The elimination of batteries in implants enables their miniaturization to millimeter (mm) scale. This can be achieved by wireless power transfer (WPT), which is also beneficial for the long-term operation of implants. Current state-of-the-art WPT techniques include inductive coupling, ultrasound (US), and magnetoelectric (ME) modalities. US and ME links operate at acoustic wave resonance, working at low frequencies (100s of kHz to several MHz) while using mm-scale receivers. In contrast, mm-scale inductive links are efficient at high frequencies as they operate at electromagnetic wave resonance. While all three modalities are attractive, the literature lacks a comparative study in which these modalities are evaluated under similar conditions (size and depth of implant) when they are optimized and operate under regulatory safety limits. This paper compares the power receiving capability of ~ 6.2×2.2×1.4 mm3ME and US receivers, and an inductive coil with comparable 20 mm3volume and 3 mm2surface area. In measurements at a 30 mm depth within a tissue medium, the inductive, ME, and US WPT links could deliver 7.7 mW, 7 mW, and 15.55 mW of power considering the safety limits, respectively. Among these modalities, the ME link demonstrated the highest robustness against angular misalignment.

Structural health monitoring (SHM) offers extended structural lifespan, cost savings, and early risk detection, ultimately contributing to enhanced overall performance of critical structures. This paper presents a multiplexed active ultrasonic node for generating ultrasonic waves using a piezoelectric transducer powered by a single optical fiber (driven by a tunable laser) towards distributed SHM with no complex wiring. The proof-of-concept prototype is built using commercial off-the-shelf components on a 41×33 mm2printed circuit board. In measurements, 2.75 mW of power is harvested by two parallelly connected Germanium photodiodes across a portion of the optical fiber with long period fiber Bragg grating at 1554 nm wavelength. This power is used to drive a piezoelectric transducer by five ~ 30 V pulses at 500 kHz. A method to program the number of driving pulses is also presented. Power scheduling technique ensures operation with limited available input voltage and power of hundreds of mV and a few mW, respectively.

This paper introduces a technique, called monotonic energy transmission (MET), for short-range wireless data transfer from small implantable devices with millimeter (mm) scale dimensions to an external unit using the magnetoelectric (ME) effect. In the proposed technique, while low-frequency magnetic field is used to power an implant which integrates a small ME transducer, data is transferred by driving the ME transducer with an initiation and a suppression sinusoid, which are 180° apart in phase. Transmitting both sinusoids improves the data rate and minimizes the inter-symbol interference (ISI). This technique was combined with pulse position modulation (PPM) to further increase the data rate. This paper describes the theory behind the proposed technique and demonstrates its operation through measurements using a$6.56\times 2.63\times 0.67 \ \text{mm}^{3}$ME transducer fabricated with Metglas and PZT-5A as the magnetostrictive and piezoelectric layers, respectively. In measurements, 220 kbps data rate was achieved using a delay detection resolution of 1 ns with an ME transducer operating at 274 kHz.

Effective and safe ultrasound neuromodulation has been demonstrated in animals and humans with often bulky off-the-shelf high-voltage (HV) drivers and ultrasound transducers. This brief presents an efficient HV ASIC for driving a piezoelectric transducer as the first step towards a small portable system. A design method is presented for finding the optimal switching frequency $\left(f_{p}\right)$ and duty cycle (DC) of the HV class DE driver for a given piezoelectric transducer. The ASIC integrates inductive power management, clock recovery, delay cell, and level shifter circuits for creating optimal switching signals for the H V driver from an A C power carrier. The ASIC was fabricated in a $0.25 \mu m$ HV BCD CMOS process and integrated with 2.7 MHz flat and 4.6 MHz curved single-element piezoelectric transducers. In measurements, the ASIC could apply 40 V peak-peak voltages across transducers with optimal fpand DC calculated from our model, generating up to 3 MPa ultrasound pressure outputs with as high as 91 % power efficiency.

Low-power and robust wireless communication is needed in implantable medical devices with the millimeter (mm) dimension, in which power is scarce. This paper presents an adaptive ASIC for low-power (and robust) data transmission from a mm-sized implant to an external unit using optimal number of ultrasonic (US) pulses. Any changes in the distance and alignment of a US transducer pair (for US wireless power and data transfer) can drastically vary the amplitude of the received signal. To mitigate this issue (i.e., improving robustness) and minimize the power consumption of the data transmitter, the number of transmitted US pulses is changed based on the received voltage at the external unit in the proposed closed-loop system. The proposed ASIC, designed and fabricated in a $0.35 \mu \mathrm{m}$ standard CMOS process, includes a power-management unit for rectification, regulation, and over-voltage protection of a 1.1 MHz US power carrier using only one external capacitor. The ASIC also includes a pulse-based data transmitter that can adaptively generate 1-8 pulses based on the received pattern modulated on the power carrier. Simulation results demonstrate the functionality of the ASIC in wireless power and data transfer with optimal number of pulses in the implant.

This paper presents the concept and some preliminary results of a millimeter-scale wireless addressable optoelectronic implant (WAOI), a network of which can be distributed over the brain for large-scale optogenetics. The WAOI contains a wireless receiver (base), which establishes wireless power transfer and data communication with an external unit, connected to an optoelectronic shank, which integrates liquid crystal-based silicon photonic on CMOS electronics for switchable optical emission. The liquid crystal-switched waveguide can provide light switching of a single light source (e.g. laser diode), which is integrated on the base, along the shank, thus minimizing heat generation within brain parenchyma. To reduce interconnect wiring between the base and the shank, a power-line communication technique is presented for data transfer from the base to the shank. Simplified prototypes of the base and shank ASICs were designed and developed in 0.35-μm 2P4M CMOS process. The simulation results of these ASICs for addressing of 16 stimulation pixels on the shank are presented. Moreover, a macroscale example of liquid crystal-switched waveguide was fabricated and measured to demonstrate basic liquid crystal switch operation.

This paper presents an accurate comparison between the performance of inductive and ultrasonic links for wireless power transmission (WPT) to biomedical implants with different sizes and implantation depth. These links' performances are evaluated based on the power transmission efficiency (PTE) at their optimized operation frequency (fp) to find out which WPT method is more efficient and robust. The geometry of several sets of inductive and ultrasonic links along with their fp have been optimized for different separation distances (d12) between the transmitter (Tx) and receiver (Rx) and two Rx diameters (D02) to achieve the highest PTE. The simulation results show that the ultrasonic link outperforms the inductive link when the Rx has D02 of 1.2 mm and implanted deep inside the tissue. However, for an Rx with the D02 of 5 mm and above, the inductive link achieves higher PTE, particularly at shorter d12 of 5 mm (46% vs. 40%) and 10 mm (40% vs. 28%). The simulated misalignment results show that the ultrasonic link is more prone to misalignments greater than 1 mm compared to its inductive counterpart.

The ubiquity of Web applications has led to an increased focus on the development of attacks targeting these applications. One particular type of attack that has recently become prominent is the SQL injection attack. SQL injection attacks can potentially result in unauthorized access to confidential information stored in a backend database. In this paper we describe an anomaly based approach which utilizes the character distribution of certain sections of HTTP requests to detect previously unseen SQL injection attacks. Our approach requires no user interaction, and no modification of or access to, either the backend database or the source code of the web application itself. Our practical results suggest that the model proposed in this paper is superior to existing models at detecting SQL injection attacks. We also evaluate the effectiveness of our model at detecting different types of SQL injection attacks.