Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA.
Department of Mechanical Engineering and Mechanics, Bioengineering Program, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
Phys Rev E. 2018 Mar;97(3-1):033105. doi: 10.1103/PhysRevE.97.033105.
Pseudopotential lattice Boltzmann methods (LBMs) can simulate a phase transition in high-density ratio multiphase flow systems. If coupled with thermal LBMs through equation of state, they can be used to study instantaneous phase transition phenomena with a high-temperature gradient where only one set of formulations in an LBM system can handle liquid, vapor, phase transition, and heat transport. However, at lower temperatures an unrealistic spurious current at the interface introduces instability and limits its application in real flow system. In this study, we proposed new modifications to the LBM system to minimize a spurious current which enables us to study nucleation dynamic at room temperature. To demonstrate the capabilities of this approach, the thermal ejection process is modeled as one example of a complex flow system. In an inkjet printer, a thermal pulse instantly heats up the liquid in a microfluidic chamber and nucleates bubble vapor providing the pressure pulse necessary to eject droplets at high speed. Our modified method can present a more realistic model of the explosive vaporization process since it can also capture a high-temperature/density gradient at nucleation region. Thermal inkjet technology has been successfully applied for printing cells, but cells are susceptible to mechanical damage or death as they squeeze out of the nozzle head. To study cell deformation, a spring network model, representing cells, is connected to the LBM through the immersed boundary method. Looking into strain and stress distribution of a cell membrane at its most deformed state, it is found that a high stretching rate effectively increases the rupture tension. In other words, membrane deformation energy is released through creation of multiple smaller nanopores rather than big pores. Overall, concurrently simulating multiphase flow, phase transition, heat transfer, and cell deformation in one unified LB platform, we are able to provide a better insight into the bubble dynamic and cell mechanical damage during the printing process.
拟晶格玻尔兹曼方法 (LBM) 可模拟高密度比多相流系统中的相变。如果通过状态方程与热 LBM 耦合，它们可用于研究具有高温梯度的瞬时相变现象，此时 LBM 系统中的一组公式即可处理液体、蒸汽、相变和热传输。然而，在较低温度下，界面上不真实的虚假电流会导致不稳定性，限制其在实际流动系统中的应用。在本研究中，我们对 LBM 系统进行了新的修改，以最小化虚假电流，从而能够在室温下研究成核动力学。为了展示这种方法的能力，我们将热喷射过程建模为复杂流动系统的一个示例。在喷墨打印机中，热脉冲会瞬间加热微流腔中的液体并引发气泡蒸汽，从而提供高速喷射所需的压力脉冲。我们的改进方法可以呈现更真实的爆炸蒸发过程模型，因为它还可以捕捉到成核区域的高温/高密度梯度。热喷墨技术已成功应用于细胞打印，但细胞在从喷嘴头挤出时容易受到机械损伤或死亡。为了研究细胞变形，通过浸入边界方法将代表细胞的弹簧网络模型与 LBM 连接。研究细胞膜在最变形状态下的应变和应力分布，发现高拉伸率有效地增加了破裂张力。换句话说，通过创建多个较小的纳米孔而不是大孔来释放细胞膜变形能。总体而言，通过在一个统一的 LB 平台上同时模拟多相流、相变、传热和细胞变形，我们能够更好地了解打印过程中的气泡动力学和细胞机械损伤。
