Medical implants that need no battery

How far are battery-free wireless implant sensors from routine clinical use?

In 2014 the FDA approved a pulmonary artery pressure sensor that Healio describes as battery-free. Since then, research groups have powered implant sensors and stimulators with ultrasound and radio fields. Much of that work is in lab tests, explanted or post-mortem tissue, or animal studies, including acute tests in anaesthetised rats. A sensor that checks whether an implant's seal is leaking has been tested only outside living animals. The main gaps are power delivery at depth, long-term tests in living animals and clinical evidence for new sensor types.

AI illustration · Illustrative scene, not a photograph of the specific device or experiment.
WHERE WE AREEngineering prototypes

Getting closer. Prototypes exist, but not in real-world use.

Healio describes the FDA-approved CardioMEMS HF System (2014) as a battery-free implant, so the approach is not limited to the lab. The newer sensors and stimulators reviewed here have been tested in vitro, in explanted or post-mortem tissue, or in animals. The sources opened show no human study of an ultrasound- or radio-powered implant sensor for seal monitoring. NFC-powered implants were not covered by the sources opened, so this review does not rate that route.

The tech tree

Everything recorded on Vrulum that this future needs, oldest foundations at the top and the goal at the bottom. Lines show what each step requires.

What it takes: Medical implants that need no battery Unlocked Being researched Locked
  1. 2012Battery-free wireless implant sensorsResearch and prototypes Being researched.
  1. 2014Battery-free pulmonary artery pressure sensor cleared for patientsDone Unlocked.
  2. 2016Ultrasound power delivered to a millimetre-scale device in tissueDone Unlocked.
  3. 2020Ultrasound-powered stimulator tested on a rat nerveDone Unlocked.
  4. 2021Wirelessly powered bioresorbable pacemaker in cardiac modelsDone Unlocked.
  5. 2022Closed-loop network of wireless, body-integrated devices with a bioresorbable pacemakerDone Unlocked.
  6. 2024Battery-free water-permeation sensor tested outside living animalsDone Unlocked.
  7. Date not recordedWater-permeation sensor tested in living animalsNot started Locked.
  8. Date not recordedPower and readout at deep implant depthNot started Locked.
  9. Date not recordedFirst-in-human study of ultrasound- or RF-powered implant sensingNot started Locked.
  10. Date not recordedPremarket approval for a new battery-free implant sensorNot started Locked.
  1. GoalMedical implants that need no batteryGoalRequires: Battery-free wireless implant sensors, Battery-free pulmonary artery pressure sensor cleared for patients, Ultrasound power delivered to a millimetre-scale device in tissue, Ultrasound-powered stimulator tested on a rat nerve, Wirelessly powered bioresorbable pacemaker in cardiac models, Closed-loop network of wireless, body-integrated devices with a bioresorbable pacemaker, Battery-free water-permeation sensor tested outside living animals, Water-permeation sensor tested in living animals, Power and readout at deep implant depth, First-in-human study of ultrasound- or RF-powered implant sensing, Premarket approval for a new battery-free implant sensor. Locked.

The road so far

6 of 10 steps done.

  1. Done · 28 May 2014Battery-free pulmonary artery pressure sensor cleared for patients

    FDA approved the CardioMEMS HF System (PMA P100045) on 28 May 2014. The FDA record describes it as a system for wirelessly measuring and monitoring pulmonary artery pressure and heart rate, in NYHA Class III heart failure patients who were hospitalised for heart failure in the previous year. Healio describes the implanted sensor as a battery-free monitor, and reports a pivotal study of 550 participants. The FDA record does not state how the sensor is powered. [1][2]

  2. Done · Aug 2016Ultrasound power delivered to a millimetre-scale device in tissue

    Seo and colleagues report that ultrasound is effective at delivering power to mm-scale devices in tissue. A battery-less backscatter device recorded nerve and muscle signals from anaesthetised rats. The sources reviewed give no depth figure for this power transfer. [3]

  3. Done · 19 Feb 2020Ultrasound-powered stimulator tested on a rat nerve

    Piech and colleagues describe a 1.7 mm³ wireless, leadless, battery-free neural stimulator powered by an ultrasonic link. The abstract reports that it was acutely implanted on the sciatic nerve of anaesthetised rats. The integrated circuit also harvested ultrasonic power in ex vivo porcine tissue. This summary relies on the abstract only. [4]

  4. Done · 28 Jun 2021Wirelessly powered bioresorbable pacemaker in cardiac models

    Choi and colleagues describe a leadless, battery-free, bioresorbable pacemaker powered by wireless energy transfer, for temporary postoperative pacing. The abstract reports pacing in mouse, rat, rabbit, canine and human cardiac models. The abstract opened does not give rat pacing durations or the form of the human work, so these are not given here. [5]

  5. Done · 26 May 2022Closed-loop network of wireless, body-integrated devices with a bioresorbable pacemaker

    Choi and colleagues describe a transient closed-loop network of wireless, skin-integrated devices, including a bioresorbable pacemaker. The abstract reports rate-adaptive pacing demonstrated in rat, canine and human heart studies. The sources opened do not state how the network's modules are powered, so this review does not rate its power source. [6]

  6. Done · 28 Aug 2024Battery-free water-permeation sensor tested outside living animals

    Mariello and colleagues built a battery-free RF-backscatter sensor that tracks water getting through an implant coating. It was tested in vitro, in explanted chicken tissue, and in post-mortem mouse tissue. The sensor draws about 3.5 mW (flexible) to 5 mW (rigid), and the post-mortem mouse test gave a water transmission rate of about 2 g m⁻² day⁻¹. The authors say the implant's performance in ex vivo and in vivo conditions could differ. [7]

  7. Not startedWater-permeation sensor tested in living animals

    The authors say full in vivo deployment will need a comprehensive setup optimisation. No living-animal test of this sensor was found in the sources reviewed. [7]

  8. Not startedPower and readout at deep implant depth

    The authors report that antenna gain decreases significantly from subcutaneous to deep implantation, and note that the antenna structure and matching network often need optimising. The sources reviewed give no depth at which readout still works reliably, and deeper placement has not been tested. [7]

  9. Not startedFirst-in-human study of ultrasound- or RF-powered implant sensing

    No human study of an ultrasound- or radio-powered implant sensor for seal or barrier monitoring was found in the sources reviewed. The only battery-free implant reviewed in patients is the approved pressure sensor.

  10. Not startedPremarket approval for a new battery-free implant sensor

    The CardioMEMS sensor was approved through premarket approval (PMA P100045). No new battery-free implant sensor of the kinds described here has been through that route in the sources reviewed. [1]

Why it matters

An implant with no battery could avoid the wear and surgery that come with battery replacement, if its wireless link is reliable. The harder problem is getting enough energy and data through tissue to a device that sits deep in the body. Each step on this path shows how much power can reach an implant, and for how long.

What stands in the way

  • Battery-free does not mean power-independent. The sensors reviewed need an external radio or ultrasound field to power them and read their response.
  • Signal strength falls as an implant sits deeper in tissue. Deeper placement has not been tested for the barrier sensor.
  • The barrier sensor has been tested in vitro, in explanted chicken tissue and in post-mortem mice. Living-animal performance is not shown.
  • The ultrasound stimulator was tested acutely in rats. Long-term power delivery and tissue response in living animals are not shown in the sources reviewed.
  • A new battery-free implant sensor would need valid clinical evidence for regulatory approval. No clinical dataset for the sensors reviewed was found in the sources opened.

Signals to watch

  • A living-animal study of the water-permeation sensor that reports readouts over weeks.
  • A deep-placement test that reports the depth at which readout still works, with the power and reader used.
  • A premarket submission or FDA decision for a new battery-free implant sensor.
  • A first-in-human study of ultrasound- or RF-powered implant sensing with published results.
  • Long-duration ultrasound-powered implants tested in living animals.

Sources

  1. government report
    CardioMEMS HF Pressure Measurement System, PMA P100045
    U.S. Food and Drug Administration, 28 May 2014.
  2. news
    FDA approves first implantable wireless device with remote monitoring for HF patients
    Healio, 28 May 2014.
  3. peer reviewed paper
    Wireless Recording in the Peripheral Nervous System with Ultrasonic Neural Dust
    Seo D, Neely RM, Shen K et al.. Neuron, Aug 2016.
  4. peer reviewed paper
    A wireless millimetre-scale implantable neural stimulator with ultrasonically powered bidirectional communication
    Piech DK, Johnson BC, Shen K et al.. Nature Biomedical Engineering, 19 Feb 2020.
  5. peer reviewed paper
    Fully implantable and bioresorbable cardiac pacemakers without leads or batteries
    Choi YS, Yin RT, Pfenniger A et al.. Nature Biotechnology, 28 Jun 2021.
  6. peer reviewed paper
    A transient, closed-loop network of wireless, body-integrated devices for autonomous electrotherapy
    Choi YS, Jeong H, Yin RT et al.. Science, 26 May 2022.
  7. peer reviewed paper
    Wireless, battery-free, and real-time monitoring of water permeation across thin-film encapsulation
    Massimo Mariello, James Daniel Rosenthal, Francesco Cecchetti et al.. Nature Communications, 28 Aug 2024.

Last reviewed 21 Oct 2026.