Implantable biomedical sensors and actuators are highly desired in modern medicine. In many cases, the implant's electrical power source profoundly determines its overall size and performance . The inductively coupled coil pair operating at the radio-frequency (RF) has been the primary method for wirelessly delivering electrical power to implants for the last three decades . Recent designs significantly improve the power delivery efficiency by optimizing the operating frequency, coil size and coil distance . However, RF radiation hazard and tissue absorption are the concerns in the RF wireless power transfer technology (RF-WPTT) , . Also, it requires an accurate impedance matching network that is sensitive to operating environments between the receiving coil and the load for efficient power delivery . In this paper, a novel low-frequency wireless power transfer technology (LF-WPTT) using rotating rare-earth permanent magnets is demonstrated. The LF-WPTT is able to deliver 2.967 W power at ∼ 180 Hz to an 117.1 Ω resistor over 1 cm distance with 50% overall efficiency. Because of the low operating frequency, RF radiation hazard and tissue absorption are largely avoided, and the power delivery efficiency from the receiving coil to the load is independent of the operating environment. Also, there is little power loss observed in the LF-WPTT when the receiving coil is enclosed by non-magnetic implant-grade stainless steel.
The objective of this study was to determine percutaneous absorption of lead compounds, including lead sulfate, lead oxide, lead powder, and lead stearate. The lead content on the skin surface of 10 lead-battery workers was measured by the method of skin stripping, and urinary lead content of rats was measured with epicutaneous application of four lead compounds: lead sulfate, lead oxide, lead powder, and lead stearate. There were significant amounts of lead on the 9th and 10th skin strippings of the dorsal hand and the back of lead workers. The amount of lead on the dorsal hand was significantly correlated with the amount in the blood (n = 10, r 2 = 0.66, p < 0.05, linear regression). In rats, after lead compounds were applied for 12 days, total lead amount in urine significantly increased to 146.0 +/- 6.4 ng (SD) for lead stearate, 123.1 +/- 7.2 ng for lead sulfate, 115.9 +/- 5.3 ng for lead oxide, 47.8 +/- 6.9 ng for lead powder, and 10.3 ng for the control, which indicated significant skin absorption. It was concluded that significant amounts of inorganic lead compounds can be absorbed through the skin, and skin protection in lead-working or any contaminated environment should be carefully considered.
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