Development of a battery-free ultrasonically powered functional electrical stimulator for movement restoration after paralyzing spinal cord injury

Table 2 Comparison of several implantable devices employing different energy transduction technologies

Publication	Method	Frequency (MHz)	Depth (mm)	Medium	Transmitter area (cm²)	Receiver area (cm²)	Input Power^a (mW)	Output Power^a (mW)	Efficiency (%)
[62]	IC	2400	15	Porcine tissue		0.78	0.15	0.0023	1.53
[27]	MF	1600	> 50	Tissue volume	< 36	0.031	500	0.2	0.04
[48]	IC	1500	< 30	Air	< 346	0.06	3200	15.7	0.49
[29]	FF	1000	1500	Air		20.4	15,000	32	0.21
[2]	MF	1600	42	Porcine tissue	< 36	0.53	800	0.45	0.056
[63]	NCC	0.25	1	Human skin	< 6.25	< 6.25		< 100
[61]	NCC	4	0.2	Insulation film	2	192			0.027
[33]	NCC	98	25	Monkey Skin	32	4	316		56
[56]	IC + APT	2 and 0.2	70	Water	0.78	0.78	6000	0.029	< 0.001
[46]	APT	1	105	Phantom	21.3	0.3	1750	28	1.6
[17]	APT	1	30	Mineral oil	0.07	0.014		0.1
[54]	APT	1	5	Porcine tissue	4.91	4.91	2000	440	22
[35]	APT	1.85	21.5	Rodent tissue		0.006		≥0.35
This Work	APT	1	8	Rat skin	7.07	0.78	1000	5.95	0.60

IC inductive coupling, MF mid-field, FF far-field, NCC near-field capacitive coupling, APT acoustic power transfer
^aelectrical

ISSN: 1743-0003