1) Nanorobots could potentially be used to treat AIDS by recognizing and converting HIV-infected white blood cells back to their original form, maintaining a constant level of immune cells and allowing the patient to defend against diseases.
2) The nanorobot would use a DNA sensor to identify HIV-infected cells and an RNA converter to change the cell's RNA and reverse the HIV infection. It would be powered by metabolizing glucose and oxygen or external acoustic power.
3) Key challenges in using nanorobots for this approach include their size needing to be small enough to avoid blocking blood flow while still performing tasks, using biocompatible materials like diamond or carbon that don't trigger an immune response, and