Wireless power transfer to deep-tissue microimplants

In the paper

“However, these methods are anatomically specific and, in their existing forms, yield power densities too low (<0.1 μW/mm 2 ) for a microimplant.”

What the sources say

• ?Not checked — no full text of the sourcecites [4] 4. Hochbaum AI, et al. (2008) Enhanced thermoelectric performance of rough silicon nanowires. Nature 451(7175):163-167. source
• Partly supported

  The introductory passage following the Abstract says earlier piezoelectric nanogenerators produced too little power for conventional components. It does not establish that thermoelectric, biopotential, or glucose-based methods are anatomically specific, nor does it give the <0.1 μW/mm² threshold or assess whether those methods can power a microimplant. The Discussion reports this paper’s generator output in mW/cm³, a different measure. (LLM, conf=0.85)

  cites [5] 5. Xu S, Hansen BJ, Wang ZL (2010) Piezoelectric-nanowire-enabled power source for driving wireless microelectronics. Nat Commun 1:93. sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [6] 6. Wang ZL, Wu W (2012) Nanotechnology-enabled energy harvesting for self-powered micro-/nanosystems. Angew Chem Int Ed Engl 51(47):11700-11721. source
• ?Not checked — no full text of the sourcecites [7] 7. Dagdeviren C, et al. (2014) Conformal piezoelectric energy harvesting and storage from motions of the heart, lung, and diaphragm. Proc Natl Acad Sci USA 111(5): 1927-1932. source
• Partly supported

  The passage on implantable energy sources (section labelled Abstract; page unavailable) says thermoelectric and piezoelectric approaches require externally worn apparatuses for mammalian applications, and describes limitations of reported biofuel cells. It does not give a <0.1 μW/mm² power-density threshold for those methods or establish that all four named methods are anatomically specific and too low-power for a microimplant. (LLM, conf=0.84)

  cites [8] 8. Mercier PP, Lysaght AC, Bandyopadhyay S, Chandrakasan AP, Stankovic KM (2012) Energy extraction from the biologic battery in the inner ear. Nat Biotechnol 30(12): 1240-1243. sourceExperimental — accuracy not yet measured

In the paper

“Though well-suited for large devices and prostheses (21,22), near-field methods do not address key challenges to powering a microimplant: weak coupling between extremely asymmetric source and receiver structures (23), dissipative and heterogeneous tissue (24), and regulatory power thresholds for general safety (25).”

What the sources say

• ?Not checked — no full text of the sourcecites [23] 23. Kim S, Ho JS, Poon ASY (2013) Midfield wireless powering of subwavelength au- tonomous devices. Phys Rev Lett 110:203905. source
• Partly supported

  The model and figure in Section 5 report permittivity and conductivity for 17 distinct tissues, supporting the cited point that tissue has differing, dissipative electrical properties. The paper does not assess whether near-field methods can address those properties when powering a microimplant. Citation (24) is attached to the tissue-property point, not the separately cited coupling or regulatory claims. (LLM, conf=0.85)

  cites [24] 24. Gabriel S, Lau RW, Gabriel C (1996) The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues. Phys Med Biol 41(11): 2271-2293. sourceExperimental — accuracy not yet measured
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites [25] 25. Institute of Electrical and Electronic Engineers (2005) IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz. IEEE Standard C95.1 (IEEE, New York).

In the paper

“With exposure levels below human safety thresholds, milliwatt levels of power can be transferred to a deep-tissue (>5 cm) microimplant for both complex electronic function and physiological stimulation.”

In the paper

“Using a patterned metal plate to control the near field, we demonstrate milliwatt levels of power transfer to a miniaturized coil deep in heterogeneous tissue (>5 cm), with exposure levels below safety thresholds for humans; this enables us to power a microimplant capable of delivering controlled electrical pulses to nearly anywhere in the body.”

In the paper

“When coupling 500 mW into tissue (approximately the output power of cell phones), we measured the power transferred to the coil to be 195 μW for the heart and 200 μW for the brain configurations.”

In the paper

“Analysis of the fields on the surface of the skin shows that the evanescent spectrum approximates the theoretical optimum (Fig. 2B), although the contribution of the radiative modes is ∼2× greater owing to the inherent directionality of the planar structure.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. 2B

In the paper

“We demonstrate wireless function by operating it in human-scale heart and brain environments, and by wirelessly regulating cardiac rhythm through a chest wall.”

In the paper

“If the power coupled into tissue is allowed to meet the maximum permitted level of exposure, Fig. 3F shows that 2.2 mW and 1.7 mW can be transferred for the configurations shown in Fig. 3 A and B, respectively.”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. 3F

In the paper

“These levels are far greater than requirements for advanced integrated circuits (Table S1); in comparison, cardiac pacemakers consume ∼8 μW (1, 29).”

What the sources say

• ?Not checked — no full text of the sourcecites [1] 1. Chandrakasan AP, Verma N, Daly DC (2008) Ultralow-power electronics for bio- medical applications. Annu Rev Biomed Eng 10:247-274. source
• ?Not checked — no full text of the sourcecites [29] 29. Wong LSY, et al. (2004) A very low-power CMOS mixed-signal IC for implantable pacemaker applications. IEEE J Solid-State Circuits 39:2446-2456. source

In the paper

“Over an S-shaped trajectory of motion, this adaptation eliminates dark regions that otherwise occur in the static case (Fig. 4 C and D), indicating a coverage area much wider than that intrinsic to the focal region (Fig. S5).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. 4 C and D
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. S5

In the paper

“When positioned above tissue, the structure couples power from the external circuitry into the tissue volume with high efficiency (>90%), as evidenced by both low levels of backside radiation and a pronounced minimum in the scattering spectrum (Fig. S2B).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. S2B

In the paper

“Using a patterned metal plate placed in close proximity to skin, the output field can be focused to dimensions much smaller than the vacuum wavelength, creating a highenergy density region within which the power-harvesting structure can be made extremely small.”

In the paper

“Cardiac rhythm can be controlled in a fully wireless manner by adjusting the operating frequencywhen coincident with the resonant frequency of the circuit, the pulse amplitudes are sufficient to pace the heart, as indicated by the increased rate and regularity of the ECG signal (Fig. 5D).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. 5D

In the paper

“The electrostimulator device shown in Fig. 5 A-C is 2 mm in diameter, weighs 70 mg, and is capable of generating 2.4-μJ pulses at rates dependent on the extracted power; its characteristic dimension is at least an order of magnitude smaller than existing commercial pacemakers (29) due to the absence of a battery (Fig. S6B).”

What the sources say

• ?Not checked — no full text of the sourcecites [29] 29. Wong LSY, et al. (2004) A very low-power CMOS mixed-signal IC for implantable pacemaker applications. IEEE J Solid-State Circuits 39:2446-2456. source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites Fig. S6B

In the paper

“The minimum power to operate the device is ∼10 μW.”

In the paper

“Although considerable progress has been made in energy storage technologies, batteries remain a major obstacle to miniaturization (2, 3) because their lifetimes are limited and highly constrained by the available volume, requiring periodic surgical replacement once the unit is depleted.”

What the sources say

• ?Not checked — no full text of the sourcecites [2] 2. Iddan G, Meron G, Glukhovsky A, Swain P (2000) Wireless capsule endoscopy. Nature 405(6785):417. source
• ?Not checked — no full text of the sourcecites [3] 3. Armand M, Tarascon JM (2008) Building better batteries. Nature 451(7179):652-657. source

In the paper

“The approach developed here should enable new generations of implantable systems that can be integrated into the body at minimal cost and risk.”

In the paper

“All testing procedures and equipment are the same or equivalent to those used to demonstrate safety compliance to international standards for consumer electronics, including cell phones and other wireless equipment.”

In the paper

“Systems based on similar concepts can be applied for any other optical or electrical stimulation task in the body, including neurons or muscle cells; they can also potentially be generalized to networks of individually addressable probes for coordinated mapping and stimulation.”

In the paper

“Because the performance characteristics shown here far exceed requirements for integrated technologies (optoelectronics, microelectromechanical systems sensors, and logic units), there are considerable possibilities for new generations of microimplants: the size, for example, can be further reduced to micrometer scales (23) or more sophisticated functions implemented, such as real-time monitoring”

What the sources say

• ?Not checked — no full text of the sourcecites [23] 23. Kim S, Ho JS, Poon ASY (2013) Midfield wireless powering of subwavelength au- tonomous devices. Phys Rev Lett 110:203905. source