Abstract
Minimally invasive medical procedures under magnetic resonance imaging (MRI) guidance have significant clinical promise. However, this potential has not been fully realized yet due to challenges regarding MRI compatibility and miniaturization of active and precise positioning systems inside MRI scanners, i.e., restrictions on ferromagnetic materials and long conductive cables and limited space around the patient for additional instrumentation. Lorentz force‐based electromagnetic actuators can overcome these challenges with the help of very high, axial, and uniform magnetic fields (3–7 Tesla) of the scanners. Here, a miniature, MRI‐compatible, and optically powered wireless Lorentz force actuator module consisting of a solar cell and a coil with a small volume of 2.5 × 2.5 × 3.0 mm3 is proposed. Many of such actuator modules can be used to create various wireless active structures for future interventional MRI applications, such as positioning needles, markers, or other medical tools on the skin of a patient. As proof‐of‐concept prototypes toward such applications, a single actuator module that bends a flexible beam, four modules that rotate around an axis, and six modules that roll as a sphere are demonstrated inside a 7 Tesla preclinical MRI scanner.
Highlights
As proof-of-concept prototypes by high magnetic field gradients inside toward such applications, a single actuator module that bends a flexible beam, four modules that rotate around an axis, and six modules that roll as a sphere are demonstrated inside a 7 Tesla preclinical magnetic resonance imaging (MRI) scanner
Wireless Lorentz force actuator primarily consists of two components: a photovoltaic cell, which can be a solar cell, photodiode, or a light-emitting diode (LED), and a coil
The initial torque given by the two fibers rolls the sphere and moves it forward along the B0 direction as shown in Figure 7e and Movie S7 in the Supporting Information. Another example of rolling and forward motion of the sphere inside MRI scanner is demonstrated in Figure S5 in the Supporting Information. These results prove that such a wireless sphere could roll on surfaces, e.g., on the skin of a patient and position an MRI marker placed inside
Summary
Wireless Lorentz force actuator primarily consists of two components: a photovoltaic cell, which can be a solar cell, photodiode, or a light-emitting diode (LED), and a coil. The current to the module (I) is supplied wirelessly by optical power through a solar cell (Figure 1a,i). The resulting actuator module dimensions are 2.5 × 2.5 × 3.0 mm3 This small-sized module prototype is expected to generate maximum force and torque values of 96 mN and 197 μNm, respectively with 10 mA current through its coil under optical power of 7 mW mm−2, where B0 = 7 T (see Note S1, Supporting Information). An optically powered actuation proof-of-concept demonstration of free wireless actuator modules on the surface of a 0.1 T permanent magnet by a spot of laser beam light can be found in Movie S1 in the Supporting Information
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