All-electronic interrogation of biofluid flow velocity by electrical nanosensors incorporated in ultra-low-power or self-sustained systems offers the promise of enabling multifarious emerging research and applications. However, existing nano-based electrical flow sensing technologies remain lacking in precision and stability and are typically only applicable to simple aqueous solutions or liquid/gas dual-phase mixtures, making them unsuitable for monitoring low-flow (~micrometer/second) yet important characteristics of continuous biofluids (such as hemorheological behaviors in microcirculation). Here, we show that monolayer-graphene single microelectrodes harvesting charge from continuous aqueous flow provide an effective flow sensing strategy that delivers key performance metrics orders of magnitude higher than other electrical approaches. In particular, over six-months stability and sub-micrometer/second resolution in real-time quantification of whole-blood flows with multiscale amplitude-temporal characteristics are obtained in a microfluidic chip.

Overcoming throughput challenges in current graphene defect healing processes, such as conventional thermal annealing, is crucial for realizing post‐silicon device fabrication. Herein, a new time‐ and energy‐efficient method for defect healing in graphene is reported, utilizing polymer‐assisted rapid thermal annealing (RTA). In this method, a nitrogen‐rich, polymeric “nanobandage” is coated directly onto graphene and processed via RTA at 800 °C for 15 s. During this process, the polymer matrix is cleanly degraded, while nitrogen released from the nanobandage can diffuse into graphene, forming nitrogen‐doped healed graphene. To study the influence of pre‐existing defects on graphene healing, lattice defects are purposefully introduced via electron beam irradiation and investigated by Raman microscopy. X‐ray photoelectron spectroscopy reveals successful healing of graphene, observing a maximum doping level of 3 atomic nitrogen % in nanobandage‐treated samples from a baseline of 0–1 atomic % in non‐nanobandage treated samples. Electrical transport measurements further indicate that the nanobandage treatment recovers the conductivity of scanning electron microscope‐treated defective graphene at ≈85%. The reported polymer‐assisted RTA defect healing method shows promise for healing other 2D materials with other dopants by simply changing the chemistry of the polymeric nanobandage.

Precise sensing of microfluidic flow is essential to advancing lab-on-a-chip development and the downstream medical applications. Contactless microfluidic flow interrogation is noninvasive, nonperturbative, and fouling-free. However, known real non-contact flow sensing technologies are limited to quantifying bulk fluids. Here, we develop an electrical approach to contactless quantification of aqueous microfluidic flow. We found that the electric potential generated by the ubiquitous contact electrification of a microfluidic flow with fluidic channel walls is interrogatable by using a probe electrode at a distance over centimeters from the microfluidic flow, and the measured voltage response demonstrates linear relationship to the microfluidic flow rate with a resolution of sub-microliter per minute (in a 1-Hz bandwidth), providing an ideal, high-precision contactless flow transduction pathway. In addition to this primary finding, by using a monolayer-graphene coated probe electrode, in comparison with a typical bare probe electrode, an overall enhancement in flow-sensory resolution of 36.4% is attained.

Electronic detection of DNA oligomers offers the promise of rapid, miniaturized DNA analysis across various biotechnological applications. However, known all-electrical methods, which solely rely on measuring electrical signals in transducers during probe–target DNA hybridization, are prone to nonspecific electrostatic and electrochemical interactions, subsequently limiting their specificity and detection limit. Here, we demonstrate a nanomechanoelectrical approach that delivers ultra-robust specificity and a 100-fold improvement in detection limit. We drive nanostructural DNA strands tethered to a graphene transistor to oscillate in an alternating electric field and show that the transistor-current spectra are characteristic and indicative of DNA hybridization. We find that the inherent difference in pliability between unpaired and paired DNA strands leads to the spectral characteristics with minimal influence from nonspecific electrostatic and electrochemical interactions, resulting in high selectivity and sensitivity. Our results highlight the potential of high-performance DNA analysis based on miniaturized all-electronic settings.