Biomechanical Feedback Research Articles

Self-powered highly stretchable ferroelectret nanogenerator towards intelligent sports

Ferroelectret nanogenerators (FENGs), recognized for their porous structures that facilitate charge retention, thereby creating giant electric dipoles and exhibiting remarkable piezoelectric properties, are utilized in the development of various flexible transducers. However, despite their flexibility, most developed ferroelectret nanogenerators lack adequate stretchability and satisfactory transverse piezoelectric properties, significantly inhibiting their widespread deployment in wearable or skin-mounted electronics. Here, we introduce a highly stretchable ferroelectret nanogenerator (HS-FENG) built from laser-induced graphene (LIG), Ecoflex and anhydrous ethanol, demonstrating exceptional flexibility and stretchability, along with longitudinal and transverse piezoelectric effects. The stretchability of HS-FENG can reach a record of 468 %, while the quasi-static piezoelectric coefficients d33 and d31 are approximately 120 pC/N and 70 pC/N, respectively. To our knowledge, this is the first demonstration of the developed FENG with remarkably high stretchability. Furthermore, leveraging the performance of the created HS-FENG, we construct a skin-mounted intelligent kinesiology tape capable of effectively monitoring motion signals from human muscles and joints, thereby offering a deeper understanding of movement for users across different levels of physical activity, from professional athletes to individuals undergoing rehabilitation. The development of intelligent kinesiology tape exemplifies the potential of HS-FENG technology in enhancing professional athletic training and personalized healthcare. It contributes to the advancement of inconspicuous skin-mounted biomechanical feedback systems and human-machine interfaces, marking progress in the field.

Integrating Real-Time Biomechanical Feedback with Cognitive-Behavioral Interventions to Enhance the Efficacy of Strength Training

This study investigates the efficacy of integrating real-time biomechanical feedback with cognitive-behavioral interventions in enhancing the outcomes of strength training programs. A mixed-methods experimental design was utilized, involving 90 participants randomly assigned to three groups: a control group receiving traditional strength training, a biomechanical feedback group, and a combined intervention group receiving both biomechanical feedback and cognitive-behavioral strategies. The interventions lasted for 12 weeks, with assessments conducted pre- and post-intervention. Key performance indicators included improvements in one-repetition maximum (1RM) strength tests and psychological well-being metrics. Results indicated that the combined intervention group demonstrated significantly greater improvements in 1RM strength, technique efficiency, and psychological resilience compared to the other two groups. The integration of biomechanical and cognitive-behavioral strategies not only improved physical performance but also enhanced mental focus and training adherence, showcasing a holistic approach to strength training. The findings suggest that a synergistic approach, encompassing both biomechanical feedback and cognitive strategies, can substantially elevate the effectiveness of strength training regimes. These outcomes have implications for coaches, athletes, and sports medicine professionals looking to optimize performance and rehabilitation protocols. The study highlights the potential for a more personalized and psychologically supportive training environment, promising for future research and practical applications in sports science and physical training.

Membrane Fluctuation Model for Understanding the Effect of Receptor Nanoclustering on the Activation of Natural Killer Cells through Biomechanical Feedback.

We investigated the role of ligand clustering and density in the activation of natural killer (NK) cells. To that end, we designed reductionist arrays of nanopatterned ligands arranged with different cluster geometries and densities and probed their effects on NK cell activation. We used these arrays as an artificial microenvironment for the stimulation of NK cells and studied the effect of the array geometry on the NK cell immune response. We found that ligand density significantly regulated NK cell activation while ligand clustering had an impact only at a specific density threshold. We also rationalized these findings by introducing a theoretical membrane fluctuation model that considers biomechanical feedback between ligand-receptor bonds and the cell membrane. These findings provide important insight into NK cell mechanobiology, which is fundamentally important and essential for designing immunotherapeutic strategies targeting cancer.

Biomechanical Evaluation of Tracheal Needle Puncture Forces: Comparative Analysis of Annular Ligaments and Tracheal Cartilage.

Percutaneous tracheotomies (PCT) are commonly performed minimally invasive procedures involving the creation of an airway opening through an incision or puncture of the tracheal wall. While the medical intervention is crucial for critical care and the management of acute respiratory failure, tracheostomy complications can lead to severe clinical symptoms due to the alterations of the airways biomechanical properties/structures. The causes and mechanisms underlaying the development of these post-tracheotomy complications remain largely unknown. In this study, we aimed to investigate the needle puncture process and its biomechanical characteristics by using a well establish porcine ex vivo trachea to simulate the forces involved in accessing airways during PCT at varying angular approaches. Given that many procedures involve inserting a needle into the trachea without direct visualization of the tracheal wall, concerns have been raised over the needle punctures through the cartilaginous rings as compared to the space between them may result in fractured cartilage and post-tracheostomy airway complications. We report a difference in puncture force between piercing the cartilage and the annular ligaments and observe that the angle of puncture does not significantly alter the puncture forces. The data collected in this study can guide the design of relevant biomechanical feedback system during airway access procedures and ultimately help refine and optimize PCT.

Validation of Inertial Measurement Units for Analyzing Golf Swing Rotational Biomechanics.

Training devices to enhance golf swing technique are increasingly in demand. Golf swing biomechanics are typically assessed in a laboratory setting and not readily accessible. Inertial measurement units (IMUs) offer improved access as they are wearable, cost-effective, and user-friendly. This study investigates the accuracy of IMU-based golf swing kinematics of upper torso and pelvic rotation compared to lab-based 3D motion capture. Thirty-six male and female professional and amateur golfers participated in the study, nine in each sub-group. Golf swing rotational kinematics, including upper torso and pelvic rotation, pelvic rotational velocity, S-factor (shoulder obliquity), O-factor (pelvic obliquity), and X-factor were compared. Strong positive correlations between IMU and 3D motion capture were found for all parameters; Intraclass Correlations ranged from 0.91 (95% confidence interval [CI]: 0.89, 0.93) for O-factor to 1.00 (95% CI: 1.00, 1.00) for upper torso rotation; Pearson coefficients ranged from 0.92 (95% CI: 0.92, 0.93) for O-factor to 1.00 (95% CI: 1.00, 1.00) for upper torso rotation (p < 0.001 for all). Bland-Altman analysis demonstrated good agreement between the two methods; absolute mean differences ranged from 0.61 to 1.67 degrees. Results suggest that IMUs provide a practical and viable alternative for golf swing analysis, offering golfers accessible and wearable biomechanical feedback to enhance performance. Furthermore, integrating IMUs into golf coaching can advance swing analysis and personalized training protocols. In conclusion, IMUs show significant promise as cost-effective and practical devices for golf swing analysis, benefiting golfers across all skill levels and providing benchmarks for training.

Exploring the applicability of haptic actuators in aquatic environments

The use of high-tech wearable devices and real-time biomechanical feedback (RTBF) is widespread in modern sports and physical rehabilitation. While the use of kinematic sensors for RTBF is well established, the question of the most efficient and appropriate way to present feedback information to the user remains largely unanswered. The haptic modality has only been used in a limited number of relatively simple studies and applications, and it has never been studied in an aquatic environment. In this study, the main motivation was to design, develop, implement, and test an RTBF system for sports and physical rehabilitation with haptic actuators suitable for use in aquatic environments. The developed miniature remote-controlled device with vibration motors as actuators was tested to determine how people perceive the haptic modality in and out of water. The results of the exploratory study with 34 participants suggest that the feedback device can be further developed for future studies. The results show that both simple and complex haptic stimuli can be understood by athletes both outdoors and in water, as well as while standing and performing simple physical activities. This study tested the use of both head and waist mounted haptic actuators, with both showing similar and promising results. The results of this study provide evidence that haptic feedback can be perceived in water, highlighting the potential for real-time haptic interventions in aquatic environments. In summary, this study represents a significant contribution to the evolving field of RTBF in modern sport training and physical rehabilitation. The development of a haptic feedback device that can be worn during aquatic and other activities is a significant advance in the field of feedback actuators. This study provides a foundation for future usability studies and the development of haptic RTBF applications in both aquatic and outdoor environments.

Interfragmentary strain measurement post-fixation to guide intraoperative decision making: a narrative review.

Interfragmentary strain influences whether a fracture will undergo direct and indirect fracture healing. Orthopedic trauma surgeons modulate strain and create optimal biomechanical environments for specific fracture patterns using fixation constructs. However, objective intraoperative interfragmentary strain measurement does not currently inform fixation strategy in common practice. This review identifies potential methods and technologies to enable intraoperative strain measurement for guiding optimal fracture fixation strategies. PubMed, Scopus, and Web of Science were methodologically queried for manuscripts containing terms related to "bone fracture," "strain," "measurement," and "intraoperative." Manuscripts were systematically screened for relevance and adjudicated by three reviewers. Relevant articles describing methods to measure interfragmentary strain intraoperatively were summarized. After removing duplicates, 1404 records were screened initially. There were 49 manuscripts meeting criteria for in-depth review. Of these, four reports were included in this study that described methods applicable to measuring interfragmentary strain intraoperatively. Two of these reports described a method using instrumented staples, one described optical tracking of Kirschner wires, and one described using a digital linear variable displacement transducer with a custom external fixator. The four reports identified by this review describe potential methods to quantify interfragmentary strain after fixation. However, further studies are needed to confirm the precision and accuracy of these measurements across a range of fractures and fixation methods. Additionally, described methods require the insertion and likely removal of additional implants into the bone. Ideally, innovations that measure interfragmentary strain intraoperatively would provide dynamic biomechanical feedback for the surgeon to proactively modulate construct stability.

A Wearable-Sensor System with AI Technology for Real-Time Biomechanical Feedback Training in Hammer Throw.

Developing real-time biomechanical feedback systems for in-field applications will transfer human motor skills' learning/training from subjective (experience-based) to objective (science-based). The translation will greatly improve the efficiency of human motor skills' learning and training. Such a translation is especially indispensable for the hammer-throw training which still relies on coaches' experience/observation and has not seen a new world record since 1986. Therefore, we developed a wearable wireless sensor system combining with artificial intelligence for real-time biomechanical feedback training in hammer throw. A framework was devised for developing such practical wearable systems. A printed circuit board was designed to miniaturize the size of the wearable device, where an Arduino microcontroller, an XBee wireless communication module, an embedded load cell and two micro inertial measurement units (IMUs) could be inserted/connected onto the board. The load cell was for measuring the wire tension, while the two IMUs were for determining the vertical displacements of the wrists and the hip. After calibration, the device returned a mean relative error of 0.87% for the load cell and the accuracy of 6% for the IMUs. Further, two deep neural network models were built to estimate selected joint angles of upper and lower limbs related to limb coordination based on the IMUs' measurements. The estimation errors for both models were within an acceptable range, i.e., approximately ±12° and ±4°, respectively, demonstrating strong correlation existed between the limb coordination and the IMUs' measurements. The results of the current study suggest a remarkable novelty: the difficulty-to-measure human motor skills, especially in those sports involving high speed and complex motor skills, can be tracked by wearable sensors with neglect movement constraints to the athletes. Therefore, the application of artificial intelligence in a wearable system has shown great potential of establishing real-time biomechanical feedback training in various sports. To our best knowledge, this is the first practical research of combing wearables and machine learning to provide biomechanical feedback in hammer throw. Hopefully, more wearable biomechanical feedback systems integrating artificial intelligence would be developed in the future.

Stronger wind, smaller tree: Testing tree growth plasticity through a modeling approach.

Plants exhibit plasticity in response to various external conditions, characterized by changes in physiological and morphological features. Although being non-negligible, compared to the other environmental factors, the effect of wind on plant growth is less extensively studied, either experimentally or computationally. This study aims to propose a modeling approach that can simulate the impact of wind on plant growth, which brings a biomechanical feedback to growth and biomass distribution into a functional-structural plant model (FSPM). Tree reaction to the wind is simulated based on the hypothesis that plants tend to fit in the environment best. This is interpreted as an optimization problem of finding the best growth-regulation sink parameter giving the maximal plant fitness (usually seed weight, but expressed as plant biomass and size). To test this hypothesis in silico, a functional-structural plant model, which simulates both the primary and secondary growth of stems, is coupled with a biomechanical model which computes forces, moments of forces, and breakage location in stems caused by both wind and self-weight increment during plant growth. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) is adopted to maximize the multi-objective function (stem biomass and tree height) by determining the key parameter value controlling the biomass allocation to the secondary growth. The digital trees show considerable phenotypic plasticity under different wind speeds, whose behavior, as an emergent property, is in accordance with experimental results from works of literature: the height and leaf area of individual trees decreased with wind speed, and the diameter at the breast height (DBH) increased at low-speed wind but declined at higher-speed wind. Stronger wind results in a smaller tree. Such response of trees to the wind is realistically simulated, giving a deeper understanding of tree behavior. The result shows that the challenging task of modeling plant plasticity may be solved by optimizing the plant fitness function. Adding a biomechanical model enriches FSPMs and opens a wider application of plant models.

Adhesion strength between cells regulate nonmonotonic growth by a biomechanical feedback mechanism

We determine how intercellular interactions and mechanical pressure experienced by single cells regulate cell proliferation using a minimal computational model for three-dimensional multicellular spheroid (MCS) growth. We discover that emergent spatial variations in the cell division rate, depending on the location of the cells either at the core or periphery within the MCS, is regulated by intercellular adhesion strength (fad). Varying fad results in nonmonotonic proliferation of cells in the MCS. A biomechanical feedback mechanism coupling the fad and microenvironment-dependent pressure fluctuations relative to a threshold value (pc) determines the onset of a dormant phase, and explains the nonmonotonic proliferation response. Increasing fad from low values enhances cell proliferation because pressure on individual cells is smaller compared with pc. However, at high fad, cells readily become dormant and cannot rearrange effectively in spacetime, leading to arrested cell proliferation. Utilizing our theoretical predictions, we explain experimental data on the impact of adhesion strength on cell proliferation and find good agreement. Our work, which shows that proliferation is regulated by pressure-adhesion feedback mechanism, may be a general feature of multicellular growth.

The effect of biomechanical feedback on the accuracy of the long serve in badminton

The primary aim of the study was to find out the values of some biomechanical variables for the long serve skill in badminton and to identify the effect of biomechanical feedback on the performance of long serve. The present study had a single group, pre-post experimental study design. The research community was determined by the intentional method of one group with a pre-and post-test. The players of the Assyrian badminton club constituted the research community. A total of 12 players were present in the research community. The badminton players falling within the age group of 15-17 years for the season 2020-2021 were recruited as the participants for the study. A total of five players were selected as the participants of the study. Based on the findings of the present study, the researchers concluded that the biomechanical feedback effectively contributed through the educational curriculum in influencing the biomechanical variables and in improving the performance of the long-serve.

The Associations Among Self-Compassion, Self-Esteem, Self-Criticism, and Concern Over Mistakes in Response to Biomechanical Feedback in Athletes.

Athletes regularly face the possibility of failing to meet expectations in training and competition, and it is essential that they are equipped with strategies to facilitate coping after receiving performance feedback. Self-compassion is a potential resource to help athletes manage the various setbacks that arise in sport over and above other psychological resources. The primary purpose of this research was to explore how athletes respond to objective biomechanical feedback given after a performance. Specifically, we investigated if levels of self-compassion, self-esteem, self-criticism, and concern over mistakes were related to one another before and after a series of sprint tests interspersed with biomechanical feedback, and whether self-compassionate athletes achieved a better sprint performance after receiving and implementing biomechanical feedback. Forty-eight athletes (20 female: Mage = 19.8 years, SD = 3.1; 28 male: Mage = 23.6 years, SD = 7.8) completed online measures of self-compassion, self-esteem, self-criticism and concern over mistakes before performing four sets of 40-m sprints. Participants received personalized biomechanical feedback after each sprint that compared their performance to gold standard results. Following all sprints, they then completed measures of self-criticism, and reported emotions, thoughts, and reactions. Self-compassion was positively correlated with self-esteem (r = 0.57, p < 0.01) and negatively related to both self-criticism (r = −0.52, p < 0.01) and concern over mistakes (r = −0.69, p < 0.01). We also found that athletes with higher levels of self-compassion prior to sprint performance experienced less self-critical thoughts following biomechanical feedback and subsequent sprint trials (r = −0.38, p < 0.01). Although the results of this study provide some support for the effectiveness of self-compassion in promoting healthy emotions, thoughts, and reactions in response to sprint performance-based biomechanical feedback, a moderated regression analysis between the first and fourth sprint time variables revealed that self-compassion was not a moderator for change in sprint performance (R2 = 0.64, ΔR2 = 0.10, p > 0.05). These findings suggest that there are likely longer-term benefits of athletes using self-compassion to cope with biomechanical feedback, but that any benefits might be limited in a short series of sprint trials.

Review of Real-Time Biomechanical Feedback Systems in Sport and Rehabilitation.

Real-time biomechanical feedback (BMF) is a relatively new area of research. The potential of using advanced technology to improve motion skills in sport and accelerate physical rehabilitation has been demonstrated in a number of studies. This paper provides a literature review of BMF systems in sports and rehabilitation. Our motivation was to examine the history of the field to capture its evolution over time, particularly how technologies are used and implemented in BMF systems, and to identify the most recent studies showing novel solutions and remarkable implementations. We searched for papers in three research databases: Scopus, Web of Science, and PubMed. The initial search yielded 1167 unique papers. After a rigorous and challenging exclusion process, 144 papers were eventually included in this report. We focused on papers describing applications and systems that implement a complete real-time feedback loop, which must include the use of sensors, real-time processing, and concurrent feedback. A number of research questions were raised, and the papers were studied and evaluated accordingly. We identified different types of physical activities, sensors, modalities, actuators, communications, settings and end users. A subset of the included papers, showing the most perspectives, was reviewed in depth to highlight and present their innovative research approaches and techniques. Real-time BMF has great potential in many areas. In recent years, sensors have been the main focus of these studies, but new types of processing devices, methods, and algorithms, actuators, and communication technologies and protocols will be explored in more depth in the future. This paper presents a broad insight into the field of BMF.

A methodical survey of mathematical model-based control techniques based on open and closed loop control approach for diabetes management

Disturbance of blood sugar level is controlled through well-known biomechanical feedback loops: high levels of glucose in blood facilitate to release insulin from the pancreas which accelerates the absorption rate of cellular glucose. Low glucose levels encourage to release pancreatic glucagon which induces glycogen breakdown to glucose in the liver. These bio-control systems do not function properly in diabetic patients. Though the control of disease seems intuitively easy, in real life, due to many differences in structure by diet and fasting, exercise, medications, patient’s profile and other stressors, it is not that easy. The mathematical models of the glucose-insulin regulatory system follow the patient’s physiological conditions which make it difficult to identify and estimate all the model parameters. In this paper, we have given a systematic literature review on mathematical models of the diabetic patients, and various kinds of disease control techniques through the development of open and closed loop insulin deliver command system and optimization of exogenous insulin rate. It demonstrates the open and closed loop type model-based control strategies underlying the assumptions of the concerned models. The combination of mathematical model with control strategies such as genetic algorithm (GA), neural network (NN), sliding mode controller (SMC), model predictive controller (MPC), and fuzzy logic control (FLC) has been considered, which provides an overview of this area, highlighting the control profile over the diabetic model with promising clinical results, outlining key challenges, and identifying needs for the future research. Also, the significance of these control algorithms has been discussed in the presence of the noises, the controller’s robustness and various other disturbances. It provides substantial information on diabetes management through various control techniques.

Macromolecular crowding limits growth under pressure.

Cells that grow in confined spaces eventually build up mechanical compressive stress. This growth-induced pressure (GIP) decreases cell growth. GIP is important in a multitude of contexts from cancer, to microbial infections, to biofouling, yet our understanding of its origin and molecular consequences remains limited. Here, we combine microfluidic confinement of the yeast Saccharomyces cerevisiae, with rheological measurements using genetically encoded multimeric nanoparticles (GEMs) to reveal that growth-induced pressure is accompanied with an increase in a key cellular physical property: macromolecular crowding. We develop a fully calibrated model that predicts how increased macromolecular crowding hinders protein expression and thus diminishes cell growth. This model is sufficient to explain the coupling of growth rate to pressure without the need for specific molecular sensors or signaling cascades. As molecular crowding is similar across all domains of life, this could be a deeply conserved mechanism of biomechanical feedback that allows environmental sensing originating from the fundamental physical properties of cells.

Cell-derived Matrix Assays to Assess Extracellular Matrix Architecture and Track Cell Movement.

The extracellular matrix (ECM) is a non-cellular network of macromolecules, which provides cells and tissues with structural support and biomechanical feedback to regulate cellular function, tissue tension, and homeostasis. Even subtle changes to ECM abundance, architecture, and organization can affect downstream biological pathways, thereby influencing normal cell and tissue function and also driving disease conditions. For example, in cancer, the ECM is well known to provide both biophysical and biochemical cues that influence cancer initiation, progression, and metastasis, highlighting the need to better understand cell-ECM interactions in cancer and other ECM-enriched diseases. Initial cell-derived matrix (CDM) models were used as an in vitro system to mimic and assess the physiologically relevant three-dimensional (3D) cell-ECM interactions. Here, we describe an expansion to these initial CDM models generated by fibroblasts to assess the effect of genetic or pharmacological intervention on fibroblast-mediated matrix production and organization. Additionally, we highlight current methodologies to quantify changes in the ultrastructure and isotropy of the resulting ECM and also provide protocols for assessing cancer cell interaction with CDMs. Understanding the nature and influence of these complex and heterogeneous processes can offer insights into the biomechanical and biochemical mechanisms, which drive cancer development and metastasis, and how we can target them to improve cancer outcomes. This protocol was validated in: Sci Adv (2021), DOI: 10.1126/sciadv.abh0363.

Evaluation of Gait and Functional Stability in Preoperative Cervical Spondylotic Myelopathy Patients.

Prospective cohort study. The aim of this study was to 1) determine postural stability and spatiotemporal gait parameters and 2) characterize dynamic stability and variances in angular momentum (AM) of preoperative cervical spondylotic myelopathy (CSM) patients compared with healthy controls. CSM is the most common cause of spinal cord dysfunction in the world and can lead to significant functional deficits including proprioception and gait disturbances. Biomechanical feedback mechanisms compensating for these deficits, specifically AM regulation, have remained largely unexplored. Fifty-six subjects: 32 preoperative Nurick grade 2 or 3 CSM patients and 24 controls were included. Standing balance trials were performed on a single force plate, while walking trials were conducted at self-selected pace over a 15 m runway and a series of five force plates. All trials were recorded with three-dimensional motion analysis cameras and gait modeling software was utilized to calculate stability, spatiotemporal gait parameters, and joint kinematics. Tilted ellipse area, a measure of center of pressure variance and postural stability, was significantly greater among CSM patients (847.54 ± 764.33 mm2vs. 258.18 ± 103.35 mm2, P < 0.001). These patients had two times as much variance medial-lateral (72.12 ± 51.83 mm vs. 29.15 ± 14.95 mm, P = 0.001) and over three times as much anterior-posterior (42.25 ± 55.01 mm vs. 9.17 ± 4.83 mm, P = 0.001) compared with controls. Spatiotemporal parameters indicated that the CSM patients tending to have slower, shorter, and wider gait compared with controls, while spending greater amount of time in double support. Compensatory AM among CSM patients was significantly increased in all three anatomic planes, where whole-body AM was approximately double that of controls (0.057 ± 0.034 vs. 0.023 ± 0.006), P < 0.001). Preoperative CSM patients showed significant alterations in spatiotemporal gait parameters and postural stability compared with controls, consistent with prior literature. Likewise, angular momentum analysis demonstrates that these patients have globally increased body excursion to maintain dynamic balance.Level of Evidence: 3.

Extracellular Matrix Composition Is Altered Alongside Dysmorphology in the Developing Palate

Normal morphogenesis of the primary palate involves directed outgrowth of the facial primordia until they meet and fuse. Gradients of cellular proliferation induced by growth factors are the current paradigm for directed outgrowth, but active cellular migration and physical force propagated through the extracellular matrix (ECM) likely also direct growth. Previously we showed that two of the main components of the ECM, collagen IV and laminin, are thinner in regions of the frontonasal process (FNP) undergoing growth, suggesting tissue stiffness may passively constrain growth in certain directions. We have also shown that increasing Fibroblast growth factor (FGF) signaling in the FNP of chick embryos prior to palate fusion caused overgrowth and disrupted cellular organization. Since cells form and modify the ECM, and since the ECM is required for cellular organization and movement, the effects of FGF signaling on morphogenesis may be due in part to active feedback between ECM and cells. Our goal was to examine the changes to the ECM in the FNP following alteration of FGF signaling. Blocking FGF signaling with SU5402 caused hypoplasia of the FNP and increased the concentration of collagen IV and laminin in regions of expected outgrowth. Conversely, increasing FGF signaling with exogenous FGF2 caused overgrowth of the FNP and decreased concentration of the ECM components. Analysis using transmission electron microscopy of the FGF2 treated samples suggests increasing FGF signaling also decreases the thickness of the epithelium and basement membrane. These results provide preliminary evidence that ECM may play an important role in facial morphogenesis, and that FGF signaling may affect an active biomechanical feedback system between cells and ECM. In the future I will further characterize ECM composition and compliance across the FNP using Fourier transform infrared spectroscopy and atomic force microscopy to generate 3-dimensional maps of biomechanical properties in the face. I will also use confocal microscopy to map cellular organization across the face. I will overlay these maps onto representative reconstructions of the face to correlate regional variation in biomechanical properties and cellular organization with dysmorphologies that occur following exogenous modulation of FGF signaling.

Myofibril and mitochondria morphogenesis are coordinated by a mechanical feedback mechanism in muscle

Complex animals build specialised muscles to match specific biomechanical and energetic needs. Hence, composition and architecture of sarcomeres and mitochondria are muscle type specific. However, mechanisms coordinating mitochondria with sarcomere morphogenesis are elusive. Here we use Drosophila muscles to demonstrate that myofibril and mitochondria morphogenesis are intimately linked. In flight muscles, the muscle selector spalt instructs mitochondria to intercalate between myofibrils, which in turn mechanically constrain mitochondria into elongated shapes. Conversely in cross-striated leg muscles, mitochondria networks surround myofibril bundles, contacting myofibrils only with thin extensions. To investigate the mechanism causing these differences, we manipulated mitochondrial dynamics and found that increased mitochondrial fusion during myofibril assembly prevents mitochondrial intercalation in flight muscles. Strikingly, this causes the expression of cross-striated muscle specific sarcomeric proteins. Consequently, flight muscle myofibrils convert towards a partially cross-striated architecture. Together, these data suggest a biomechanical feedback mechanism downstream of spalt synchronizing mitochondria with myofibril morphogenesis.

Ultra-sensitive and resilient compliant strain gauges for soft machines.

Soft machines are a promising design paradigm for human-centric devices1,2 and systems required to interact gently with their environment3,4. To enable soft machines to respond intelligently to their surroundings, compliant sensory feedback mechanisms are needed. Specifically, soft alternatives to strain gauges-with high resolution at low strain (less than 5 per cent)-could unlock promising new capabilities in soft systems. However, currently available sensing mechanisms typically possess either high strain sensitivity or high mechanical resilience, but not both. The scarcity of resilient andcompliant ultra-sensitive sensing mechanisms has confined their operation to laboratory settings, inhibiting their widespread deployment. Here we present a versatile and compliant transduction mechanism for high-sensitivity strain detection with high mechanical resilience, based on strain-mediated contact in anisotropically resistive structures (SCARS). The mechanism relies upon changes in Ohmic contact between stiff, micro-structured, anisotropically conductive meanders encapsulated by stretchable films. The mechanism achieves high sensitivity, with gauge factors greater than 85,000, while being adaptable for use with high-strength conductors, thus producing sensors resilient to adverse loading conditions. The sensing mechanism also exhibits high linearity, as well as insensitivity to bending and twisting deformations-features that are important for soft device applications. To demonstrate the potential impact of our technology, we construct a sensor-integrated, lightweight, textile-based arm sleeve that can recognize gestures without encumbering the hand. We demonstrate predictive tracking and classification of discrete gestures and continuous hand motions via detection of small muscle movements in the arm. The sleeve demonstration shows the potential of the SCARS technology for the development of unobtrusive, wearable biomechanical feedback systems and human-computer interfaces.