Controlled transport of biological cells in biomedical applications such as sorting, cell sequencing, and assembly of multicellular structures is a technological challenge. Research areas such as drug delivery or tissue engineering can benefit from precise cell location resulting in faster response rates or more complex tissue structures. Using computational methods, different soft magnetic elements with curved edges are designed to form a transport network, enabling transport and all functionalities for the manipulation of microbeads and cells on surfaces by rotational magnetic fields. Building blocks with bimodal functionalities due to segments of differently curved edges permit breakpoints as well as switchable transport via splitting and combining elements. Connecting the elements, networked paths are realized which allow variable movement patterns of magnetic carriers and cells. The direction of magnetic field rotation is altered to direct the beads and cells into different transport lines, and the exact timing is not critical. The networks are used to achieve deterministic movement of microbeads and cells with minimal intervention. Programmed transport over one millimeter with cell transport velocities of several micrometers per s is demonstrated. Based on scalable microchip technology, the networks can be integrated with CMOS-compatible materials and straightforwardly combined with sensing and diagnostic structures.

Precise movement control is a key feature for the use of superparamagnetic microbeads in medical and biological lab-on-chip applications. We demonstrate the unidirectional transport of magnetic and biological carriers along a chain of oval shaped magnetic thin film elements by in-plane rotating magnetic fields, enabling controllable manipulation and separation schemes. The same fundamental unidirectional movement is realized independent of the sense of magnetic field rotation and orientation of the magnetic pathway. The flowless directional transport of magnetically labeled rat embryonic fibroblasts is presented, validating the applicability of the structures for biological purposes. The lined up ferromagnetic structures are a critical building block for the construction of flexible pathways for biological lab-on-a-chip applications.

The simultaneous separational control of motion of individual objects is vital to achieve high efficiency separation for biological analytes in biomedical applications. Here, we show the selective and directed movement of different populations of microbeads depending on their size in a flowless environment by means of a hexagonally structured soft-magnetic microchip platform. By adjusting strength and asymmetry of a modulated in-plane magnetic field, discrete and switchable movement patterns of two different types of beads above a magnetic surface structure are achieved. Starting from a heterogeneous mixture of bead populations and depending on the type of field sequences, directional forward transport of one type of beads is achieved, while the other bead population is immobilized. Despite significant size and magnetic content distributions within each population of microbeads, high separation efficiencies are demonstrated. The selection and movement processes are supported by full-scale magnetofluidic numerical simulations. The magnetic platform allowing multidirectional and selective microbead movement can greatly contribute to the progress of functional lab-on-chip and future diagnostics devices.

The manipulation of superparamagnetic microbeads for lab-on-a-chip applications relies on the steering of microbeads across an altering stray field landscape on top of soft magnetic parent structures. Using ab initio principles, we show three-dimensional simulations forecasting the controlled movement of microbeads. Simulated aspects of microbead behaviour include the looping and lifting of microbeads around a magnetic circular structure, the flexible bead movement along symmetrically distributed triangular structures, and the dragging of magnetic beads across an array of exchange biased magnetic microstripes. The unidirectional motion of microbeads across a string of oval elements is predicted by simulations and validated experimentally. Each of the simulations matches the experimental results, proving the robustness and accuracy of the applied numerical method. The computer experiments provide details on the particle motion not accessible by experiments. The simulation capabilities prove to be an essential part for the estimation of future lab-on-chip designs.

The guidance of labeled microcarriers in microfluidic environments is a prerequisite to the development of magnetic pattern assisted lab-on-chip technology. Square wave modulations of in-plane applied magnetic fields enable the forward and backward locomotion of superparamagnetic microspheres on discrete hexagonally arranged ferromagnetic structures in a flowless microfluidic environment at a single bead level. By using distinct magnetic field sequences, selective directional transportation and two-way separational motion of different ensembles of beads across a varying stray magnetic field pattern is achieved. Microbeads can be moved along different directions along spatial microcorridors. The demonstrated realization of multifunctional patterned magnetic surfaces enables the controlled positioning and sorting of mixed populations of functionalized microcarriers for biodiagnostic applications.

The guidance of labelled microcarriers in microfluidic environments is vital for lab-on-chip technology. In article number 1801201, Umer Sajjad, Enno Lage and Jeffrey McCord realize the independent positioning and sorting of mixed populations of superparamagnetic beads across magnetic patterns for biodiagnostic applications. Using hexagonally arranged ferromagnetic elements, a flexible two-way separational motion of beads along spatial microcorridors is achieved.

The motion of functionalized superparamagnetic beads provides the foundation for the manipulation of labelled chemical and biological species in microfluidic environments, where patterned ferromagnetic thin films serve as a versatile and reconfigurable platform for biomedical applications. A recurring release and capture of superparamagnetic microbeads is achieved by moving stray magnetic field gradients generated by a circulating micromagnetic state of a soft magnetic disc. The full micromagnetic analysis of the transport dynamics fully describes the fundamental alternating behaviour of microsphere motion. An excellent level of agreement is obtained between experiment and modelling for all stages of motion, confirming the validity of describing particle motion dynamics in the applied quasi ab initio modelling approach. The demonstrated comprehension of the non-linear microbead displacement opens the way towards the modelling of various alternative dynamic excitation schemes, even for complicated integrated micromagnetic platforms, for controlled biological analytesuperparamagnetic bead manipulation.