Instrumentation & Measurement Magazine 23-4 - 73

coil group and the transmitting coil array. Consequently, the
transmission efficiency is stable even when the receiving terminal is in different positions. This technology is also the
basis for one-to-many wireless charging. According to the
required power of the load and the relative position between
the transmitting terminal and the receiving terminal, the device can achieve the coupling between the multi-input and
the multi-output, effectively reducing the design difficulty
of the high-power resonant transmission link, and greatly
improving the transmission efficiency. It is foreseen that the
implantable devices in the future will enable wireless charging without space limitation.

Fig. 10. LDO transient response waveform.

When the load current switches between 12 μA and 5 mA
with a rising and falling time of 20 ns, the overshoot and undershoot are 80 mV and 150 mV, respectively. It takes 10 ns for
LDO to recover to stable voltage. The experiment shows that
the output of LDO has less than 10% variation even under
wireless charging condition.

Applications
Vital Sign Sensors
As the leading supplier of wireless charging solutions in the
world, Sprouting Technology Co., Ltd. first announced a
new generation of wireless charging devices-"RiCharge"
which can be used for implantable biomedical applications
in a three-dimensional space, and the output power of the
device can be dynamically adjusted to a maximum of 100
W. The technical results have been delivered to customers
for acceptance and have successfully entered the evaluation stage.
As shown in Fig. 11a, researchers arrange the wireless charging transmitter of the "RiCharge" in the wall of
a transparent incubator with length, width and height of
20 cm, 30 cm and 20 cm, respectively. The organism in the
box is implanted with a vital sign sensor which includes the
wireless charging receiver shown in Fig. 11b. The experimental results show that the sensor can be charged stably
when the organism moves in the incubator. This device employs Sprouting's independent research which is called "the
magnetic field equal distribution technology." It can make
three-dimensional space generate the equal magnetic field
distribution by dynamic coupling between the excitation

Heart Pumps
According to the World Health Organization, cardiovascular
disease causes approximately 17.9 million deaths each year,
accounting for 31% of the global total. An important reason
for the dramatic increase in the number of patients with cardiovascular disease is that fast-paced lives deprive people of
the time and energy to maintain a healthy lifestyle. The cost
of treating cardiovascular diseases in the United States is expected to reach $1 trillion by 2035 [18].
Most cardiovascular diseases manifest as heart failure. When the heart partially or completely loses function
due to disease and cannot maintain normal blood circulation throughout the body, the heart pump can temporarily
or permanently, partially or completely, replace the heart
function and promote blood circulation. Clinically used
heart pumps are powered by rechargeable batteries currently. Since the charging wire is passed through the body,
the wound makes it is easy to cause infection. Patients must
pay great attention to the battery level, because they only
have 15 minutes to recharge after the device is powered off,
which will bring great danger to their lives. Recently, a wireless charging device for heart pumps was released, which
can be mounted on a vest. The device uses coplanar energy
transfer technology to charge the heart pump stably and
can maintain power supply for at least 8 hours [19]. Patients
have double protection to ensure proper operation of the
heart pump. Since the heart pump is not directly connected
to the outside, there is no wound. Experiments show that
the device can charge a heart pump made by Jarvik Heart
Inc. wirelessly.

Micro-implants

Fig. 11. Experimental scheme of the "RiCharge" system. [17]. (a) Experimental
simulation scheme; (b) RiCharge receiver.
June 2020

Micro-implants can achieve drug delivery, continuous monitoring and personalized treatment in a compact device.
Researchers at the Massachusetts Institute of Technology
(MIT) have developed a new system that can communicate
with outside and be powered wirelessly.
As shown in Fig. 12a and Fig. 12b, the proposed microimplant is only about the size of a rice grain, and it can be
placed deep in the body and powered by radio frequency
waves. During animal testing, the researchers demonstrated that these radio frequency waves were able to power
devices located 10 cm deep under tissue with a distance of

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