publications

Flow past obstacle clusters in micro-channels is central to a wide range of microfluidic applications, yet its fundamental hydrodynamics remain poorly understood under strong geometric confinement.

No-slip boundary conditions on all walls enforce inherently three-dimensional (3D) flow structures in fully confined micro-channels, fundamentally altering wake formation, momentum transport, and drag mechanisms. A combined experimental and numerical investigation of wake dynamics behind obstacle clusters in laminar micro-channel flows is presented. High-resolution micro-particle image velocimetry and resolved 3D computational fluid dynamics simulations are employed to systematically explore the effects of Reynolds number and cluster porosity. We demonstrate that full wall confinement suppresses classical wake–regime transitions commonly observed in shallow and unconfined flows, including shear layer instabilities and vortex shedding. Instead, wake recovery is governed primarily by secondary flows that promote rapid momentum redistribution across the channel depth. As a result, wake length exhibits only weak dependence on Reynolds number and is controlled predominantly by cluster porosity. We further introduce the relative bleeding velocity as a unifying metric to characterize the transition from macro-particle to individual particle behavior. The relative bleeding velocity is the ratio of the mean velocity through the cluster’s main axis perpendicular to the inflow and the mean inflow velocity. These findings establish a distinct physical regime of confined wake flows, bridging the gap between classical shallow flow theory and microfluidic hydrodynamics, and provide a foundation for improved prediction of pressure losses, transport, and mixing in micro-reactors and porous microfluidic systems.

Efficient mixing in microfluidic systems is bottlenecked by laminar flow and diffusion-dominated transport, limiting the performance of biochemical assays such as conversion rates of enzymatic processes. Here, we present an acoustofluidic micromixer based on two-photon polymerization (2PP)-printed three-dimensional microneedles that act as ultrasonic microresonators to generate localized acoustic streaming. The freeform arrangement of the microneedles enables integration into diverse microfluidic channel layouts and produces strong, tunable streaming vortices that enhance transport. We characterize the streaming flow fields as a function of actuation frequency, and demonstrate rapid and voltage-dependent mixing with a 2.5-fold enhancement. When applied to the alkaline phosphatase–fluorescein diphosphate (ALP–FDP) reaction, acoustic mixing doubles the fluorescein signal under optimal conditions and significantly reduces the assay time and channel footprint required in continuous flow. These resultsdemonstrate that 3D microneedle-based acoustofluidics is a compact, versatile, and integrable solution for enhancing transport-limited biochemical processes in lab-on-a-chip systems.

Magnetic remote actuation of soft materials is attractive for applications such as transforming materials and medical robots. However, due to manufacturing limitations, microscale magnetoactive devices are scarce and light-based additive manufacturing methods, despite achieving microscale resolution, struggle with particle-induced light scattering. Moreover, large hard-magnetic microparticles restrict ultimate feature sizes and deformation of soft-magnetic nanoparticle composites requires impractically high loading and field gradients. Among successfully fabricated microscale soft-magnetic composites, limited control over particle loading, distribution, and matrix-phase stiffness has hindered their functionality. Here, we combine two-photon polymerization with iron oxide nanoparticle co-precipitation to fabricate 3D-printed microscale nanocomposites with spatially tunable nanoparticle distribution. We controlled nanoparticle content by locally modulating the two-photon dose, imbuing parts with varied magnetic functionality and achieving millimeter-scale elastic deformations, demonstrated by a soft robotic gripper and a bistable bit register and sensor. Our approach enables precise control of mechanical and magnetic properties toward microscale metamaterial and robotics applications.

Magnetic remote actuation of soft materials is attractive for applications such as transforming materials and medical robots. However, due to manufacturing limitations, microscale magnetoactive devices are scarce and light-based additive manufacturing methods, despite achieving microscale resolution, struggle with particle-induced light scattering. Moreover, large hard-magnetic microparticles restrict ultimate feature sizes and deformation of soft-magnetic nanoparticle composites requires impractically high loading and field gradients. Among successfully fabricated microscale soft-magnetic composites, limited control over particle loading, distribution, and matrix-phase stiffness has hindered their functionality. Here, we combine two-photon polymerization with iron oxide nanoparticle co-precipitation to fabricate 3D-printed microscale nanocomposites with spatially tunable nanoparticle distribution. We controlled nanoparticle content by locally modulating the two-photon dose, imbuing parts with varied magnetic functionality and achieving millimeter-scale elastic deformations, demonstrated by a soft robotic gripper and a bistable bit register and sensor. Our approach enables precise control of mechanical and magnetic properties toward microscale metamaterial and robotics applications.

Magnetic remote actuation of soft materials is attractive for applications such as transforming materials and medical robots. However, due to manufacturing limitations, microscale magnetoactive devices are scarce and light-based additive manufacturing methods, despite achieving microscale resolution, struggle with particle-induced light scattering. Moreover, large hard-magnetic microparticles restrict ultimate feature sizes and deformation of soft-magnetic nanoparticle composites requires impractically high loading and field gradients. Among successfully fabricated microscale soft-magnetic composites, limited control over particle loading, distribution, and matrix-phase stiffness has hindered their functionality. Here, we combine two-photon polymerization with iron oxide nanoparticle co-precipitation to fabricate 3D-printed microscale nanocomposites with spatially tunable nanoparticle distribution. We controlled nanoparticle content by locally modulating the two-photon dose, imbuing parts with varied magnetic functionality and achieving millimeter-scale elastic deformations, demonstrated by a soft robotic gripper and a bistable bit register and sensor. Our approach enables precise control of mechanical and magnetic properties toward microscale metamaterial and robotics applications.

In this work, we demonstrate the fabrication as well as immediate application of 3D printed spiral phase plates on the ends of FC/PC fiber adapter ferrule tips using a NanoOne 1000 two-photon polymerization 3D printer from UpNano. The spiral phase plates were fabricated to alter the orbital angular momentum of incoming light, and a direct application of modal filtering in an indoor, short-range, free-space optical communication link was shown. The mode conversion quality of six different 3D printed spiral phase plates on ferrule tips is presented. An l=4 and an l=−4 spiral phase plate were chosen to demonstrate the ability to suppress an aggressing Gaussian signal in a free-space communication link, with the l=4 being printed on a FC/PC ferrule tip used as the transmit, and the l=−4 printed on a glass slide in the receive architecture of the system. Multiple iterations of the experiment were performed, and it was found that the 3D printed structures were able to suppress the aggressing Gaussian beam on average by approximately 32.7 dB and allowed for error-free communication at 10 Gbps on a vortex beam with the co-propagating aggressor at an identical wavelength to the communication link.

Diseases or injuries that affect neuromuscular tissues severely impact human health, motivating the development of in vitro models of the motor control system. Current platforms either have limited reproducibility or require complex fabrication protocols that preclude high-resolution imaging and scalable functional analysis. We have developed a one-step method for fabricating an all-hydrogel limb-on-a-chip that addresses key challenges of current systems by enabling reproducible and scalable manufacturing of neuromuscular tissues compartmentalized into “spinal cord” and “limb” chambers. Co-cultures of motor neurons and skeletal muscles within this platform enable longitudinal tracking of neuromuscular junction formation and visualization of changes in muscle contraction in response to motor neuron stimulation. We demonstrate tissue-wide recordings of muscle force and single-cell-resolution measurements of muscle calcium activity. Our accessible method for fabricating reproducible in vitro neuromuscular models that are compatible with high-resolution imaging and functional readouts provides a powerful tool for investigating the neuromuscular interface in health and disease.

Surface modifications of polycaprolactone (PCL) implants influence osseointegration by altering cell adhesion, proliferation, and differentiation. Osteon-like microtopography has been shown to enhance these parameters compared to untreated PCL. Additional treatments, such as cold atmospheric plasma (CAP) and extracellular matrix (ECM) coatings, may further improve bioactivity. This study evaluates and compares the osteogenic potential of osteon-like microtopography, CAP treatment on non-microstructured PCL, ECM coating on non-microstructured PCL, and their combination. Modified PCL samples were analyzed for cell adhesion, proliferation, and differentiation using primary human mesenchymal stem cells. Compared to osteon-like microtopography, CAP-treated and ECM-coated surfaces the combination of all three increased cell adhesion by nearly two-fold. Cell proliferation followed a similar trend, with the combination treatment showing the greatest enhancement by day 10. Alkaline phosphatase activity peaked with osteon-like microtopography, while mineralization was maximized with the combination treatment. In summary, the integration of osteon-like microtopography with CAP treatment and ECM coating synergistically improves cell adhesion, proliferation, and differentiation, offering a promising strategy for optimizing PCL implants to improve osseointegration.

Endovascular interventions—i.e., minimally invasive procedures that involve navigating guidewires and/or microcatheters through a patient’s vasculature to access target treatment sites—have emerged as a preferable alternative to traditional open surgery in many clinical contexts. Unfortunately, maneuverability constraints inherent to conventional guidewire-microcatheter systems can hinder effective navigation to target sites, elevating the risk of procedural complications or failed catheterization. Soft robotic surgical instruments that harness fluidic actuation schemes hold unique promise to overcome such challenges; however, manufacturing-induced limitations remain a critical barrier to their miniaturization, reproducibility, and clinical translation. To address these issues, in this work, a novel additive manufacturing strategy is presented to realize fluidically steerable soft robotic microcatheters via “two-photon direct laser writing (DLW)”. As an exemplar relevant to 3-French (1 mm-in-diameter) microcatheters used for transarterial chemoembolization (TACE), a 3D-printed soft microrobotic tip is fabricated, which enables localized steering driven by microfluidic inputs while simultaneously facilitating fluidic payload delivery through a central lumen. By providing a pathway to new classes of soft robotic microsurgical instruments that enable on-demand steerability via fluidic means, the presented strategy offers notable potential for navigating narrow, complex, tortuous, and/or delicate vasculature to enhance the safety and efficacy of endovascular therapy.

Swimming bacteria move through a fluid by actuating their moving body parts. They are force-free and can be described as hydrodynamic force dipoles: pushers or pullers. This modelling description is broadly used in biological physics and active matter research, and it has successfully predicted, for example, the superfluid behaviour of suspensions of pushers or the bend instability and emergence of turbulent flows in active nematics. However, this description accounts only for the translational motion of the swimming body and neglects the effects of hydrodynamic torque dipoles, which are relevant to bacteria with rotary motor-driven flagella, such as swimming Escherichia coli. Here we show that the torque dipole of confined swimming E. coli can power the persistent rotation of symmetric discs. The torque dipole leads to a traction force on the discs, an additive mechanism that is both contactless and independent of the orientation of the bacteria. Our results indicate that the torque dipole of swimming E. coli is notable in confined geometries, which is relevant to bacterial transport through porous materials, biofilms and the development of chiral fluids.

Purpose
Surface micropatterning is being explored as a strategy to mitigate thrombus formation and reduce long-term anticoagulation requirements in left ventricular assist devices (LVADs). This study investigated whether specific micro-topographies can modulate platelet deposition under LVAD supraphysiological wall shear stress (WSS) conditions.

Materials and Methods
A custom microfluidic platform was developed to generate a linear WSS gradient from 16 to 130 Pa. Microchannels were patterned with reverse cones and hemispheres in small (1–3 µm) and large (3–9 µm) sizes using two-photon polymerization and nanoimprinting. Human blood was perfused through the microchannels, and platelet deposition was quantified over time as the area coverage ratio (Aₚₗₜ/Aₜₒₜ) and area under the curve (AUC). Platelet detachment events were counted as an indicator of thrombus stability, and computational simulations supported the interpretation of local shear conditions.

Results
Consistent trends emerged, although no statistical differences were observed relative to flat controls. Aₚₗₜ/Aₜₒₜ increased with WSS for all surfaces. At 16 Pa, small and large cones reduced platelet adhesion by approximately 84 and 98%, respectively, compared to flat controls. At 49 Pa, the reduction was about 95% for small cones and 80% for large cones. Conical geometries also promoted platelet washout at higher WSS. Small hemispherical features showed more than 50% lower platelet adhesion than flat surfaces for WSS > 16 Pa, with limited thrombus growth.

Conclusion
Conical micropatterns may be most effective at limiting platelet adhesion at lower WSS, while small hemispheres may perform better at higher WSS. These trends suggest a surface–shear interaction that warrants further investigation for LVAD surface optimization.

We present a scalable cryo-CMOS controller for color-center-based quantum processors. A diamond waveguide micro-chiplet with NVs is pick-and-placed on CMOS with a 3D-printed prism for scalable photonic readout. A serial qubit driver array using grid inductors and pulse-width modulators generates a programmable 2.87GHz magnetic field for each qubit with low power and strong confinement. Up to 144 qubits can be operated on a single chip, with 204μW power consumption per qubit under active control.

The success of cardiovascular devices is hindered by non-physiological flow conditions and surface materials, which can trigger platelet activation and lead to thrombus formation with severe consequences for patients. While anticoagulation treatments help prevent thrombus formation, they can compromise hemostasis and thereby increase the risk of bleeding. In this study, physical surface modifications through specific micropatterning, cones, riblets, grids, and hemispheres were investigated as a non-pharmacological strategy to reduce platelet adhesion on blood-contacting devices. Fabrication methods based on two-photon polymerization (2PP) 3D printing combined with nanoimprinting lithography were employed to achieve high micro-scale resolution. Platelet adhesion was investigated under low-WSS conditions, and adhering platelets were reduced by 45%, 29%, 25%, and 41%, respectively, for cones, riblets, grids, and hemispheres compared to the flat reference control. Our findings demonstrate that surface micropatterning at the blood–material interface represents a promising approach to modulate thrombus formation risk in cardiovascular devices.

Shape memory polymers capable of recovering their original form after deformation are highly desirable for applications in soft robotics, biomedical engineering, and microfabrication. However, integrating shape memory properties into 3D-printed microstructures with ultra-low mass remains a challenge, as most existing systems lack sufficient resolution or mechanical robustness at the microscale. In this study, a poly(ε-caprolactone)-based material, crosslinked via thiol–ene chemistry, is developed to fabricate mechanically stable 3D-microstructures using two-photon polymerization. This process enables sub-micron features down to approximately 550 nm. Printing parameters, including laser power, scan speed, hatch distance, and layer height, are optimized to produce complex micro-architectures with high CAD-CAM fidelity. Micrometer-scale geometries are successfully printed, including hollow scaffolds weighing 0.89 µg. These scaffolds exhibit excellent shape memory behavior, fully recovering their original shape upon heating even after compressive loads exceeding five million times their own weight. This microscale demonstration confirms that shape memory functionality translates reliably from macro- to microscale without compromising structural integrity. Macroscale dynamic mechanical analysis shows excellent shape fixity (Rf >99.45%) and shape recovery ratios (Rr >99.07%) across multiple thermal cycles, while nanoindentation validates microscale stiffness and structural integrity.

In the pursuit of realizing reliable clean energy generation via inertial confinement fusion (ICF), wetted foam (WF) capsule targets have long been coveted due to their potential to simplify the target fielding process and suppress hydrodynamic instabilities and material mixing that limit achievable energy output, yet producing and deploying a WF target has proven challenging. In this work, we demonstrate the design, fabrication, metrology, and testing of fully additively manufactured (AM) foam-lined capsules using two-photon polymerization (2PP) for ICF. We successfully fielded an AM polymeric foam capsule with a 3-mm outer diameter, a nominally 15-µm-thick solid outer layer, a 120-µm-thick inner foam layer, and a 250-µm outer diameter copper fill tube on the National Ignition Facility for a polar direct-drive shot, and we showcase deuterium wetting of the capsule foam layer inside an ignition target proofing station. Our exploration showed that 2PP can produce fieldable targets with complex geometries and potentially shorten the design iteration turnaround time and the overall target fabrication time.

We present a modular design strategy for the one-step fabrication of arrays of magnetically responsive microactuators connected to the substrate via compliant hinges. We use direct laser writing in the form of two-photon crosslinking within bilayer films to generate three-dimensional microstructures in which magnetic nanoparticles are embedded in the upper layer. This part of the generated structure drives the actuation, while the hydrogel bottom layer is used to form a mechanically compliant hinge structure. The chemical composition and geometrical features of the hinge control the actuation amplitude, the mechanical properties, and the environmental adaptability. Hydrogel hinges provide stability and strong actuation in an aqueous environment, while stimulus-responsive hinges allow for the dynamic reconfiguration of the actuation and bistable behavior without altering the magnetically driving component. This hinge-based approach establishes a new class of adaptive microactuators and provides a generalizable platform for programmable soft micromachines.

Two-photon polymerization (2PP) has garnered increasing attention for engineering hydrogels with tailored architectures and controlled cellular responses. However, current 2PP strategies typically rely on (meth)acrylated proteins and inefficient chain-growth crosslinking mechanisms. Although thiol-ene photo-click reactions can enhance 2PP efficiency, commercial water-soluble thiol crosslinkers (e.g., DTT—dithiothreitol) tend to form intramolecular loops and introduce structural defects due to their short molecular length. As a result, high polymer concentrations (often up to 20%–50%) are required to achieve satisfactory print fidelity. Here, we develop a series of water-soluble, polyvinyl alcohol macromolecular thiol (PVASH, bearing 10–35 thiol groups) for fast high-fidelity hydrogel microfabrication via 2PP. A two-step synthesis yields PVASH with tunable degrees of substitution and excellent water-solubility. Compared to DTT and polyethylene glycol di-thiol, PVASH-based hydrogels exhibit reduced swelling, enhanced mechanical properties, and significantly improved printing fidelity. Notably, several complex hydrogel structures are fabricated at laser power as low as 20 mW and high scanning speeds of up to 400 mm s−1, achieving sub-micron feature size at 3% polymer concentration. After biofunctionalization with RGD motifs, the micro-scaffolds support cell infiltration, adhesion, proliferation, and osteogenic differentiation. Altogether, this work reports a new strategy for 2PP microfabrication of cell-interactive hydrogel structures with unprecedented printing efficiency and precision.

Optically driven robotic actuators are synthetic materials capable of reversible shape-morphing under the control of incident light.Conventional approaches typically require a favorable illumination condition, that is small incidence angle excitement coveringlarge sample area, which poses challenges for optical integration and applicability in optically restricted environments. Here,we present a method that utilizes two-photon polymerization laser-printing of micromirrors on the surface of a soft actuator toredirect parallel incident light into the material. This mirror reflection enables photomechanical actuation at 90◦ incidence angle.To validate the concept, we employ a liquid crystalline elastomer thin film as the soft actuator operated under photothermalmechanism. The actuator exhibits only moderate deformation at oblique incidence and no deformation at grazing incidence (90◦)without micro mirror assistance. Integrating the micro mirrors manifests the photomechanical deformation at oblique angles.The merits of this micro mirror deflection strategy are illustrated by two demonstrations: a walking robot driven by an opticalbeam that is confined to the locomotive 2D plane, and an optical fiber tip integrated gripper can manipulate objects. These resultsprovide the facts that the photomechanical deformation can be elevated significantly by microscopically constructed pattern onthe actuator surfaces, providing new designs for micro robots.

The integration of biologically inspired materials into photonic device fabrication offers a promising route toward sustainable and biocompatible alternative to conventional in inorganic or petroleum based synthetic materials used in optoelectronic systems. In this work, we present a biosynthetic approach for waveguide fabrication utilizing a biomimetic – de novo designed elastin-like polypeptide (ELP) formulated into an all-water-based photoresist compatible with two-photon polymerization (2PP). The ELP was genetically engineered and recombinantly produced in microbes for enhanced molecular stability, a critical feature for withstanding both localized and bulk temperature increases that occur during high-intensity laser exposure during printing. The resulting ELP formulation supported direct writing of waveguide architecture without the need for organic solvents, harsh processing steps, or post-functionalization. This aqueous resist formulation exhibits high stability during printing and retains its structural integrity upon curing, making it a promising candidate for environmentally friendly, soft-material photonics. This work establishes a foundation for using biosynthetic polypeptides in the fabrication of functional photonic elements and demonstrates a step toward greener, protein-based optoelectronic manufacturing technologies.

The detection of trace gases is crucial in environmental monitoring, industrial safety, and medical diagnostics. Optical sensing technologies, particularly those leveraging photothermal spectroscopy, offer high sensitivity and selectivity, enabling the identification of gases based on their unique absorption spectra. Among these, photothermal interferometry offers exceptional sensitivity due to its use of an interferometric signal transducer. In this work, we performed numerical simulations to systematically explore the influence of cavity geometry and mirror curvature on sensitivity. This guided the design of the most sensitive configurations. To validate the theoretical enhancement, we present a systematic comparison of 18 Fabry–Pérot interferometers (FPI) fabricated via two-photon polymerization (2PP) directly onto optical fiber-tips. These FPIs were rapidly prototyped using a commercial 2PP printer. They span three cavity lengths (110, 200, and 300 µm), each configured with flat or spherical mirrors. Single-cavity and Vernier-enhanced FPIs were implemented. The latter were also modified by gold coating of the terminal interface to enhance reflectivity. We evaluated the sensitivity optimization for collinear photothermal spectroscopy in a wavelength modulation setup. By exploiting the Vernier effect and tailored cavity geometries, we demonstrate a 12-fold improvement in the photothermal 2f-signal compared to a single-cavity FPI configuration. This highlights the versatility of 2PP-printed fiber-tip FPIs for next-generation trace gas sensors.