3D Rotation-Trackable and Differentiable Micromachines with Dimer-Type Structures for Dynamic Bioanalysis

emulsion-templated assembly approach. The magnetite nano-12 particles dispersed in vinylbenzene monomers are partitioned into a pair of 13 emulsions with conserved volume, which are wrapped by an aqueous hydrogel 14 shell and ﬁ nally polymerized to form discrete structures. Tunable synchronous – 15 asynchronous rotation over 60 dB is unlocked in magnetic dimers, which is 16 shown to be dependent on the magnetic moments induced. This leads to a new 17 class of magnetic actuators for the parallelized assay of distinctive virus DNAs 18 and the dynamic optical evaluation of 3D cell cultures. The work suggests a new 19 perspective to design smart multifunctional microstructures and devices by 20 exploring their natural variance in magnetic coupling. TBS containing 0.1% Casein) added to react with the structures 23 for 1 h. After the structures with tris buffer three times, ﬂ uores-24 cent dye-labeled probe DNAs (200 pmol) in a reaction buffer were added 25 to react with the structures. The ﬂ uorescence images of the structures 26 were captured by a ﬂ uorescence microscope (FV1000, OLYMPUS).

Gungun Lin,* Yuan Liu, Guan Huang, Yinghui Chen, Denys Makarov, Jun Lin,4 Zewei Quan, and Dayong Jin* 21 1. Introduction 22 Bottom-up assembly of micro-and nanostructures is of general 23 interest to construct functional materials and devices at different 24 scales. [1][2][3][4] The assembly process can be driven by the spontane- 25 ous or directed organization of random building blocks to form 1 ordered structures through localized 2 interactions. Depending on the properties 3 of the building elements, the assembled 4 structures can be endowed with peculiar 5 functions, enabling applications in 6 sensors, [5] actuators, [6,7] photonics, [8,9] and 7 electronics. [10,11] 8 Discrete magnetically actuated assembly 9 structures [12][13][14][15] are preferred for non-10 tethered and contactless operations, flexible 11 motility, and insensitivity to ambient 12 environment, such as temperature, ionic 13 strength, and conductivity, enabling 14 applications in microactuators, motors, 15 and robotic devices. The building blocks 16 can include ferromagnetic, [14] diamag- 17 netic, [16,17] or super/paramagnetic [18,19] 18 micro-and nanostructures. Magnetic inter- 19 actions exist between magnetic entities 20 located in proximity. The interactions can 21 transition from exchange [20] to dipolar-type 22 coupling [21] at different length scales. 23 Assembly of ferromagnetic particles has 24 been relying on the magnetostatic interaction through the 25 magnetic field emanating from the particles designed with 26 specific morphologies and anisotropic properties. [14,21,22] On 27 the other hand, magnetic dipole-dipole coupling is the driving 28 force to guide the assembly of most paramagnetic or superpar-29 amagnetic particles. Most often, particles have been assembled 1 into 1D to 3D arrays to deliver ensemble magnetoproperties, [4] 2 including magnetochromatic [23][24][25] and magnetothermal effects. 3 Limited approaches have been available to assemble a definite 4 number of microparticles, which, nonetheless, is critical to 5 control the inter-particle interactions. Chemical conjugation 6 has been used to link a couple of magnetic microbeads to form 7 discrete microswimmer structures, [26] but it has been difficult to 8 decide the number of magnetic microbeads to be attached. 9 Arrays of microparticles can be potentially patterned with precise 10 inter-particle distance using microfabricated magnetic molds. [16,19] 11 Nevertheless, the formation of discrete magnetic particle pairs and 12 the elaborate engineering of the magnetic coupling thereof 13 have not been addressed, as this typically requires the control 14 over the size and encapsulated magnetic content of the particle 15 building blocks. 16 Actuation-assisted bioanalysis represents an emerging 17 application of micromachines, including microactuators, 18 motors, and microrobotic devices. A range of external stimuli, 19 such as heat, [27] light, [28][29][30][31][32][33] moisture, [34] chemical, [35,36] and 20 magnetic field, [37][38][39][40] have been available to power the microma-21 chines. For instance, light-driven mechanisms can enable local 22 and site-specific actuation of a device. On the other hand, micro-23 machines responding to humidity or chemicals are adaptive to 24 the dynamic variations of chemical environments. Exploring 25 such a variety of mobile micromachines in the bioanalytical field 26 can further provide a range of benefits, including increased 27 reaction binding kinetics, real-time, dynamic, and in situ meas-28 urements. [41][42][43][44][45][46][47][48] Beyond the precise control of a single micro-29 structure, groups of microstructures are of utmost interest for 30 applications that rely on collective behaviors, such as the dynamic 31 sensing of toxins, [41][42][43] cleaning of environment pollutants, [44][45][46][47] 32 and assembly of tissue scaffolds. [49] Large-scale and high-33 throughput biochemical analysis can benefit the most by parallel- 34 izing the assays using differentiable groups of stimuli-responsive 35 microstructures, with each group allocated with a specific task. 36 However, differentiation of microstructures using a single global 37 control signal has proved challenging. [50] Furthermore, micro-38 structures of biocompatible interfaces are ideal for handling 39 small-scale tissues and tissue-like multicellular constructs that 40 are often grown on 3D extracellular matrix. The dynamic analysis 41 of the orientation-dependent features of such 3D structures 42 remains a formidable task. Their tiny scale and opaque nature 43 present major obstacles for both precise positioning and high-44 quality microscopy evaluation. [51] 45 Here, micrometer-sized magnetic emulsions are artfully 46 assembled in polymer gels to achieve tailorable magnetic 47 coupling in magnetoresponsive dimer-type assemblies. Based 48 on a rationally designed emulsion polymerization process 49 in microfluidics, multicompartment microstructures are con-50 structed by partitioning magnetic nanoparticles into a pair of 51 micrometer-sized emulsions with conserved total volume. 52 They are subsequently assembled and finally immobilized with 53 a high level of structural order. The coupling between the 54 emulsion compartments unlocks new degrees of freedom to 55 elaborately engineer magnetic anisotropy within the structures. 56 This leads to the design of 3D rotation-adaptive microactuators 57 that can be manipulated and differentiated using a single global 58 control signal, thereby closing the gap for dynamic bioanalysis, 59 such as the precise positioning and optical evaluation of 3D To tailor the interaction between the magnetic building blocks, 7 we put forth a compartmentalization-assembly strategy 8 (Figure 1) to synthesize dimer-type structures consisting of two 9 magnetic particle compartments. Compartmentalization refers 10 to encapsulating magnetic nanocores, in isolated micrometer-11 sized emulsions. The total energy of the dimer system can be 12 approximated by 13 with the first term describing the Zeeman energy, and the lat-14 ter the dipole coupling energy. Here, L is the distance between 15 the dipoles, m 1 and m 2 are the moments of each dipole entity, 16 and μ 0 is the magnetic permeability. Here, individual magnetic 17 building blocks with definite sizes, e.g., r 1 and r 2 , are approxi-18 mated as interacting dipoles. Anisotropy is induced by the dipo-19 lar coupling and control over the geometric factors, such as L, r 1 , 20 and r 2 , thus opening a window to investigate the interaction 21 in a more systematic manner. This involves the way the assem-22 bled microstructures respond to external magnetic stimuli 23 (Figure 1b). Exploring the variance in coupling between the mag-24 netic building blocks may endow the resultant microstructures 25 with built-in differential response ( Figure 1c) without turning 26 to external addressable actuation. 27 To assemble the structures, a two-step microfluidic emulsifi-28 cation process was implemented using microcapillaries co-axially 29 aligned and connected with two flow junctions ( Figure 2a and 30 Figure S1, Supporting Information). The rapid re-circulation 31 in emulsion droplets is ideal for homogeneously dispersing 32 nanoparticles in polymers. [52,53] Based on such design, the 33 number (N) of the compartments can be regulated by the ratio of 34 the emulsification frequencies (v 1 and v 2 ) at different steps [54,55] (2) 35 Here, Q 1 , Q 2 , and Q 3 are the flow rates of the inner, middle, 36 and outer fluid phases, respectively; a 1 , a 2 , b 1 , and b 2 are all 37 constants determined by the dimension of the fluidic junctions. 38 As the multiphase emulsification is purely mediated by the flow 39 rate without any other free parameters, distinct multicompart-40 ment core-shell structures can be generated on demand. 41 To be noted, the above-mentioned dependency typically 42 applies for general scenarios when N is well above 1. [55] It is 43 shown that by bringing the emulsification frequency ratio (N) 44 below 1, a typical unexplored regime, the frequency ratio reflects 45 the size ratio of internal compartments (Figure 2b). This provides 46 a new approach to fine tailor the above-mentioned geometric 1 parameters based on the emulsion fission. To facilitate this pro-2 cess, elaborate control over the flow rates was implemented to 3 ensure that emulsions generated at the first junction break up 4 well before they pass through the second junction. The resultant 5 dimer structures are of unique pear shapes, as presented in 6 Figure 2c. The total volume of the magnetic compartments is 7 conserved for a series of dual-compartment structures as they 8 are generated by the fission of one parental emulsion compart-9 ment. Systematic adjustment of the relative portion of magnetic 10 compositions, hence, becomes possible. To explore the major 11 flow regimes, the careful control of the flow parameters, namely, 12 the Q 1 /Q 2 and Q 3 /(Q 1 þ Q 2 ), reveals four major distinct struc-13 tural patterns such as those shown in Figure 2c. Their size 14 can be ranging from 50 to 500 μm, depending on the diameter 1 of the fluidic orifice and specific flow rates chosen. Among these 2 patterns, two are stable and characteristic, representing both 3 digital and analogue modulation of magnetic compartments: 4 one comprising uniform compartments, and the other resem-5 bling pears, with N experimentally tunable from 0.5 to 6. 6 Based on the controlled emulsification process, polymeriza-7 tion techniques were next used to construct multicompartment 8 magnetic assemblies. Ferrofluid magnetite particles (SPIONs) 9 with a nominal size of 10 nm were used as the magnetic nano-10 cores. The SPIONs were blended with oily divinylbenzene (DVB) 11 and emulsified into an aqueous solution using a microfluidic 12 flow-focusing junction. Figure 2d shows two critical steps to 13 synthesize the magnetic structures with polymer shells 14 and desired compartmental layout (details are given in Figure 1. Engineering magnetic coupling in microstructure assemblies consisting of multiple magnetic compartments. a) Conceptual illustration of the approach to distribute active magnetic nanocores in a polymer matrix. (Left) Single compartment of magnetic nanocores that are dispersed in the polymer matrix. (Right) Controlled organization of individual microcompartments (denoted by i-iii) to form long-range structural order, which allows tailoring the magnetic interactions between the compartments. Here, r 1 , r 2 , and L denote the size of each compartment and spacing thereof, respectively. The red arrow denotes the magnetic moment. Gaining control over the above-mentioned parameters virtually allows engineering magnetic coupling thereof. b) Multicompartment microstructures can be tracked using a rotating magnetic field (B) with definite strength, orientation, and frequency. c) Groups of multicompartment structures can be differentiated based on their rotation states, namely, how they perceive and interact with the magnetic control source. Fully magnetically isotropic micromachines exhibit only synchronous rotation that are not different in the way they respond to a rotating magnetic stimulation. In contrast, multicompartment microstructures with elaborately engineered magnetic anisotropy exhibit differentiable asynchronous rotation.
In brief, to quickly immobilize the ordered 2 compartments, alginate hydrogel polymers were first applied as 3 the encapsulation layer of the emulsion compartments, formed 4 during the second emulsification step at the second junction. 5 By introducing Ca 2þ ions in the outer oil phase, the alginate shell 6 was rapidly crosslinked to protect the highly volatile magnetic 7 emulsion compartments from coalescence. In addition to the 8 ionic crosslinking mechanism, covalent crosslinking was next 1 implemented to reinforce the stability of the alginate layer. For 2 this, the preformed structures were collected in a bath containing 3 aqueous poly(ethylene glycol) diacrylate (PEGDA) precursors, 4 which were introduced in the alginate matrix by diffusion through 5 the pores of alginate polymers. This processing step strengthened 6 the shell by forming stronger covalent bonds under UV exposure. 7 The final microstructures consisting of varied compartment and 8 biocompatible hydrogel shell interfaces are shown in Figure 2e. Construction of multicompartment magnetic structures using microfluidic emulsion-templated assembly. a) Schematic illustration of a microfluidic setup to synthesize the multicompartment magnetic structures. The setup is consisting of microcapillaries connected by two flow junctions. The first junction is to generate emulsion compartments, and the second junction is used to form a shell that encloses the compartments in discrete entities. Q 1 , Q 2 , and Q 3 are the flow rates of inner, middle, and outer fluidic phases, respectively. b) Representative regimes of fabricating multicompartment double emulsion structures of different levels of structural order. UC: uniform compartments; UPC: uniform pear-shaped compartments; DPC: discrete pear-shaped compartments; and DUC: discrete uniform compartments. c) Images of distinct ordered structures formed in the channel consisting of uniform emulsion compartments, pear-shaped structures with uneven compartments, and non-uniform structures with single compartments. Q 1 , Q 2 and Q 3 are the same as (a). d) Two processing steps are involved: Step 1 is to form in situ the alginate shell by adding Ca 2þ to generate ionic crosslinks, and Step 2 is to form covalent bonds in the polymer shell by UV illumination to generate covalent crosslinks. (Inset) Compartment (core)-shell composition of the structures. e) Microscopy images of representative magnetic microstructures with digital modulation embodied by varied compartment number, or analogue modulation embodied by tailored volume-compartment ratio, compartment-size ratio, and compartment layout. Scale bar for all images in (e): 300 μm. To study the rotation response, magnetic dimer-type structure 4 assemblies were suspended in water and subject to rotation 5 under an external rotating magnetic field with adjustable 6 strength and frequencies (Figure 3a). The critical rotation state 7 is defined as a threshold point when a structure transitions from 8 synchronous rotation when it can still follow the pace of the rotat-9 ing field to asynchronous rotation when it no longer does and 1 simply wiggles (Figure 3b). A sudden drop of the rotating fre-2 quency of the structure was observed at the critical state when 3 the external field frequency is gradually increased from 0 to 4 25 Hz (Figure 3c). Upon that case, the rotation curves manifest 5 themselves as an additional oscillation superimposed on the lin-6 early growing curves. The oscillation of the curves tells that the 7 structures rotate backward as opposed to the rotating direction of 8 the magnetic field. Such a backward movement, as termed 9 "wiggling," is due to the fact that the angle (Δθ) between the 10 direction of the magnetization of the structures and that of Figure 3. Exploring synchronous-asynchronous rotation transition using a rotating magnetic field. a) Schematic illustration of characterizing a dualcompartment magnetic dimer-type structure using a rotating magnetic field. The directions of the magnetic field at different time, e.g., t 1 and t 2 ¼ t 1 þ Δt, are indicated by the arrows. The compartment-to-compartment direction of the structure corresponds to the uniaxial direction of the structure. The rotation angles of the field and the structure with respect to the reference axis are denoted by φ f and φ ma , respectively. Accordingly, the frequencies of the field and the structure are denoted by f field and f ma , respectively. b) Time-dependent rotation angle, φ ma , of a structure driven by a magnetic field (1 mT) at different rotation field frequencies. Inset shows the time-sequenced images of the structure in synchronous (b1) and asynchronous (b2) rotation states. Arrows show the uniaxial direction of the structure. c) Dependence of the rotation frequency of single-compartment structures with different volume-compartment ratios under the same rotating magnetic field of 2.5 mT at different rotating frequencies. d) Plot of the critical frequencies ( f critical ) of the single-compartment structures against the volume-compartment ratio. Line is a fit to the data. e) Dependence of the required magnetic field strength to rotating different micromachine structures to the same critical frequency of 10 Hz. There is a significant drop of magnetic field strength needed for dualcompartment structures, despite that they contain the same amounts of magnetic content as the single-compartment ones with volume-compartment ratio of 1.4. f ) Plot of the critical rotation frequency ( f critical ) against the geometric factor, r 1 r 2 /(r 1 þ r 2 ) of dual-compartment structures. The solid line is a fit of the data using the polynomial function displayed in the figure. Error bars in all plots represent the accuracy of the measured quantities.
1 the magnetic field reaches 90 . With increasing driving fre-2 quency of the field, the time taken for Δθ to reach 90 is propor-3 tionally reduced. This accounts for the scaling of the oscillation 4 frequency with the driving frequency of the field. 5 For idealized superparamagnetic microspheres with purely 6 induced magnetic moment, there is no explicit dependence of 7 the rotating frequency of the structures on the external driving 8 field at low frequencies. [56] However, the apparent dependency of 9 the critical rotation frequency ( f critical ) on the driving field ( f field ) 10 and on the size ratio of the magnetic compartment, as shown in 11 Figure 3c, suggests the existence of mesoscopic "permanent 12 moments." In this regard, the "permanent moments" refer to 13 "part of the materials in the structures that do not instan-14 taneously align its magnetic moment with the field as permanent 15 at the time scale of experiments" in previous studies. [57] In the 16 case that structures driven mainly by permanent moments, 17 its critical rotating frequency is obtained by balancing the hydro-18 dynamic torque and magnetic torque [58] 19 where μ 0 is the magnetic permeability, m is the magnetic 20 moment, H is the magnetic field, η is the dynamic viscosity, 21 and V is the total volume of the rotating body. This relationship 22 suggests a cubic law dependence of the critical frequency on the 23 size ratio between the compartment and the total volume, which 24 is reflected in Figure 3d. This result further confirms that the 25 major magnetic driving force comes from the minor permanent 26 moment for the class of single-compartment structures. 27 Figure 3e compares a series of single-and dual-compartment 28 dimer-type structures. It is shown that by introducing additional 29 compartments to the structures, the magnetic torque is 30 enhanced, and the magnetic field to drive the structures to the 31 same critical rotating frequency of 10 Hz can be reduced by 32 threefold. Based on Equation (1) and details of the derivation pro-33 vided in Supplementary Section 1, Supporting Information, the 34 rotation frequency of the dimer-type structures can be estimated 35 using the relationship as follows f ma ¼ 2πðω i critical sin 2θ þ ω p critical cos θÞ (4) 36 We define θ as the phase lag between the structure and the 37 field, and ω i critical and ω p critical are the critical angular frequencies 38 of induced and permanent moments, respectively. The validity of 39 the above-mentioned relationship was confirmed by applying the 40 structure as a viscometer ( Figure S2, Supporting Information). 41 In this regard, the viscosity of water at different temperatures 42 as well as that of the aqueous glycerol solutions with different 43 concentrations have been successfully determined using the 44 critical rotation frequency of the microstructures. 45 We realize that the relative contributions of the induced or 46 permanent moments can have a strong influence on the critical 47 frequency, which can be either tuned or independent on the 48 structural modulation. In the former case, the critical frequency 49 of the structure can be approximated as 1 To understand the relative roles of permanent and induced 2 moments, the dependence of the critical frequency is plotted 3 against the geometric factor defined by r 1 r 2 /(r 1 þ r 2 ), where r 1 4 and r 2 are the size of the compartments (Figure 3f ). Fitting 5 the above-mentioned data to the relationship described in 6 Equation (5) yields the magnetic susceptibility of the structures 7 (%9.1) that is consistent with the provided value (18.6) of the fer-8 rofluids (EMG 900) with a volume fraction of 50%. This result 9 indicates that tuning the synchronous-to-asynchronous transi-10 tion states of the unconventional class of dual-compartment 11 microstructures relies on induced magnetic moments, which 12 is in stark contrast with that of single-compartment ones. It 13 can be further concluded that the rotation transition states result-14 ing from magnetic dipole-dipole coupling can be effectively 15 tuned through the structural modulation of magnetic building 16 blocks with primary contribution from induced magnetic 17 moments. Remarkably, the unlocked tunability in the character-18 istic critical rotation frequency, found in dual-compartment 19 microstructures, can be spanning over 60 dB owing to the 20 enhanced magnetic field-structure interactions (Supplementary 21 Section 1, Supporting Information).

24
The dipole-dipole coupling-induced magnetic anisotropy of 25 dimer-type structures opens the possibility to design functional 26 actuation tools for complex cellular analysis. The magnetic 27 dimer-type structures were applied as 3D extracellular matrix 28 of multicellular constructs. To facilitate the operation, a compact 29 device was fabricated by inserting a permanent magnet into a 30 3D-printed slide rail with a footprint of 3 cm Â 3 cm Â 1.5 cm, 31 as shown in Figure 4a. It is shown that the structure can be com-32 passed precisely by the magnet (Figure 4b, and Video 2, 33 Supporting Information). In this way, the rotation of the 3D 34 extracellular matrix embodied by the dual-compartment 35 structures can be tracked by the position of the magnet, which 36 is further used to index the orientation of the 3D cell cultures 37 grown on the hydrogel-based extracellular matrix. 38 The cells were seeded in agarose wells where the structures 39 were suspended. The agarose wells were casted from a mold 40 fabricated by 3D printing (Figure 4c). The hydrogel surface 41 of the assembly structures can facilitate cell adhesion and 42 growth. The hydrogel shell of the assembly structures was 43 coated with positively charged poly-Lysine to further enhance 44 the adhesions of the negatively charged cells [59] and to form 45 3D cultures. While a confocal microscope only provides 46 single-axis details of the cells, using the structures with 3D 47 rotational degrees of freedom, it is shown that the distribution 48 of cells on the side and bottom of the entire spheroid was 49 revealed (Figure 4d). In 3D multicellular constructs, cells 50 were distributed around the entire 3D extracellular matrix. 51 In bright-field imaging, cells were hidden above the dark 52 background of the magnetic components (Figure 5a). We find 53 that by expanding the ratio between the extracellular matrix 54 and the assembly, the hidden cells were revealed by rotating 55 or inclining the imaging planes, as shown in Figure 5b,c.
To expand the matrix, the structures were soaked in a culture 2 medium depleted with Ca 2þ . This controllably expands the size 3 of the alginate-based extracellular matrix by swelling. On the 4 other hand, in the most case of using fluorescent labels to stain 5 the cells, where the above-mentioned dark contrast-related 6 issues could become circumvented. 7 In this study, without innovating the imaging algorithm that 8 aims to reduce noises and separate cell clusters, a basic dem-9 onstration of analyzing cell distributions in 3D was conducted 10 using the rotation-trackable structures. Cells were recognized 11 using Image J as colored spots (Figure 5d). As the cells are 12 distributed around a well-defined sphere, the cell positions 13 extracted from a 2D imaging plane (x-y) can be translated into 14 coordinates in other planes using rotation matrices using math-15 ematical calculations (Supplementary Section 4, Supporting 16 Information). With this capability to image on different planes, 17 the cell culture conditions were evaluated. For instance, cells 18 were previously found to have different growing tendencies 19 on the sedimentation flux densities of seeding cells. [60,61] 20 It was revealed that the effects limit the seeding cells to either 21 self-aggregate or adheres on the 3D extracellular matrix 22 (Figure 5f,g) that can be evaluated by the rotational-trackable 23 structures. The tunability and distinguishability in the rotational actuation 3 of magnetic assembly structures will further meet the need 4 for the dynamic screening of multiple distinctive biomolecular 5 analytes, [62] such as viral oligo species. As the differentiable 6 critical rotation frequencies, as the rotational signature, can be 7 fine-tuned on demand using the variance in the dipole-dipole 8 coupling strength built into the structures, an unconventional 9 collection of responsive magnetic microcarriers is established 10 to simultaneously detect an array of target pathogenic DNAs 11 using a microfabricated fluidic chip (Figure 6a). 12 Here, five batches of rotation-differentiable structures exhib-13 iting five unique critical rotation frequencies were synthesized, 14 ranging from 2 to 19 Hz with deviation of the frequencies within    Figure 6c, the critical 4 frequencies of each micromachine can be well identified, so that 5 the target DNAs species can be detected simultaneously in a 6 single test. 7 3. Conclusion 8 In this article, we have demonstrated a new emulsion partition-9 ing approach to engineer the inter-particle coupling in basic 10 dimer-type assembly structures. A collection of microstructures 11 consisting of magnetic emulsion compartments embedded in 12 polymers has been assembled with the assistance of microflui-13 dics due to its superior control over individual emulsions in a 14 continuous flow process. The emulsion partitioning approach 15 allows allocating the magnetic content between the compart-16 ments of the dimer structures. The assembly of the magnetic 1 compartments unlocks new degrees of freedom to modulate 2 dipole-dipole coupling through the tunable compartmental 3 size and size ratio. We have found that the synchronous-4 asynchronous rotation transition relies primarily on the mag-5 netic moment induced for the dimer structures, rather than 6 on the permanent ones inheriting from the original magnetic 7 nanocores for single-compartment ones. This shines light on 8 the roles of different types of magnetic moments in the actuating 9 engineered magnetic structures using a magnetic field. The 10 unique dimer-type emulsion assembly with tunable coupling 11 strength leads to an unconventional class of magnetic actuators, 12 of potential use in complex and dynamic bioanalysis. While it 13 has been known that magnetic anisotropy contributes to the 14 enhanced magnetomechanical effect, this work enables the 15 quantification of the enhancement. 16 The magnetic assembly structures with differentiability in 17 terms of the rotational properties could potentially streamline 18 the process of mixing, washing, separation, and identification 19 of multiple target analytes in a single test using a microchip.  ). d,e) 2D and 3D distributions of cells, respectively. Here, a cell is denoted by a dot, the distribution of which is extracted from the initial greyscale image shown in (a) using an image processing program. f,g) Analyzing cell distributions under different culture conditions using culture wells of f ) 6 mm and g) 3 mm diameters.
www.advancedsciencenews.com www.advintellsyst.com The magnetorotation response, used as barcode signature, is 2 independent to the optical domain as used in traditional 3 suspension arrays, which suggests a promising alternative to 4 conventional fluorescence-based approaches where the spectral 5 crosstalk between the fluorescence encoder and reporter chan-6 nels is a concern. We anticipate that the unique characteristics 7 of dimer-type assembly structures may serve as potential 8 building blocks to construct more complex systems, including 9 smart sensors, actuators, and robotic devices.  The middle phase was 2% Alginate in water containing 0.5% w/w sodium 5 dodecyl sulfate, 0.25% w/w poly(ethylene glycol)-block-poly(propylene gly-6 col)-block-poly(ethylene glycol) (Pluronic F108, BASF, Florham Park, NJ, 7 USA), and 1% w/w photo-initiator (2-hydroxy-2-methylpropiophenone,