# Phase Transition and Controlled Zirconia Implant Patterning Using Laser-Induced Shockwaves
## 2 Materials and Methods
### Laser-Induced Plasma  
Laser-induced template imprinting via nonthermal plasma is a precision surface modification technique that leverages laser-material interactions and plasma dynamics. The process involves the use of a nanosecond-pulsed, 1064 nm Nd:YAG laser operating at 10 Hz, coupled with a metal template and a confined plasma environment, to transfer template patterns onto zirconia surfaces [33].  
The process begins with the laser pulse interacting with an ablative layer, typically made of aluminum or copper. These materials are selected for their excellent thermal and electrical conductivity, which ensures efficient absorption of laser energy. Upon irradiation, a thin layer of the template material undergoes rapid heating and vaporization, producing a nonthermal plasma [34]. The nonthermal plasma generated in this process plays a crucial role in efficient and localized energy transfer.  
Unlike thermal plasmas, where all species are in thermal equilibrium, nonthermal plasmas have much higher electron temperatures compared to ions and neutrals. This temperature disparity arises because electrons, being lighter and more mobile, absorb and donetransfer energy more rapidly than their heavier counterparts. The electron temperature \(T_{e}\) is given by:  
\[T_{e}=\frac{2}{3}\frac{E_{e}}{k_{B}}\]  
where \(E_{e}\) is the average electron energy, and \(k_{B}\) is the Boltzmann constant. This disparity is a defining feature of nonthermal plasmas, enabling efficient energy localization during the imprinting process.  
This characteristic enhances energy transfer efficiency and allows for precise surface modifications without excessive bulk heating. The generated plasma, composed of energetic ions, electrons, and neutral particles, is confined using a glass slide placed above the template. This confinement prevents the plasma from expanding freely, resulting in an increase in localized temperature and pressure. The confined plasma acts as a highly energetic medium, transferring its energy to the zirconia surface and inducing localized melting and ablation. This process enables the zirconia to conform precisely to the template's pattern under the combined thermal and mechanical effects of the plasma.  
Key parameters governing the plasma and energy transfer include the laser's wavelength, pulse duration, and energy density. The 1064 nm wavelength is particularly effective due to its high absorption efficiency in metals like aluminum and copper, facilitating optimal plasma generation [35]. Additionally, the choice of nanosecond-pulse durations balances thermal and mechanical effects, providing sufficient energy for material processing while maintaining control over the heat-affected zone.  
The absorbed laser energy (\(E\)) can be quantified as follows:  
\[E=\int I(t)dt\]  
\(I(t)\) represents the laser intensity as a function of time [36]. The confined plasma pressure (\(P\)) is given by the following:  
\[P=\frac{2E}{A\times t}\]  
where \(A\) is the laser spot area, and \(t\) is the pulse duration [36]. Beam spot area (\(A\)) is a fixed value in this setup, as it should be irradiating the 3 mm template used for imprinting. The resulting high temperature and pressure induce localized melting and solidification of zirconia, ensuring the imprinting of precise patterns [37]. Upon cooling, the imprintedzirconia retains these patterns, which are characterized by techniques like AFM and SEM to evaluate their dimensions, uniformity, and depth.