Fajer Mushtaq

Magnetically driven Bi2O3/BiOCl-based hybrid microrobots for photocatalytic water remediation

In this work, we have developed 3D hybrid microstructures consisting of a short ferromagnetic CoNi segment for wireless magnetic control, coupled to a photocatalytic Bi2O3/BiOCl segment for water remediation under UV-visible light. These hybrid microstructures (pillars and helices) were fabricated using 3D photolithography and template-assisted electrodeposition, followed by in situ creation of a Bi2O3/BiOCl heterojunction after oxidation of Bi. This heterojunction is not only active under a wider solar spectrum but also ensures sufficient charge separation and hence low electron–hole recombination rate. As a result, these hybrid microstructures were able to degrade rhodamine B dye with a 90% efficiency in 6 hours. On application of magnetic fields we were able to precisely control the structures and collect them for reuse. Cytotoxicity tests were performed on our hybrid structures and a 95% cell viability was reported showing that our structures are biocompatible.

Hybrid Magnetoelectric Nanowires for Nanorobotic Applications: Fabrication, Magnetoelectric Coupling, and Magnetically Assisted In Vitro Targeted Drug Delivery

An FeGa@P(VDF-TrFE) wire-shaped magnetoelectric nanorobot is designed and fabricated to demonstrate a proof-of-concept integrated device, which features wireless locomotion and on-site triggered therapeutics with a single external power source (i.e., a magnetic field). The device can be precisely steered toward a targeted location wirelessly by rotating magnetic fields and perform on-demand magnetoelectrically assisted drug release to kill cancer cells.

Ultrasound-mediated piezoelectric differentiation of neuron-like PC12 cells on PVDF membranes

Electrical and/or electromechanical stimulation has been shown to play a significant role in regenerating various functionalities in soft tissues, such as tendons, muscles, and nerves. In this work, we investigate the piezoelectric polymer polyvinylidene fluoride (PVDF) as a potential substrate for wireless neuronal differentiation. Piezoelectric PVDF enables generation of electrical charges on its surface upon acoustic stimulation, inducing neuritogenesis of PC12 cells. We demonstrate that the effect of pure piezoelectric stimulation on neurite generation in PC12 cells is comparable to the ones induced by neuronal growth factor (NGF). In inhibitor experiments, our results indicate that dynamic stimulation of PVDF by ultrasonic (US) waves activates calcium channels, thus inducing the generation of neurites via a cyclic adenosine monophosphate (cAMP)-dependent pathway. This mechanism is independent from the well-studied NGF induced mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) pathway. The use of US, in combination with piezoelectric polymers, is advantageous since focused power transmission can occur deep into biological tissues, which holds great promise for the development of non-invasive neuroregenerative devices.

Small‐Scale Machines Driven by External Power Sources

Micro- and nanorobots have shown great potential for applications in various fields, including minimally invasive surgery, targeted therapy, cell manipulation, environmental monitoring, and water remediation. Recent progress in the design, fabrication, and operation of these miniaturized devices has greatly enhanced their versatility. In this report, the most recent progress on the manipulation of small-scale robots based on power sources, such as magnetic fields, light, acoustic waves, electric fields, thermal energy, or combinations of these, is surveyed. The design and propulsion mechanism of micro- and nanorobots are the focus of this article. Their fabrication and applications are also briefly discussed.

Robotically controlled microprey to resolve initial attack modes preceding phagocytosis

The behavior of phagocytes to capture intruders is tracked using remotely rotated and translated nanoparticles. Phagocytes, predatory cells of the immune system, continuously probe their cellular microenvironment on the hunt for invaders. This requires prey recognition followed by the formation of physical contacts sufficiently stable for pickup. Although immune cells must apply physical forces to pick up their microbial prey, little is known about their hunting behavior preceding phagocytosis because of a lack of appropriate technologies. To study phagocyte hunting behavior in which the adhesive bonds by which the prey holds on to surfaces must be broken, we exploited the use of microrobotic probes to mimic bacteria. We simulate different hunting scenarios by confronting single macrophages with prey-mimicking micromagnets using a 5–degree of freedom magnetic tweezers system (5D-MTS). The energy landscape that guided the translational and rotational movement of these microparticles was dynamically adjusted to explore how translational and rotational resistive forces regulate the modes of macrophage attacks. For translational resistive prey, distinct push-pull attacks were observed. For rod-shaped, nonresistive prey, which mimic free-floating pathogens, cells co-aligned their prey with their long axis to facilitate pickup. Increasing the rotational trap stiffness to mimic resistive or surface-bound prey disrupts this realignment process. At stiffness levels on the order of 105 piconewton nanometer radian−1, macrophages failed to realign their prey, inhibiting uptake. Our 5D-MTS was used as a proof-of-concept study to probe the translational and rotational attack modes of phagocytes with high spatial and temporal resolution, although the system can also be used for a variety of other mechanobiology studies at length scales ranging from single cells to organ-on-a-chip devices.

Piezoelectrically Enhanced Photocatalysis with BiFeO3 Nanostructures for Efficient Water Remediation

Summary Designing new catalysts that can efficiently utilize multiple energy sources can contribute to solving the current challenges of environmental remediation and increasing energy demands. In this work, we fabricated single-crystalline BiFeO3 (BFO) nanosheets and nanowires that can successfully harness visible light and mechanical vibrations and utilize them for degradation of organic pollutants. Under visible light both BFO nanostructures displayed a relatively slow reaction rate. However, under piezocatalysis both nanosheets and nanowires exhibited higher reaction rates in comparison with photocatalytic degradation. When both solar light and mechanical vibrations were used simultaneously, the reaction rates were elevated even further, with the BFO nanowires degrading 97% of RhB dye within 1 hr (k-value 0.058 min−1). The enhanced degradation under mechanical vibrations can be attributed to the promotion of charge separation caused by the internal piezoelectric field of BFO. BFO nanowires also exhibited good reusability and versatility toward degrading four different organic pollutants.