of laser interactions with materials) computer modeling. For a constant film thickness and initial sp³ content, we obtain different microstructures with increasing pulse energy density as a result of different quenching rate and undercooling. This is related to decreasing undercooling with increasing pulse energy density. The structure of thin film Q-carbon evolves into Q-carbon nanoballs with the increase in laser annealing energy density. These Q-carbon nanoballs interestingly self-organize in the form of rings with embedded nanodiamonds to form Q-carbon nanoballs/diamond composites. We form high quality, epitaxial nano, and micro diamond films at a higher energy density and discuss a model showing undercooling and quenching rate generating a pressure pulse, which may play a critical role in a direct conversion of amorphous carbon into Q-carbon or diamond or their composites. This ability to selectively tune between diamond or Q-carbon or their composites on a single substrate is highly desirable for a variety of applications ranging from protective coatings to nanosensing and field emission to targeted drug delivery. Furthermore, Q-carbon nanoballs and nanodiamonds are utilized as seeds to grow microdiamond films by HFCVD. It is observed that the Q-carbon nanoballs contain diamond nuclei of critical size, which provide available nucleation sites for diamond growth, leading to stress-free, adherent, and denser films, which are needed for a variety of coating applications.

Improved performance of lithium-ion batteries (LIBs) plays a critical role in the future of next- generation battery applications. Nickel-rich layered oxides such as LiNi_0.8Mn_0.1Co_0.1O₂ (NMC 811), are popular cathodes due to their high energy densities. However, they suffer from high surface reactivity, which results in the formation of Li₂CO₃ passive layer. Herein, we show the role of nanosecond pulsed laser annealing (PLA) in improving the current capacity and cycling stability of LIBs by reducing the carbonate layer, in addition to forming a protective LiF layer and manipulating the NMC 811 microstructures. We use high-power nanosecond laser pulses in a controlled way to create nanostructured surface topography which has a positive impact on the capacity retention and current capacity by providing an increased active surface area, which influences the diffusion kinetics of lithium-ions in the electrode materials during the battery cycling process. Advanced characterizations show that the PLA treatment results in the thinning of the passive Li₂CO₃ layer, which is formed on as-received NMC811 samples, along with the decomposition of excess polyvinylidene fluoride (PVDF) binder. The high-power laser interacts with the decomposed binder and surface Li⁺ to form LiF phase, which acts as a protective layer to prevent surface reactive sites from initiating parasitic reactions. As a result, the laser treated cathodes show relative increase of the current capacity of up to 50%, which is consistent with electrochemical measurements of LiB cells.