In the care of patients with abnormal intracranial pressure, it is important to continuously and accurately measure the intracranial pressure so that treatment can be instituted. Strain gage pressure cells have successfully replaced the open-end manometer for chronic use but have lacked the stability for accurate long-term measurements. The system described uses a capacitive pressure transducer with excellent long-term stability. The transducer, electronics, and transmitter package can be implanted to telemeter the pressure transcutaneously, reducing the danger of infection by the elimination of transcutaneous leads. The pressure modulates the frequency of an oscillator in the 8-10 MHz region and provides an easily telemetered signal. To eliminate the problems of periodic battery replacement, the system is energized inductively by a coil placed externally over the implant device, so that the operating life is virtually unlimited.
This paper discusses design optimization of an electromagnetic soft actuator composed of two antagonistic solenoids that share a permanent magnet core. First, calculation of the magnetic field and applied force of a solenoid with a permanent magnet plunger is presented as the principal component of this electromagnetic actuator. Design optimization of the coil is discussed considering the geometrical parameters of the coil, including its length, inner and average diameters, number of turns and packing density while the power consumption is bounded. The impact of the actuator size on the resultant force is presented and scaling limitations are discussed. Then, due to the soft nature of the actuator's component, the impact of the cross-section, i.e. lateral deformation of the actuator on the magnetic field at the center of section is investigated as well. The deformation might happen to the actuator due to the load in the transverse direction, especially when the actuator is made of flexible materials.
