Liquid biopsy, as a minimally invasive method of gleaning insight into the dynamics of diseases through a patient fluid sample, has been growing in popularity for cancer diagnosis, prognosis, and monitoring. While many technologies have been developed and validated in research laboratories, there has also been a push to expand these technologies into other clinical settings and as point of-care devices. In this review we discuss and evaluate microchip-based technologies for circulating tumor cell (CTC), exosome, and circulating tumor nucleic acid (ctNA) capture, detection, and analysis. Such integrated systems streamline otherwise multiple-step, manual operations to get a sample-to-answer quantitation. In addition, analysis of disease biomarkers is suited to point of care settings because of ease of use, low consumption of sample and reagents, and high throughput. We also cover the basics of biomarkers and their detection in biological fluid samples suitable for liquid biopsy on-chip. We focus on emerging technologies that process a small patient sample with high spatial-temporal resolution and derive clinically meaningful results through on-chip biomarker sensing and downstream molecular analysis in a simple workflow. This critical review is meant as a resource for those interested in developing technologies for capture, detection, and analysis platforms for liquid biopsy in a variety of settings.

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Self‐sustainable energy generation represents a new frontier to significantly extend the lifetime and effectiveness of implantable biomedical devices. In this work, a piezoelectric energy harvester design is employed to utilize the bending of the lead of a cardiac pacemaker or defibrillator for generating electrical energy with minimal risk of interfering with cardiovascular functions. The proposed energy harvester combines flexible porous polyvinylidene fluoride–trifluoroethylene thin film with a buckled beam array design for potentially harvesting energy from cardiac motion. Systematic in vitro experimental evaluations are performed by considering complex parameters in practical implementations. Under various mechanical inputs and boundary conditions, the maximum electrical output of this energy harvester yields an open circuit voltage (peak to peak) of 4.5 V and a short circuit current (peak to peak) of 200 nA, and that energy is sufficient to self‐power a typical pacemaker for 1 d. A peak power output of 49 nW is delivered at an optimal resistor load of 50 MΩ. The scalability of the design is also discussed, and the reported results demonstrate the energy harvester's capability of providing significant electrical energy directly from the motions of pacemaker leads, suggesting a paradigm for biomedical energy harvesting in vivo.

ventricular dysrhythmias, and congestive heart failure. [1] Currently, lithium-based batteries provide the power for operations of implantable biomedical devices, such as cardiac pacemakers and AICD. Although the advances in microelectronics technology reduce the internal current drain concurrently allowing for a smaller volume and greater reliability of implantable biomedical devices, the batteries used in those devices only have a few years operating lifetime. Patients are still exposed to health risks associated with doing periodic surgeries to replace the depleted lithium-based batteries of the implantable biomedical devices. Therefore, energy consumption and battery replacement are key to the lifetime and effectiveness of implantable biomedical devices. This work represents an effort in tackling the challenges in extending the lifetime of the batteries for such biomedical devices as cardiac pacemakers and AICDs.Given the advances in low power consumption in implantable biomedical devices (such as 0.3 µW for cardiac activity sensing, [2] 10-100 µW for pacemakers, [3,4] 100-2000 µW for cochlear implant, [5] and 1-10 mW for neural recording [6] ), it is desirable to make them self-sustainable by having their own renewable power supply. One promising way to provide this alternative power source is by means of energy harvesting, i.e., to convert the source energy to electrical energy in order to power implantable biomedical devices. Emerging new approaches on energy harvesting for powering biomedical devices are discussed in the literature. [7][8][9][10][11] In recent development, in vivo studies have been conducted to further advance the energy harvesting capabilities of these devices in living systems. [12,13] For example, a piezoelectric energy harvesting device using single crystalline (1-x) Pb(Mg 1/3 Nb 2/3 )O 3-x PbTiO 3 (PMN-PT) was implanted into the heart of a live rat and the device was then used to show functional electrical stimulation of the heart. [14] Heartbeats of pigs were also used to power wireless communication systems, [15] of which the integration with energy harvesting devices would allow for further implementation into implantable medical devices. Moreover, implantable triboelectric nanogenerators (iTENG) have been employed to convert the mechanical energy from the contraction from breathing of a rat to electricity, which was then used to power a pacemaker. [16] In another application, Self-sustainable energy generation represents a new frontier to greatly extend the lifetime and effectiveness of implantable biomedical devices, such as cardiac pacemakers and defibrillators. However, there is a lack of promising technologies which can efficiently convert the mechanical energy of the beating heart to electrical energy with minimal risk of interfering with the cardiovascular functions. Here a unique design is presented based on existing pacemaker leads tailored for compact energy harvesting. This new design incorporates flexible porous polyvinylidene fluoride-trifluoroethylene thin film withi...

Vibration‐based energy‐harvesting technology, as an alternative power source, represents one of the most promising solutions to the problem of battery capacity limitations in wearable and implantable electronics, in particular implantable biomedical devices. Four primary energy transduction mechanisms are reviewed, namely piezoelectric, electromagnetic, electrostatic, and triboelectric mechanisms for vibration‐based energy harvesters. Through generic modeling and analyses, it is shown that various approaches can be used to tune the operation bandwidth to collect appreciable power. Recent progress in biomechanical energy harvesters is also shown by utilizing various types of motion from bodies and organs of humans and animals. To conclude, perspectives on next‐generation energy‐harvesting systems are given, whereby the ultimate intelligent, autonomous, and tunable energy harvesters will provide a new energy platform for electronics and wearable and implantable medical devices.