The wave-particle duality is not limited to "manipulated" particles used in laboratory experiments like the double-slit experiment. It is a fundamental concept that applies to all particles, including ordinary matter.
The behavior of particles at the quantum level, where wave-particle duality is observed, is not dependent on whether the particles are specially prepared or manipulated in a laboratory setting. The wave-like and particle-like behavior is inherent to the nature of particles themselves.
In fact, all particles, including those that make up ordinary matter like electrons, protons, and neutrons, exhibit wave-particle duality. However, the wave-like properties become more apparent and significant at the microscopic scale, where quantum effects dominate.
While we don't directly observe the wave-like nature of macroscopic objects in our daily lives because their wavelengths are extremely small and quickly decohere due to interactions with the environment, the underlying wave-particle duality still applies to them. However, the wave-like behavior becomes less noticeable and is effectively averaged out, leading to the classical behavior we observe.
The double-slit experiment with particles such as electrons and photons is just one way to demonstrate and study the wave-particle duality. But the principles of quantum mechanics, which include wave-particle duality, have been tested and verified through numerous experiments and observations across various contexts, not limited to manipulated particles in a laboratory. The behavior of particles in these experiments aligns with the predictions and mathematical framework of quantum mechanics, supporting the idea that all particles possess both wave-like and particle-like characteristics.