Hugh Bruck

University of Maryland, College Park | UMD, UMCP, University of Maryland College Park · Department of Mechanical Engineering

Flapping Wing Air Vehicles (FWAVs) have proven to be attractive alternatives to fixed wing and rotary air vehicles at low speeds because of their bio-inspired ability to hover and maneuver. However, in the past, they have not been able to reach their full potential due to limitations in wing control and payload capacity, which also has limited endu...

With advances in micromachinery, the aggregation of sensors, and more powerful microcontroller platforms on satellites, the size of avionics for space missions are getting dramatically smaller with faster processing speeds. This has resulted in greater localized heat generation, requiring more reliable thermal management systems to enhance the ther...

There is increasing interest in creating materials by design, like layered jamming materials, that offer enhanced or novel performance, such as the ability to vary properties in situ (i.e., programmable). Many of these materials rely on microstructural characteristics consisting of interfaces, material distributions, and geometric complexity that p...

New materials and structures with complex microstructural distributions are being rapidly developed using advanced manufacturing approaches, such as Additive Manufacturing (AM). For example, it is possible to fabricate metals using AM processes, such as Direct Metal Laser Sintering (DMLS), with spatial variations at sub-millimeter scales in texture...

Metal additive manufacturing has revolutionized the manufacturing industry due to its capability of building complex parts without any part-specific tooling. Wire arc metal additive manufacturing is a process that uses the arc welding technique to build parts layer by layer. Robotic manipulators equipped with arc welding hardware can perform wire a...

In the marine industry, designers utilize 5052-H32 marine grade series aluminum for its strength to weight ratio, and the ability of this series to resist marine corrosive environments. During the operating lifetime of a marine vessel, it experiences constant and variable amplitude loading conditions from the sea environment, plus overloads/underlo...

The emergence of additive manufacturing (AM) technologies, such as fused deposition modeling (FDM), have enabled the realization of structures with superior mechanical performance through lightweighting and multi-material architectures. However, the complexity associated with the internal geometric features and potential material configurations hav...

In the search for thermal management of advanced avionics packaging, materials such as eutectic liquid metal (LM) alloys and synthetic ceramics with superior thermophysical properties offer reliable and effective solutions. Conductive ceramic tubes can be used to contain LM as a coolant for heat exchangers. However, conductive ceramics will still n...

As electronics get smaller and faster, novel thermal management systems are needed that are capable of dissipating higher heat fluxes. Additive manufacturing and advanced materials, such as liquid metals and synthetic ceramic, offer new opportunities to realize thermal systems. This paper investigates the use of additive manufacturing to develop th...

Aluminum materials of various grades are utilized across many industries, spanning from the cycling, automotive, aerospace, and the marine industry. In the marine grade, aluminum materials are utilized to construct entire vessels of various lengths or portions of them by taking advantage of the lower weight characteristics of the materials and impa...

Composite patch repairs are an alternative to weld repair methods to arrest crack growth in metal plates. While these repairs have been effective, it has been difficult to use basic linear elastic fracture mechanics (LEFM) theories and design methods based on LEFM to predict the efficacy of patch repairs because the repaired plate exhibits bending...

This paper presents a hybrid flapping-gliding dynamic model for a flapping-wing unmanned aerial vehicle (UAV). The model combines the nonlinear phugoid dynamics of gliding flight, the equations of motion of the onboard servo motors, and an equivalent circuit discharge model for the onboard battery. The resulting state-space representation relates t...

Two material configurations, applications methods, and geometric scales of specimen were used to study the effect that one-sided low modulus composite patch repairs have on crack tip plastic strain to develop a simplified ultimate failure pre- diction method. Digital image correlation and three-dimensional finite element analysis with first order e...

Fatigue crack detection and measurement play an essential role in the remaining useful life (RUL) estimation of sensitive structures. The current use of non-destructive testing (NDT) methods is usually limited to the out-of-service inspections and measurements. The ability to detect structural changes resulting from redistribution of the stress wit...

Background The use of layer jamming materials has promising applications in soft robotics and vibration control, where there is a need to have materials that can change their properties in situ. However, there is limited research on analytically modeling the plastic deformation response of layer jamming materials attributed to the level of cohesion...

Composite patch repairs of aluminum structures are designed using linear elastic fracture mechanics, which compares crack tip predictions to a critical strain energy release rate or stress intensity. Analytical and numerical predictions are reasonable for linear-elastic behavior, but do not account for the elastic-plastic behavior observed at the c...

Sensitive structures, such as airframes, need careful inspection and maintenance to avoid fatigue failures. These activities are expensive, discrete and imperfect, since catastrophic failure may occur before cracks can be detected. This paper focuses on using information entropy of acoustic emission (AE) signals to identify precursors to fatigue cr...

Biological creatures demonstrate tremendous feats of maneuverability and dexterity. Some of these feats are achieved by intelligent usage of mass and inertia. For example, lizards use their tail mass and inertia to change body pose during jumping to self-right in mid-air. In a similar fashion, having shown passive mass position effects during fligh...

Current approaches to fatigue life prediction are mostly based on classical fracture mechanics and it is difficult to predict lifetime under different loading conditions, particularly under overload spectrums. A thermodynamic entropy-based approach is less sensitive to variability in loading conditions and provides a dependable measure of damage. V...

A new flapping wing aerial vehicle (FWAV) simulation methodology is presented that combines models of the key subsystems: (1) the actuator, (2) the battery, and (3) the wings. This approach captures component interactions that are inherently coupled in order to realize system-level designs for optimal system performance. The approach demonstrates t...

NiTi SMA thermal bimorph actuators have potential as high-force, high-displacement MEMS actuators. Historically, even microscale SMA actuation response has been limited to a maximum of ˜100 Hz. As NiTi film and device dimensions are scaled down into the micro and nano scales, heat transfer, and thus device cycling speeds can be significantly improv...

The high mechanical performance of common structural materials (e.g., metals, alloys, and ceramics) originates from strong primary bonds (i.e., metallic, covalent, ionic) between constituent atoms. However, the large formation energy of primary bonds requires high temperatures in order to process these materials, resulting in significant manufactur...

Long flight durations are highly desirable to expand mission capabilities for unmanned air systems and autonomous applications in particular. Flapping wing aerial vehicles are unmanned air system platforms offering several performance advantages over fixed wing and rotorcraft platforms, but are unable to reach comparable flight times when powered b...

Many applications require structures composed of layers of heterogeneous materials and prefabricated components embedded between the layers. The existing additive manufacturing process based on layered object manufacturing is not able to handle multiple layer materials and cannot embed prefabricated components. Moreover, the existing process impose...

Composite patch repairs of aluminum structures used in marine and aerospace industries are designed using closed form solutions assuming thin, plane stress, linear-elastic structures or numerical methods for repairs of thick aluminum. Both methods are based on linear elastic fracture mechanics and compare crack tip predictions to a critical strain...

The 2D-DIC Challenge is organized by an international committee working to understand the accuracy of digital image correlation (DIC) through standardized image sets. The DIC Challenge is run under the auspices of the Society for Experimental Mechanics (SEM) and the International DIC Society (iDICs). The 2D-Challenge incorporates 19 image sets that...

Recent advances in additive manufacturing have enabled the realization of concepts in layered materials that were not previously viable. We have created a layered manufacturing process using robots to fabricate actuators using pre-fabricated materials, e.g. solar cells and batteries. This has allowed us to design and fabricate multifunctional struc...

Tactile sensing is of interest for facilitating interactions between robots and humans. To aid the robot's interpretation of human contact, the use of a multi-layer cutaneous tactile sensing architecture that can provide more information and an expanded force sensing range was explored, revealing differences in the signal generated by a machine ver...

Three-Dimensional Digital Image Correlation (3D-DIC) is a technique used widely in both academic and industrial settings to measure object morphology, velocity, and full-field strain. However, conventional methods require the use of two synchronized cameras and a lengthy calibration process of taking thirty or more images of specialized target, aft...

Additive manufacturing (AM) processes, such as Selective Laser Sintering (SLS), have enabled the fabrication of geometrically complicated designs. However, undesired distortions due to thermally-induced residual stresses may lead to loss of tolerance or failure of the part. One potential failure mode is buckling, particularly when realizing high as...

Thin multifunctional structures need to be composed from many different materials. Currently, very few additive manufacturing processes are capable of working with multiple materials. Additive manufacturing processes that work with multiple different materials pose significant constraints on material options. This significantly limits the kind of m...

Poly(urethane-urea) (PUU) has been infused into ultrahigh volume fraction carbon nanotube (CNT) forests using a heat-curable polymer formula. Polymer nanocomposites with carbon nanotube volume-fractions of 1%, 5%, 10%, 20%, and 30% were fabricated by overcoming densification and infusion obstacles. These polymer nanocomposites were nanoindented qua...

To allow robots to interact with humans via touch, new sensing concepts are needed that can detect a wide range of potential interactions and cover the body of a robot. In this paper, a skin-inspired multi-layer tactile sensing architecture is presented and characterized. The structure consists of stretchable piezoresistive strain-sensing layers ov...

The exceptional static and dynamic physical properties of poly(urethane-urea) (PUU) elastomers make them prime candidates for impulsive loading structural applications, such as blast protection coatings. Since the theoretical physical properties of carbon nanotubes (CNTs) are among the best for any currently known material, a number of previous stu...

Synthetic structural materials with exceptional mechanical performance suffer from either large weight and adverse environmental impact (for example, steels and alloys) or complex manufacturing processes and thus high cost (for example, polymer-based and biomimetic composites)1,2,3,4,5,6,7,8. Natural wood is a low-cost and abundant material and has...

Morphing structures are needed for many challenging missions for flapping wing air vehicles (FWAVs), but they will increase electrical power consumption in order to drive actuation systems and will require additional support systems to deliver and control the power. These power demands and associated support systems will comprise the ability of FWA...

With the rapid spread in use of Digital Image Correlation (DIC) globally, it is important there be some standard methods of verifying and validating DIC codes. To this end, the DIC Challenge board was formed and is maintained under the auspices of the Society for Experimental Mechanics (SEM) and the international DIC society (iDICs). The goal of th...

The use of electrical contact resistance (ECR) is investigated as a force sensing mechanism in silicon-on-insulator DRIE MEMS devices. Using both direct mechanical and indirect inertial loading, ECR relationships were evaluated for high aspect ratio silicon microstructures as a function of applied contact forces up to 45 mN. Forces applied via prob...

A challenge in fabricating compliant electrical sensors for various applications, such as wearable electronics, has been the lack of compatible connection concepts that are reliable and can support large levels of force without failure. Recently, we have developed compliant, carbon-based strain and thermal sensors using nanosized exfoliated graphit...

Biologically-inspired flapping wing flight is attractive at low Reynolds numbers and at high angles of attack, where fixed wing flight performance declines precipitously. While the merits of flapping propulsion have been intensely investigated, enhancing flapping propulsion has proven challenging because of hardware constraints and the complexity o...

Inspired by nature, Flapping Wing Aerial Vehicles (FWAVs), also known as “robotic birds” use flexible compliant wings that deform while flapping for aerodynamic force generation to achieve flight, just like real birds. However, unlike real birds, these vehicles require an artificial power source, like a battery, which limits flight time depending o...

This paper is focused on design of dive maneuvers that can be performed outdoors on flapping wing air vehicles (FWAVs) with a minimal amount of on-board computing capability. We present a simple computational model that provides accuracy of 5m in open loop operation mode for outdoor dives under wind speeds of up to 3 m/s. This model is executed usi...

A novel process for synthesizing poly(urethane-urea) (PUU) based vertically-aligned carbon-nanotubes (CNTs) has been demonstrated. This method employs the use of blocked diisocyanate which permits thermally-controlled polymerization. The resulting polymer nanocomposites (PNCs) had a 1% V f of CNTs with consistent alignment and dispersion, following...

Current mission planning typically involves feed-forward strategies that do not adapt flight conditions and mission properties according to live vehicle power state updates. This results in autonomous flights that adhere to rigid rules for flight time, potentially missing opportunities to enhance mission range or improve recovery likelihood. To add...

A tactile sensing architecture is presented for detection of surface features that have a particular target size, and the concept is demonstrated with a braille pattern. The approach is akin to an inverse of mechanical profilometry. The sensing structure is constructed by suspending a stretchable strain-sensing membrane over a cavity. The structure...

To improve food safety there is a need to develop simple, low-cost sensitive devices for detection of food-borne pathogens and their toxins. We describe a simple, low-cost webcam-based detector which can be used for various optical detection modalities, including fluorescence, chemiluminescence, densitometry, and colorimetric assays. The portable b...

There is a need for simple and affordable techniques for cytology for clinical applications, especially for point-of-care (POC) medical diagnostics in resource-poor settings. However, this often requires adapting expensive and complex laboratory-based techniques that often require significant power and are too massive to transport easily. One such...

Flapping-wing flight is a challenging system integration problem for designers due to tight coupling between propulsion and flexible wing subsystems with variable kinematics. High fidelity models that capture all the subsystem interactions are computationally expensive and too complex for design space exploration and optimization studies. A combina...

Streak mode imaging flow cytometry for rare cell detection involves imaging moving fluorescently labeled cells in the video mode with a CCD camera. The path of the moving cells results in a "streak", whose length is proportional to the exposure time. The dynamic imaging conditions introduce detection challenges (e.g., images with high signal-to-noi...

Carbon has become an attractive material for electronic packaging applications, such as interconnects, because of its low density and reasonable electrical conductivity. One challenge in these applications is overcoming the inherent chemical incompatibility between carbon and metals that limits adhesion. Recently, we explored a new technique for el...

This paper describes the design, fabrication, testing and modeling of the SUR Hand. The SUR Hand is a soft, under actuated robotic hand. Through an iterative design and manufacturing process, SUR Hand’s soft, actuating components have been adapted from the original PneuFlex, pneumatically actuated finger to be highly flexible and capable of actuati...

Flapping wing flight is a challenging system integration problem for designers due to tight coupling between propulsion and flexible wing subsystems with variable kinematics. Due to the fluid-structure interactions present in such a system, models must be tailored to a particular design instantiation to provide high accuracy and a clear picture of...

In this work, we investigate the integration of ultrathin galvanic cell batteries with high energy density and flexibility into the highly deformable wings of the flapping wing air vehicle (FWAV) known as “Robo Raven” that we previously developed for independent wing control. The goal of this research was to create a multifunctional wing structure...

Flapping wing unmanned aerial vehicles (FWUAVs) provide an alternative to traditional platforms because they are more maneuverable than fixed wing platforms while being faster, quieter, and more natural looking than rotary wing platforms. While real birds are able to execute complex and highly controlled aerobatic maneuvers, executing FWUAV aerobat...

Resource-poor countries and regions require effective, low-cost diagnostic devices for accurate identification and diagnosis of health conditions. Optical detection technologies used for many types of biological and clinical analysis can play a significant role in addressing this need, but must be sufficiently affordable and portable for use in glo...

For robots that work collaboratively with people, often referred to as 'co-robots', it would be beneficial for them to be soft or padded and to have a touch-sensing 'skin' to enable tactile environmental awareness. However, a sensing skin over a padding material that undergoes large deformations requires 'stretchable' materials, which may possess t...

Co-robotics is interested in understanding how robots interact with other structures, such as humans, for the purpose of decision-making. Robots are currently designed to execute programmed actions to satisfy specific commands and motions. If a robot could be taught to perform an action by a guiding touch from a human, rather than specific programm...

Inspired by nature, Flapping Wing Aerial Vehicles (FWAVs), also known as Robotic Birds, use flexible compliant wings that deform while flapping to generate the aerodynamic forces necessary for flight. These vehicles sustain short flights due to the limited payload for on-board energy storage. Using flexible solar cells, energy can be harvested duri...

Flapping wing aerial vehicles (FWAVs) may require charging in the field where electrical power supply is not available. Flexible solar cells can be integrated into wings, tail, and body of FWAVs to harvest solar energy. The harvested solar energy can be used to recharge batteries and eliminate the need for external electrical power. It can also be...

The desire to produce more geometrically complex components from pin-reinforced X-Cor® sandwich composite structures requires that the effects of curvature on the flexural behavior be investigated experimentally and numerically. This will enable development of validated design tools accounting for the effects of the load distributions associated wi...

For certain autonomous applications, flapping wing unmanned air vehicles (FWUAVs) provide a desirable balance between fixed wing and rotary air vehicles because they are fast, quiet, and maneuverable. Combined with autonomous stabilization and navigation, these platforms have the potential to allow close up chemical and visual inspections of areas...

The design of a flapping wing air vehicle is dependent on the interaction of drive motors and wings. In addition to the wing shape and spar arrangement, sizing and flapping kinematics affect vehicle performance due to wing deformation resulting from flapping motions. To achieve maximum payload and endurance, it is necessary to select a wing size an...

Flapping flight is impressive because aerodynamic performance increases whereas fixed wing aircraft performance declines in low Reynolds regimes. In order to achieve biologically-inspired flapping, motion in multiple degrees of freedom is required and power density requirements must be satisfied. Given the mass of high output actuators, weight is a...

Flapping wing aerial vehicles (FWAVs) are limited to small batteries due to constraints on the available onboard payload. To increase the energy available for the vehicle, solar cells can be integrated to harvest energy during flight. This addition of available onboard energy increases the flight time of the vehicle and could eventually lead to an...

Currently, flapping wing unmanned aerial vehicles (a.k.a., ornithopters or robotic birds) sustain very short duration flight due to limited on-board energy storage capacity. Therefore, energy harvesting elements, such as flexible solar cells, need to be used as materials in critical components, such as wing structures, to increase operational perfo...

Sensing temperature distributions over an area is of interest for many applications, and it is currently performed using sensors that are attached to the structure. In this work a conductive “smart paint”, made from latex and exfoliated graphite, is introduced for temperature sensing. This provides, as an alternative to manual fixation, the ability...

Metal-hydride phase transformations in solids commonly proceed with hysteresis. The extrinsic component of hysteresis is the result of the dissipation of energy of internal stress due to plastic deformation and fracture. It can be mitigated on the nanoscale, where plastic deformation and fracture are suppressed and the transformation proceeds throu...

Detection of rare cells, such as circulating tumor cells, have many clinical applications. To measure rare cells with increased sensitivity and improved data managements, we developed an imaging flow cytometer with a streak imaging mode capability. The new streak mode imaging mode utilizes low speed video to capture moving fluorescently labeled cel...

We describe here a compact smartphone-based fluorescence detector for mHealth. A key element to achieving high sensitivity using low sensitivity phone cameras is a capillary array, which increases sensitivity by 100×. The capillary array was combined with a white LED illumination system to enable wide spectra fluorescent excitation in the range of...

There is a new potential to address needs for medical diagnostics in Point-of-Care (PoC) applications using mHealth (Mobile computing, medical sensors, and communications technologies for health care), a mHealth based lab test will require a LOC to perform clinical analysis. In this work, we describe the design of a simple Lab-on-a-chip (LOC) platf...

Flow cytometry is used for cell counting and analysis in numerous clinical and environmental applications. However flow cytometry is not used in mHealth mainly because current flow cytometers are large, expensive, power-intensive devices designed to operate in a laboratory. Their design results in a lack of portability and makes them unsuitable for...

In this investigation, we report on experiments and models we have developed for compliant multifunctional robotic structures using arrays of conducting polymer composites have been developed to form a “nervous system” to sense shape and force distributions. The objective of this research is to enable better training of robots by enabling them to p...

Many current bird-inspired flapping-wing air vehicles (FWAVs) achieve their flight characteristics through deformations associated with compliant wings during the flapping cycle. Most FWAVs use a single actuator to flap both wings. This couples and synchronizes motions of the wings, which only provides variable rate flapping at constant amplitude t...

Flapping wing unmanned air vehicles (UAVs) are small light weight vehicles that typically have short flight times due to the small size of the batteries that are used to power them. During longer missions, the batteries must be recharged. The lack of nearby electrical outlets severely limits the locations and types of missions that these UAVs can b...

Flapping wing miniature aerial vehicles (FWMAVs) offer advantages over traditional fixed wing or quadrotor MAV platforms because they are more maneuverable than fixed wing aircraft and are more energy efficient than quadrotors, while being quieter than both. Currently, autonomy in FWMAVs has only been implemented in flapping vehicles without indepe...

There is a great deal of interest in understanding the mechanics in pin-reinforced composite sandwich structures. In particular, characterizing the relationship of the mechanics in smaller to larger specimens due to changes in the pin response can expedite the development of more advanced models, as well as the assessment of new materials and proce...

Here we describe a novel low-cost flow cytometer based on a webcam capable of low cell number detection in a large volume which may overcome the limitations of current flow cytometry. Several key elements have been combined to yield both high throughput and high sensitivity. The first element is a commercially available webcam capable of 187 frames...

Pin-reinforced sandwich composites have recently attracted the attention in lightweight structural applications where it substantially improves out-of-plane and shear properties for sandwich composites. However, there is not a great deal of understanding in regards to how shaping these composites affects their mechanical performance when the orient...

The flight time of miniature air vehicles (MAVs) is limited by the need for a portable, light weight power source. The development of multifunctional, power generating wings has the capability of extending flight time without compromising overall flight performance. This paper seeks to investigate the feasibility of integrating flexible solar cells...

This paper describes RoboTerp, a quadrupedal amphibious robot that achieves locomotion on land and in water with the same legs by switching gaits to match the terrain. The central idea hinges on a passive compliant mechanism attached to the lower leg that enables it to behave like a valve during movement in water. The direction of this valve-like m...