  To address these limitations of optogenetics, here we propose two new methods
for optogenetic stimulation. The first is x-optogenetics, which uses visible
light-emitting nanophosphors stimulated by focused x-rays. This idea is not new
but the application to optogenetics is novel. X-rays can penetrate much more
deeply than infrared light and could allow for nerve cell stimulation in any
part of the brain. In this paper, we discuss the feasibility and possibilities
of such a method by describing the advances in nanomaterials, x-ray focusing,
and x-ray sources. Also, we discuss concerns when dealing with x-rays such as
radiation dosage. Through the use of quantities and assumptions backed by
recent literature, manufacturer specifications, and personal correspondence, a
full feasibility analysis of x-optogenetics is completed. The second proposed
method we explore is u-optogenetics, which is the application of
sonoluminescence to optogenetics. Such a technique uses ultrasound waves
instead of x-rays to induce light emission, so there would be no introduction
of radiation. However, the penetration depth of ultrasound is less than that of
x-ray. The key issues affecting feasibility are laid out for further
investigation into both x-optogenetics and u-optogenetics.
