Wen-Wei Tsai

Osteogenesis of adipose-derived stem cells on polycaprolactone-β-tricalcium phosphate scaffold fabricated via selective laser sintering and surface coating with collagen type I.

The current study aimed to fabricate three‐dimensional (3D) polycaprolactone (PCL), polycaprolactone and β‐tricalcium phosphate (PCL–TCP) scaffolds via a selective laser‐sintering technique (SLS). Collagen type I was further coated onto PCL–TCP scaffolds to form PCL–TCP–COL scaffolds. The physical characters of these three scaffolds were analysed. The osteogenic potential of porcine adipose‐derived stem cells (pASCs) was compared among these three scaffolds in order to find an optimal scaffold for bone tissue engineering. The experimental results showed no significant differences in pore size and porosity among the three scaffolds; the porosity was ca. 75–77% and the pore size was ca. 300–500 µm in all three. The compressive modulus was increased from 6.77 ± 0.19 to 13.66 ± 0.19 MPa by adding 30% β‐TCP into a 70% PCL scaffold. No significant increase of mechanical strength was found by surface‐coating with collagen type I. Hydrophilicity and swelling ratios showed statistical elevation (p < 0.05) after collagen type I was coated onto the PCL–TCP scaffolds. The in vitro study demonstrated that pASCs had the best osteogenic differentiation on PCL–TCP–COL group scaffolds, due to the highest ALP activity, osteocalcin mRNA expression and mineralization. A nude mice experiment showed better woven bone and vascular tissue formation in the PCL–TCP–COL group than in the PCL group. In conclusion, the study demonstrated the ability to fabricate 3D, porous PCL–TCP composite scaffolds (PCL:TCP = 70:30 by weight) via an in‐house‐built SLS technique. In addition, the osteogenic ability of pASCs was found to be enhanced by coating COL onto the PCL–TCP scaffolds, both in vitro and in vivo. Copyright

CORDIC-based inclination sensing algorithm using three-axis accelerometer-based inertial sensors

In this paper, we present a low complexity and memory-less algorithm for angle calculations of a system using 3-axis accelerometers. Accelerometers have been widely used to determine the inclination or tilt of a system where the net acceleration or force on a system over time is gravity. However, the angle calculations are complicated and most of the work either implementing with look-up tables or simply transmit the data to systems with more powerful computation resources, such as a PC, to calculate the angles. To reduce the computational complexity and release the memory burden, we propose a 2D CORDIC-based algorithm for the inclination or tilt angle calculations so that it is feasible on a low-cost and low power microcontroller in an embedded system.

Laser sintered porous polycaprolacone scaffolds loaded with hyaluronic acid and gelatin-grafted thermoresponsive hydrogel for cartilage tissue engineering.

The aim of this study is to evaluate a soft/hard bi-phase scaffold for cartilage tissue engineering. Chondrocyte proliferation, glycoaminoglycan production and total collagen content are compared between laser-sintered porous polycaprolactone (PCL) scaffolds with and without a thermoresponsive hydrogel grafted with hyaluronic acid and gelatin. The in vitro results show that scaffolds loaded with hydrogel have a higher initial chondrocyte attachment than PCL scaffolds. At day 21 and 28, scaffolds loaded with hydrogel have a significantly higher glycosaminoglycan (GAG) production than PCL scaffolds alone, and total collagen content including collagen type II in the hydrogel-loaded group is three times higher than the group without hydrogel. It is concluded that the laser-sintered porous PCL scaffold has good cytocompatibility, and that the hydrogel phase is able to enhance initial chondrocytes attachment as well as GAG and collagen production of chondrocytes. This study suggests that a soft/hard bi-phase scaffold may be used for cartilage tissue engineering to enhance in vitro chondrogenesis.

MMG-torque estimation under dynamic contractions

Torque estimation using mechanomyographic (MMG) signal is typically calculated by the root mean square (RMS) amplitude. Raw MMG signal is processed by rectification, low-pass filtering, and mapping to estimate torque. However, one-to-one mapping is not accurate because if the input is interfered by noise, the output follows directly. In this work, beside RMS amplitude, another significant feature of MMG signal, i.e., frequency variance, was found and used for constructing the MMG-torque estimator. Seven subjects produced constant posture and torque contractions about the elbow while MMG signal and torque were recorded. We found that MMG RMS amplitude increased monotonously and frequency variance decreased under incremental voluntary contractions. A MMG-torque estimator was introduced using MMG RMS amplitude and frequency variance as inputs and a two-layer neural network as the modeling algorithm. Experimental evaluation of the estimator was done under constant posture and sinusoidal contractions at 0.5Hz, 0.25Hz, 0.125Hz, and random frequency. The results of the proposed MMG-torque estimator and MMG RMS amplitude linear mapping were also compared. The estimation of MMG-torque estimator has better accuracy than linear mapping for all contraction frequencies. The mean absolute error decreased 6% for the 0.5Hz contraction, 43% for 0.25Hz contraction, 52% for 0.125Hz contraction, and 30% for random frequency contraction.

A quantitative method for evaluating inferior glenohumeral joint stiffness using ultrasonography

Subluxation of the affected shoulder in post-stroke patients is associated with nerve disorders and muscle fatigue. Clinicians must be able to accurately and reliably measure inferior glenohumeral subluxation in patients to provide appropriate treatment. However, quantitative methods for evaluating the laxity and stiffness of the glenohumeral joint (GHJ) are still being developed. The aim of this study was to develop a new protocol for evaluating the laxity and stiffness of the inferior GHJ using ultrasonography under optimal testing conditions and to investigate changes in the GHJ from a commercially available humerus brace and shoulder brace. Multistage inferior displacement forces were applied to create a glide between the most cephalad point on the visible anterosuperior surface of the humeral head and coracoid process in seven healthy volunteers. GHJ stiffness was defined as the slope of the linear regression line between the glides and different testing loads. The testing conditions were defined by different test loading mechanisms (n=2), shoulder constraining conditions (n=2), and loading modes (n=4). The optimal testing condition was defined as the condition with the least residual variance of measured laxity to the calculated stiffness under different testing loads. A paired t-test was used to compare the laxity and stiffness of the inferior GHJ using different braces. No significant difference was identified between the two test loading mechanisms (t=0.218, p=0.831) and two shoulder constraining conditions (t=-0.235, p=0.818). We concluded that ultrasonographic laxity measurements performed using a pulley set loading mechanism was as reliable as direct loading. Additionally, constraining the unloaded shoulder was proposed due to the lower mean residual variance value. Moreover, pulling the elbow downward with loading on the upper arm was suggested, as pulling the elbow downward with the elbow flexed and loading on the forearm may overestimate stiffness and pain in the inferior GHJ at the loading point due to friction between the wide belt and skin. Furthermore, subjects wearing a humerus brace with a belt, which creates the effect of lifting the humerus toward the acromion, had greater GHJ stiffness compared to subjects wearing a shoulder brace without a belt to lift the humerus under the proposed testing conditions. This study provides experimental evidence that shoulder braces may reduce GHJ laxity under an external load, implying that the use of a humeral brace can prevent subluxation in post-stroke patients. The resulting optimal testing conditions for measuring the laxity and stiffness of the GHJ is to constrain the unloaded shoulder and bend the loaded arm at the elbow with loading on the upper arm using a pulley system.

A new trunk sway assessment protocol using biofeedback inertial-based sensing modality for stroke patients

The ability to control postural steadiness is an important determinant of overcoming the internal and external environmental stimulus across the falls for stoke patients. Traditionally, assessments of postural steadiness are based on patients ability to control the angular deviation of the center of mass (COM) within the base of support. In this study, a wireless inertial-based sensing modality with augmented biofeedback training protocol was developed and used for clinical evaluation. Eighteen cerebral vascular accident patients were recruited for the assessment. The experimental results revealed that biofeedback strategy together with motor skill learning protocol appears to be an important variable for improving postural steadiness during tandem stance.