Knowledge Base

DEM for Pharmaceuticals

Numerical analysis is a branch of mathematics that applies designing methods which give approximate but accurate numeric solutions to problems that have no exact solution. The discrete element method (DEM) is a numerical technique used in computational mechanics and physics to analyze the behaviour of systems consisting of discrete, interacting particles. It is commonly employed to study the behaviour of granular materials, such as pharmaceutical powders, grains, rocks, and other particulate systems.

In the discrete element method, the particles are considered as individual entities that interact with each other through contact forces. These forces can include friction, cohesion, repulsion, and other relevant physical interactions. By modelling the behaviour of each particle and its interactions, the collective behaviour of the entire system can be simulated and analyzed.

FEM vs DEM It is worth noting here that Finite Element Method (FEM) is distinct from DEM. FEM is a numerical technique primarily used for analyzing the behaviour of structures and continua, such as solid bodies, fluids, and heat transfer. FEM is widely used for structural analysis, heat transfer, fluid flow, and various multiphysics problems. On the other hand, DEM is specifically designed for simulating the behaviour of discrete, interacting particles or granular materials. In DEM, individual particles are treated as discrete entities with their own properties and interactions. It is commonly used to study granular materials and other particulate systems, including their behaviour under different loading and boundary conditions.

DEM Methodology
The DEM typically involves the following steps:

  • Particle Representation: Each particle in the system is represented as a discrete entity with its own properties such as mass, size, shape, and mechanical behaviour.
  • Contact Detection: The DEM software algorithm determines which particles are in contact with each other. This involves checking for overlaps between particle boundaries.
  • Force Calculation: The forces acting on each particle due to contact with other particles are computed. These forces are typically based on the material properties and interaction laws defined for the system.
  • Integration: The equations of motion for each particle are solved numerically to determine their positions and velocities over time. This integration step takes into account the forces acting on the particles.
  • Time Stepping: The simulation progresses in discrete time steps, with the positions and velocities of particles being updated at each time step based on the computed forces.

By repeating these steps, the discrete element method allows researchers and engineers to study a wide range of phenomena, including the behaviour of granular materials under different loading conditions, the flow of particles in hoppers or silos, the compaction of powders, and the stability of structures composed of discrete elements.

DEM has found applications in various fields, including civil engineering, mining, geotechnical engineering, pharmaceuticals, and agriculture, where the understanding of particle interactions and their effects on system behaviour is crucial.

The computational demands of the discrete element method (DEM) are indeed significant, and advancements in computing technology, particularly faster CPUs and higher computing power, have played a crucial role in making DEM simulations more feasible and efficient. Furthermore, the availability of high-performance computing (HPC) resources, such as clusters or cloud-based computing platforms, has further accelerated the execution of DEM simulations. HPC systems provide access to large-scale computational resources, allowing researchers to distribute the computational workload across multiple processors or nodes, thus reducing simulation time.

DEM in the Pharmaceuticals Sector
Let us now see how DEM serves the pharmaceuticals sector. It is particularly useful in the analysis and design of particulate systems and processes. Here are some ways DEM is used in pharmaceuticals:

  • Tablet Compression: DEM can be utilized to simulate the tablet compression process, where powders are compressed to form solid tablets. By modelling the behaviour of individual particles and their interactions during compression, DEM can provide insights into tablet properties such as density, porosity, and mechanical strength. This information helps in optimizing tablet formulations and manufacturing processes.
  • Powder Flow and Mixing: DEM is employed to study the flow behaviour and mixing of pharmaceutical powders. By simulating the movement and interactions of particles in hoppers, mixers, and conveying systems, DEM can analyze powder flow characteristics, identify potential segregation or blockage issues, and optimize powder handling processes.
  • Granulation and Coating Processes: DEM can aid in understanding and optimizing granulation and coating processes in pharmaceutical manufacturing. It can simulate the behaviour of particles during wet granulation, where powders are agglomerated into larger granules, as well as during coating operations, where particles are coated with a layer of material. DEM helps evaluate the impact of process parameters on granule size distribution, coating uniformity, and overall product quality.
  • Inhalation Drug Delivery: DEM can be employed to model the behaviour of inhalable particles used in drug delivery systems such as dry powder inhalers and nebulizers. By simulating particle-particle and particle-device interactions, DEM can assess the dispersion and deposition patterns of inhalable particles in the respiratory system, aiding in the design and optimization of efficient drug delivery devices.
  • Tablet Dissolution: DEM can be utilized to investigate tablet dissolution processes, which involve the disintegration and release of drug substances from solid dosage forms. By considering the dissolution behaviour of individual particles within a tablet, DEM simulations can provide insights into drug release profiles, dissolution kinetics, and the impact of tablet microstructure on dissolution rates.
  • Mixing and Tableting: DEM can help optimize a range of pharmaceutical manufacturing processes including mixing, milling, tableting, and tablet coating.

These are just a few examples of how DEM is applied in pharmaceuticals. By leveraging DEM simulations, pharmaceutical researchers and engineers can gain a deeper understanding of particulate systems, optimize manufacturing processes, improve product quality, and enhance drug delivery systems. DEM serves as a valuable tool for studying the behaviour of pharmaceutical powders, granules, tablets, and other particulate materials, aiding in the development and production of safe and effective pharmaceutical products.

There are several commercially available software packages that offer discrete element method (DEM) capabilities. As an example, EDEM for Altair  provides a co-simulation capability within the Altair HyperWorks platform. EDEM accurately simulates and analyzes the behaviour of powders, tablets and capsules. It can provide key insight into operations and processes otherwise difficult or impossible to obtain using experiments alone. This increases process efficiency and capability, improves product quality, reduce prototyping costs, and helps pharmaceutical manufacturers get products to the market quicker.